Aluminum Anodizing

Buffing and Polishing

2012-01-06T18:52:00.000-08:00

Mechanical polishing and buffing have the objective to make a rough surface into a smooth surface. If the work piece have different condition it will need different procedures. Buffing is like an abrasion process to the hill that have jagged mountains and valleys. Polishing also treat to the article that have been anodized, this process to make the article more lustre and bright.

One of the major applications of anodized aluminum involves the production of finishes resembling bronze, brass, gold, silver and their alloys. In such cases apart from the choice of suitable coloring materials, an important part is played by the conditioning and preparation of the surface of the metal prior to anodizing.

Before the article being polished, it should follow the pretreatment before polished first. The articles are pressed against the abrasive loaded rim of rapidly rotating flexible wheels made of leather or coarse cloth discs. Two or three successive processes are usually used with progressively finer abrasives; grease or oil lubricant is applied during the final cuts, and the surface is brought to a satin smooth but entirely lusterless condition. The grease not only lubricates the operation, but supports and to some extent masks the abrasive particles; it also removes the frictional heat and prevents burning or scorching of the surface.

Anodizing Practice

2011-12-23T18:56:00.000-08:00

Anodizing aluminum is practiced as has been described on the anodizing article as previous blog. Anodizing pocess will protect the aluminum parts by aluminum oxide film on the aluminum surface. Aluminum that is grown outside surface of aluminum then becomes aluminum hydrate that is extremely hard. The porous surface of the anodized layer allows the product to be dyed any color as required. This all anodizing theory has been describe on the last articles.

To more understand about anodizing process follow the article belows:

Aluminum Anodizing Without Sulfuric Acid

2011-11-26T02:16:00.000-08:00

The normal anodizing process of aluminum use sulfuric acid as the liquid media to open the pore of aluminum. But for other kind of steel this process may can’t work. Sulfuric acid is not suitable for steel anodizing, yes of course because steel have different properties not like aluminum.

Anodizing forms an oxide protective barrier on aluminum but if you form iron oxide over steel it will not protect it adequately, for that reason a different compound has to be developed. You may want to explore blackening, galvanizing or phosphate coating of steel.

Some companies claim that they know an Electrochemical Process for stainless steel wherein Chrome Oxide can be produced/enhanced and by varying the thickness it attains different color. But anodizing process just apply to aluminum steel and aluminum alloy if possible. Other steel can be process by aluminum process if that steel is coated first by aluminum steel.

Anodizing Machine

2011-11-13T05:43:00.000-08:00

As seen on the picture is a small anodizing kits that use in laboratory, small modular anodizing system are become more available and affordable. The price of this kind module that able to anodize aluminum or titanium parts up to 1 cubic foot can have price about $60,000 to $100,000 or more depending upon your production needs.

Anodizing module need several boxes to finalize anodizing process, such as cleaning, electropolishing, coloring and sealing. Coloring itself may can made in many boxes because need box for every color effect. The box that contains of certain dye is not discharged after use because it can be use for other coloring process.

Black Anodizing Aluminum Problems

2011-10-09T00:19:00.001-07:00

As theoretically on aluminum anodizing seem have no problem if we want to make coloring on anodizing aluminum, but actually some problem may happen unpredictable. The example problem is on black anodizing some parts. The material is .090" 5052 aluminum. The part size is 5 x 8 with about 30 - 40% of the panels cut away. The pieces are putting in the anodizing tank at one time. The parts are finely grained (sanded). Our procedure is as follows:

After graining, then clean in a mild detergent solution.
Water rinse
Dip in caustic etch (Oakite 360L) for 2 minutes
Water rinse
Dip in deoxidizer (Oakite Deox) for 1 minute
Water rinse
Anodize in sulfuric acid (24 Baume A) at 76 - 78 degrees Fahrenheit for 55 minutes at 15 volts
Water rinse for 5 minutes
Dip in black dye (Sandoz) tank for 20 minutes at 110 - 140 Fahrenheit
Water rinse for 2 minutes
Seal in boiling water with nickel acetate solution for 15 minutes
Water rinse

Several problems can happen on some process:
There appear to be stains of some sort that are in/under the anodic layer. They do not rub off of the panels. Then can getting a bluish hue around the edges and holes.

Solution from smut - we are trying to clean with a scotchbrite pad and either mild detergent or naphtha.

About the smut- do you manually clean and handle the pieces in between the anodizing processes? If you're still having problem with the smut even after deox then, you may have problem with the deox solution or you need to adjust your deox time.

What about your rinse process, is it enough?
Have you tried at 70 deg, 30 min anodizing?

Have you attempted to strip and re-anodize the parts?
If so, after stripping the parts down, take a piece of mild scotch-brite pad and go over the part. Don't press too hard on the material when you're rubbing, but generally speaking this can do the trick. If that still doesn't work consider some alternative form of "sanding" the material. By sanding assuming that you mean with a sanding belt of determined grit to achieve a certain grained finish.

What grit you using?
Have you considered a lighter/heavier grit to possibly eliminate this problem?
Are you using varying grits, such as, 200 then 400?
Its been years since I've been around polishing and buffing myself, but I seem to recall we used a pretty heavy belt, like around 120, it did a really nice job cutting the material, left it with a heavily satined grain, and when anodized really showed through well.
>We are getting a bluish hue around the edges and holes.

How are these parts cut?
Are they stamped?
Were they laser cut?
How did your customer get their end product that you have?
This is probably the biggest determining factor here.
What you're seeing is likely a stress in the material from the manufacture of the parts. Its not something that can be seen before the anodizing. But because of the anodizing and the potential stress thats been employed to make the parts, you may have varying coloration around the holes and the sides because of this.

Its not common, I'll say that, but it does exist. Micro burrs on the edges can also contribute to some odd looking streaks and comet tails around the edges.
>Smut - we are trying to clean with a scotchbrite pad and either mild detergent or naphtha.
So many people have their own personal smut and no one persons seems to be able to relate to another persons in terms of conditions and what the stuff looks like or acts like. Is it slimy; is it chalky, does it have a pattern to it?

There's really no way I could figure out what to do with the smut without having a part of two to fix myself.
I've seen some unwanted layers that are smoky in appearance from a sealing bath. Generally these can be rubbed with a terry cloth to a nice, smooth, beautiful bright finish. This generally happens with a fresh seal bath and the subsequent first few loads that leave the seal. After that, it disappears.

Anodizing Process

2011-09-18T17:01:00.000-07:00

Anodizing process usually apply to the aluminum metal, but the principle of the anodizing aluminum may can be applied to other kind of metal. Aluminum have special properties that different with other metal like iron, alloy. Aluminum will not continue to anodize (rust) once the surface have covered with anodized layer. This oxide film on the surface is extremely thin and loosely adhered to, and is easily removed by handling.

After anodize on the aluminum then have the following characteristic:

have corrosion resistance
have durability/wear resistance
able to be colored through dying
electric insulation
have excellent base or primer for secondary coating

Anodizing process using sulfuric acid and DC electrical current that is passed through a bath of sulfuric acid while the aluminum being treated serves as the anode. On this process, aluminum will clear or remove their film oxide on the surface.

On the process of aluminum anodizing need several process should be applied in order have perfect result, these are the order of anodizing process:

Pretreatment or cleaning using detergent
Rinsing using clean water or demin water
Etching or chemical milling
Desmutting or rinsing in acidic solution to remove unwanted surface alloy particles
Anodizing
Coloring, anodized aluminum can be colored through chemical reaction process coloring or using dying agent.
Sealing, this process is to close the pores of aluminum surface by dipping in hot water.

Color Hard Anodizing

2011-07-30T03:45:00.000-07:00

Color anodizing is depend on the color type that implemented on the finished product, the coloring process on anodizing is applied on the coloring process before the metal being sealed. The mechanism of coloring is varied depend on the color finished product want to be resulted. Like the coloring using oxalic acid can produce color in many kind of colors, it depend on the thickness of the anodized oxide film. Anodizing using oxalic acid can produce color like silvery, brass or bronze that should be use in different voltage, bath temperature and duration of anodizing.

Anodizing with chemical dyes like on textile industry also can result in many color of finished product, and if you want a bright product that apply polishing method by satin anodized finished. Anodizing also can produce non reflective finish like bead blasting prior. Teflon coated anodizing also available in many color, clear anodizing, or super thick finished.

Teflon impregnated anodizing is merely an additional step to the anodizing process that puts a Teflon seal in the anodizing giving the metal a very slick and naturally lubricated finish. Bead blast service of all metals can be done on site with 50 horsepower screw compressor and glass bead room.

Anodizing at Home

2011-06-29T09:01:00.000-07:00

Anodizing aluminum can make the aluminum more durable to the season effect and atmosphere chemical contain that make the aluminum corrode. Principally anodizing will make the aluminum have the below characteristics:

Make the aluminum surface hardness more tough
Anodizing will protect the aluminum from corrosion
Anodizing will make the color of aluminum more interesting

As have discussed at the previous blog on anodizing process, the step of this process as follows:

Use sulfuric acid that can take from battery acid or accu-sir
Rinse the aluminum tube or plate by water, rinse and immerse in a bath of caustic soda solution.
Rinse again the aluminum plate with distilled water
Using car battery charger to anodize the aluminum, you can use two plate of aluminum or one aluminum and one from lead plate to make anodized
Hook the aluminum one plate use as cathode and connect to negative pole of battery charge. The other part use as anode is hooked up with aluminum wire to the battery charger.
Dipped on acetic acid solution and turn on the battery charger with 2 ampere at first. Increase the current until 10 ampere after a few minutes.
After 105 minutes the part was showing a slight yellow tint and surface wasn’t quite as shinny, the current flow will off. This indicate that the anodizing have finished.
Rinse the part on distilled water
Immerse in the dye solution, then the final process is sealing process.
Rinse with distilled water again and then placed in boiling water for 30 minutes to seal the surface

By those process can result many kind of color surface depend on the dye color you applied.

Aluminum Anodizing not use Sulfuric Acid

2011-06-04T06:40:00.000-07:00

On Aluminum Extrusion and Finishing Company, the anodizing facility for aluminum profiles using sulfuric acid. The companies get inquiries for anodizing steel. But using sulfuric acid process is not suitable for steel.

Can anyone give some guidelines / process (suitable electrolyte and other data) to carry out industrial anodizing of steel?

Anodizing forms an oxide protective barrier on aluminum but if you form iron oxide over steel it will not protect it adequately, for that reason a different compound has to be developed. You may want to explore blackening, galvanizing or phosphate coating of steel.

Some companies claim that they know an Electrochemical Process for stainless steel wherein Chrome Oxide can be produced/enhanced and by varying the thickness it attains different color. May be, you are talking about that. But, to the best, the term "Anodizing" is used only for Anodizing of Aluminum.

Form more information about anodizing process can see on the following process; aluminum anodizing.

Anodizing on Titanium

2011-05-14T18:01:00.000-07:00

This is actually the metal that actually seldom to use because it very expensive metal to use in general application. Anodizing on titanium may apply as follow to the anodizing definition itself that Anodizing define as electrolytic passivation, the process that affect on the metal to increase the thickness of the natural oxide layer on the surface of metal parts.

The surface of titanium metal will covered by oxide of titanium, this similar as happen on aluminum anodizing. After anodized on the titanium metal then can be coloring by heating. The most common method is to form an oxide layer by electrolytic means, similar to the process of electroplating. The work to be colored is attached to the positive connection of power supply (anode), and usually another piece of titanium is connected to the negative side (cathode) of the supply. Both of this electrode than submerge in a middle conductive solution, such as phosporic acid, TSP (Tri Sodium Phosphate).

When the power is applied to the contacts, a uniform layer of titanium oxide forms on the anode. As the voltage increases, the thickness of the layer also increases. Certain color will appear at specific voltage levels, the change from one color to another is not sharply defined, but rather shades gradually through a limited spectrum.

The basic setup for anodizing titanium as follows:

A container - large enough to hold the work to be anodized
An electrolytic solution Acid phosphoric, TSP or TSP PF cleaning solution, etc)
A variable power supply - ideally this should be able adjusted from 0 - 150 Volt DC and can sustain 10 - 15 Ampere of current.
A cathode - usually a strip of scrap titanium
An anode - this is the titanium piece to be anodized

Good Treatment is the Quality

2011-04-16T18:29:00.000-07:00

To make a consistent result on the process of plating on aluminum, pretreatment become the key of this process to get success. Especially on immersing treatment, the various cleaning and conditioning treatments provide a surface of uniform activity.

The principle on surface treatment before through plating process, the surface should free from oil and grease or other foreign material. Oil and grease can be removed by alkaline cleaning, that use of alkaline solution that is made from sodium hydroxide dissolved in water.

The type of alkaline cleaner can be prepared from 23 g/l sodium carbonate (Na₂CO₃) and 23 g/l trisodium phosphate (Na₃PO₄.12H₂O) and is used at 71 to 83^oC for 1 to 3 minutes. Another Solution frequency used is 5% sodium hydroxide (NaOH), operated at 60 to 65^oC for 30 to 60 sec.

Chromic Acid Anodizing

2011-03-03T15:34:00.000-08:00

Chromic acid anodizing is coating process on the metal that refer to both method of chromium electroplating and anodizing process, this process if frequency referred to as type I anodizing as designated by the MIL-A-8625 standard. It is also covered in the AMS 2470 and the ASTM B580 specifications. By chromic acid anodizing enhances the corrosion resistance of aluminum parts and produces a thin opaque film that is soft, ductile, non-conductive, and to a degree self healing. The result thickness after using this process usually about 0.00005 to 0.0001 inches or 0.00125 mm to 0.0025 mm.

Chromic acid anodizing may be applied as a pretreatment before painting to enhance adhesion and it is harder to dye that sulfuric acid anodize. After the metal being chromic acid anodize has over other anodizing process is that it does not lower the fatigue strength of the aluminum or damage the base material if it is entrapped in lap joints or blind holes. As other anodizing process, after chromic acid anodize the solution may be sealed in either hot water or sodium dichromate solutions.

Anodizing Products

2011-02-22T08:39:00.000-08:00

Many products that processed by anodizing, mostly use aluminum as the raw materials. We don't realize that many of products that use at our home using anodizing of aluminum. Product that use of this process also use as decorative finished. As on the picture below decorative finished products can be use with electronic base product. This often use as the base electronic product because current product most dominated by electronics. Electronic product also very fashionable and often change their model overtime. To completed the new model that will be released anodized producer use this change to involve on the electronic fashioned.

Many product as on the picture may have used by us, some of them just a toys that anodized, and some of them often an ornament part.

Other anodized products that often use by is windows frame that made from aluminum. The brown color as the picture below is the result of anodizing process.

Other kind product that often use in our home is lamp reflector, this reflector is made from aluminum that completed by anodizing process. Good reflector effect on this product have no doubt.

Silver Plating

2011-01-29T02:51:00.000-08:00

Silver plating often applied for decorative finished for less demanding applications on electronics, silver is often used as a cheaper replacement for gold, as the best corrode resistant materials. Although silver have better conductor properties than gold it does oxidize and so gold is better of contacts.

Care should be used for parts exposed to high humidity environments. Silver rather stand to porous but if this layer is porous or contains cracks, the underlying copper undergoes rapid because of galvanic corrosion, flacking off the plating and exposing the copper itself, a process known as red plague.

Silver plate was to provide a cheaper version of items that might otherwise be made of silver, including cutlery and candlesticks. The method for silver coating on metal usually use silver electroplating, but in glass industry other method to create a mirror use Tollen's Test. Using Tollens method, the final reaction can occur by placing Tollen's Reagent in a glass and then adding Glucose/Dextrose and shaking the bottle to form the reactions as follows:

AgNO₃ + KOH ---> AgOH + KNO₃
AgOH + 2 NH₃ ---> [Ag(NH₃)₂]¹⁺ + [OH]^-1
^{[Ag(NH ₃₂]¹⁺[OH]^-1}+ Aldhehyde -----> Ag + 2 NH₃ + H₂O

Chemical Finishing

2011-01-11T15:41:00.000-08:00

Chemical finish is a part of process to make brightness and smooth on the surface of metal. Chemical treatment is done to anodizing when all the process of anodizing have completed. Cleaning also called as pre anodizing process or can be said as pretreatment or clean up or polishing after anodized as a part of process phase.

Beside use chemical treatment, smooth process also can be done by mechanical process. Parts after anodized can be smoothed by 1. mechanical polishing with abrasive coated wheel or belts. 2. Tumbling with abrasive media or 3. Vibration with media. Abrasives with a size range of 220 to 300 mesh glued on cloth usually used for mechanical polishing. Wheel rotate with a speed from 2100 to 1400 m/min. Abrasive belt should be lubricated by small amount of grease. Die casting usually are polished individually in 30 sec or less. Larger casting sometimes require 5 to 6 minutes.

Metallurgical Structure on Aluminum Plating

2010-11-21T03:56:00.000-08:00

Aluminum Alloy metal have many kinds of composition and it mean has been difficult to find a certain preplating procedure that will be equally satisfactory for all types and tempers of aluminum alloys, since the various alloys and products exhibit different metallurgical structures and different electrochemical behavior. Every alloy elements have different characteristic and structure that can effect to the behavior when treat with electroplating on aluminum metal.

When alloying elements are added, they may appear in an aluminum alloy in several different forms - in solid solution in the aluminum lattice, as micro-particles of the elements themselves, or as particles of intermetallic compounds formed by combination with the aluminum or other alloying elements.

The several solid solution matrices and the 20 or more microconstituents that may occur in commercial alloys may have different chemical and electrochemical reactivities, and their surfaces may not respond uniformly to the various treatments.

Basic pretreatment to obtain consistent result with any process for plating on aluminum and especially for those involving an immersion treatment, it is essentially that the various cleaning and conditioning treatments provide a surface of uniform activity. Basically of this treatments are remove of metal surface from oil, grease, or other foreign material.

Anodizing Energy Sources

2010-10-23T18:30:00.000-07:00

Anodizing energy source use direct current electric source (DC) or may use pulse anodizing with the pulses gap just in millisecond. If the pulses of electric current to big, anodizing product results are too bad, big pores and the finished product can not stand for long time. Processing time to produce anodizing product with 20 μm of oxide thickness is about 60 minutes.

Using pulse current should be optimizing, pulsating between two value of current density work because it gives the aluminum surface time to recover during low current density periods. The length of periods should be 10 – 240 second, because if two different dissolution mechanisms are taking place during anodizing.

Oxide film that produce on anodizing process will no longer can transfer electric current, so constant current during the anodizing process will result in an increase voltage due to the growing of aluminum oxide layer. The increasing of voltage will directly proportional to current density.

Pulse current is use alternating current (AC) that passes through rectifier. To apply this method should be understand that rectifier that use on this process must able to stand for current density until 20 A/dm2. This condition are very important because need to gain a basic understanding of process, but also need to maximize the expected advantages of pulses anodizing in daily production.

To optimize of current source of aluminum anodizing process, the tool should be possible to switch from DC to pulse anodizing and also interchangeable between pre and post anodizing processes. Flow process for pretreatment, racking and rinsing process should not become a bottleneck.

Plating On Aluminum Metal

2010-08-20T01:55:00.000-07:00

Pure Aluminium will difficult to be electroplate by other metal because aluminium tend to oxidize very fast and other metal will difficult to deposit over the aluminium metal. But alluminum alloy can be electroplated because the properties of this alloy have changed if compare to pure aluminum. Many metals are electrodeposited on aluminium alloys to obtain various decorative and functional finishes. The deposits applied for decorative finishes include chromium, nickel, copper, brass, silver, and gold, as well as alloys and oxidized modifications of these. The function of these electroplate material are like silver applied to improve conductivity, brass to facilitate adhesion of rubber, copper, nickel or tin for assembly by soft soldering, chromium to reduce friction and impart wear resistance; zinc to lubricate threaded part and tin to reduce friction on bearing surface.

It has long been recognize that aluminium and its alloys require specific surface preparation for successful electrodeposition. Such special treatment is necessary because of the high position of aluminium in the electromotive force series and because its relatively impervious and rapidly formed natural oxide film.

Cleaning Chemicals

2010-07-08T06:00:00.000-07:00

To select cleaning chemicals are depend on the kind of materials that want to clean. There are several factor to be based as the chemicals materials selection. The factors that influence on the selection of chemical cleaning are as follows:

Surface to be cleaned
Dirt or soil to be removed
Degree of cleanliness required
Method of application of cleaning chemicals
Disposal of the spent solution.

In many plants today, those factor will be the first question asked by environmental control engineers to determine what kind of cleaning chemicals will be used. A building permit for a new plating plant will not be issued unless the plans provide for acceptable waste treatment or the effluents are acceptable by the municipal system.

The dirt or soil to be removed affects to the selection of the cleaner composition. For many types of hydrophobic soils, a standard alkaline cleaner is perfectly satisfactory. If tarnish or oxides to be removed, a chelating cleaner works better.

Soil to be removed may be divided into two groups, organic and inorganic. Organic soils are mineral oil, animal and vegetable oil, and cleaning and pickling residue. These soils result from slushing, quenching and cutting oils, and buffing and drawing compounds used in fabrication or the metal object. They are never present as pure compounds but rather as complex mixtures.

Animal and vegetable oils can be saponified by reaction with the alkaline cleaner, mineral oils can’t work. This reaction is so slow, however, that removes very little oil. Emulsification, solubilisation, and preferential wetting are the primary mechanisms for the removal of both types of oil.

The ease of removal depends on the composition of the soil. Soils containing polar groups will be adsorbed on the metal surface, and if they contain high percentages of free fatty acids, metal soaps will form which are strongly attached to the metal surface. The bond is strengthened with time, particularly when the metal part is heated. These bonded soaps are very difficult to remove, their formation should be avoided if possible. The pickle and cleaner residue are either inhibitors, which are used to control the corrosive action of the acidic treating solutions, or metallic soaps that may form during the cleaning operation when an alkaline cleaner is used.

The inorganic soils, which include rust and tarnish, solid particle dirt, scale, smut, and cleaning residues, are usually removed by alkaline degreasing or an acid pickle. Rust and tarnish, being insoluble in water, are removed in acidic or alkaline chelating solution, with or without electric current. Water insoluble solid particles often adhere to oil present on the surface and are therefore removed simultaneously with the oil. Smuts which result from pickling are very troublesome and should be avoided. Inorganic cleaning residues may be films of oxides, phosphates, silicates, and the like remaining on the metal surface after alkaline cleaning and not removed by the rinses and mild acid dips that follow. Care in rinsing is the best way to eliminate trouble from this source.

Not all plating operations require the same degree of cleanliness of the basis metal. It is possible to plate from an alkaline cyanide plating solution articles that are dirty compared to those that may be processed in acid plating baths such as nickel plating. Therefore, a much shorter cleaning cycle may be employed for alkaline cyanide plating. It is poor practice, however, to contaminate a plating solution by using it as a combination cleaning and plating bath.

By definition, a chemically clean surface is one that has no film on it that might be detected by chemical or physical tests, obviously such a surface can be realized only with extreme difficult even in the laboratory. It is generally agreed, however, that surface substantially free of grease, oils, and gross oxide films are needed for the best electroplating. Therefore it is standard practice to clean as thoroughly as is economically feasible.

The method of application is very important owing to the effect of agitation on those cleaners that contain foaming surface active agents. For electro cleaners and spray cleaners, low surface active agent must be used.

The quality of water supply has a direct bearing on the type of cleaner that may be used. For example, where soft water is available cleaners containing soaps may employed, but with hard waters, the use of soaps should be avoided unless the water is properly treated, or the cleaner contains water softening, sequestering or chelating agents.

Disposal of waste solutions may be a problem and can influence the use of a particular compound. For example, a very satisfactory bath for the removal of oxide or tarnish films from copper and copper base alloys is a sodium cyanide solution, but disposal of the cyanide may be so troublesome as to make such a bath undesirable.

The Formula of Anodizing Process

2010-06-24T20:02:00.000-07:00

	Formula
	Anodizing
	Process


	Solvent
AlCl₃	400 g/l	3 M
LiAlH₄	15 g/l	0.4 M

Adhitives
Reduce of grain size and treeeling
2,2 Dichlorodiethyl ether
1,2 Dichlorodimethyl ether
2,2 Dichlorodiisophropyl ether
3,3 Dichlorodiisopropyl ether
Methyl borate
Tetrahydrofuran
Anisole
Water
Xylene
5,6 Benzoquinolin
methyl Lithium

Colouring Process on Anodizing

2010-06-22T09:13:00.000-07:00

Coloring process on anodizing process name as dyeing. Coloring is proposed to produce a decorative finished product with many kind of color. The dyeing is preferably done immediately after anodizing process. The anodized components should be thoroughly washed free for all residues of the anodizing solution and stored in cold water. Coloring with inorganic colouring matters is affected by precipitating a coloured compound in the pores of the film. It this process, the anodized parts are immersed first in a solution of one compound. In both solutions, the parts are kept for 5-10 minutes. The solution are used at room temperature. The component of some suitable solutions of this type are given in the table.

Color	Solution 1 (g/lt)	Solution 2 (g/lt)	Pigment Formed
Blue	Potassium Ferro cyanide (10 – 50)	Ferric Chloride (10 – 100)	Prussian Blue
Brown	-do-	Copper Sulfate (10 – 100)	Copper Ferro Cyanide
Black	Cobalt Acetate (50 – 100)	Potassium Permanganate (15 – 25)	Cobalt Oxide
Yellow	Potassium Bichromate (10 – 50)	Lead Acetate (10 – 50)	Lead Chromate
Golden Yellow	Sodium Hyposulfite (10 – 50)	Potassium Permanganate (10 – 50)	Manganese Sesquioxide
White	Barium Acetate (10 – 50)	Sodium Sulfate (10 – 50)	Barium Sulfate
Orange	Potassium Chromate (10 – 50)	Silver Nitrate (50 – 100)	Silver Chromate

Solution Type for Electropolishing

2010-06-11T03:54:00.000-07:00

Electropolishing method can also be used for cleaning metal materials that have been plate by other metal material like corrode that stick on the metal surface or oxide film that create a film layer on the metal base. The metal which will be polished act as Anode, anode on this process is connected to positive pole of DC current source.

The effect of this electropolishing then the metal will change more bright because of the covered layer on the surface like being peels and the rest is new metal surface. A normal metal will convert the metal on the surface become a metal ion and usually will dissolve in the solution. Especially for Aluminum this surface metal are not dilute in the solution but covert into Aluminum oxide which have noble properties and stick in the aluminium surface. Aluminium oxide have characteristic as inhibitor and will burden the current flow from aluminium to the solution. More long the process, more aluminium metal covered by aluminium oxide, and finally the current flow will stop because all the surface have covered by aluminium oxide that can’t conduct the electric current.

The chemicals composition that possible to make electropolishing are as the list below:

Chemicals	Wt (%)	Current Flow, Amp/ft²	Voltage (Volt)	Temp. ^oC	Time, min
Orthophosphoric Acid Sulfuric Acid Chromic Acid Water	65 15 6 14	200-250	12-15	70-80	2-5
Orthophosphoric Acid Sulfuric Acid Chromic Acid Water	43 43 3 11	300-500	12-15	70-80	2-5
Orthophosphoric Acid Sulfuric Acid Chromic Acid Water	36 36 4 24	200-400	12-15	70-90	1-5
Orthophosphoric Acid Chromic Acid Water	82 12 6	209-400	12-15	70-80	1-3
Trisodium Phosphate Soda Ash (anhydrous)	5 15	30-60	12-15	80-90	5-8
Hydrofluoboric Acid	1.25	15-30	20-30	30	10-20

In addition to the above solutions, solution of perchloric acid and acetic anhydride have also been recommended for polishing of aluminium. The use of this electrolyte, however, involves taking certain precautions, because of the risk of explosion effect.

Aluminum Oxide Problem

2010-03-24T07:54:00.000-07:00

Some experience of practitioner of anodizing have problem as follows: They anodized of boat hardware such as cavitations plates. The problem is the dyed coating becoming faded after being subjected to normal sunshine. This particular boats are not subjected to salt water on using, but after sun exposure, a non adherent powder forms. Other problem is seem any an irregular pattern caused by hand cleaning with solvent to remove polishing compound.

The answer from other website I think is not right, because the non adherent powder that merge on the anodized part actually that aluminum is become oxidized and convert into aluminum oxide. This can happen if aluminium that is used in anodized in not a good quality, more pure of using aluminium part will get better result of anodizing. The next step after anodizing process are colouring an sealing the anodized part. This step are very important to get a good long life product.

A simple sealing on anodizing is just using of dig the part on hot water but for extended method should fit with the colour agent and the sealing thickness you want. Preparation and finishing on anodizing process become the important part of anodizing process. If the preparation don’t serve in a good way, the product result won’t get satisfied, if the finishing process is not treat as is, the result also can not stand for longer. Anodizing is really need more knowledge and should be prepared before, beside the tools, technology and the process itself.

Aluminum Production

2010-01-25T05:37:00.000-08:00

Metallic aluminum is produced by the electrolytic reduction of pure alumina. In a bath of fused cryolite. For pure alumina, possible to reduce alumina with carbon because Al₄Cl₃ is formed and a back reaction between aluminum vapor and CO₂ in the condenser quickly reforms the original aluminum oxide again. The enthalpy change involved in the reaction is equivalent to 20.3 MJ of energy per kilogram of aluminum produced.

Al₂O₂ + 1 ½ C ==► 2 Al ++ 1 ½ CO₂ ∆H = 1100 kJ at 1000 oC

In actual practice, however, some energy is used to bring reactants up to temperature and some is lost in the sensible heat of the products. Some carbon monoxide is formed in the reaction thus increasing the positive ∆H, which amounts, in practice, to 47.5 to 71.4 MJ/kg. consequently this metal can’t be made economically unless low priced requires from 0.5 to 0.6 kg of carbon per kilogram of metal. Although the theoretical amount required by the equation to 0.33 kg, the carbon dioxide evolved contain from 10 to 50% carbon monoxide, so more is required in practice the step involved in the production of the metallic aluminum are:

The cell lining is installed or replaced
Carbon anode are manufactured and used in the cell
The cryolite bath is prepared and the composition controlled
Alumina is dissolved in the molten cryolite bath.
The solution of alumina is fused cryolite is electrolyzed to form metallic aluminum, which serve as the cathode.
The carbon electrode is oxidized by the oxygen liberated
The molten aluminum is tapped from the cells, alloyed off desired, cast into ingots, and cooled.

The electrolytic cells are huge boxy steel containers. Inside each is a cathode compartment lined with either a rammed mix of pitch and anthracite coal or coke baked in place by the passage of electric current, or prebaked cathode blocks cemented together.

This cathode compartment cavity may be from 30 – 50 cm in depth and up to 3 m wide and 9 m long depending on type of the cell and the load for which it is designed. The cavity lining thickness varies from 15 to 25 cm on the side and 26 to 46 cm on the bottom. Thermal insulation consisting of free brick, asbestos blocks, or other similar materials is placed between the cavity lining and the steel cell. Large steel bars, serving as cathode current collectors, are imbedded in the bottom portion of the cavity lining and extend out through to the cathode collectors which is dissolves or penetration of metal out of the steel shell where it leak out around the collectors.

Cell relining is an appreciable part of production expense, including not only the cost of labor, collectors, lining, and insulating materials, but also the loss of electrode materials absorbed by the spent lining (producers now reclaim at least some of these electrolyte materials).

Aluminum Metal and Aluminum Alloy

2010-01-22T04:12:00.000-08:00

Aluminum was discovered in 1827 by Friedrich Wohler. Its importance was established after the inventing of the dynamo (1887) because a great deal of electricity is consumed in its extraction.

Occurrence and extraction
Aluminum does not occur naturally in the pure form. In compound, it is the commonest metal on the earth (about 8% of the earth’s crust). The mineral richest in aluminum is bauxite. Among the EEC countries, France, Italy and Greece have significant reserves. Corundum is crystalline aluminum oxide. When pure and clear, it takes the form of gemstones’ (sapphire, ruby, topaz, amethyst).

To begin with, pure aluminum oxide (Al2O2) or alumina is extracted from bauxite. The Oxygen is then removed from alumina by electrolysis. Kryolith (Na2AlF6) is added as fluxing agent, in order to reduce the melting point from 2000 oC to 960 oC. The end of aluminum product uses in semi-finished goods (sheets, rods, profile, tubes) are super pure aluminum, Al 99.98 R or aluminum, e.g. 99.5 (DIN 1712T3).

Properties of Aluminum
Physical Properties:Melting Point: 658 oC
Density: 2.7 kg/dm3
Best electrical conductor after silver and copper.

Chemical Properties:
Corrosion resistant, impermeable oxide layer.

Mechanical Properties:
Tensile strength cast 160 to 320 N/mm2 rolled 150 to 400 N/mm2
Extensibility: 2% to 35 %

Technological:
Aluminum can be forged, rolled (down to thin foils), stretched, milled, cast, welded and soldered. Thermite, for instance, which is used in welding together bars, is a mixture of aluminum powder and iron oxide. In aluminum coating, a mixture containing powdered aluminum can be sprayed on to steel and then burned in by annealing.

Anodized Metal For Lasering

2010-01-14T22:10:00.000-08:00

There are a question about anodizing metal like this:

I am an artist who also do laser engraving, sometimes I ask to engrave metal with my laser but unable to do so. I was told that the metal can be anodized but needs a special solution which is not readily available here. Is there a substitute or am I looking for the wrong thing?

Before that question be answered better to read this article about anodizing practice and theory, because I am wory that that persons don't understand what is anodized process.

Engraving and Anodizing is different method and different application so engraving will use for different purposed. Engraving is to omitting of metal layer using chemicals, if some chemicals react with the metal while on certain pattern is cover with coating agent than the chemicals can be prevented to react with the metal. While anodizing is creating of layer on aluminum or other kind of metals.

Calcium - Chemical Process

2009-12-23T23:04:00.000-08:00

More knowledge about many chemicals can find here on http://chemistry.health-tips-diseases.com/. Many chemicals are describe detail in here and also the chemical that is used for anodizing and electroplating are founded here.
Chemicals for certain purposes have diferent properties and different handling, some of chemicals dangerous in solid state but more of them more dangerous if in gases state.

Calcium - Chemical Process

Aluminum Alloy List

2009-12-10T23:11:00.000-08:00

Aluminum alloy is aluminum metal mixed with other metals, with the purpose will change the original properties of that metal and hope will have a better metal properties and have light weight as aluminum.
Aluminum alloy have many use in various application, from decorative metal until structure metal. Aluminum is prefer use in structure in plane, conductor and building because this metal is light but originally have soft properties, to create aluminum have better properties than mix with other metal and hope will have benefit original properties as metal and will change to strong metal like iron or steel.

The kind of aluminum alloy are list as follows:

Al-Li (aluminum metal mix with lithium metal)
Alnico (aluminum metal mix with nickel and cobalt); this alloy are used for permanent magnets.
Duralumin (aluminum metal mix with copper)
Silumin (aluminum metal mix with silicon)
AA-8000: used for building wire in the US per the National Electrical Code.
Magnalium (5% magnesium)/used in airplane bodies, ladder, etc.
Aluminum also forms complex metallic alloys, like β-Al-Mg, ξ'-Al-Pd-Mn, T-Al3Mn

Read Others:
Aluminum Plated
Copper Plating
Master Anodizer
Plating Difficulties
Post by Aluminum Anodizing.

Anodizing Definition

2009-11-29T23:59:00.000-08:00

Anodizing define as electrolytic passivation, the process that affect on the metal to increase the thickness of the natural oxide layer on the surface of metal parts. The process to make this happen called as anodizing, this name merge from the source of process that use of anode electrode and electrical circuit.
Anodized metal will have a benefit to increase the corrosion resistance and wear resistance, and provides of better adhesion for paint primers and glues that bare metal. Other benefit of this treatments that the anodic films can be used as cosmetic effect, either with thick porous coating that can absorb dyes or with thin transparent coatings that add interference effect to reflected light. Anodizing also can be used to prevent of galling of threaded components and to make dielectric film for electrolytic capacitors. Anodic films are most commonly applied to protect aluminum alloys, although processes also exist for titanium, zinc, magnesium, niobium and tantalum. This process is not a useful treatment for iron or carbon steel because these metals exfoliate when oxidized,i.e. the iron oxide flakes off.

Thick coating are normally porous, this condition need for further treatment that is called as sealing process, this sealing process will make the oxide film change to more strong film. As an example of process application is on aluminum metal. Anodized aluminum surfaces are harder that aluminum but have low to moderate wear resistance that can be improved with increasing thickness or by applying suitable sealing substances.

Anodizing As Decorative Finished

2009-11-11T19:41:00.000-08:00

Anodizing process often use as decorative finished in surface coating industries, beside the product will appear more interesting, anodized can applied as protection of metal from further corrode.

Products that is used of anodizing process for a finishing like on window or door handle, on car wheel, on window frame, on cover of many electronic product and on game trophies. Many accessories product also use anodizing process as finishing process to make them more interesting, like on key chains, and on doll parts.
Anodizing process on many part and on building structure is used as final protection on aluminum metal in order this metal will pretend from further corrosion. Actually aluminum without anodized process also will protect their self by build thin layer called as aluminum oxide that will prevent to aluminum metal from further protection but this layer is not strong enough, different with the anodized layer that deliberately created by the industry. This anodized layer is stronger and not easy from scratch.

Anodized result also can produce many colors on the aluminum surface that depend on the mechanism of coloring, this color is produce from chemical composition reaction or from textile dyes that is inserted into the below of the top layer of aluminum oxide. To make the top aluminum oxide layer stronger that natural oxide layer, anodized aluminum layer than sealed with special treatment. After the product is sealed than rinse with clean water

Surface Coating Industries

2009-10-28T21:18:00.000-07:00

To coat materials certain metal can use severa method be applied, such as using electroplating, anodizing, galvanizing, oiling and painting, or using integrated between painting and adhesive, or anodizing with painting.
Product of the surface coating industries are essential for the prevention of all types of architectural structures, including factories, from ordinary attacks of weather. Uncoated wood and metal are particularly susceptible to deterioration, especially in cities where soot and sulfur dioxide accelerate such action. Aside from their purely protective action, paints, varnishes, and laquers increase the attractiveness of manufactured goods, as well as the aesthetic appeal of a community of homes and their interiors. Coatings that are used to cover buildings, furnitures, and the like are referred to as trade sales or architechtural coatings in finished are applied to a wide variety of materials, such as metal, textiles, rubber, paper, and plastics, as well as wood. Architechtural coating are usually applied to wood, gypsum wall board, or plaster surfaces.

The surface coating industry, is indeed as ancient one, in fact. Noah was told to use pitch within and without the Ark. The origin of paints dates back to prehistoric times when the early inhabitants of the earth recorded their activities in colors on the walls of their caves. These crude paints probably consisted of colored earths or clays suspended in water.

The Egyptians starting very early, developed the art of painting and by 1500 a.c. had a large number and wide variety of colors. About 1000 a.c.they discovered the forerunner of our present day, varnishes, usually naturally occuring resins or beewaxes were the film forming ingredient.

Master Anodizer

2009-10-19T21:17:00.000-07:00

To control an aluminum anodizing process we can use aid tool like Master Anodizer for controlling anodizing rectifier. Using master anodizer we can reduce the costs and improve the quality. Master anodizer implement technology developed over many years of practical anodizing shop experience.
This equipment is exist after the technology improved and equipped in the tank cathode system and electrolyte that we can get better quality controlled of hard anodizing, as virtually eliminate a part of burning, reduce raw materials, reduce energy cost and shortest cycle times for using in the large industry.

Using this equipment the operator is very simple, just set the target coating thickness for certain anodizing application, number of parts, and the area of one part using simple and uncluttered keypad. Choose current density and ramp time, or just accept previous value or change for certain parameter value. Then put the part in the tank and press start.

When the job is done, master anodizer give an alerts to the operator and either shut down the rectifier or sets it to an idle or soak value, as desired. We also can pause the process if there any problem during the running process, for example to monitor the progress, and carry on from where you left off.

Anodized Aluminum Supplier

2009-10-08T19:10:00.000-07:00

Stamped Metal Parts
Aluminum Stamping Top Plate with anodized finish, suitable for plasma.
Product type: Metal Stamping, Automotive Metal Stamping Parts
Supplier Name: Art Precision Technoloty Development Ltd. 150 products.
Country: Hong Kong SAR
Seamless Aluminum Tube
Seamless aluminum tube made of super hard aluminum alloy with powder coating and anodized finish.
Product Type: Precision Turned Parts, Precision Turned Parts
Supplier Name: Shanghi ESME Corp. Ltd.

CNC Machining
Aluminum Shaft with CNC Precision Part and Anodizing Surface Treatment
Product Type: Precision Turned Parts, Metal Stamping
Supplier Name: Kingdom manufacture (Shen Zhen) Co. Ltd.

Precision Turning Part
Precision Turning Part with anodized surface treatment, made of aluminum.
Product Type: Precision Turned Part, Metal Stamping
Supplier Name: Kingdom Metal Manufacture (Shen Zhen) Co. Ltd.

CNC Machining
Aluminum Shaft with CNC Precision Part and Anodizing Surface Treatment
Product Type: Precision Turned Parts, Metal Stamping
Supplier Name: Kingdom manufacture (Shen Zhen) Co. Ltd

Precision Turning Part
Precision Turning Part with anodized surface treatment, made of aluminum.
Product Type: Precision Turned Part, Metal Stamping
Supplier Name: Kingdom Metal Manufacture (Shen Zhen) Co. Ltd.

Machined Part
Machined Part with anodized surface, made of aluminum, precise turned parts
Product Type: Precision Turned Part, Metal Stamping
Supplier Name: Kingdom Metal Manufacture (Shen Zhen) Co. Ltd.

Machined Part
Machined Part with anodized surface, made of aluminum, precise turned parts
Product Type: Precision Turned Part, Metal Stamping
Supplier Name: Kingdom Metal Manufacture (Shen Zhen) Co. Ltd.

Aluminum Extrusion
Aluminum extrusion with anodized color and champagne finish, available in size of 280 mm.
Product Type:. Plastic Cap
Supplier Name: Shanghai Brilliance Alu Co. Ltd

CNC Machining
Aluminum Shaft with CNC Precision Part and Anodizing Surface Treatment
Product Type: Precision Turned Parts, Metal Stamping
Supplier Name: Kingdom manufacture (Shen Zhen) Co. Ltd

Aluminum Profile
Aluminum profile with anodizing colors and 7m length
Product Type: Aluminum profile
Supplier Name: Shanghai Brilliance Alu Co. Ltd.

CNC Machining
Precision CNC Machining Parts with anodized surface treatment made of aluminum.
Product Type: Precision Turned Parts, Metal Stamping
Supplier Name: Kingdom manufacture (Shen Zhen) Co. Ltd

Aluminum Extrusion
Aluminum extrusion with anodized color and 8 to 25 µm film thickness, made of 6061 alloy.
Product Type:. Plastic cap
Supplier Name: Shanghai Brilliance Alu Co. Ltd

Aluminum Profile
Aluminum profile with anodizing colors and 7m length, made of T6 alloy
Product Type: Aluminum profile
Supplier Name: Shanghai Brilliance Alu Co. Ltd.

Stainless Steel Muffler
Stainless steel muffler with anodizing of aluminum
Product Type: Plastic auto parts, CV Joint Axle, Molds
Supplier Name: Qingdao Huirun Hardware Product Co, Ltd,

Pipe
Special pipe, made of aluminum, anodized and powder coating surface treatment
Product type: Solar panel frame
Supplier name: Changshu Jingcheng Aluminum Co.Ltc.

Aluminum Extrusions
Aluminum extrusion with maximum length of anodizing is 6400 mm.
Product type: aluminum extrusion, extrusion
Supplier name: Guang Ya Aluminum Industries (HK) ltd.

Aluminum Tube
Aluminum tube and anodized color, ML-A-8625F Type-II, Class I and Class II
Product Type: Stamping and forming parts, aluminum stamping parts, stamped metal parts.
Supplier name: Guang Ya Aluminum Industries (HK) Ltd.

Extrusion
Aluminum extrusion (anodized finish) with maximum length for anodizing of 6400.
Product type: Aluminum extrusion
Supplier name: Guang Ya Aluminum Industries (HK) Ltd.

Aluminum Raw Material of Anodizing

2009-09-15T08:34:00.000-07:00

As the main raw material for anodizing of aluminum metal, its always depend on the aluminum quality. If we can choose the type of pure aluminum on this process we can result with perfect result.
Aluminum is a soft, durable, lightweight, malleable metal with appearance ranging from silvery to dull grey, depending on the surface roughness. Because in pure condition of aluminum metal is too soft so this metal rare on pure metal. Usually aluminum is in alloy metal form in the market. But the composition is vary and more bigger aluminum concentrated will result in good anodized product.

Corrosion resistance can be excellent due to a thin surface layer of aluminum oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminum alloys are less corrosion resistant due to galvanic reactions with alloyed copper.

The form of aluminum on the market is in many kinds as below:

Aluminum Powder
Aluminum Sheet
Aluminum Ball
Aluminum Rod, use for welding rod
Aluminum Wire, use for electric cable wire

Wheel and Spin Polishing

2009-08-17T03:16:00.000-07:00

Spin polishing like wheel polishing and other kind of polishing like barrel polishing , usually induces scratches with directional characteristics, which must subsequently be smoothed by buffing. Any subsurface porosity only 25 to 50 micrometer below surface, which is encountered with some coatings, usually is exposed by wheel polishing or leveling copper is required to avoid defective electroplates when subsurface pores are exposed.
Vibrating tube loaded with plastic media, such as polyurethane impregnated with an abrasive such as aluminum oxide, smooth the surfaces of die castings in 4 hr or less when frequencies are in the range of 1600 3000 cycles/min and amplitudes are adjusted to 0.8 to 6.4 mm. Vibratory machines produce a finish of 0.15 to 0.20 micro meter. Media and zinc parts are usually loaded in a ratio of 5:1 to 6:1. Surface gouges might occur with a smaller ratio.

Small parts adaptable to barrel cleaning and plating are frequently prone to blistering when they are heated after barrel plating if surface defects are not removed beforehand. Vibratory finishing appears to be the best method of erasing defects, densifying surface layers before plating, and minimize process blistering. The use of dual shaft machines reduces the time required for removing surface defects.

Many kind of cleaning to the anodized material also can be treated like dip in chemicals such as acid dip cleaning, electrolitic cleaning and using a mechanical cleaning process.

The Difficulties of Aluminum Plating

2009-07-29T08:23:00.000-07:00

Aluminum is an even more difficult metal to electroplate. Although aluminum is a very reactive metal, it is normally covered with a protective oxide film, which is rapidly reformed when a fresh metal surface is exposed. The oxide is also insoluble in most acids. It thus cannot be prepared in the normal way by acid dip. The most successful method of preparation is by immersion in a strongly alkaline solution of sodium zincate. The alkali dissolves off the oxide film, and then the naked metal reacts chemically with the zincate to form a double cyanide solution, and any other electroplate subsequently applied. Nevertheless aluminum is even more active than zinc, and thus is anodic to any metallic coating. The electroplating of aluminum and its alloys is therefore not advisable, especially as there are a number of protective and decorative processes, unique to aluminum which can be applied instead.

Magnesium and its alloys are too reactive to be electroplated. Control of electroplating process relies largely on measurements of currents, temperatures and pH values, also on periodic chemical analysis of the solution. However, even today control relies very largely on the skill, knowledge and experience of the operator.

Electroplating plants are large quantities of water, which is expensive to buy and equally expensive to purify before disposal. Considerable attention to the economical use of water and also to recovery of rinsed off chemicals is worth while. Water supplies suitable for drinking and domestic purpose may be unsuitable for electroplating, because of their contains of dissolve salts and are often worth while. Large ammount of heat are required to maintain solutions at the required temperature, and for heating air which is afterwards thrown out of the fume extraction ducts. Care in design can often materially reduce such cost.

Vitreous Enamels Coating

2009-07-18T08:54:00.000-07:00

Vitreous enamels are essentially glasses, that is solidified mixtures of fused sodium and other silicates. Often with the addition of boro-silicates and phosphates. The chemical resistance of the glass, and hence of the enamel, its co-efficient of thermal expansion, and its softening point can be varied by additions of the silicates of calcium, magnesium, manganase, lead, cadmium and tin, the formulation of a glass for a particular use in vitreous enamelling is a complex exercise in compromise.

In the preparation of vitreous enamel, the ingredients of the glass are fused and coated together in a crucible, and are then cast into water, where the glass shatters into fragments. The glass needs to be design with a view to a suitable melting or flowing temperature, and also so that its coeficient of thermal contraction is similar to, if not identical with, that of steel. The glass fragments are then ground in pebble or ball with water to a fine powder of slurry are sieved.

Iron and steel parts must be freed from scale by pickling before enamelling, and must then be thoroughly dried, but a small amount of superficial oxide is not harmful. There are two main methods of applying vitreous enamel. The most commonly used, and that universal for sheet steel product, is a wet process. A carefully formulated charge of glass frit, opacifying oxides-usually titanium oxide (rutile), or tin, antimony or zirconium oxides (which are all white) -together with coloring oxides and suspending agents are milled with water in a pebble mill to give a thin cream like slurry, which is called the slip. The coloring materials are cadmium, iron or selenium compounds or oxides for reds, chromium compounds, for greens, cobalts compounds for blues, and antimony, vanadium and tungsten compounds for yellows. The available color are rather limited and perhaps crude.

The steel articles are then coated with the slip all over by spraying or somtimes by dipping. The suspending agents added to the slip ensure that it is a colloidal suspension which can be uniformly spread. The article is meanwhile supported on a few spikes called perrits, the marks from which will not be obtrusive. It is usually to dry off the slip, leaving the article covered will a thin film of dry, but loosely adherent mud before it is fired.

Wire

2009-07-11T00:12:00.000-07:00

Wire is a usually flexible metal rod or thread of uniform diameter. It has many uses, particularly in electrical wire and cable applications; in medical, farming, and industrial tools; and needles, and in hardware such as bolts, nails, nuts, screws, rivets, and needles. In construction, steel-wire cables are used to reinforce suspension bridges. Wire is also used in more delicate apparatuses, such as stringed instruments and watch springs.

Production
Wire is made by drawing out metals such as copper, iron, brass, aluminum, gold, silver, and platinum. In wire drawing, the metal is first heated and then run through a series of rollers that press it into thin rods. The rods are then coiled by machine, allowed to cool, cleaned with sulfuric acid or other chemicals, neutralized, and lubricated, followed by reheating to alleviate brittleness. They reach their final form by being drawn through a series or progressively smaller holes, known as dies, which reduce their diameters and increase their lengths. The finished wire is then wound around a rotating drum.

History
Wire was used as an ornament by the Egyptians as early as 3000 ac. Although the Romans used perforated places of iron as drawing dies, until the Middle Ages wire drawing was largely done by hand; the resulting threads has to be hammered and joined to each other to produce wire of a desired length. The first mechanical wire drawing equipment was developed (c. 1350) by Rudolf of Nuremberg.

Because of the industrial Revolution, the demand for cable suspension bridges, the telegraph, the telephone, and the electric light, as the growing demand for fencing and barbed wire, spurred production of greater lengths and strengths of wiring. In this century, carbide drawing dies were developed that could withstand high speed and long wear and provide increased accuracy. With a die capable of standing up to the drawing of greater quantities of wire at the desired gauge through a single hole, machines that drew continuously came to the fore. Advance welding techniques now long, continuous coils rod and wire to be drawn.

Cable
A cable is a cord or rope made from strands of fiber or wire, of great tensile strength, used to support a bridge or cable car, to secure a ship at anchor; for towing, hauling, and construction work, or for similar purposes. Transmission cables carry electric power or communications signals.

Continues of AAC/ACSR Process

2009-06-28T10:11:00.000-07:00

When the wear ring in the approach angle of a wire drawing die becomes too deep, it causes the coating to be loosened and stretching and further ringing results. Just when to service dies has to be determined by experience and use in the mill. It is advisable to clean and examine dies each time they are taken out of a machine. The greatest amount of wear will occur in the first few hundred kilograms of wire drawn through the die, thereafter the die becomes work and lubricated, and the rate of wear per tonne reduce to a uniform factor related to miles passing a point per minute and the hardness of the material drawn.

Next operation after wire drawing is stranding. Two types of stranded are employed-the sun and planet type and the tubular type. In the former, bobbins or spools of wire are charged in two or more cages which can be rotated independently in either direction. As the machine operates the cage revolve round the central wire which moves forward and layers of wire are formed on the central wire which move forward and layer of wire. For alternate layers the cages are rotated in the opposite direction. In the tubular type strandler, bobbins are carried in candles inside a tube. In the usual stranding operation a single wire is used as the base; it is wound first with six wires followed by multiples of six in the consequent operations. Sometimes a tranded conductor containing wires is employed as base. Stranded conductors are designated by numbers such as 13/2.11, the first number indicating the total number of wire in the strand and the second the diameter of the wire in mm.

Manufacturing of AAC/ACSR Conductors

2009-06-21T06:08:00.000-07:00

The first step in the manufacture of AAC/ACSR conductors is the manufacture of aluminum conductor wire of required diameter which is obtained by wire drawing of E.C. grade aluminum rods. One end of the aluminum rods of 9.8 mm O.D is tapered and pointed on a pointing machine before the actual drawing operation begins. Wire drawing is a process of converting higher cross sectional wires of rods into lower cross section by way of cold drawing the material through smaller diameter dies. These machines contain from 3 to 4 dies from the larger finished wire sizes to 9 dies for fine wire sizes. The reduction in area per die usually varies from 20 to 25 per cent. The wire is drawn through each die by a power driven drum to the next die and coiled in the following power driven drum and so on. The size of the wire is progressively reduced till the wire emerging from the last die is of the required cross section. The peripheral speeds of drums are increases with each reduction and appropriate dies selected to match the peripheral speeds.

For drawing wires to sizes finer than 1.5 mm diameter, cone type machines with diamond dies are employed. As many as 25 dies may be accommodates in one machine, but machines with 12-17 dies are more common. Finishing speeds range from 5,000 to 8,000 ft.per minute fro medium fine size and upto 4,000 ft. per minute for fine size. Aluminum wire are cold drawn with adequate supply of aqueous lubricant is maintained on the wire during their passage through dies. Lubricants in paste, powder, or solid from held in boxes in front of the dies, are used for bull-blocks. A mixture of tallow, mineral oil, or compounded oils and greases are used for drawing aluminum wires. Multiple die machines are wet lubricated and die blocks, emulsion of beef tallow, compounded mineral oils, and proprietory drawing paste emulsions are used for aluminum wires. Oils give better and brighter finishes than emulsion.

Frequently the die is roughened. Several machine are available for die maintenance. A rough driller and semi automatic polishers are required. The rough driller is so-called because a coarse abrasive (silicon carbide 220 grit) is used as an abrasive for drilling the approach angles accurately and economically. The semi automatic polisher are used to polish the approach angles, using diamond dust or finer carbide as an abrasive. It is advisable to bend slightly the back relief at the 90 angle.

Reinforced Galvanized Used

2009-06-07T10:45:00.000-07:00

The wire used in the construction of a galvanized steel-reinforced aluminum conductor shall, before stranding, satisfy all the relevant requirement of this standard. The lay ratio of the different layers shall be within the limits given in the limitation table. The ratio of the nominal diameter of the aluminum wires to the nominal diameter of the galvanized steel wires in any particular construction of galvanized steel reinforced aluminum conductor, shall conform to the appropriate value as given on the table. In all construction successive layer shall have opposite direction of lay, the outer most layer being right handed. The wires in each layer shall be evenly and closely stranded. In conductors having multiple layers of aluminum wires, the lay ratio of any aluminum layer shall be not greater than the lay ratio of the aluminum layer immediately beneath it.

Unless otherwise agreed to between the purchaser and the manufacturer:

galvanized steel reinforced aluminum conductors shall be supplied in the manufacturer’s usual production lengths and with a permitted variation of ± 5 percent in the length of any one conductor length
it shall be permissible to supply not more than 10 percent of the lengths on any one order in random length

None of them shall be shorter than one third of the nominal length. The standard specifies various tests including selection of test samples, breaking load test for both aluminum and galvanized steel wires, ductility test on galvanized steel wires, wrapping test for both aluminum and galvanized steel wires, resistances test on aluminum wires, galvanizing test on galvanized steel wires, etc.

Galvanized Steel Reinforced

2009-05-26T19:25:00.000-07:00

These are conductors consisting of seven or more aluminum and galvanized steel wires built upon concentric layers. The center wire or wires are of galvanized steel and outer layer or layers of aluminum. The conductor shall be constructed of hard drawn aluminum and galvanized steel wires which have the mechanical and electrical properties specified in the table. The coating on the galvanized steel wires may be applied by the hot process or the electrolytic process. When specified by the purchaser, neutral grease may be applied between the layers of wires. The wire shall be smooth and free from all imperfections, such as spills and splits.

The aluminum and galvanized steel wires for standard constructions covered by this standard shall have the diameters specified in the table. A tolerance of ± 2 percent for galvanized steel wires shall be permitted on the nominal diameter specified in this table. The sizes of standard aluminum conductors, galvanized steel reinforced shall be as given in the table.

In galvanized reinforced aluminum conductors containing any number of aluminum wires, joint in individual aluminum wires are permitted, in addition to those made in the base rod before final drawing, but no two such joints shall be less than 15 meters apart in the complete standard conductor. Such joints shall be made by resistance or cold pressure butt welding. They are not required to fulfill the mechanical requirements for un-joint wires. Joints made by resistance butt welding shall, subsequent to welding, be annealed over a distance of at least 200 mm on each side of the joint.

There shall be no joint, except those made in the base rod or wire before final drawing, in steel wires forming the core of a steel reinforced aluminum conductor, unless the core consists of seven or more galvanized steel wires. In the later case joint in individual wires are permitted in addition to those made in the base rod before final drawing, but no two such joint shall be less than 15 meters apart in the complete steel core. Joint in galvanized steel wire shall be made by resistance butt-welding or brazing and shall be protected against corrosion.

Post by Aluminum Anodizing

AAC/ACSR Conductors

2009-05-17T08:03:00.001-07:00

Specifications
The Indian Standards Institution has brought out the following specifications on AAC/ACSR conductors. IS: 398-1979 ‘Specification for Aluminum Conductors for Overhead Transmission Purposes’ which consists of three parts. Part 1 details with Aluminum Stranded Conductors: Part 2 with Aluminum Conductors Galvanized Steel Reinforced: and Part 3 with Aluminum Conductors, Aluminized Steel Reinforced.

Aluminum Stranded Conductors
A stranded conductor consists of seven or more aluminum wires of the same nominal diameter twisted together in concentric layers. When the conductor consists of more than one layer, successive layers are twisted in opposite directions. The diameter of the stranded conductor is the mean of two measurements at right angles taken at the same cross section. The direction of lay is considered as right hand when the conductor is held vertically and left hand if they conform to the direction of the central part of the letter S. The lay ratio is defined as the ratio of the axial length of a complete turn of the helix formed by and individual wire in a stranded conductor to the external diameter of the helix.

The conductor shall be constructed of hard drawn aluminum wires having mechanical and electrical properties. When specified by the purchaser, neutral grease may be applied between the layers of wires. The wires shall be smooth and free from all imperfections, such as spill and splits. The aluminum wires for the stranded construction covered by this specification shall have the diameter as per spect. A tolerance of ± 1 per cent shall be permitted on the nominal diameter. There shall be no joint in any wire of a stranded conductor containing seven wires, except those made in the base rod or wire before final drawing. In stranded conductors containing more than seven wire, joints in individual wires are permitted in addition to those made in the base rod or wire before final drawing, but no two such joint shall be less than 15 meters apart in the complete stranded conductor. Such joints shall be made by resistance or cold pressure butt welding. They are not required to fulfill the mechanical requirements for unjointed wires. Joints made by resistance butt welding shall, subsequent to welding, be annealed over a distance of at least 200 mm on each side of the joint.

The wire used in the construction of stranded conductor shall, before stranding, satisfy all the relevant requirements of the specifications. The lay ratio of the different layers shall be within the following limits. When the number of wire is 7, the lay ratio for 6 wire layer shall be between 1 and 19. When number of wire is 19, the lay ratio for 6 wire layer and 12 wire layer shall be between 10 and 16, and 10 and 14, respectively.

Spin Polishing

2009-05-09T10:19:00.000-07:00

Spin Polishing like wheel polishing, usually induces scratches with directional characteristics, which must subsequently by smoothed by buffing. Any subsurface porosity only 25 to 50 µm below the surface, which is encountered with some castings, usually is exposed by wheel polishing or spin polishing. Depending on the size of these pores, relatively thick leveling copper is required to avoid defective electroplates when subsurface pores are exposed.

Vibrating tubs loaded with plastic media, such as polyurethane impregnated with an abrasive such as aluminum oxide, smooth the surfaces of die castings in 4 hr or less when frequencies are in the range of 1600 to 3000 cycles/min and amplitudes are adjusted to 0.8 to 6.4 mm. Vibratory machines produce a finish of 0.15 to 0.20 µm. Media and zinc parts are usually loaded in ratio of 5.1 to 6.1. Surface gouges might occur with smaller ratio.

Small parts adaptable to barrel cleaning and plating are frequently prone to blistering when they are heated after barrel plating if surface defects are not removed beforehand. Vibratory finishing appears to be the best method of erasing defects, densifying surface layers before plating, and minimizing process blistering. The use of dual shaft machines reduces the time required for removing surface defects.

Vitreous Enamel

2009-05-04T09:55:00.001-07:00

Vitreous enamel coating on metal are films of glass, opacified with inorganic pigments. Such coatings have the excellent chemical resistance and inertness of glass, together with both hardness and gloss. This makes them very suitable for coating on metals to resist the weather, water, chemical solutions, foodstuffs and beverages, as well as heat.

Vitreous enamel coatings have been used since ancient times on a craft scale for jewellery and decorative table and toilet wares, because of the attractive effects, which could be obtained. In these cases they were usually applied to silver or copper. They have also been used on other non-ferrous metals for instrument parts, such as watch dials. Enamels steel pots and pans, kettles, basins and jigs were formerly very common, but have now largely been replaced by aluminum, stainless steel and plastics.

Vitreous enamels is still much used for baths and other sanitary ware, and for chemical and food handling plant. Another considerable use of enamelled steel is in the construction of signs where the significant lettering or symbolism stands out from the back ground by the use of a different color.

Whilst the surface of vitreous enamel withstands exposure to the weather of to water for many years without appreciable change, its suffers from the inherent brittleness of glass. Thus if the vetreous enamelled sheet is bent, dented or flexed, the enamel cracks, and may even spall off. In such cases the exposed steel rusts; this disfugures the coating over adjecent areas, but more seriously, it may spread laterally under the adjecent enamel, which becomes prised off. Paint film are much less brittle, but formerly had poorer weather resistance. As the quality of paints has improved in recent years they have tended to supplant vitreous enamed. It may in fact sometimes be quite difficult to differentiate between a well-applied stoved paint finish and a fired vitreous enamed. However only vitreous enamel will withstand elevated temperatures without change, it is therefore much used for stove parts, cooking appliances and similar articles.

Anodized Flat Printing Plates

2009-04-26T04:46:00.000-07:00

Anodizing is used in the printing industry to increase the life of that aluminum printing plates. The increase life is due to the high mechanical resistance of the anodic oxide film and also to its high adsorptive capacity for the greasy transfer ink. This later property ensures a film fixing of the image of the plate. In the same way, the colloidal water adsorbing film, obtained. In the etching of the plates, is also firmly held. It appears that when printing from anodized plates, less moisture is required, which helps to reduce dimensional changes in the paper. The oxide films used on printing plates must be hard, wear resistant, and should have a good adsorptive capacity. In making plates for printing maps, the aluminum is anodized with alternating current in a 1-2 per cent sulfuric solution with current density 5 amps/ft2, solution temperature not above 30oC, anodizing time 30 minutes and distance between electrodes 150-200 mm.

The process comprises chemical or electrolytic degreasing in an alkaline solution, washing in running water; smudge removal in 50 per cent nitric acid solution, washing in running water; anodizing; washing in running water, drying in a drying oven at 40-50 oC; application of the light sensitive layer and its substance processing. The anodized printing plates are etches with a solution of phophoric acid to which starch is added to act as a colloid. The PH of the etching solution is about 1.

The use of alternating current simplifies the necessary equipment since no D.C. generators or rectifiers are required but the mechanical strength of films obtained by using direct current is better. One set of conditions which has been recommended for the anodizing of printing plates is as follows; solution 150 g/l sulfuric acid, anodic current density, 5-8 amps per sq.ft, temperature of solution, 15-23oC; anodizing time, 15-20 minutes. Films obtained by this treatment have a thickness of 0.0025 min to 0.005 mm and double the life of the printing plate.

Rough or Defective Surface

2009-04-19T05:01:00.000-07:00

Rough or defective surface are smoothed by:

mechanical polishing on rotating wheels or continuous, abrasive coated belts
spin finishing
vibratory finishing

Fissures, skin blisters, and other defects with a depth of 25 to 50 μm can usually be erased with these metal removal methods, when conditions are adopted to reach the bottom of the defects. Deeper defects are infrequent.

Rough or defective surface are often polished on wheels or belts, while parting lines are polished by the same operator. If polishing is mechanized to advance die castings attached to a conveyor through successive belts or wheels to polish different areas, a manual operation might be required later to complete the smoothing of parting lines if they are too curvy. The finish range from 0.2 to 0.4 μm, depending on the abrasive and the pressure.

Smoothing by spinning in abrasive is accomplished by attaching die castings to spindles or drums rotated with a peripheral speed of about 600 m/min in a slurry of abrasive material such as ground corn cobs or nut shells mixed with a small amount of grease or other lubricant. Time periods usually range from 5 to 10 min and the finish from 0.1 to 0.2 μm, depending on the abrasive.

Applications of Anodized Aluminum

2009-04-09T20:13:00.000-07:00

Aluminum anodized products are used in many application either for industrial product for construction material, and for household applications. Anodized aluminum products have better strength and good for long live construction materials.

The anodic oxide film effectively protect the metal against corrosion and can serve as electrical insulator. It is also used to provide a decorative finish, as a base for photographic reproduction, and in the manufacture of printing plates.

Corrosion Protection
The sulphuric acid process is commonly used to produce corrosion resistant films on aluminum and its alloys and is capable of producing films of adequate thickness (not less than 0.015-0.02 mm) having high adsorptive and protective properties. Sealing in chromate solution for corrosion protection is essential. Part subjected to serve corrosive conditions are protective with anticorrosive varnish primer applied after chromate sealing. In practice use is made of solution of linseed oil in suitable solvents, colorless oil varnishes, phtalate varnishes and zinc chromate primers.

Electric Insulation
Oxide film insulation on aluminum has a number of advantage over other forms of insulation. The oxide film is thin, heat resistant, has a good thermal conductivity and resist to action of water vapor and of many corrosive agents. Its drawbacks include its limited elasticity, the difficulty of obtaining film having a breakdown resistance of more than few hundred volts, and the appreciable hygroscopic nature of the films.

Bright Anodizing of Aluminum Alloys for Bright Trim

2009-03-19T01:21:00.001-07:00

A combined process of chemical for electrolytic brightening of bright purity aluminum alloy articles, followed by thin anodizing has achieved considerable industrial importance. The aluminum alloy in the form of sheet of extrusion is formed into finished parts, taking every care to avoid superficial damage or marking, particularly parts for the exterior decoration of motor cars an domestic appliances, such as fascia panels, name plates, window and windscreen surrounds, wiper parts, radiator grills, etc. These are then chemically brightened by the phosbrite of Erftwerk process or by an electrolytic brightening process. Because the alloy is of high immediately film is completely transparent and invisible, but it provides lasting protection from tarnish and corrosion by the weather. It is also hard and scratch resistant. The part thus appears to be gleaming, tarnish resistant bare metal: it maches well with chromium plate. At the present time a large proportion of the bright trim on the more popular makes of motor car, which is generally believed to be chromium plated is in fact bright anodized aluminum.

To the manufacturer this has the advantage of a much be set the higher cost of the special aluminum alloy over steel, and the greater care necessary in forming; the strength of the finished article is also less. To the car owner it has the advantage that there is no chance of rust appearing because of defective electroplating or of the plating peeling off.

Deposit Test of Copper Plating

2009-02-22T08:00:00.000-08:00

The thickness of copper in zinc die casting is measured on magnified microsections, or by anodic dissorlution in accordance with colometric principles. Magnetic instruments can be used for measuring the thickness of copper deposits on steel.

Copper plated steel wire for electrical cable is tested for thickness and thickness uniformity, electrical conductivity, and tensile strength. Electroformed shapes are frequently given physical tests, in order to control strength and ductility, by determining such properties as hardness, tensile strength, elongation and resistance to impact or denting.

Copper is deposited from the sulfate bath as fcc crystals that are randomly oriented, unless deposited at less than 1.5 A/dm2, when the basis metal can exert an influence on the structure so that crystals in the basis metal and plate are oriented similarly. Hardness has generally been associated with fine grains, yet it can be increased by introducing crystal orientation in the absence of grain refinement.

Grain orientation from the basis metal into sulfate copper deposit has been detected by many investigators. Thus the structure of the deposit is often influenced by that of the basis metal. The basis metal structure was reproduced in an acid solution before plating, but was not reproduced when the basis metal was cleaned by not dipped in acid solution before plating. The grain size of the substrate appeared to influence the reproduction of the basis metal structure in the copper deposit. The structure of copper electrodeposited from sulfate solution was not influenced by dislocations such as pits in the substrate surface, unless the etch pits contained oxides or sulfides. Oxide and sulfide particles in the surface layer of the substrate behaved as nucleation sites.

Performance of Plated Aluminum

2009-02-20T06:41:00.000-08:00

Because of its position in the electromotive force series, aluminum trends to protect electrolytically most of the other metals that may be used as electroplates. Therefore, once a break develops in the coating, conditions are favorable for corrosive attack. The amount and extent of attack will depend not only on the difference in potential but also on the amount of current that flows. One of the more important characteristics of chromium plating when applied over a nickel deposit on aluminum is its ability to reduce greatly the amount of current flowing from any exposed aluminum areas.

In addition to this, any process involving a layer of zinc between the aluminum and the electrodeposit introduces a specific corrosion problem. In many environment zinc is anodic to aluminum and consequently tends to protect both the aluminum and the electrodeposit. Because this sacrificial corrosion of the zinc tends to undermine the electrodeposit, the best corrosion resistance is obtained with the thinnest practical zinc films on aluminum alloys having the lowest solution potentials.

For this reason, zincate solution containing heavy metals can produce improved corrosion resistance by altering the potential of the immersion film. Other things being equipped the Alstan stannate process should have the capacity for producing excellent corrosion resistance through the complete elimination of the anodic zinc from the immersion deposit.

Although salt spray testing is often considered of questionable value, it does have a definite role as applied to plated aluminum. Grooved samples exposed to the salt spray demonstrate the effect of the zinc immersion film on the resistance to corrosion of the plated part. Atmospheric exposure, of course, is the ultimate controlled test for obtaining data on the outdoor life expectancy of plated aluminum. With conventional copper-nickel-chromium-plated aluminum, applied according to the best practice, a thickness of 38 μm of nickel under the chromium should prevent blistering for at least three years in an industrial atmosphere such as that of Pittsburgh, Pensylvania.

Chemical Composition For Cleaning

2009-02-08T08:25:00.000-08:00

The detail of chemical composition and conditions of use of cleaning materials for aluminum, copper, copper plate, iron, steel, magnesium, and zinc by various methods of application are discussed by Myers and Spencer.

Typical cleaner formulas were given in the table before. Typical operation conditions are given on the table below. Proprietary metal cleaner are developed for specific metal cleaning applications and include vendor technical service. This service can be a big asset to the user.

The controlling factors in cleaning are the concentration of the cleaner, the temperature of the solution, the time of the cleaning action, and the applied energy. Each can be varied to obtain maximum results. The concentration should be in the recommended range. The time must be sufficient to do the job. The temperature should be adjusted for maximum cleaning efficiency, but must not be too high or dry down residues will cause plating problems. The applied energy in the form of agitation, circulation, hydraulic spray action, electric current, or ultrasonic pulsation will be helpful only if the cleaner is right for the job at band. A spray cleaner is not a good soak cleaner or a good electrocleaner. A soak cleaner will foam too much to be used for spray cleaning or electrocleaning.

Metal Being Cleaned	Cleaner Cons. g/l	Dirrect Current, A/dm²	Temperature ^oC
Steel	60-120	5-10	82 to boiling
Copper	30-60	2-5	71-82
Brass	25-45	1.5-5	60-82
Zinc die casting	30-45	2-5	66-77
Lead	30-45	1.5-5	60-71
Aluminum	30-60	None	71-82

Good solution control by chemical titration or automatic controls and a complete running record of the concentrations and the additions are recommended for all cleaning operations. This information is necessary for establishing costs and is useful in determining dumping cycles. A good maintenance program with good records is a big asset in preventing plating shop emergency problems. Many hours are lost and rejects pile up when cleaning solutions are not maintained. Poor cleaning leads to poor plating. Good cleaning and rinsing are necessary for quality electroplating.

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Final Electrolytic Cleaning

2009-01-30T17:54:00.000-08:00

The final electrolytic cleaning removes the last traces of residual soils. In this step the very adherent solid soils and the residual hydrophobic soils, which have survived both the precleaning and the intermediate cleaning, are removed by the efficient agitation provided by the gas generation and evolution on the surface. The usual treatment is 1 to 3 min as cathode followed by a 3 to 20 sec treatment as anode for nonferrous alloys.

Steel are generally cleaned anodically, which in the trade is often called reverse current cleaning. Reverse current cleaning removes smuts, some oxides, and other metallic contaminants that will be dissolved in the cleaning solution. Where both cathodic and anodic cleaning are included in a cleaning cycle, separate cleaning tanks are recommended for each operation. If a single tank is used, smuts will form during cathodic cleaning because of metal contamination of the cleaner. This is especially true if chelated cleaners are used.

Alkaline cleaning is usually followed by an acid dip, this dip neutralizes alkaline films, removes any oxides that form during the alkaline cleaning, and provides a microetch on the surface which improves adhesion of the electroplate. The strength of the acid dip varies with each metal. One percent sulfuric acid by volume or less is adequate for zinc die castings, but copper and cold rolled steel required 4 to 10 %. If the surface requires considerable activation for plating, as do nickel and stainless steel, special treatment may be required.

Recommended Cleaning Cycles

2009-01-19T16:16:00.000-08:00

The cleaning cycle recommended by ASTM and Myers has four parts: precleaning, intermediate (alkaline) cleaning, final electrolyte cleaning, and the acid dip. Not all step are needed in every case. The precleaning and intermediate cleaning may be combined in one operation, or one or the other or even both eliminated, depending on the conditions of the parts as they are received by the plating department.

The object of precleaning is to remove large excesses of soil, especially deposits of solid particles, such as pigmented drawing and buffing compounds. The types of precleaners are solvent, emulsifiable solvent, spray or soak emulsion, soap/detergent soak, alkaline spray, and alkaline soak.

The intermediate cleaning removes residual soils softened or conditioned by precleaning. This is usually accomplished by soak or spray cleaning. For soak cleaning 30 or 120 g/l of alkaline cleaner at 82oC up to boiling for 3 to 15 min in generally used. A typical soak cleaner for steel would contain:

Sodium dydroxide ------------------- 35% wt
Anhydrous sodium metasilicate --- 25% wt
Sodium carbonate ------------------- 22% wt
Sodium tripolyphosphate ---------- 12% wt
Anionic surfactant ------------------ 5% wt
Nonionic surfactant ---------------- 1% wt

Spray cleaners are used at about 4 to 16 g/l at 68 to 74oC with spray pressure from 0.7 too 3.5 kg/cm2. only low foaming surfactants may be incorporated in spray cleaners. Fortunately a number of low foaming nonionic surfactant are available. The compression of the spray cleaner is very similar to that of the soak cleaner except for the surfactant.

Acid Dipping Baths for Plating Lines

2008-12-29T08:40:00.000-08:00

1. Low Carbon Steel:

4 to 10% (vol) sulfuric acid at room temperature
5 to 15% (vol) hydrochloric acid at room temperature
60 to 120 g/l dry acid salts at room termperature

2. High Carbon Steel

10% (vol) hydrochloric acid at room temperature

3. Stainless Steel:

20 to 50% (vol) sulfuric acid at 65 to 82oC followed by 1% sulfuric acid plus 0,1% hydrochloric acid at room temperature.
5 to 50% (vol) sulfuric or hydrochloric at room temperature.
120 g/l of dry acid salt at 70oC and cathodic current.

4. Copper and Copper Base Alloys:

4 to 10% (vol) sulfuric acid at room temperature

5. Lead and Alloys:

10 to 25% (vol) fluoboric acid at room temperature

6. Nickel:

5% (vol) sulfuric acid at room temperature
20% (vol) hydrochloric acid at room temperature
120 to 180 g/l dry acid salts at room temperature

7. Zinc:

0.25 to 1.0% (vol) sulfuric acid at room temperature

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Bath For Pickling and Scale Removal

2008-12-22T15:25:00.000-08:00

Low Carbon Steel: - 5 to 15% sulfuric acid at 50 to 82 oC. - 25 to 85% (vol) hydrochloric acid to room temperatur. - Dry acid salts, 120 g/l at 25 to 60 oC.
High Carbon Steel:- Because of the tendency to smut in acid, mechanical methods of scale removal usually precede short acid dips.
Stainless Steel: - 10 to 20% (vol) nitric acid plus 1 to 2% hydroflouric acid at 50 to 60%.
Copper and copper base Alloy: - 10 to 40% (vol) sulfuric acid at room temperature. - 10 to 15% (vol) sulfuric acid plus 15 to 30 g/l of sodium dichromate at room temperature. - 25% (vol) sulfuric acid plus 12.55% (vol) nitric acid at room temperature.

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Electric Current for Pickling

2008-12-14T05:53:00.000-08:00

Electric current is used to make pickling more effective. Cathodic pickling is practiced on stainless steels. It increases the effectiveness of the pickling and is a good way of activating the surface so it will plate satisfactorily. Anodic etching of high carbon steel with sulfuric acid (135 – 550 g/l) is an effective method of removing the last traces of smut and scale from high carbon steel before plating.

Corrosion inhibitor are used in many heavy duty descaling baths to protect the basis metal. However, inhibitors are widely used in plating line because they can cause plating problems. If inhibitors are required, adequate cleaning to assure their complete removal is necessary.

Many acid baths with varying concentration and combining of acids are used to obtain the desired descaling, brightening, and acid dipping qualities necessary for good plating. A few typical bath that suitable for pickling process will describe more detail in the next blog.

Pretreatments

2008-12-05T17:17:00.000-08:00

Some heat scales are not rapidly soluble acids or may dissolve so slowly that attack on the basis metal occurs before the scale is removed. If this is the case, a pretreatment step can be used to change the scale so that it becomes readily soluble in dilute acids. Sometimes a good alkaline cleaning using a chelated alkaline derusting compound is beneficial.

Posselt et al. found that a caustic soda permanganate pretreatment made many types of heat scales easy to remove in regular acid pickling baths.

Fore metals that form difficult to remove scales, molten salt are often used. The du Pont sodium hydroxide bath containing 1.5 to 2 % sodium hydride and operating at 370 to 400 oC is an effective reducing bath. After such treatment, many scales are easily removed by a water quench and dilute acid with no attack on the basis metal. Some molten sodium hydroxide bath contain oxidizing agents such as sodium nitrate. These bath 450 to 540 oC and oxidize the scales so they can be removed by a water quench and dilute acid. Two widely known bath are Kolene bath and the Virgo bath.

Post by Aluminum Anodizing.

Pickling Scale-2

2008-12-03T07:10:00.000-08:00

Hydrochloric acid has the advantage of being on effective pickle for many metals at room temperature. Its one disadvantage is the fumes of HCl that may cause secondary problems.

Nitric acid is an ingredient of many bright dips. It finds wide use in combination with hydrofluoric acid for removing heat scale from aluminum, stainless steels, nickel and iron base alloys, titanium, zirconium, and certain cobalt base alloys.

Phosphoric acid is widely used for removing rust from steel and in special baths for stainless steel, aluminum, brass and copper. The phosphoric nitric acetic acid bath is often used to prepare aluminum for bright anodizing. Fluoboric acid has proved to be a most effective pickle for lead base alloys or soldered copper and brass parts that are to be plated. It seems to work when other acids fail.

Sodium bisulfate (NaHSO₄) is the basis for most dry acid pickling salts. It is a convenient way of handling sulfuric acid in dry powder form and eliminates the handling of carbon of carboys.

Proprietary acid salts also incorporate compatible surface active agents and activating chemicals that make them more effective for certain plating lines than raw acids.

Chemicals for Pickling

2008-11-26T01:12:00.000-08:00

Sulfuric acid is the workhorse of the industry and finds wide application for pickling steel, copper, and brass. It is used with chromic acid and the dichromates for deoxidizing and desmutting aluminum. It is used with hydrofluoric or nitric acid or both for descaling stainless steel. The anodic sulfuric acid etch is an effective way of removing the last traces of smut and scale from steel before plating. The Bullard-Dunn process using sulfuric acid with tin or lead salts and cathodic current is still used for picklng parts where dimensional change must be minimized.
Hydrochloric acid has the advantage of being an effective pickle for many metals at room temperature. Its one disadvantage is the fumes of HCl that may cause secondary problems.

Nitric acid is an ingredient of many bright dips. It finds wide use in combination with hydrofluoric acid for removing heat scale from aluminum, stainless steels, nickel- and iron-base alloys, titanium, zirconium, and certain cobalt base alloys.

Phosphoric acid is widely used for removing rust from steel and in special baths for stainless steel, aluminum, brass and copper. The phosphoric-nitric-acetic acid bath is often used to prepare aluminum for bright anodizing. Flouboric acid has proved to be most effective pickle for lead base alloys or soldered copper and brass parts that are to plated. It seems to work when other acids fail.

Sodium bisulfate (NaHSO4) is the basis for most dry acid pickling salts. It is a convenient way of handling sulfuric acid in dry powder form and eliminates the handling of carboys. Proprietary acid salts also incorporate compatible surface active agents and activating chemicals that make them more effective for certain plating lines than raw acids.

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Pickling Scale and Oxide Removal

2008-11-14T21:50:00.001-08:00

It is essential that metal to be plated be free of scale and oxide for quality plating. Good shop practice can prevent or minimize scale problems. Such things as cleaning before heat treating, wearing gloves to keep fingerprints off metal surfaces, proper control of heat treat furnaces, and taking step to prevent rusting of steel parts pay for themselves. It is literally true that "an ounce of (scale) prevention is worth a pound of cure."

Every shop has methods of removing rust and scale. Both mechanical and chemical methods are employed. Acid pickling is one of the most widely used. It has been reported that scale and oxide removal consumes 5 % of all the sulfuric acid, 25% of the hydrochloric acid, most of the hydrochloric acid, and large quantities of nitric acid, most of the hydrofluoric acid, and large quantities of nitric acid and phosphoric acids.

Inorganic acids and acid salts used for scale removal are as follows:

Acids	Acid Salts
Sulfuric	Sodium acid sulfuric and ferric sulfate
Hydrochloric	Ferric Chloride
Nitric	Ammonium persulfate
Phosphoric	Acid phosphate
Hydrofluoric	Acid fluoride
Hydrofluosilicate	Acid Flousilicates
Flouboric	Acid flouborates
Chromic	Dichromic
Sulfamic	Ferric Chloride

Rinsing

2008-11-08T17:14:00.001-08:00

Rinsing is a process that does in between of anodizing process step, rinsing also do in preparation for plating. The result quality will depend on the rinsing process, if many chemicals or organic substance left on the metal surface will result a bad electroplated or anodized product.

Proper and complete rinsing is a necessary part of all cleaning operations. Complete rinsing is not accomplished until all the partially dissolved, loosened, or emulsified soils adhering to the metal surface have been removed along with the film of cleaning solution that clings to the surface as the work is removed from the cleaner. Since the material rinsed from the surface of the work will end up in the rinse tank, all rinse tanks should be kept overflowing continuously with a large volume of incoming fresh water. Rinse water that is too cold will be slow in action, and in machines with fixed time cycles it may cause trouble; this problem arises only in winter. Spray rinsing is generally more effective and more economical thank rinsing. Details of rinse tank and spray rinsing equipment are given by Lux and Linford and Pinkerton.

Recycling of rinse water to converse water and reclaim chemical is becoming not only important but necessary. Seek the advice of an expert before investing large sums of money in any water conservation program.

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Barrel and Vibratory Cleaning

2008-11-01T07:31:00.000-07:00

Barrel Cleaning on Anodizing

Barrel cleaning is a specialized method of preparing large volumes of small parts. It is effectively when used on parts that are too small or too light for spray washing or have a tendency to pack or nest when placed in baskets for immersion in soak or electrocleaners. The method should not be used on thin or easily deformed parts since there will be considerable mechanical action in the process. Because it is impractical to inspect individual pieces, the cleaning cycle must be thoroughly reliable. Great care should be used to make sure that rinsing is thorough.

Vibratory Cleaning

The development of methods of deburring, finishing, and polishing by vibratory means has advanced rapidly. Parts move slowly in a vibrating and moving bed of abrasive media and detergent compound solution and are scoured, scrubbed, and finished to the desired surface finish in relatively short times and in large volume. Fragile parts that would be badly damaged by barrel finishing methods can be processed by vibratory methods

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Electropolishing Bath

2008-10-24T20:09:00.000-07:00

As have known that electropolishing is the fast and effective way on preparing the metals before anodized or electroplating process applied. This process also become a key on getting a best result, because if you do in careless way on this process you will difficult to get a best result or even no metal is stick to the product.

The most common used in electropolishing bath are based on sulfuric and phosphoric acids in about 50/50 weight proportion at about 54 to 105^oC for ferrous alloys, 85% phosphoric acid for copper at about 43 to 60^oC; and phosphoric acid with about 5 to 7% chromic anhydride (CrO₃) at about 60^oC for brass.

Current density of practical electropolishing range from 5 to 40 A/dm², depending on the metal being finished, type of bath, and temperature. The time required usually is 2 to 7 min for current densities of 15 to 30 A/dm² and temperature of 54 to 82^oC.

Electroplating bath are less subject than electroplating bath to contamination and are easily controlled to maintain optimum result. Except for the perchloric acid – acetic acid type of bath, safe operation is easily maintained. Perchloric acid-acetic bath require failsafe temperature controls and strict avoidance of contamination with easily oxidizable materials.

Electropolishing

2008-10-18T18:23:00.000-07:00

Electropolishing is an excellent preparation of metals for electroplating this is a kind of metal surface treatment before anodizing process or other kind of process. In addition to providing a chemically and physically clean surface, electropolishing removes mechanically surface damage. As a result, subsequent electroplates have the best adhesion possible and a decreased tendency toward developing pits and voids that lower corrosion protection. Metal surfaces that have been machined, ground, picked and rolled, abrasive polished, and buffed, have asperities that are detrimental to uniform and pit-free electroplates, adhesion of the plate, and strength of the interface region of the plate basis metal.

Electropolishing removes light tarnish films and light oil or grease. However, removal of oils and grease by cleaners is preferred before electropolishing. This is because such oils and grease eventually form a floating layer of oily-tarry degradation products on the surface of the electropolishing bath. Such a layer contaminates clean surfaces as they pass through the layer on entering the bath. The contamination becomes an irregular stopoff that is revealed as a pattern in the electropolished surface. Heavy rust and heat scale should be removed before electropolishing. These surface oxides also have a nonuniform stopoff effect.

For electropolishing, part are racked as they are for electroplating. Because the current density is five to ten times higher, contacts and splines are heavier. Equipment, racks, and power sources are analogous to those for chromium plating, except that usually the work rod is moved in back and forth motion as for bright plating. The same racks can carry the parts through cleaning and plating. In the electroplating step, excess plate is removed from contact areas. Therefore, the racks are stripped.

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Metal Spraying

2008-10-11T19:13:00.000-07:00

Protective metal coatings can also be sprayed into cleaned and roughened article in the form of molten metal droplets, which congeal and bond immediately on impact. The article does not become unduly heated (even paper can be metal sprayed) and the coating does not wet or alloy with the basis metal, so that the adhesion of the coating is only mechanical. The coating is only an aggregate of flattened quenched droplets, interspersed with oxide films and some porosity so that is very brittle.

Nevertheless the process has the special advantage over most of the processes so far described, that it can be applied to structures of any size and, if necessary, in situ. It is thus specially suitable for the protection of ships hulls, structural steel work, bridges and other civil engineering steel parts. The steel surface must be freed from all scale and rust before coating; this is usually done by shot-blasting or sand-blasting, using compressed air. This preparation also roughens the surface and facilities the mechanical adhesion of the coating.

Metal spraying is chiefly for applying zinc or aluminum onto steel. Three main methods are used. The most popular and most highly developed utilizes a hand held or machine-held pistol in which a wire of the coating metal is continuously fed into an oxyacetylene flame, where it is melted, and the droplets of molten metal are impelled on the work by compressed air. In another method, the coating in the form of powder is blown through a melting flame onto the work by the compressed air. In a third method, pre melted metal from a reservoir is atomized and blown onto the work piece. The rate of deposition is quite fast, but only a small area is covered at one time. Coatings of at least 0.002 in, and usually of 0.005 in, are applied; such thick coatings are necessary because the deposit is rather porous. The outer surface is rough and unattractive in appearance but is an excellent base of subsequent paint coatings. The porosity is less harmful than in thinner for it soon seals itself with corrosion product.

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Hot Dip Aluminizing

2008-10-04T23:56:00.000-07:00

Aluminum can also be coated on to iron and steel articles by hot dipping, but the process is considerably more difficult than in the case of tin and zinc, for a number of reasons. Because of the higher melting point of aluminum the process must be carried out at about 700^oC, at which temperature it is very difficult to preserve the steel in an oxide free condition. The aluminum melt itself cannot be kept without an oxide film on its surface, even in an inert atmosphere. The major difficulty in aluminizing, however, is the rapidity of the formation of an intensely brittle aluminum iron intermetallic compound at the interface. The growth of this layer can be restrained to a limited extent by additions of silicon or beryllium to the melt. A 6% silicon aluminum alloy is usually used.

The steel is freed from oxide by pickling, but must be dried before entry into the molten alloy. Simple and partially successful schemes of providing a thin replacement film of copper on the surface, and then coating it with glycerin, have been used, but for large scale aluminizing very complicated plant for deoxidizing the sheet and introducing it into the molten bath under a protective gas are employed. Aluminized coatings are bright and metallic in appearance, although usually marred by streaks and patches of oxide, drawn off the surface of the melt. They will not withstand even slight bending without spalling and cracking, because of the inevitable layer of intermetallic compound at the interface. They have excellent resistance to exposure to the whether, to waters and to damp conditions without much change of appearance. However, their major field of application is in resisting the effect of high temperatures which would oxidize and scale the steel base. Aluminized steel thus finds its chief application for such purposes as motor car silencers and exhaust systems, for gas heater heat exchangers and for similar applications where hot products of combustion are concerned. A usual thickness is 0.001 to 0.002 in.

Solution of Hot Dipping

2008-09-27T08:29:00.000-07:00

During galvanizing the parts are taken from the fluxing solution and well drained, or even dried off, without rinsing, and immersed into the clean molten zinc. They are then withdrawn as quickly as possible, and encouraged to drain by shaking of brushing, special attention being given to the lower edges. The parts are then put aside to cool or quenched in an air blast or in water. The thickness of the zinc coating can be controlled are usually expressed by the weight of zinc and the period of immersion. Coatings are usually expressed by the weight of zinc per unit area; 2 oz zinc per ft² = 0.0018 in thickness is a usual coating, but thickness of 4 to 6 oz are possible. As a result of surface tension forces, small reentrant crevices and angles, such as screw threads, tend to become clogged, whilst the coating may be thinner than average on sharp edges, except at the bottom edge where may be a thickening.

The surface appearance is irregularly crystalline because the solidification of the zinc proceeds from nuclei, and causes characteristic and decorative spangles. Small additions of aluminum increase the fluidity of the molten bath, and restrain the growth of the alloy layer. Dross and oxide films floating on the bath surface are liable to become entangled in the molten zinc coating and impair its appearance. The zinc use is often rather impure (about 99%). Moreover, it reacts with the iron immersed in it and with the pot; eventually it becomes saturated with the iron-zinc intermetallic compound, which crystallize out. These crystals tend to sink to the bottom of the zinc pot, but some may get caught up in coating causing unsightly lumps.

Steel sheets are galvanized mechanically by processing them through the molten zinc by power driven rolls. Sheet wire is passed mechanically through the zinc bath, and is usually drawn through a wiper on the exit side.

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Zinc Coating by Hot dipping (Galvanizing)

2008-09-20T01:20:00.000-07:00

The zinc coating of steel by hot dipping is confusingly known as galvanizing, although no use is made of electricity in the process. It provides a cheap and effective method of producing a good rust-resisting coating on steel sheet, steel wire and on miscellaneous fabricated steel and cast iron articles, such as tanks, vessels, hardware, pipes and fittings and structural components, most of which will be exposed to the weather, or to damp air or water. Galvanizing is carried out on a very large scale and, with perhaps the exception of paint, is the most widely used protective coating system. Thus in 1965 in the UK, out of the total consumption of 357,000 tons of zinc, a total of 92,052 tons (25%) was used for galvanizing, comprising sheet and strip 23,836 tons, wire 19,596 tons, tube 13,4333 tons, and general 35,187 tons.

Galvanizing consists on essence of dipping the cleaned and fluxed steel into a skimmed bath of molten zinc, and then withdrawing and cooling it as soon as possible. A certain rapidity of processing is necessary because the molten zinc not only wets the steel, but actively reacts with it to form an intermetallic compound which grows rapidly in thickness at temperatures above the melting point of zinc. This alloy layer is intensely brittle, therefore it is essential to keep it as thin as possible; and galvanized articles should not be deformed excessively for fear of fracturing this layer.

Hot dip galvanizing of steel sheet (corrugated or otherwise) and of steel wire can be mechanized; galvanizing of fabricated parts is mostly done by hand. The parts must first be free from scale, rust and oxide; casting must be free from sand. This is mainly accomplished by pickling in acid, but large castings are sometimes shot-blasted or sang-blasted, followed by a lighter pickling process. It may be necessary to brush off detritus and residues adhering to the surface after pickling. The parts are then thoroughly rinsed and immersed in a fluxing solution, usually an aqueous solution of zinc ammonium chloride. They can held in this solution without danger of further oxidation or attack until required for galvanizing.

The galvanizing bath is a heavy vessel of welded steel plate, fired from below and from the sides. Although this is often unlined, it may be lined with refractory brick. Such a vessel may hold many tons of molten zinc (spelter)-usually between 30 and 75 tons. During galvanizing the temperature is about 450^oC. The surface of the molten metal must be kept clean by constant skimming when galvanization is in progress, or a thin film of ammonium chloride may be present, although this volatilizes to irritating fumes.

Type of Nickel Plating

2008-09-14T00:53:00.000-07:00

Many other types of nickel plating solution have been advocated, mostly based on nickel sulfate, although nickel chloride and nickel sulphamate baths can be worked more quickly. All these yield matt deposits and are called dull plating baths. The electroplated coating from the Watt bath is smooth but of a matt, pearly milk-white texture and must be mechanically polished if, as is usual, a high luster is required. This process is called coloring or color buffing, and is fairly readily accomplished by pressing each part of the surface of the article against a revolving wheel built up of soft cloth discs. The wheel is dressed with very fine lime or similar powder bound in grease, the powder flowing or smearing the surface rather than abrading it.

The major modern change in the practice of nickel plating has been the use of brightening and leveling additions to the nickel plating solution of the Watts bath type. These are complex organic substances which, although present in solution only in small quantities, are adsorbed on the growing electroplate and modify its metallurgical structure. Not only is the size of the crystalline grains in it reduced, but the additions have a specific effect of restraining the growth at any place which tends to grow out above the general level. In this way the electroplate is kept microscopically smooth and hence it is bright and lustrous as plated. It is also much harder and more wear resisting which is an important advantage in service. The advantage to the electroplater is not only that the cost and labor of mechanical polishing is eliminated, but also that the articles can proceed direct to chromium plating without unracking or rewiring. Rinsing and drying must, however, be carefully carried out to avoid water staining.

The operation and control of nickel plating calls for much care and experience. Temperature and clarity of solution, and the pH value must be constantly checked, e.g. twice daily; analysis for the main constituents, especially nickel, is required at longer intervals. Nickel plating solutions are especially sensitive to trace contiamination by traces of copper, zinc and chromium, and by organic materials of a colloidal or glue-like nature. The inorganic contaminations can be eliminated by long continued plating onto a piece of scrap sheet metal at a low current density; organic materials are removed by oxidation with permanganate or by absorption on activated charcoal.

In addition to its use as undercoating to chromium, nickel plating is often used alone fro protection of chemical plant and food processing equipment, or parts, such as the electrodes of thermion valves, which must be protected from scaling by the action of heat.

Thicker deposit of electrodeposited nickel are sometimes applied to worn or wrongly machined steel parts to restore them to size or make them oversize. In such cases great attention must be paid to the preliminary etching process, to ensure good adhesion, and to the mechanical properties of the electrodeposited coating. The deposit can be confined to specific areas of the steel part by applying a thick layer of adherent and chemically neutral wax to the remaining area. This is called stopping off and is also used to prevent unwanted plating on the shaft of suspension jigs, etc. in decorative plating.

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Nickel Sulfate, Nickel Chloride and Nickel Sulphamat Bath

2008-09-06T00:55:00.000-07:00

Many other types of nickel plating solution have been advocated, mostly based on nickel sulfate, although nickel chloride and nickel sulphamat bath can be worked more quickly. All these yield matt deposits and are called dull plating baths. The electroplated coating from the Watts bath is smooth but of a matt, pearly milk-white texture and must be mechanically polished if, as is usual, a high luster is required. This process is called coloring or color buffing, and is fairly readily accomplished by pressing each part of the surface of the article against a revolving wheel built up of soft cloth discs. The wheel is dressed with very fine lime or similar powder bound in grease, the powder flowing or smearing rather than abrading it.

The major modern change in the practice of nickel plating has been the use of brightening and leveling additions to the nickel plating solution of the Watts bath type. There are complex organic substances which, although present in solution only in small quantities, are adsorbed on the growing electroplate and modify its metallurgical structure. Not only is the size of the crystalline grains in it reduced, but the additions have a specific effect of restraining the growth at any place which tends to grow out above the general level. In this way the electroplate is kept microscopically smooth and hence it is bright and lustrous as plated. It is also much harder and more wear-resisting which an important advantage in service. The advantage to the electroplater is not only that the cost and labor of mechanically polishing is eliminated, but also that the articles can proceed direct to chromium plating without unracking or rewiring. Rinsing and drying must, however, be carefully carried out to avoid water staining.

The operation and control of nickel plating calls for much care and experience. Temperature and clarity of solution, and the pH value must be constantly checked, e.g. twice daily; analysis for the main constituents, especially nickel is required at longer intervals. Nickel plating solutions are especially sensitive to trace contamination by trace of traces of copper, zinc and chromium, and by organic materials of a colloidal or glue like nature. The inorganic contaminants ca be eliminated by long continued plating onto a piece of scrap sheet metal at a low current density; organic materials are removed by oxidation with permanganate or by absorption on activated charcoal.

In addition to its use as undercoating to chromium, nickel plating is often used alone for protection of chemical plant and food processing equipment, or for parts, such as the electrodes of thermionic valves, which must be protected from scaling by the action of heat.

Thicker deposits of electrodeposited nickel are sometimes applied to worn or wrongly machined steel parts to restore them to size or make them oversize. In such cases great attention must be paid to the preliminary etching process, to ensure good adhesion, and to the mechanical properties of the electrodeposited coating. The deposit can be confined to specific areas of the steel part by applying a thick layer of adherent and chemically neutral wax to the remaining area. This is called stopping off and is also used to prevent unwanted plating on the shafts of suspension jigs, etc. in decorative plating.

Nickel Plating Baths

2008-08-29T04:39:00.000-07:00

Many other type of nickel plating solution have been advocated, mostly based on nickel sulfate, although nickel chloride and nickel sulfamate bath can be worked more quickly. All these yield matt deposits and are called dull plating baths. The electroplated coating from the Watt bath is smooth but of a matt, pearly-milk-white texture and must be mechanically polished if, as is usual, a high luster is required. This process is called coloring or color buffing, and is fairly readily accomplished by pressing each part of the surface of the article against a revolving wheel built up of soft cloth discs. The wheel is dressed with very fine line or similar powder bound in grease, the powder flowing or smearing the surface rather than abrading it.

The major modern change in the practical of nickel plating has been the use of brightening and leveling additions to the nickel plating solution of the Watt bath type. These are complex organic substance which; although present in solution only in small quantities, are absorbed on the growing electroplate and modify its metallurgical structure. Not only is the size of the crystallize grain in it reduced, but the additions have a special effect of restraining the growth at any place which tend to grow out the general level. In this way the electroplate is kept microscopically smooth and hence it is bright and lustrous are plated. It is also much harder and more wear resisting which is an important advantage in service. The advantage to electroplater is not only the cost and labor of mechanical polishing is eliminate, but also that the article can proceed direct to chromium plating without unracking or rewiring. Rinsing and drying must, however, be carefully carried out to avoid water staining.

The operation and control of nickel plating calls for much care and experience. Temperature and clarity of solution, and the pH value must be constantly checked, e.g. twice daily; analysis for the main constituents, especially nickel, is required at longer intervals. Nickel plating solutions are especially sensitive to trace a contamination by traces of copper, zinc and chromium, and by organic materials of a colloidal or glue like nature. The inorganic contaminants can be eliminated by long continued plating onto a piece of scrap sheet metal at a low current density; organic material are removed by oxidation with permanganate or by absorption on activated charcoal.

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Materials Combination Effect

2008-08-24T21:55:00.000-07:00

Metal coating can prolonged the life age of those metal, but if coating using electroplating method still using other stabile metal to cover certain metal. On installation sometime can make the metal that is join on combine can cause corrode effect because of merge electro-voltage because of metal difference. We must intense on this metal joining or combination on installation.

The selection of material to resist deterioration in service is outside the scope of the B31.3 code. Experience has, however, resulted in the following material considerations extracted from the code with the permission of the publisher, the American Society of Mechanical Engineers, New York.

General Considerations to be evaluated when selecting combining materials are:

Possible exposure to fire with respect to the loss of strength, degradation temperature, melting point, or combustibility of the pipe or support material;
Ability of thermal insulation to protect the pipe from fire;
Susceptibility of the pipe to brittle failure, possibly resulting in fragmentation hazards, or failure from thermal shock when exposed to fire or fire-fighting measures;
Susceptibility of the piping material to crevice corrosion in stagnant confined areas (screwed joints) or adverse electrolytic effects if the metal is subject to contact with a dissimilar metal;
The suitability of packing, seals, gaskets, and lubricants or sealants used on threads as well as compatibility with the fluid handled; and
The refrigerating effect of a sudden loss of pressure on volatile fluids in determining the lowest expected service temperature.

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Thicker Nickel Plating

2008-08-22T18:58:00.001-07:00

Against these considerations the commercial electroplater has to balance the fact that this plant is occupied longer for the nickel deposits and the costs rise proportionately. The adequate of thickness of the nickel electroplates does not become apparent until long after it is delivered. For these reasons a British Standard Specification and numerous other private and foreign specifications lay down the minimum permissible thickness of nickel plating on any part of an article for various types of service, and describe and specify means of checking this. To achieve safely the minimum thickness specified for steel motor car parts exposed to the weather (0.0012 in) may involve depositing at least 0.002 in average thickness, i.e. h plating at 20 A/ft2 or 40 m at 60 A/ft2. Thinner nickel plating for use under milder conditions of exposure or other basis metals is also covered in these specifications.

It should be made clear that many articles may be nickel plated at the same time in one nickel plating tank, provided that they do not shield one another from the flow of current from the anodes. The entire article may be put in and withdrawn together, or they may be put in and withdrawn in sequence, provided only that each one gets its proper share of the current and the requisite time.

After the selected period of electroplating the racks or wires carrying the articles are lifted out of the plating tank, thoroughly rinsed in running water to avoid stains and then dried, usually in a current of warm air. The parts may be then detached from the racks or wires. Inevitably, valuable nickel plating solution adheres to the parts or is trapper in recesses, etc. This is called 'drag-out' and is lost during rinsing. Except for this loss the nickel plating solution is little changed in the plating process since the nickel metal plated out from it is automatically replenished from the anodes.

Nickel Electroplating Voltage

2008-08-17T08:25:00.000-07:00

The low voltage direct current is supplied to the tank from the normal mains alternating current supply via a step down transformer and a static rectifier. It is now usual current supply can be adjusted by variation of the transformer ratio, and the serves to adjust the magnitude of the current. A voltage range of 3 to 7 V is sufficient for this. It is unusual to have a switch in the low voltage circuit, as it is highly desirable that always an ammeter in circuit. The current to be applied must be calculated from the surface area of the article to be plated. At 35^oC with moderate agitation, 15 to 30 A/ft² of area can be used, whereas at higher temperature and with more violent agitation of the solution, current densities of up to 100 A/ft² are possible. If these current densities are seriously exceeded the electroplate is dark colored and powdery; this is called burning. The rate of growth of thickness of the deposit is strictly proportional to the current density, and at 20 A/ft² almost exactly 0.001 in (25 µm) per hour. It is thus possible to calculate the time for which the articles must remain in the plating tank to attain any desired thickness of deposit. During this time the current must not be interrupted for any appreciable time, or the plating is liable to be laminated and to peel off. It is, obviously, often difficult to compute the exact surface area of complex articles; in such cases the operator applies the voltage known from experience to produce the desired current density, but this method of current adjustment is not too reliable.

The thickness of current plating to applied must be determined in the light of the type of basis metal and, particularly, with regard to the protection from corrosion which is desired. Although a thin deposit of nickel, e.g. 0.0001 in thick, is visually continuous, it is found that it contains numerous, invisible tiny pores or holes. As the thickness of the plate is increased the number of these decrease until at about 0.001 in (25 µm) thickness; the number in negligible. This thickness (0.001 in) is considered to be minimum reliable thickness if good protection to steel against the weather outdoors is required. Of course if the purpose of the electroplating is mostly decorative, and on a metal not easily corroded, a lesser thickness will suffice. It must, however, be borne in mind that on an article of intricate shape, the current density at any point may differ from the average current density, because of the shape of the electrical field. It will be appreciably less in recesses and appreciably greater on projecting areas. The thickness of plating will accordingly be much less than the reliable minimum in recesses, even enough the average thickness is adequate. Some electroplating solutions compensate for this to some extent by a property called throwing power. In any case some reduction of thickness must be allowed for in the subsequent polishing operation.

Nickel Plating Maintenance

2008-08-07T20:59:00.001-07:00

In nickel plating maintenance of a steady, but very slight acidity is most important. Satisfactory nickel plate can only be obtained in the pH 5.2 to 5.8. The pH value of the nickel plating solution tends to rise slowly in use, due to a small proportion of current discharging hydrogen ions rather than nickel ions, especially at lower pH values of the solution, and must be adjusted from time to time by adding sulfuric acid, or alternatively, if it has become too acid, by adding nickel carbonate. The presence of the boric acid in the solution ensures that these changes of pH value are less sudden than would otherwise be the case.

The nickel plating solution is held in an open topped, lead lined or hard rubber lined tank. The solution is heated by immersed steam coils or electric heaters, or in some other way. A temperature of at least 35 oC is usual, but because higher current densities, and hence faster electroplating, can be achieved at higher temperatures, the bath are often operated at temperature up to 65 oC or 70 oC. The plating solution is stirred or agitated, usually by compressed air, which is blown in through a perforated pipe on the floor of the tank.

The tank is provided with a central metal rod at the top, from which the articles to be plated can be hung by the wires or jigs on to which they were fixed prior to degreasing. This rod is connected to the negative side of the low voltage direct current supply. Similar rods are arrange a long two opposite sides of the tank, and are connected to the positive side of the current supply. On these the nickel anodes are hung by metal hooks. Nickel anodes are usually cast with some care from metal containing oxide and other trace elements to facilitate their dissolution, and these are called depolarized anodes. Nickel (and other electroplating) anodes are therefore enclosed in heavy cotton twill bags. The electric current and the solution can percolate through the fabric, but the particles are retained. It is nevertheless quite common for nickel plating solutions to be filtered continuously, or from time to time.

Nickel Coating

2008-08-05T01:06:00.000-07:00

Nickel plating is by far the most important electroplating process, chiefly because it is the best undercoating immediately below chromium plating. Nickel is a hard, yellowish-white, non-toxic metal with takes a high polish and has considerable resistance to tarnish and corrosion by weather. After prolonged exposure to damp industrial atmospheres it loses its polish and form a superficial haze or bloom, but the metal is not deeply corroded and the original luster can readily thick coating of nickel protects iron and steel from rusting, but only by excluding the corrosive environment from contact with the exposed spots is accelerated by its presence on adjacent areas.

Soon after the metal become commercially available, about 1870, nickel plating became popular for the protection and establishment of harness part and then fashionable bicycle. Subsequently it was used for all kinds of metal articles. Its use was stimulated by the advent of the motor car, particularly after 1930, when chromium plating became the major decorative, as well as the protective medium on motor cars and many other manufactured products. Out of total consumption in the UK in 1963 of 36,000 tons of nickel it is estimated that about 5,000 tons were used in electroplating, i.e. approximately one-seventh of the total consumed.

The most useful type of electroplating solution for nickel is the Watts solution. A typical composition is: see on nickel plating.

These condition correspond to a rate of deposition of 0.0008 to 0.0053 in/h. The voltage necessary varies with the current density, the temperature and the size of the vat, but is in the range of 3 to 7 V.

In the above formula, the nickel salts are quoted in the form of the hydrated crystalline material commercially available; in solution. Of course, this water of crystallization is no longer attached to the salts. The use of two different nickel salts is necessary to ensure the presence of some chloride ions, because with sulfate anions alone the nickel anodes do not dissolve freely, and the solution would become impoverished in nickel during use. The solution is almost saturated with nickel salts, to have the maximum amount of nickel ion available and to achieve a high current density.

Copper Electroplating Practice in Industry

2008-07-31T20:23:00.000-07:00

Two aspects of this process should be noted, firstly, that the amount of copper transferred from one electrode o the other is exactly proportional to the current passed, one copper atom for each two electrons; secondly, that no chemical work has been done by the current, copper has merely been transferred from one electrode to the other. Everything else is as before. Thus the current density controls the rate of electroplating and only a small voltage is required to drive the current round.

The process describe above is a completely practical commercial electroplating process; the copper sulfate solution is usually made slightly acid to decrease its electrical resistance. Apart from its use in electroplating this process is also used for the electroplating of all copper used for electrical purpose.

However, in general, such simple salts of metals are not always used for electroplating in industry. There are two main reasons for this:

1. The simple salt solutions tend to give rather coarse crystalline deposits, which are more difficult to polish.

2. When a metal is baser (more negative in the electrochemical series) than metal of the electroplating solution which it is immersed in, there is a tendency for an exchange reaction to take place, without any applied current. For example, if steel is immersed in the copper sulfate plating solution mentioned above, some of the iron dissolved and is replaced by a film of copper, but this is loose and Powderly. It is not a good foundation for electroplating.

This explains why complex salts of a metal are sometimes used for electroplating rather than simple ones.

There is one other principle of electrolysis which must be understood in connection with electroplating. The principal constituent of the aqueous electroplating solution is of coarse water (H₂O). This itself dissociates to come extent to yield positively charged hydrogen ions, and negatively charged hydroxyl ions (OH^-), thus H₂O <====> H⁺ + OH^-

In copper sulfate solution, although the positively charged hydrogen ions are attracted to the cathode they cannot be discharged there because copper ions are more easily discharged. In a sodium sulfate solution or in an aluminum sulfate solution, however, it is far easier for the hydrogen ions to be discharged, so sodium or aluminum cannot be electroplated from aqueous solutions. As the table of electrochemical series, that it would be impossible to electroplate lead, tin, nickel, cadmium and zinc from aqueous solutions, but fortunately there is a further overvoltage of about 0.5 to 0.7 V which is necessary to evolve hydrogen gas on these metals.

Coated With Copper

2008-07-28T02:18:00.001-07:00

Sulfuric acid is used as solution which has two hydrogen ions. Copper is a metal atom of which has two easily removable electrons. Copper sulfate (CuSO₄) is the copper salt of sulfuric acid. In aqueous solution the copper ions, each with two positive charges due to loss of two electrons, separate them selves from the doubly charged negative sulfate ion SO₄²

If two copper plates, which may be called electrodes, are dipped into the solution of copper sulfate and a direct current applied to them, one plate will become negatively charged and the other positively charged. The negatively charged plate is called the cathode. When a copper ion touches the cathode, two electrons will transfer themselves from the cathode to the copper ion, and thus turn it back into metallic copper, simultaneously, at the positive electrode, the anode, a metallic atom on the electrode will slip away into the solution as a copper ion, leaving its two electrons behind. In this way the aqueous solution remains electrically neutral, but two electrons have been able to move down to connecting wire into the cathode, and another two up from the anode along its connecting wire. In other words a current (of electrons) flows in the metallic circuit, and a metallic atom has disappeared from the anode and another has appeared at the cathode.

Ions (whether anions or cations) do not move so freely in a solution as electrons do in a metal, so the rate at which that the current can pass from the solution to the cathode and deposit smooth copper is somewhat limited. The amount of current is obviously related to the area of the solution/metal interface, so it is called a current density. Under ordinary conditions it is limited in this case to about 30 A/ft² of cathode area. This may be compared with a safe current of at least 1000 A/in² of cross section in a metal. However, this rate of 30 A/ft² of area corresponds to a growth of thickness of the coating of about 0.002 in/h (25 mm). This is fairly typical for most electroplating process, so that it will be seen that electroplating is essentially a rather slow method of metal coating.

Metal Coating Use of Electroplating

2008-07-23T02:24:00.000-07:00

Electroplating is a method of producing a smooth, compact and fairly uniform film of metal from an aqueous solution of one of its chemical compounds by means of a direct electric current. The current flows from the aqueous solution to the article being electroplated, which must of course itself be electrically conducting, and which forms the cathode. The current enters the aqueous solution through another metallic electrode, called the anode. The rest of the circuit is of coarse metallic. The anode is usually made of the metal being plated out at the cathode; it dissolves under the action of the current and thus replenishes the solution, so that the net overall effect is to transfer metal from the anode and distribute it more or less uniformly over the cathode, leaving the composition of the solution unchanged. It is, however, incorrect to think of the metal passing at any appreciable speed between the electrodes in combined form. The metal is produced from the solution in one place (the cathode) and returned to it at another (the anode); in continued practical operation if the solution is not stirred it will become unduly concentrated around the anode, and impoverished around the cathode.

Electroplating dates from the 1930s, and is closely associated with the name of Michael Faraday. Gold, silver and copper were first electroplated soon after the invention of the Daniel cell, the first reliable source of continuous electric current. Electromagnetic generation of electricity by rotating machinery was not available at that time, dynamos; in fact were first applied commercially in the electroplating industry, but not until 1841.

To understand the electroplating it is necessary to recall the general principles of electrolysis and the nature of the simpler chemical compounds and of their aqueous solutions. Metals are chemical element (alloys are mixtures of elemental metals). Metals are distinctive among the elements because the atoms of which they are composed have one or two (occasionally three) outer electrons which are rather loosely attached to the rest of the atom. In the solid metal these outer electrons are shared by all the atoms present, and are very mobile. Their mobility is the cause of the distinctively high electrical and thermal conductivity of metals.

Etching for Metallic Coating

2008-07-19T19:42:00.001-07:00

The degreased articles are not yet ready to receive the electroplated coating, because the metal surface may not be sound and it may have superficial oxide films or stains on it. If a clean, sound metal surface can be exposed the subsequent electroplate will bond atomically to it, but any impediment to this intimate contact will lead to poor adhesion, and the plating may peel off later in service. The extreme outer surface of the metal is indeed not representative of the sound metal below, because it may have been disturbed and fragmented by previous manufacturing operations and by the smoothing processes. For this reason, after degreasing, the articles are lightly etched in a dilute acid solution, e.g. by dipping into 10% sulfuric acid.

A cyanide solution is often used for lightly etching copper alloys and brass. Where thick and particularly adherent deposit must be formed on steel and the adhesion is very important, an electrolytic anodic etching process may be used. After this etching treatments the articles are gain thoroughly rinsed and placed without delay into the electroplating tank. It is advisable for their entry to complete the electrical circuit so that plating starts immediately.

The technique of electroplating is fairly similar for different metals, but naturally the composition of the solution is different, and temperature, current density and other conditions may also vary. The process will therefore be illustrated by describing nickel and chromium plating in some detail, since these are by far the most extensively used electroplating used electroplating process, and then outlining process for other metals.

Degreasing Small Parts

2008-07-14T08:24:00.000-07:00

Degreasing action for normal parts need some time and 5 min or more immersion is usual; the action is most rapid in an almost boiling solution, but too high temperature has the disadvantage that the articles dry off when removed before they can be rinsed. Dislodgement of the grease can be encouraged by evolving hydrogen gas electrolytically at the surface by passing a current between the steel tank acting as anode (positive) and the articles as cathode (negative). The magnitude of the current is less important than a copious evolution of gas; 50 to 100 A/ft of cathode urea is suitable, for which a voltage of 4 to 6 V suffices.

For small and intricate parts the degreasing action of both organic solvents and aqueous alkaline solutions can be assisted by ultrasonic action. This consist of electronically generated alternate pulses of compression and rarefaction in the liquid, at a frequency above that of the highest pitched audible sound, e.g. 100.000 c/s. The rare faction pulses are so rapid that they generate bubbles of vacuum on the liquid at the metal surface, and particularly in holes, crevices and recesses. These collapse equally suddenly during the compression pulses, in fact they implode. The resultant violent disturbance at the metal surface greatly assists in the degreasing action.

After degreasing, the article must be rinsed very thoroughly to remove all traces of emulsified oils and soaps, which would be precipitated by subsequent acid dips. The articles will then show an unbroken film of water over the whole surface, and should not be allowed to dry off.

Degreasing Metallic Article

2008-07-08T08:09:00.000-07:00

Degreasing metallic article prior to electroplating is therefore accomplished by immersing them for some time in a tank containing the hot, mixed alkaline solution. The typical formulation is given in the table below:

Chemicals	Formula	Heavy Duty Oz/gal (g/l)	Medium Duty Oz/gal (g/l)	Light Duty Oz/gal (g/l)
Caustic Soda	NaOH	6 (37.5)	2 (12.5)	-
Sodium Carbonate	Na₂CO₃*	4 (25)	4 (25)	-
Trisodium Phosphate	Na₂PO₄.12H₂O	1 (6.2)	2 (12.5)	4 (25)
Sodium Metasilicate	Na₂SIO₂.5H₂O	-	2 (12.5)	4 (25)
Sodium Cyanide	NaCN	-	-	2 (12.5)**
Wetting Agent		0.25 (1.5)	0.12 (0.75)	0.12 (0.75)

* Anhydrous sodium carbonate, commercially known as soda ash. The decahydrate Na2CO3.10 H₂O, known as washing soda, may be used in proportionately greater amount.
** Sodium cyanide optional, but particularly valuable with copper alloys.

The stronger and harsher alkalis are the most effective for saponification, but not necessary for emulsification; they also tend to stain iron and steel, and attack zinc and aluminum. Potassium hydroxide is even stronger and harsher than sodium hydroxide and is much more expensive. Caustic alkalis rapidly absorb carbon dioxide from the air; they are also not compatible with many useful synthetic detergents. For these reasons most degreasing solutions today are formulated from the milder alkalis, such as sodium carbonate, sodium silicate and sodium phosphate. Sodium cyanide is often also included in cleaners for copper alloys and other non-ferrous metals as it dissolves oxide and sulphide stains chemically.

Alkaline degreasing solutions can conventionally be contained in mild steel tanks, which are not attacked by alkalis. Such tanks are cheap and can easily be heated by external flames or internal steam coils. Handling the articles themselves after the degreasing operation would be likely to re-contaminate them, so it is universal practice first of all to fasten the articles onto wires or jigs of convenient design, by means of which they can be handled and supported in the various tanks, not only for degreasing but throughout the electroplating processes.

Surface Degreasing Problem

2008-07-04T02:21:00.001-07:00

The article is thus quickly cleansed by being continuously bathed in clean solvent at its boiling point. The oil and grease is not re-vaporized with the solvent. No solvent is consumed but care must be taken that it is not waste by being drawn out on degreased articles or by disturbance of the vapor, for it is quite expensive. Chlorinated hydrocarbon solvent vapors are dangerously narcotic if inhaled, and they also decompose to poisonous fumes if drawn through a flame. Solvent vapor degreasing is therefore controlled by statutory regulations, but these are not irksome in a well-conducted plant.

Solvent vapor degreasing alone does not produce a water wet table surface and it must be followed by a wet degreasing process. This process works through a combination of saponification, emulsification and change of surface tension, all based on the use of alkaline solutions and all in fact operative in domestic washing. Whereas acids, as a class, are characterized by a high concentration of hydroxyl ions, i.e. by a low pH number, alkalis are characterized a high concentration of hydroxyl ions, i.e. by a low concentration of hydrogen ions, and hence a high pH number. It is high concentration of hydroxyl ions which facilitates metal cleaning. Sodium and potassium hydroxides (soda and potash) are the strongest and harshest alkalis; sodium metasilicate (waterglass), sodium cyanide and sodium borate (borax) are milder alkalis.

Alkaline solutions attack and combine with the polar groups of greasy compounds to form soaps which are soluble in water. This action proceeds best in hot solutions, and is called ‘saponification’. Soaps, and also a large number of synthetic detergens, have ability to break up oil and grease into small droplets and to hold them suspended in aqueous solution, without much tendency to recoalesce or to deposit on the solid surface. They do this by coating the exterior of each oil drop with a monomolecular film of the detergent molecules. These molecules are of elongated shape, one end favor contact with water but the other end prefer to be in oil. Thus the molecules arrange themselves in the surface of the oil drops with the water favoring end outwards and the oil-favoring end inwards. This stabilizes the oil droplets. Soaps and other specially formulated synthetic detergents also have the property of changing both the surface tension and the interfacial tension of liquid.

Degreasing and Etching before Electroplating

2008-06-28T19:38:00.000-07:00

Sound, continuous, adherent electroplated coating can only be obtained on a chemically clean and firm metal foundation. Therefore the degreasing, thorough cleaning and etching of a metal article before electroplating is a vital preliminary step. Similarly, through cleaning is necessary before most wet finishing processes, and also to some extent before painting and other dry finishing processes.

The first part of the preparation is the removal of all traces of grease or oil, so that the metal article is freely wetted by the electroplating solution. Indeed the test for the satisfactory completion of the degreasing process is that the metal surface remains completely wetted all over, without any visible 'water-break', even after dipping in a slightly acid solution.

Metal article will often be lubricated with oil or grease during their manufacture, on smoothed articles traces of greasy or oily films to the articles. Metal surfaces have types of organic compounds, such as fatty acids and fatty alcohols, which are common polar groups attach themselves tenaciously to a metal surface, whilst the long tails of carbon atoms form a thick greasy barrier to the approach of any other substance to the metal. Deliberate use is made of this property in lubricants by including these polar substances and dirt. Sometimes, by the action of heat, light or pressure, the organic material is further changed, or polymerized, on the surface to resinous or tarry materials, which are even more difficult to dislodge. The purpose of the degreasing step is to different in principle from those used domestically for dry-cleaning, clothes washing or dish washing except that they are more through.

To remove of heavy film of oil or grease is most conveniently done by dissolving them in an organic solvent. Normal hydrocarbon solvent such as petrol, paraffin and white spirit present too great a fire hazard; their light vapors form an explosive mixture with air, and spread readily. Heavy, non-inflammable chlorinated hydrocarbons are therefore used, principally trichlorethylene (C2HCl2) (colloquially known to the plater as 'tri'), and perchlorethylene (C2Cl4).

Barrel Polishing

2008-06-25T07:13:00.000-07:00

Another long practiced, but crude method of overcoming the need for mechanization is known as barrel polishing. Originally this was only suitable for small, fairly simple and robust shapes, which were placed in a cylindrical container or barrel, together with a mass of pebbles or rounded abrasive shapes and a lubrication liquid. The whole assembly was then slowly rotated for some hours. The rubbing and tumbling of the abrasive shapes against the work pieces smoothed them in a rather unselective manner, but the process often inflicted as much damage as it removed. This process has been much improved, sometimes by substituting vibratory or other more gentle motion, so that quite delicate and fragile parts can be treated. Even so, these processes do not produce the best finish, but they have the merit of requiring little labor.

Metal finishing is the last step in the production process, and it is at this stage that a flawless surface must be produced in spite of any substance damage, dents, scratches, etc. which the article may have acquired during previous processes. It is obvious, but little regarded in practice, that care in the selection of the original material and in the handling during all stages of the manufacturing process can materially reduce the cost of the final smoothing operations.

In conclusion to this section it can not be too strongly emphasized that although these pre-polishing treatments do not themselves produce a lustrous and polished surface, they, and they only lay the foundation for a high quality final finish. The quality of a polished surface lies not in reflected in it. Only if the preliminary smoothing has been conscientiously done can clear, sharp reflected images be obtained. Fuzzy, distorted images can not be corrected by the final 'shining-up' operation and are a sure sign of insufficient pre-polishing.

Pre-polishing of Metal Coating

2008-06-22T02:57:00.001-07:00

Where a final smooth or polished metallic surface is intended, most of the smoothing must be applied to the uncoated article, since the metallic coating would be unduly and irregularly thinned by the smoothing process. All these processes are loosely described as 'polishing', but as applied at this stage, they consist in fact only of careful grinding with progressively finer abrasives. The articles are pressed against the abrasive loaded rim of rapidly rotating flexible wheels made of leather or coarse cloth discs. Two or three successive processes are usually used with progressively finer abrasives; grease or oil lubricant is applied during the final cuts, and the surface is brought to a satin smooth but entirely lusterless condition. The grease not only lubricates the operation, but supports and to some extent masks the abrasive particles; it also removes the frictional heat and prevents burning or scorching of the surface. These processes are known in the trade by various names such as bobbing, scuffing and buffing a finer and milder abrasive is applied to a sisal or cloth wheel from a grease bound cake. In sand is fed between the article and a rotating leather rimmed wheel. The abrasive used in the final stages is often Tripoli, or diatomaceous earth. Of recent years the coarser grinding has often been performed on long endless belt of emery cloth, supported between a soft faced pulley, against which the work is pressed, and another pulley some distance behind. This process is called back-stand emerying.

Because of the irregular shape and contour of most article sent for decorative electroplating, they mostly have to be presented to the revolving wheels by the hands of operatives, who turn and twist them to ensure that the whole area is smoothed, and who also visually check that all blemishes and rough nesses are ground out. This is heavy, dirty and tedious work, which nevertheless requires considerable skill and experience. Its is moreover a serious bottleneck in production because the work is unattractive to labor.

Pickling (Preparation for Metal Coating)

2008-06-19T08:17:00.000-07:00

Articles which are intended for coating with metal must first be cleaned free from heavy and dirt; oxide scale which may have been formed during hot fabrication operation such as annealing, casting and welding must also accomplished by solvent vapor degreasing or by immersion in a hot alkaline metal cleaning solution. These processes are describe n the section dealing with preparation for electroplating because they must, in any case, be repeated at that stage, especially if the article has been polished with greasy polishing compounds.

Oxide scale on iron and steel is removed by pickling, that is by immersion in hot dilute (about 10%) sulfuric acid solution or in hydrochloric acid solution. Similar acid solution are used for scaled copper and its alloys, for brass and for nickel-silver. The dissolution of the oxide copper of the oxide in the acid is a purely chemical reaction and is rather slow, taking many minutes to complete if the scale is thick. As the clean metal becomes exposed, it too would become attacked, which is undesirable, if small quantities of complex organic pickling inhibitors were not added. Unlike the dissolution of oxide, the acid attack on the metal is electrochemical and anodic, as already explained, and hydrogen gas is evolved in cathode places. Inhibitors are chosen to block either the anodic or the cathodic part of this process. Apart from the loss of sound metal caused by attack of the acid, the hydrogen evolved may be absorbed in part into the metal itself. With hardened high tensile steel this may lead to dangerous hydrogen embrittlement, to such an extent that section which are already stressed may crack during pickling. Pickling inhibitors, however, reduce the hydrogen absorption. The absorbed hydrogen can be driven out subsequently by a low temperature baking treatment.

Pickling also removes the casting skin and burnt sand residue from castings. Scales and sand can alternatively be removed from rigid objective by sand or shot blasting. This process is rather costly and leaves a rough and pitted surface which is unfavorable for electroplated or hot dipped coatings, but which provides a useful mechanical key for sprayed metal coatings and for paints.

Choice of Metallic Coating (2)

2008-06-15T08:34:00.001-07:00

The metals above hydrogen in the electrochemical series, which have a more positive potential than hydrogen, are less pores to progressive corrosion in aqueous solutions. Those metals with the most positive potentials, such as gold and platinum metals, indeed have practically no tendency to pass into the combined state, accordingly they are designated noble metals.

The position of iron in the electrochemical series should particularly be noted; it is more negative or base than hydrogen, and considerable more negative than copper, tin, and nickel, almost identical in position to cadmium, and considerable more positive than zinc.

Where two different metals are in electrical contact with each other an also with an aqueous solution, they form a galvanic cell or battery, because of their difference of potential. The metal with the more negative potential is stimulated to corrode faster, and the metal with the more positive potential is discouraged by the difference of potential. A current flows around the circuit made up from the two metals and the solution, it passes out of the corroding metal (the anode) into the solution and thence back into the protected metal (the cathode). The anode and the cathode may be some distance apart in this action, since both the metals and the solutions are electrically conducting to the electron transfer.

This situation of two different metals in contact being exposed to a corrosive liquid, arises when a protective metallic coating is discontinuous for some reasons. It may be inherently porous, or it may be locally deficient, or it may have become cut or damaged in service, or even by former corrosion. The corrosion of the basis or undermetal thus exposed will be stimulated or protected, according to the relative potentials in the electrochemical series of the coating and the basis metal. The more positive metal will always stimulate the corrosion of the more negative metal. If it is the corrosion of the basis metal which is stimulated in this way the effect can be serous, because the area exposed will be small compared with that of the undamaged coating metal, and therefore the current generated by the difference of potential will be concentrated on a small area of reactive basis metal. On the other hand, if the corrosion of the basis metal is inhibited by the adjacent presence of a more negative coating quite large gaps in the coating may not be very detrimental.

Next Pickling

Metallic Coating

2008-06-13T20:41:00.000-07:00

Choice of Metallic Coating

In choosing a metallic coating for the protection of a metallic article it is not sufficient to consider the behavior of the coating metal alone. It's necessary also to have regard to the effect of the mutual exposure of coating metal and bases metal at pores, cuts and other initial or subsequent breaks ion the thin film of coating.

This is a consequence of the predominantly electrochemical nature of the corrosion of metals by the whether, by water and by aqueous solutions, which must now be briefly considered. All metal atoms in the metallic state are characterized by having one or more rather loosely attached electrons, the mobility of which accounts for the high electrical and thermal conductivity of metals. Metal atom in the combined state has lost these electrons and is bound to other atoms by their resultant positive charge.

Corrosion of a metal is therefore essentially the loss of one or more electrons from its atoms. But since both the metals and both the metals and the aqueous solutions which corrode them are conductors of electricity, the absorption of electrons essential to corrosion may occur elsewhere than at the site of the attack; that is to say, corrosion is electrochemical in nature.

The various metals differ in the relative ease with which they part from their outer electrons, and a table, known as the electrochemical series, can be arranged to show this. For this purpose hydrogen gas can also be considered to be a metal, because its atoms each have one loosely attached electron. In the combined state hydrogen loses this electron and becomes the hydrogen ion, which is present in all aqueous solutions to a greater of a lesser extent, because it is present both in water and in acids.

Metal with the properties more negative potential than hydrogen ion will have a greater willingness to part with their outer electrons than that of hydrogen. Some of the metallic potential properties show in the table below:

Table of Electrochemical series of Metal
Gold	+ 1.42 V	Nickel	- 0.23
Rhodium	+ 1.40 V	Cadmium	- 0.40
Silver	+ 0.80 V	Iron	- 0.44
Copper	+ 0.52 V	Chromium	- 0.56
Hydrogen	0 V	Zinc	- 0.76
Lead	- 0.13 V	Aluminum	- 1.67
Tin	- 0.14 V	Sodium	- 2.71

Next in Continuous of Choice Metallic Coating

Choice of Surface Treatment

2008-06-07T09:15:00.000-07:00

Metallic coatings have the advantage of being hard and strong and of resisting moderately high temperature; they are thus fairly robust. They can usually be chosen to give a high degree of protection against most types of corrosive environment, excluding strong acids and chemicals. Where low cost is important and good protection is required, without much emphasis on appearance, hot dipped coatings are cheap and very effective. Where a neat, highly polished surface is required costs are much greater and electroplating is pre-eminent. Both hot dipping and electroplating evolve immersion of the articles into a liquid held in a container, so the maximum size of object which can be treated is limited. Metal coatings can be applied by metal spraying to objects of any size, if necessary in situ.

Vitreous enamel coatings can only be applied to a restricted number of metals which withstand the high temperature of application. As they are composed in effect of glass, they are highly resistant to most chemicals, but are extremely brittle and can only be applied to relatively rigid article.

Paint systems can be applied to articles of any size; if necessary to selected areas the hardest stoved paints are damaged relatively easily, are not very heat resistant and are seldom absolutely impermeable to water. Although they are fairly cheap as regards raw materials, paints are expensive and wasteful to apply.

The choice of coating is also dictated to some extent by the basis metal or alloy, iron and steel predominate and as they are so readily and disfiguringly corroded, they need special protection. Copper alloy, such as brass and nickel silver, are much less corrodible, but are more expensive and thus justify a more costly finish. The lower melting point metals and alloys of head, tin and zinc obviously cannot endure a hot process. Zinc, which is used very extensively in the form of zinc base die-casting, is a very active metals and needs effective protection.

Aluminum is a special case, since both the metal and its alloy have a very high resistance in the uncoated condition to atmospheric corrosion and to water, and do not readily accept coatings of other metals or of paints. This natural resistance is a consequence of an anodic film which forms automatically on the metal.

Alone of the cheaper industrial alloys, stainless steel does not need further protection, but its full appearance can only be brought out by suitable polishing, which is made expensive by the hard and tough nature of the material.

Metal Surface Protection

2008-05-31T18:21:00.000-07:00

Metals are essentially artificial and unstable materials, that is to say, they are not found as such in nature (excepting gold and copper) and they tend, under the influence of the weather, waters and similar corrosive exposure, to revert back to a non-metallic state. It is convenient for reasons of cost, strength and ease of working to manufacture metallic articles without too much regard to their external appearance or to their behavior against corrosion, and then to deal with these purely surface characteristics by a subsequent treatment, which may therefore be designed in general as surface treatment of metals. Since iron and steel are by far the most commonly used metals, and also unfortunately among the most prone to rust, decay and corrosion, they figure very largely, but not by any means exclusively, in the general subject of the surface treatment of metals.

The main purpose of the surface treatment of metals are predominantly twofold, with emphasis on one or the other to different degrees in different cases, viz:

1. To improve the appearance
2. To improve resistance to corrosion, tarnish or staining under the conditions of use which are foreseen.

There are other objectives, each important in its own sphere, but these together are only of minor importance compared with the above main purposes. Examples of these minor objectives are to provide resistance to scaling by heat, to facilitate other subsequent surface treatments or to change the surface hardness or other surface properties, or even to change the overall dimension.

The surface treatment of metal almost invariably consist of applying a coating of some kind to the metal, and thus providing an external skin which can be selected solely for its appearance and corrosion resistance. If such a coating can be applied without any discontinuities, and if it is firmly adherent to the behavior of the coating. However, such external coatings must inevitable be thin, unless the whole character of the article is changed. In the normal course of use these coatings therefore entail the risk of penetration through to the basis metal by mechanical damage or flexing; the effect of the small areas of basis metal thus exposed can't be ignored, not only because of the local corrosion of the exposed metal, but because of the risk that the remainder of the coating may be undermined and thrown off.

In the choice of surface treatment for any particular metallic article, many factors must be considered, such as cost, type of corrosive environment to be withstood, and compatibility with special materials such as foodstuffs or washing materials. In very many cases an additional factor of continuing good appearance must be considered. Metal surfaces, especially satisfying appearance. It is obviously appropriate to provide a metallic article with a metallic coating of higher corrosion resistance and more attractive appearance, so that the whole system is a unity. But very few metallic coatings are absolutely resistant to corrosive influences, and these few are the most expensive. In particular, metallic coatings are not completely resistant to some of the many chemical substances now involved in everyday life, such as washing chemicals, fruit acids and many foodstuffs. Nor do they provide much opportunity to introduce colors, including white, which may be desired to conform to decorative schemes or fashions. Thus non-metallic coatings, such as vitreous enamels, paint and lacquer, are applied to metallic articles for decorative as well as protective reasons.

Before any surface coating can be applied it is essential that a clean, sound surface must be provided on the article to be coated. In particular, scale and oxide, grease and dirt remaining from the manufacturing operations, must be removed; the surface usually must be smoothed or even polished. It may also need to be prepared physically or chemically to ensure satisfactory adhesion of the coating. These preparatory treatments are an integral part of the surface treatment process, and obviously have to be applied at the end of the main manufacturing process. For this reason these cleansing, protective and preliminary decorative treatments are almost invariably applied as the final stage of the manufacturing process of a metallic articles, to such an extent that the processes are often collectively referred to under the term 'metal finishing'. In the cases of hot dipping tinning and hot dipping galvanizing of sheet steel the protective films are applied to the semi-fabricated material; here, however, the subsequent process are limited to cutting, bending and joining; moreover, decorative effects are subordinate to economics.

Metal with Plastic Coating

2008-05-24T06:56:00.000-07:00

Protecting metal from corrode effect have used with many way, using anodizing for aluminum metal, electroplating for steel and other metal coated with other stabilize metal and endure from corrosion.

Metal coated with plastic may well be the constructional materials of the future. Already large quantities of strip steel are laminated with a performed plastic film, using adhesives. One such product is marketed under the trade name Stelvitite. Plastic is extruded around a metal core for curtain rails. These processes, however, must be considered as methods of manufacture rather than of surface treatment.

Plastics do not melt to a limpid on heating and cannot be applied in a liquid form. As their name implies, on heating they become plastic and sticky. A very successful method of coating metal, especially wire work goods, e.g. racks and light structures, chain-link fencing and grills, with polyvinyl chloride or similar thermoplastic material is as follows. The plastic is finely powdered and is placed is a deep box; a perforated bottom plate permits air to be blown up through the plastic powder. This maintains it in a mobile or fluidized condition. The metal articles are preheated to about 150oC and the plunged into the seething mass of powder. This particles which touch the hot metal become softened and sticky; they adhere to it. After withdrawal the metal part is re-heated for a short time to allow the individual plastic particles to coalesce and draw up to a smooth coating by surface-tension forces. The resultant coating is about 0.005 in thick.

Alternatively, colloidal dispersions of partially polymerized in plasticizer, or of completely polymerized thermoplastic material in the minimum of water, consisting of very thick creamy liquids may be used for coating metal objects by dipping. These are called plastisols or organosols. The solidification of the plastic is accomplished by subsequent heating.

Copper Plating on Zinc

2008-05-20T03:23:00.000-07:00

A copper strike applied in a copper cyanide solution is normally the first plating step for all die castings electroplated with nickel and chromium. The thickness of the strike should be at least 1.0 µm for castings that will be plated with nickel after copper striking. A thickness of 3 to 4 µm is recommended for die castings that will be subsequently electroplated with bright, leveling copper in copper sulfate-sulfuric acid solutions. The copper strike is a critical step in plating zinc die castings that is sometimes inadequately controlled.

Solutions containing 20 to 45 g/l of copper cyanide, 10 to 20 g/l of free sodium cyanide, and 15 to 75 g/l of sodium carbonate are customary for strike solutions. A solution containing 20 to 27 g/l of copper cyanide and 10 to 15 g/l of free sodium cyanide is relatively popular. A few formulations include the molecular equivalents of potassium cyanide in place of sodium cyanide. Other contain 15 to 25 g/l sodium hydroxide or 30 to 45 g/l of sodium potassium tartrate in addition to the major constituents. Agent such as sodium hydrosulfite that reduce hexavalent chromium ions are sometimes added to prevent the reduction in efficiency caused by only a few parts per million of Cr(VI). Periodic additions of such as reducing agent may be required, especially in solutions containing tartrate ions. Cathode current densities range from 2.3 to 5.5 A/dm2 and solution temperatures from 50 to 57oC should be avoided, or there will be danger of blister formation.

The average cathode current density dust be balanced with the free sodium cyanide and the temperature of the solution, or burning might occur at edges and other high current density areas. With an average cathode current density of 2.3 A/dm2 the cathode current efficiency varies from 30 to 60% for strike plating, depending on the free sodium cyanide concentration. Although a low concentration (10-15 g/l) favor a high efficiency, throwing power is reduced, so that recesses receive thin deposits that are unsatisfactory for protecting the zinc from chemical attack during nickel plating in acid solution. Ultrasonic agitation increases the cathode efficiency, the covering power in recessed areas, and the density of the copper deposit.

High purity copper anodes are recommended for copper cyanide strike solutions. Solutions should be continuously filtered to avoid the inclusion of small particles that nucleate nodules during subsequent plating operations. Anode bagging is sometimes adopted for ensuring smooth copper strike deposits. In this connection, the control of the free cyanide concentration is important. A relatively high free cyanide concentration is also to maintain satisfactory anode dissolution in solution operated at 50 to 57oC.

Alkaline Cleaning

2008-05-15T07:46:00.000-07:00

Emulsion cleaning in agitated emulsions of soap, kerosene, or other hydrocarbon and water is effective for removing non saponifiable oil and grease when heated to at least 54oC, or up to 70oC. Time cycles range from 2 to 4 min, as a rule. Emulsion spraying is sometimes adopted for other surface indentations. Thus power-spray equipment might include both emulsion and alkaline washing. Emulsion cleaning must be followed by alkaline soak cleaning or thorough water spray rinsing.

Alkaline soak cleaning is frequently used in place of solvent degreasing, power-spray alkaline washing, or emulsion cleaning especially for unbuffed castings. A typical soak cleaning solution contains 25 to 35 g/l of sodium tripolyphosphate and 2 to 3 g/l of surface-active agents. To avoid prolonged contact with the alkaline solution, cleaning periods usually are restricted to 1 or 2 min. Alkaline cleaners with a high pH (> 10.5) preferentially attack the aluminum phase of zinc alloys. Aluminum phase corrosion coinciding with subsurface porosity induces cavities that tend to entrap corrosive solution which subsequently causes blistering when the solution entrapped under the electroplate reacts with the zinc alloy to produce hydrogen gas. Loosely adherent gelatinous aluminum compounds formed on the surface of the aluminum rich phase have also been cited as a cause for blistering. Operating temperatures for cleaning zinc die castings are 70 to 82oC. Ultrasonic agitation will facilitate the softening and removal of buffing compounds from buffed surfaces. A soak and spray rinse, preferebly with warm water, is recommended after alkaline soak cleaning to remove the bulk of the alkali, surfactant, and soil before electrolytic alkaline cleaning.

After precleaning, anodic cleaning is usually selected for zinc alloy in preference to cathode cleaning. Anode current density usually ranges from about 1.6 to 3.2 A/dm2. Time cycles vary from 25 to 45 sec. A typical solution contains 30 to 40 g/l of mixed alkali such as sodium tripolyphosphate and sodium metasilicate, 0.5 g/l of surfactant, and not more than 0.5 g/l sodium hydroxide, and is heated to 70 to 82oC. Solution with lower concentration of alkaline compounds or lower temperatures are adopted if time cycles must be prolonged for more than 45 sec, or if the transfer time from the electro-cleaner to the rinse is more than about 30 sec.
A cycle including a hot water overflow rinse, a cold water overflow rinse, and water spray rinse is recommended after alkaline electro cleaning. The overflow rinses should be agitated with air to dilute as much as possible the concentration of alkaline solution in blind holes, groove, and other surface indentations and cavities.

Cleaning of Plating on Zinc

2008-05-13T09:14:00.000-07:00

Cleaning cycles include three vital steps:

1. The bulk oils, grease, soil, or buffing compound must be removed by pre-cleaning because prolonged contact in the subsequent alkaline electro-cleaner will cause etching or smutting.

2. To ensure the good electroplate adhesion, electro-cleaning must be used to complete the removal of oil, grease, and soil.

3. An acid dip must follow alkaline cleaning to remove zinc oxides and hydroxides and any alkaline compounds carried over from the electro-cleaning operation.

Die castings are pre-cleaned by:

1. Solvent Degreasing

2. Power Spray alkaline washing

3. Emulsion cleaning, or

4. Alkaline soak cleaning.

Buffed die casting should be pre-cleaned as soon as possible after buffing, preferably within 24 four hours, before the compound hardened and becomes difficulty to remove by conventional cleaning.

Solvent degreasing utilizes trichloroethylene or perchloroethylene solvent in facility equipped with heating and condensing equipment. Die castings usually are sequentially immersed in the heated solvent, dipped in cold solvent, and suspended in the heated vapors. Solvent spraying also is included in the cycle if buffing compound has been hardened on the die cast surfaces. The solvent should be inhibited to prevent the formation of hydrochloric acid caused by decomposition. The cost of the chlorinated solvents has encourage the use of alternative pre-cleaning methods. However, a diphase system consisting of a layer of solvent such as trichloroethylene, perchloroethylene, or methylene chloride and an upper layer of water is sometimes adopted to reduce costs associated with the evaporation of solvent. Diphase cleaning is generally followed by power-spray washing.

Power spray alkaline washing is accomplished with conveyorized units usually equipped with washing, draining, rinsing and draining sections and is the most popular method for pre-cleaning. Solution heated to about 80 ^oC is sprayed with a pressure of 1.8 to 2.1 kg/cm² through nozzles on 20 to 30 cm centers in the washing area.

Rough of Defective Surface

2008-05-10T23:06:00.000-07:00

Rough of defective surface are smoothed by mechanical polishing on rotating wheels or continuous, abrasive coated belts, spin finishing, or vibratory finishing. Fissures, skin blisters, skin blisters, and other defects with a depth of 25 to 50 µm can usually be erased with these metal removal methods, when conditions are adopted to reach the bottom of the defects. Deeper defects are infrequent.

Rough or defective surface are often polished on wheels or belts, while parting lines are polished by the same operator. If polishing is mechanized to advance die castings attached to a conveyor through successive belts or wheels to polish different areas, a manual operation might be required later to complete the smoothing of parting lines if they are too curvy. The finish range from 0.2 to 0.4 µm, depending on the abrasive and the pressure.

Smoothing by spinning in abrasives is accomplished by attaching die castings to spindles or drums rotated with a peripheral speed of about 600 m/min in a slurry of abrasive material such as ground corn cobs or nut shells mixed from 5 to 10 min and the finish from 0.1 to 0.2 µm, depending on the abrasive.

Spin polishing, like wheel polishing, usually induces scratches with directional characteristics, which must subsequently by smoothed by buffing. Any subsurface porosity only 25 to 50 µm below the surface, which in encountered with some casting, usually is exposed by wheel polishing or spin polishing. Depending on the size of these pores, relatively thick leveling copper is required to avoid defective electroplates when subsurface pores are exposed.

Vibrating tubs loaded with plastic media, such as polyurethane impregnated with an abrasive such as aluminum oxide, smooth the surfaces of die castings in 4 hr or less when frequencies are in the range of 1600 to 3000 cycles/min and amplitudes are adjusted to 0.8 to 6.4 mm. Vibratory machines produced a finish of 0.15 to 0.20 µm. Media and zinc parts are usually loaded in a ratio of 5:1 or 6:1. Surface gauges might occurs with a smaller ratio.

Die casting can be buffed to produce a mirror-like finish suitable for plating with conventional solutions. Buffing is omitted, however, for die castings which have good cast surfaces or which have been uniformly polished to a finish of a 0.15 to 0.2 µm. If solution with good leveling power are available for copper and nickel plating.