Aluminum Anodizing Experiment

To try for aluminum anodizing use sulfuric acid as the electrolyte, Rit brand dye and the boiling water seal method. Picked up a five gallon container of battery acid, which is about 50/50 sulfuric acid and water mix from an auto parts store. The Rit brad dye is available from pretty much any grocery store. A 10 gallon Rubbermaid plastic tub was purchased for the anodizing tank as well.

Safety:
Always wear safety glasses, gloves and an apron or really old clothes. Both the lye and acid used here could be lethal, and may cause serious damage to people and property. Keep a good supply of baking soda solution to neutralize acid spills, and have a large supply of fresh water available if you spill on yourself, you better provide a water spray like shower in your bathroom.

For trial used an extra piece of aluminum tube 6061. The aluminum was washed with soap and water, rinsed, then immersed in a bath of 3 tablespoons lye in one gallon of water. All of the water used in this first batch was distilled water. The caustic bath will etch, or eat into the surface of the aluminum to clean the part. You'll know the surface is perfectly clean when the water sheets over the surface, as opposed to forming drops, or areas of wet and dry spots on the surface. Two or three minutes and this part was etched nicely.

Picked up 5 gallons of sulfuric acid at an auto parts store for the electrolyte. You can use small battery charger to supply electrical. The tank is a 10 gallon Rubbermaid tub. Initially added three gallons of distilled water to the tub, then added one gallon of battery acid. Remember: Always Add Acid to water, don’t add water to Acid it will sprayed.

Two aluminum (or lead) plates are used as cathodes and hook up the negative lead of the battery charger. The part to be anodized (anode) is hooked up with aluminum wire to the battery charger positive lead. The part is suspended off the bottom by the wire. Make sure you vent the gas from the process; a good respirator wouldn't hurt either.

Power was turned on and charger set to 2 amps at first. Then increased the setting to 10 amps after a few minutes. Notice the white "fog" or bubbles coming off the cathodes, that indicates current is flowing. The part will emit a few small bubbles too, but most of it is coming from the cathode plates. At the charger 2 amp setting the charger was drawing 2.5 amps, when increased the power to the 10 amp setting, the meter indicated a draw of about 3.5 amps.

While the part was in the acid bath you can mixed up a batch of dye, 4 tablespoons in 1/2 gallon of distilled water. The part was immersed in the dye at room temperature, then the temperature slowly increased to 100 oF. A pot of distilled water was started boiling for the final sealing process. After 15 minutes the part was removed from the dye, rinsed in fresh water, then placed in the boiling water for 30 minutes to seal the surface.

After 30 minutes in the boiling water, the now anodized part was removed. It seems to have worked very well with a navy blue dye, and it came out very dark.

Buffing and Polishing

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

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:

• Formulation
• Electropolishing of Aluminum
• Operating Condition of Electroplating
• Fluoboric Acid Solution
• Alkaline Solution
• Phosphoric Sulfuric Chromic Acid Solution
• Anodizing in Oxalic Acid
• Sealing Oxide Film
• Anodizing Practice
• Polishing
• Jigging
• Anodizing
• Anodizing Plant
• Decorative Finishing
• Polishing After Anodize
• Chemical Composition
• Anodizing for Photographic Reproduction
• Anodizing Result
• Aluminum Definition
• Aluminum Source
• Miscellaneous Product of Aluminum

Aluminum Anodizing Without Sulfuric Acid

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.