June 11, 2010

Solution Type for Electropolishing

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.