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Polishing and anodizing of casted aluminum




2004

We are looking at the

What kind of casted aluminium alloy(s) will give the best effect when polishing? Are there any safe chemicals that could be used to improve the polishing result.

We would like to anodize die casted and gravity casted aluminium components. What kind of alloys are preferred? Any limitations compared to extruded aluminium parts?

Thomas Olsson
Engineer - Stockholm, Stockholm, Sweden



You only anodize aluminum. Die Cast is loaded with silicon and copper. You do not anodize silicon and copper. Stay out of the alkaline etch which increases the area of silicon and copper on the surface and decreases the area of aluminum on the surface. Use a cook book formulation of Nitric Acid and Ammonium Bifluoride (50% Nitric + 1 Pound/gallon Ammonium Bifluoride) which will decrease the area of silicon on the surface and increase the area of aluminum on the surface. Be aware that thin walls in die cast cool faster than thick walls and therefore have more silicon in the surface.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
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2004


Thank you for your answer. This means that if we use die casting/gravity casting of an almost pure aluminum alloy there is no problem to anodize. The problem will instead be the casting process of almost pure aluminum.

Thomas Olsson
- Stockholm, Sweden
2004



dear olsson, never be afraid of casting. Select lowest Si and Cu content alloy.and follow the sequences below.

1- mass or vibrating polishing. First abrasive and then shot peening. Use appropriate media for cleaning .
2- immediately anodize with low CD and limited time in order not anodize other element except aluminum.
3-follow dyeing or E-Ccoloring and sealing at last.

hadi khosravi
- tehran iran
2004




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