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-----Alodining or chromic acid anodizing is the same?
I am a new comer to finishing.com. In fact, its my second day running to the Site. My question is: Are Alodining and chromic acid anodizing the same process? I am new also to chromic acid anodizing. I found this site very interesting and informative. I've already posted a question at 30613, which is to 'publish' soon.
Sohail ur RahmanStudent - Islamabad, Capital Territory, Pakistan
2004
Alodine is a Henkel trade name for chemicals used in
MIL-C-5541 chromate conversion coating of aluminum. Chromate conversion coating does not involve electricity, and it leaves the aluminum conductive, with a very thin film of reaction products.
Anodizing is a process which uses electricity to build a non-conductive aluminum oxide film on aluminum. Sulfuric acid anodizing is the most common type, but chromic acid anodizing results in a much thinner disturbed layer than sulfuric acid anodizing (which means less loss of fatigue strength on critical components); and if a pocket of anodizing solution is inadvertently left unrinsed, the chromic acid will not attack the aluminum like sulfuric acid would.
In general, both chromate conversion coating and chromic acid anodizing are corrosion resistant, but the anodizing is more so. And which to use will also depend on whether you want the aluminum to be electrically conductive or not.
Ted Mooney, P.E.
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2004
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