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Fine etch for aluminium

I am a metal design student in my final year, the problem I need help with is etching Aluminium. I have been Given a formula that gives a very coarse etch, when I anodize this the etched areas are very grey in colour but the un-etched parts are fine. The solution is a mix of Hydrochloric acid (2 ounces) with copper sulphate(1/2 teaspoon) and distilled water(8ounces), this solution is very quick, it will eat through 2 mil sheet in 5mins. Would diluting the soultion work or does anybody know another soultion that would give a finer etch?

Anthony O'Connor
- Dublin, Ireland

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Sodium hydroxide would work better. But the problem may be alloying materials left behind when you dissolve the aluminum--in which case you need a desmut step.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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