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Anodizing of Brass

I'm having a bit of a problem with a customer over the brass anodizing business. The best response (which means the one I agree with) says no anodizing of brass, but mentions aluminum, titanium, and magnesium as anodizable materials. I know that you can anodize aluminum, and have no idea about magnesium. I was under the impression that titanium does not respond to the anodizing process, and that is why high volume anodizing racks are usually made from titanium. Can someone enlighten me?

John Cooper
- Rose Hill, North Carolina
August 11, 2008

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August 12, 2008

Hi, John. I'm pretty confused here. Is the issue anodizing of brass or anodizing of titanium?

Titanium can be anodized with a thin light-defracting coating for jewelry use or with a heavy coating for anti-gall applications. But when titanium racks are used in aluminum anodizing solution, the intention is not to anodize the racks, that's just a consequence of its use. The solution used, 10 percent sulfuric acid, generates a very thin anodization layer on the titanium, thin enough that it is still conductive enough to use for a rack.

Brass is an alloy of copper and zinc. Copper cannot be usefully anodized. Zinc can be anodized but only at very high voltages (hundreds of volts). My understanding is that brass cannot be anodized. Letter 1785 alludes to an historical oxidized finish for brass without making any claim, though, that electricity has anything to do with it.

Regards,

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