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Peroxide-sulfuric bright-dip for brass wire becomes saturated with copper

My name is David and I am a Manufacturing Manager. We are trying to launch a new product line of brass (85/15) stamped parts with a bright, mirror like gold finish. We are currently running a continuous process with 50% Hydrogen Peroxide and 98%Sulfuric Acid. The problem we are having is that, as we run, the copper is building up in the bath and we lose our mirror gold finish. Is there another chemical process to achieve the mirror gold finish which will not allow the copper from the brass to reduce the effectiveness of the bath and is environmentally friendly.

David Spitler
R&D - Oxford, North Carolina
April 7, 2010

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April 8, 2010

Hi, David. When the sulfuric-peroxide process was originally conceived, it was meant to be an equilibrium process whereby the copper was dissolved in the hot bright-dip tank, and the solution then flowed to a cooling chamber and crystallizer tank where copper sulphate ⇦this on eBay or Amazon [affil links] crystals would be continuously removed. I was involved in such installations many years ago but I don't know if that is a common way to employ sulfuric-peroxide solutions anymore. Contact your chemical supplier about the feasibility of such a continuous crystallization option.

Regards,

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

I like the idea of using a cooling chamber and a crystallizer tank, but our suppliers are not familiar with this technology. Can anyone recommend a supplier? If not we are open to different chemistries. Any help would be greatly appreciated.

David Spitler
- Oxford, North Carolina, USA
May 3, 2010

Back when I was involved, Dart Industries owned Electrochemicals of Maple Plain, MN (a supplier of sulfuric-peroxide etches) and Lancy Laboratories (a designer and supplier of waste reduction and treatment systems, who supplied the regeneration equipment). These systems were offered due to the sister-company relationship. Lancy has since become part of Alcoa, then part of US Filter, and may no longer be involved. Electrochemicals still offers the sulfuric-peroxide etch, and could be a starting point.

It is not finishing.com's policy to recommend switching suppliers, I'm simply telling you what I know about regeneration of this solution. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 3, 2010

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Try a search on "sulfuric peroxide etch crystallizers"; I found one supplier there with some additional process details for the inexperienced.

James Totter, CEF
- Tallahassee, Florida
May 6, 2010