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Gold-Copper Alloy Plating--How to control the relative deposition?

I'm interested in a decorative plating of a thin decorative coating of shakudo or shibuichi; shakudo is a 4% Au 96%Cu alloy, shibuichi is 30%Ag70%Cu. These are of great interest as they produce beautiful and unique colors when patinated. Plating is a method of interest due to the difficulty in obtaining the alloy commercially (what is essentially 1K gold falls well below purity restrictions) and of course the decorative potential and cost benefits of electroplating.

Is it simply a matter of mixing a solution in the desired ratio (e.g. 9.6g/L copper sulphate, 0.4 g/L gold cyanide) and hoping for the best? How must one take into account the metals' relative deposition rates when timing for coating thickness or renewing the bath? I might add there is some leeway here: shakudo can be between 3-5%Au, while shibuichi varies in silver content from 30-40%

Thanks!

Benjamin

Benjamin Shirley-Quirk
Designer/Maker/Blacksmith - Hereford, United Kingdom
February 2, 2009

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Hi, Benjamin. I'd suggest that you contact the major suppliers of precious metal plating processes and see if they have a solution for you. Because of the difference in electrochemical potentials, you generally cannot plate an alloy from a simple mixture of plating salts; rather, you need a plating solution that complexes the more noble metal.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 2, 2009