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Plating copper and /or nickel on low temp lead eutectics

We are trying to plate nickel and copper onto a lead bismuth alloy. We plate nickel with a sulfamate solution at 55 C, and we plate copper using a sulfuric acid, copper sulphate ⇦this on eBay or Amazon [affil links] solution at room temperature. The deposits don't look too good. We plate nickel and copper all the time on other metals (stainless for example) without any trouble. Is there something regarding the lead bismuth (which has a low melting point (155 F). Anybody have any experience plating low melting point lead eutectics?

Kevin W. Kelly
Mezzo Systems - Baton Rouge, Louisiana
2003

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Lead and lead alloys are not the easiest of systems to plate onto. Make sure your pretreatment is suitable for such alloys. You do not mention the surface finish of your alloy; if it is not very good, then you will not get a good final surface finish. With such gaps in information, I would suggest you use a preplate of cyanide copper followed by a good leveling copper, followed by the nickel. Obviously keep all processing temperatures as low as possible. Sulphamate nickel can be operated as low as 40 °C, but it is essential to remember that the maximum current density will be reduced by a reduction in operating temperature. I would suggest a ccd of no more than 25ASF and preferably lower.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003