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topic 652

Nickel-Free plating of Tin-based costume jewelry

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(1996)

Is anyone successfully gold plating tin-based spin-cast costume jewelry without nickel? We are plating cyanide copper, acid copper, palladium, gold. Parts look good out of the acid copper, but we cannot get good coverage of palladium over the copper in areas where the castings are porous. We have tried two different palladium plating processes with the same result. It appears that there is a galvanic effect which inhibits deposition of copper into the pores and palladium onto the copper around the pores. We have perfect results using the same method on brass-based jewelry. Any suggestions?

Graham Hammond
(1996)

Graham, In case you do not get a good answer from anyone, I think that this subject was covered a couple of years ago in Larry Durney's column in Product Finishing. Larry retired recently. Marty Borruso writes the column Finishers Think Tank in the Plating and Surface Finishing magazine from AESF and might be able to help. I was an engineering metals plater but from what I have read, porosity is hard to keep out of spin casting. I assume that hand polishing is not cost effective and that shot tumbling is too aggressive . I assume that you can not cover the porosity with a longer strike and acid copper plate. My personal guess is that the porosity (pits) are not being cleaned or activated.

James Watts
- Navarre, Florida


(1996)

Dear Graham, We are successfully casting and plating nickel-free but with a tin barrier before gold.Being a model-maker,mold-maker by trade I can assure you,you can get rid of porosity.It is in all how you gate the mold and the type of metal that you use and the temp.When we don't polish, we use 36% metal,vibe in aluminum oxide for 4-6 hours, then thru the plating process. David

David Guleserian
- Rhode Island



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