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Letter 3005
Plating White Metal
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We plate and restore small antique items. Recently, we had the
occassion to replate an old lamp with a white metal base. We
attempted to plate with non-cyanide silver, acid electroless nickel
and alkaline electroless nickel. All were unsuccessful and produced a
lot of smut and some plating of exposed glass.What is the proper
method for plating white metal? Do we need a preliminary copper
strike or other special procedure? Any suggestions are greatly
appreciated. Thanks.
Jay Alford
- Hanahan,SC
June 15 -
Jay, You are on the right track with the copper strike idea. The
problem you are encountering is that your base metal is primarily
zinc and wants to dissolve in the plating baths you have tried thus
far. Start by activating the part in 0.25% sulfuric acid, rinse well
and then strike in a copper cyanide strike followed by a cyanide
copper plate. The part can then be built up with the final deposits
you require. If you don't have cyanide copper, you may be able to use
a sulfamate nickel but the hydrogen overvoltage may be too great if
your pH in the sulfamate tank is too low.
Keith Wicklund, CEF-SE
avionics - Minneapolis, Minnesota
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