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Nickel sulphamate questions for wiping contact surface

2002

I am having a plating process performed on CDA260 brass using a nickel sulphamate solution (historic selection) which is then used in a low voltage (<24v dc) contact wiping application. I have two questions...

1. What is the best economical method of nickel plating that will ensure good adhesion of the nickel to the brass (have had issues with poor adhesion) - suggestions of acid washing or thin flash pre-plating processes have been suggested?

2. What can you expect as a resistivity of the finished plating? Is this a direct function of the Nickel purity used?

Thanks in advance, all the best,

Brian Iman
- Sydney, NSW, Australia

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2002

1. Use the formulation by Barrett for Nickel Sulfamate Strike, unless CDA260 is lead containing, in which case strike in a Nickel Fluoborate formulation. I can interpret the Barrett strike in non-commercial terms if you desire.

2. Nickel oxidizes slowly at room temperature. probably not fast enough to impede 24 volts but certainly fast enough to insulate from 1 volt(I have actually experienced this per se'), so as time goes on and the oxide builds, first 1 volt will not pass, then 2 volts, and on up to some number that is a guess on my part.

The purer the nickel, the faster it will oxidize. Also some organics out-gas from surrounding plastics (and palladium)and this will catalyse the formation of the oxide.

Best bet, depending on really what voltage you must transfer, is to gold plate to a thickness of 0.0001 inches over the nickel. A cobalt hardened gold would be first choice.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

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