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Cadmium Plating is flaking

We are working on a switch for use in military applications. Our bushing is brass, followed by a copper strike, cadmium plated, with clear chromate coating. We have a process in which we are "rolling" the edges over on the top of the bushing to hold the switch together. When this rolling is done, we are getting "flakes" of plating that are coming off. We trying to get a lower amount of plating, but that was no help. We have contacted the plater and he is going to try a thicker copper strike. Any ideas of why this is happening/how to fix the problem? My expertise is not in this field so any help would be appreciated.

Thanks,

Chris Renis
switch manufacturing - Chicago, Illinois
2003

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The brass is probably "leaded" to facilitate easy machining. Copper Cyanide will not adhere to lead very well. Most likely the plater is activating (removing oxides) from the brass by dipping in Hydrochloric Acid or Sulfuric Acid both of which form an insoluble salt with smeared lead on the surface. When he copper cyanide strikes and later builds cadmium thickness over the insoluble salt then the adhesion fails and you see peeling.

Tell your plater to remove oxides in 50% Fluoboric Acid and to Copper Strike in a Copper Fluoborate solution. The copper will then adhere to the machine smeared lead. You can see the lead with a 10X magnifying glass.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003

Thank you for a prompt answer to my query. We will take this to our supplier. Just for my clarification, the lead is smeared on machining, and stays when plating? The problem occurs when the salt stands between the brass/lead and the copper? Thank you again for your assistance.

Chris Renis
switch manufacturing - Chicago, Illinois
2003