Discolored Gold Plate

My gold plating is discoloring. Do you have any suggestions as to what might be causing this problem?


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Q. My gold plating is discoloring. Sometimes the discoloration shows up immediately after plating; in other cases, it appears after the parts are packaged and shipped to my customer. Do you have any suggestions as to what might be causing this problem? A. R.

 

A. There are a number of possible reasons why your gold plate discolors. For example, if gold is applied directly to copper, the copper will discolor the gold layer when it migrates through the gold layer. This type of problem is easily solved by plating a barrier layer on the copper prior to plating with gold. Nickel is often used as a barrier layer.

Gold may also become discolored if the plating solution is contaminated with other metals. Sometimes this is a desired effect, particularly in jewelry and other decorative applications.

Another cause of discoloration is if the gold layer is too thin and porous. A thin, porous layer of gold plated directly over silver can discolor over time. The silver will migrate through the pores in the gold and form silver sulfide on the surface.

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