Another Cadmium Problem

What is causing black spots to appear on the surface of a steel part that is cadmium-plated and then treated with a chemical conversion coating?


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Q. We have an ongoing issue with a steel part that is cadmium-plated and then treated with a chemical conversion coating. After a period of time, black spots start to appear on the surface. What is causing this? –M.C.

A. As mentioned above, there are two probable causes for this problem: inadequate rinsing and a porous cadmium deposit. Your final rinse procedure following the plating step should be alternating cold and warm rinses, ending with a warm rinse.
Check your cyanide concentration and make changes to bring the concentration up to specifications.

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