Cad plating getting a "mottled" appearance. Why?
I'm doing some small-scale cad plating at home. I'm having problems with getting a "mottled" appearance. What am I doing wrong?
- San Francisco, California, USA
The answer to your question of "what am I doing wrong" is "cad plating at home" :-)
Cadmium is a bioaccumulative poison like lead and mercury, with very similar effects on development. For that reason, it is the law that every worker doing cadmium plating must have their blood periodically tested for cadmium by a physician.
Also, when your rinsewater becomes contaminated, if the city finds you disposing of it in the sewer system, you may find yourself in more trouble than you could possibly believe. Cities periodically sample the sewers for cadmium to track it to its source because of its tremendous and cumulative toxicity and the money it costs them if they must dispose of their sludge in a hazardous waste landfill because of cadmium contamination.
Then there is the question of what you will do with the cadmium plated parts. Only the most critical military and aerospace parts are plated with cadmium these days in the USA, and it is completely illegal in many countries. If your parts somehow eventually found themselves in food service, say on a backyard barbeque grill, it might be dangerous.
This finally brings us to your "mottled appearance" problem, and why you won't find help. No supplier anywhere is going to assist you in troubleshooting your problem because of the liability. I am having trouble imagining where you were able to buy cadmium anodes and cadmium plating solution as I thought that no supplier has shipped cadmium chemicals to a residential address for many years. Unfortunately, you also have a major disposal problem as it may cost you thousands of dollars to dispose of even a relatively small cadmium plating bath.
Ted Mooney, P.E.
Pine Beach, New Jersey
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