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Bubbles after black chromium

2003

Hello,

I am responsible for operation of a chromium plating plant. One of the finishings that I do is black chromium. I plate only brass parts that come into the plant right after sand blasting. The parts are well degreased in Ultrasonic as well in electrolytic degreasers, then are activated before they go to Nickel plating. After Nickel I can not find any problem. Then they go to the black chromium plating. It happens that after chromium plating the coating has bubbles and if I strip the chromium I can see that the bubbles are also on the nickel layer. I think that reason of my problem must be on the adhesion of the nickel to the brass. I already tried to improve the activation of the brass before the nickel but I had no good results. I would appreciate if someone can give me some ideas about that.

Best regards,

Pedro Miguel Oliveira
Surface Engineering - Porto, Portugal

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It is common for brass to include lead for easy machineability. You may need to use a lead-free brass, or a proprietary activator containing a fluoride salt.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003