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Zinc plating and Cr6

2006

We are a speaker manufacturing company trying to become RoHS compliant. In doing research for plating issues we have a question that we are trying to get answered.

What does black zinc plating consist of regarding Cr6? I would appreciate any help you could lend into our gaining insight into this question?

Thank You,

Oliver Gambrell
Speaker manufacturing - Chester, Pennsylvania, USA

Black zinc plating involves two steps: electroplating with zinc, which should be RoHS compliant without difficulty, followed by black chromate conversion coating. The chemical meaning of 'chromate' is 'Cr03', implying hexavalent chromium--so traditionally chromating is not RoHS compliant. In recent years there has been a been a strong push towards trivalent chromates, which are RoHS complaint because the chromium is in trivalent form rather than hexavalent form. Some say good trivalent black chromates are available, some say they are unavailable, but if you are to stay with black zinc you must specify that RoHS compliant black chromate must be used.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

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