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Europe to restrict hexavalent chrome

With hexavalent chrome plated part being restricted from use in Europe would bright zinc plate be alternative for zinc dichromated parts? Is it true that triavalent chrome is present in bright zinc plated parts and hexavalent is present in the zinc dichromated parts? If so, then the bright zinc plated parts would be able to be used in products being sold in Europe? What problems could arise from the use of zinc plate and would a plating thickness of .003-.005 be adequate?

Barton Rowe
- Bryan, Ohio
2003

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Dichromate is theoretically Cr2O7 while chromate is theoretically CrO3. Both are hexavalent chromium anyway. But these terms are used improperly all the time including by everyone in the industry including me. Some people call the yellow chromate finishes 'dichromate' and the clear finishes 'chromate', but again this is incorrect and misleading too.

Unprotected zinc plating will form white rust quite quickly, so almost all zinc plating (including bright zinc) has a chromate topcoat of some sort. What you really need to do is to specify a trivalent chromate coating free of hexavalent chromium, and then you will be in compliance with the EU-EOL standards.

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

Hello Barton,

Well yes if the parts been di-chromated (or chromated) it will have hex chromium on it. As for bright zinc, it must have some sort of surface treatment - otherwise it'd finger mark very easily. Could be tri chromium, could be a lot of things, chromate even. Ask your supplier. As to how thick it should be, I don't work in inches, so I think .003-.005 is about 100 micrometers, which sounds like plenty to me. However you'd be better taking advice from someone you can sue if this turns out not to be the case.

I'm sorry I haven't been much help but you need a more detailed question and a professional to answer it.

Ian Brooke
university - Glasgow, Scotland
2003