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Does clear zinc Dichromate exist?

Hello, I am Jason Pahl from Coleman, Michigan. We are a packaging supplier to the automotive and they have asked us to supply them with a Clear Zinc Dichromate nut and bolt. From my understanding, there isn't such an item. Am I correct in the assumption. Thanks for the help.

Jason Pahl
buyer - Coleman, Michigan
June 3, 2009

June 4, 2009

Hi, Jason. The problem is probably not so much whether this thing exists or not, but that our industry has become rather casual and inaccurate in the terminology :-)

To a chemist, dichromate is Cr2O7 and chromate is CrO3. In both cases the oxidation state of the chrome is hexavalent. But we now call RoHS-compatible coatings 'trivalent chromate', which I believe is actually an oxymoron. Common usage for some people has also been to call 'dark' chromates "dichromate". They'll call the tank with the clearer solution 'chromate' and the one with the amber or orangeish one "dichromate" -- perhaps based on the fact that chromate ions are yellow and dichromate ions are orange.

What you probably want to supply is zinc plating with a RoHS-compatible clear trivalent zinc conversion coating; but you need to get the spec changed. Good luck.

Regards,

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

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