Metal finishing Q&As since 1989

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Is Color a Distinction between Trivalent and Hexavalent?

I'm a Sales Rep. for a company listed on the stock exchange under symbol "B". I would like to get info. if Zinc Silver color Dichromate can be considered as Hexavalent and Yellow Dichromate a Trivalent? Or is there a color distinction between Tri and Hex. If Appreciate your response and knowledge sharing.

Elmer Hufana
- Oshawa
October 26, 2009

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Hi, Elmer. No, unfortunately it isn't.

In the "old days", say more than 5 years ago, the yellow color came from the hexavalent chrome, so dark yellow finishes had much more hexavalent chrome than clear or blue finishes.

But today, the old clear hexavalent chromates still have too much hex to be RoHS compliant, while the trivalents may be yellow naturally or via dye -- so color just doesn't say anything.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 27, 2009