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Hexavalent versus Trivalent Chromate as a zinc passivation

2007

Is it true that Hexavalent Chromate is considered resilient and repairs itself when used as a conversion coating or post treatment with electroplated Zinc?

And is the opposite true with Trivalent Chromate when used in the same manner that it is not resilient and does not repair itself?

Repair in terms of self healing of slight surface scratches, so that corrosion resistance is restored.

Raymond Lafferty
- Elmhurst, Illinois, USA

I believe that that is still true, Raymond. A complicating factor, however, is that all trivalent replacement chemistry is very highly proprietary and several radically different approaches have been taken: thin film vs. thick film, topcoat vs. no top coat, etc. It is very hard to say anything hard and fast about trivalent chromates except that they comply with hex-free requirements.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

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