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Corrosion Resistance of Trivalent Chromate

A) As compared to each other, What is the difference between Zinc plating with
1) Trivalent Blue
2) Trivalent Yellow
3) Hexavalent Blue

B) How can material be distinguished by Visual Inspection?

Somnath Patel
Product Designer - Greater Noida, India
September 29, 2010

Hi, Somnath.

Ten years ago, before modern trivalent chromates, the answer would have been that yellow chromate offered far better corrosion resistance than hexavalent blue chromate, which in turn offered far better corrosion resistance than trivalent blue.

Today, trivalent chromates regardless of color are supposed to offer the corrosion resistance of the old yellow hexavalent chromates. Unfortunately it is not possible to determine from visual inspection that chromates are hex-free.

Regards,

Ted Mooney, P.E.
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finishing.com - Pine Beach, New Jersey
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