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Trivalent / Hexavalent Chrome passivation

September 14, 2011

1. What is the difference between Cr3+ and Cr6+ passivation.

2. Which chemical presence in Cr3+ and Cr6+ passivation.
Cr6+ passivation carried out by chromic acid. Then what is in Cr3+?

3. What is the chemical mechanism of both Cr3+ and Cr6+ passivation on a metallic/plated component.

4. What is the difference between Cr3+ blue/clear , Cr3+ yellow and Cr3+ black passivations?

5. For Cr3+ passivation, which chemicals are used for each blue/clear, yellow and black ?
passivation. Regards,

S. Divahar,

Divahar Selvaraj
Surface finishing - R&D - Chennai, Tamil Nadu, India

Most Cr+3 chemistries are proprietary and each formulation differs somewhat from another. You should ask your preferred chemical vendor to explain their particular chemistry to you. It is difficult to provide an answer to your questions in a general case without writing a book on the subject. I think you may be able to answer a few of your questions by searching for posts already made on this site.

Jon Barrows, MSF, EHSSC
Kansas City
September 16, 2011

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