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Passivation Of 416 Steel

2001

Hello Passivation Experts,

When I do passvation on 416 steel to QQ-P-35C (canceled) [link is to free spec at Defense Logistics Agency, dla.mil] type II the parts always come out discolored "like a Dark Black" and not very goodlooking cosmeticly. Is this normal for 416 steel or should I try another type of passivate on the 416 steel that would pervent discoloration?

Thank You in Advance,

Kevin Duncan
- Los Angeles, California

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Hello Kevin!

You first want to check out the FAQ on the topic, at www.finishing.com/faqs/sstpass.html where you'll find you are not alone. Reading the FAQ, you'll also notice that all of the problems are occurring in Type II baths- the one with the dichromate added. So, we've gone to a type VIII bath: no dichromate, no etching problems, fine stain test results.

Good luck!

Lee Gearhart
metallurgist - E. Aurora, New York
2001

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Kevin:

Excellent results can also be attained without discoloration by using the correct citric acid formulations. Citric 4 in ASTM A967 (which replaced QQ-P-35c) works well with the correct solution.

We would be happy to help you with this if you need it.

Regards,

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2001