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400 Series Passivation

Is nitric acid the preferred method of 400 series SS?

Rickey Phillips
finishing dept. supervisor - Startanburg, South Carolina
June 23, 2008

Hi, Rickey. Nitric vs. citric has been debated in depth several times on this site. If you put "nitric citric passivation" in the search box, you'll immediately find those many threads.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.
June 24, 2008

July 1, 2008

Rickey,
It is perhaps best to say that nitric is an approved method in the major passivation specs (ASTM ASTM A967, AMS2700). Citric is of course also an approved method. The specs do not speak to a preference between the two, and that's about as close to an official industry standing on the matter as you can get.

Naturally there is nothing to stop you from evaluating both methods and coming to a personal preference.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

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