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Must we remove heat treatment discoloration on stainless steel?

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My company does a little bit of heat treating in house. We heat treat 17-4 stainless steel (doing an H900 heat treat). Because we do an air cool we get a heat treat discoloration on all of our parts. Normally we remove this discoloration via a bead blast and/or polishing before we clean and passivate the parts. We are wondering if this is a necessary process. If we leave the discoloration due to heat treat on the parts is there a larger chance of rust and corrosion?

Thanks,

Mara Schwartz
Product designer - Minneapolis, MN, USA
October 14, 2009

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Generally not, as long as a good passivation treatment is still performed, though most customers still want to see a discoloration-free surface even for parts that are destined to be buried inside a mechanism where aesthetics are not a concern.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

October 23, 2009

If you can't use a mechanical method or a electropolish to remove the heat treat discoloration, and soaking in Chemetall Oakite 90 does not remove all the discoloration, what other method is there that will not remove material? We place a very fine thread on the end of a part to aid in adhesive assembly and can not remove any significant material.

Robin Mahoney
- Memphis, Tennessee, USA
November 2, 2009