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topic 17883

Passivating Super Invar (32-5)


Does anyone have any ideas on passivating super Invar 32-5? I was told a 20% by volume nitric acid from 120-140 deg. F for 30 minutes.

Greg Wasielewski
- Palo Alto, California


Warm Nitric Acid will remove the iron from the surface and controlled oxidize the nickel in the surface which is the very definition of "passivation".

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como
and co-author of The Sulfamate Nickel How-To Guide



I'm not sure that Super Invar 32-5 is a corrosion resistant alloy, and therefore passivation may not be a good idea. You'd be wise to contact the manufacturer of your material.

Good luck!

lee gearhart
Lee Gearhart

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