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Passivating Super Invar (32-5)

2002

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

Greg Wasielewski
- Palo Alto, California

2002

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 H Probert
Robert H Probert Technical Services

Garner, North Carolina

2002

Greg,

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
metallurgist - E. Aurora, New York

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