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Passivation of Stainless


pkrankow

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I was canning some pickle peppers yesterday, and missed cleaning some vinegar that was under the cutting board, and on the stainless stove top. Wherever the vinegar was became rust colored. I scrubbed the area with cooking salt and water, then used a rinse rag. The salt is an abrasive, so use enough that it doesn't dissolve. This removed the rust effectively, and restored the appearance of the area, which is neither a polished nor brushed finish, yet is a good, high finish.

I then started to look up passivization of stainless and had no hits on IFI, but found an interesting article through Google. Maybe I was using the wrong terms in IFI search.

How To Passivate Stainless Steel Parts: MMSOnline.com

This article talks about using citric acid and nitric acid, concentrations, time and temperature vs specific grades of stainless. It specifically recommends against using chlorine products, so I'll tell you in a few days if the stove re-rusted from the salt.

I am also wondering if the salt may be a good first pass for some work, especially since it can be washed out with plain water.

Phil

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"Passivating" stainless steel is done where the surface has been removed and the part needs to be cleaned and the thin layer of chromium oxide restored. It is not what is needed after forging a part.

From "modern Machine Shop" http://www.mmsonline.com/articles/how-to-passivate-stainless-steel-parts.aspx "Passivation remains a critical step in maximizing the essential corrosion resistance of parts and components machined from stainless steels".

Forged parts need to be heated to 2000 degrees and cold water quenched to restore their stainless properties.

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That's good to know Grant. When I give this stainless stock I have laying around a try I won't worry about chemically treating it unless it proves to rust afterward.

I'll still post if the salt caused further rusting on the stove. I don't want to heat that up to 2000F as that might do bad things to the house!

Phil

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  • 1 month later...

Hi Grant,
how do you know approximately when you reach the 2000 degre temp?
yellow, orange color? What about doing sand blasting after forging. Would the blasting affect stainless properties? I`d like to have an interesting texture while cleaning the stainless, to then go on to passivate. Thanks for input. nelson.:confused:

Forged parts need to be heated to 2000 degrees and cold water quenched to restore their stainless properties.

Edited by nelson
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