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Fluoroboric and nitric acid passivation of steel

I will be passivating stainless steel in a bath with fluoroboric acid and nitric acid. Does anyone know what the mechanism for this passivation might be? I don't understand the role of the fluoroboric acid in the process.

Michael Kelly
National University of Ireland, Galway - Galway, Ireland

Michael:

You are dealing with some pretty hazardous material there. The fluoroboric acid is probably there to remove scale from welds, etc., or oxides that the nitric will not. I have heard of this combination, but have never tried it. Unless you are removing some scales or discoloration, I would not advise using this material.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

adv.
I can suggest our environmentally safe electropolishing method which completely removes any impurities or burrs or stains, etc., from the surface, leaving it medically clean, mirror finish, and of course completely passivated.

Anna Berkovich
~~Russamer Lab~~ - Pittsburgh, Pennsylvania
(ed. update July, 2025: sorry, Anna has retired)

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