Nitric acid passivation is probably better (it also removes some scale and
discoloration, too) but citric acid does pretty well. I use 8-10% by volume
citric acid in distilled water for at least an hour at 150 F with agitation.
Should be longer than necessary but time is cheap in this case. I've done
comparisons using small pieces of 304 16 ga sheet with tig beads run in one
direction and then cut up into strips so each strip had 2 or 3 beads across
it, and the citric makes a big difference compared to nothing. Glass
beading first helps slightly but of course gets rid of all the bluing.
Glass bead or not, passivate or not, bake at 450 F for an hour or not, then
submerge in concentrated salt water for a few days and look for rust. All
three is best. McMaster Carr sells citric acid.

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Regards,
Carl Ijames

"Karl Townsend" wrote in message
anews.com...
I need some nitric acid to passivate some stainless. Anybody know of a
common local source? I see my favorite McMaster Carr don't have it.

For example, you cab buy hydrochloric acid as muratic acid at any hardware
store. or phosphoric acid as "Lime Away" at any farm and fleet store or
sulfuric acid as battery acid at any auto parts store.

I see citric acid is also use to passivate. Know a local source for this?

Karl