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David Billington[_2_]

On 28/10/14 22:11, wrote:
On Monday, October 27, 2014 7:34:36 PM UTC-4, Carl Ijames wrote:

had zero luck removing orange red Fe2O3 rust spots
or the blue to orange film from welding on 304SS.
. If you make it work, please
post how.
Oxalic acid will, which is why I suggested BarKeepersFriend.
Wasn't sure it had abrasive, which is why I suggested testing in a
non-visible site. Under the handgrip would be good. Start by just dripping
some on and let it soak, you may not have to rub at all in which case the
abrasive won't matter.
I guess I never tried citric acid on rusty mild
steel, so can't say if that works or not but my strong expectation is not.

-----
Regards,
Carl Ijames

I have not tried fluxes to protect stainless when welding, but have read about them. One is Solar Flux and another is Superior Flux 9. Not especially cheap, but there are some sellers on Ebay that sell small amounts. Ernie says using flux to protect stainless when welding is not as good as argon purge, but it is worth using.

Citric acid does work to remove rust from ordinary steel. I have used it on a bunch of files that got wet.

I have not tried oxalic acid on ordinary steel. I will do that.

Dan
Various people have mentioned weak acids for this de-rusting and Ernie
has mentioned a number of times a Citric acid based weld discolouration
removal chemical AFAIK Citrisurf? but what hasn't been mentioned is that
it is used in conjunction with an electric power supply and wand to
assist the scale removal. A local fabricator near me in the UK uses a
similar system but it is phosphoric acid based and again uses electrical
assist. I know phosphoric acid is used for rust removal on steel but
don't know of its effects on stainless, I suppose it should work as it
is removing rust. I do have some phosphoric acid based alloy wheel
cleaning solution so intend to try that for removing the discolouration
of SS welds at some point.