[gnabgib]

I'm doing a few small components with 2 parts welded together from 316 stainless and pre-finished before welding with a 320 grit belt. It's a 20mm tube fitted at 90deg into a 6mm plate.
Now of course there is the colouration after. So other than pickling are there straight forward alternatives? I want to keep the brushed finish

[tweake]

I'm doing a few small components with 2 parts welded together from 316 stainless and pre-finished before welding with a 320 grit belt. It's a 20mm tube fitted at 90deg into a 6mm plate.
Now of course there is the colouration after. So other than pickling are there straight forward alternatives? I want to keep the brushed finish

not sure what your asking.
alterative to what ?

you need to do pickling for clean up and corrosion resistance. then grind, polish etc to what ever finish you want.

[gnabgib]

not sure what your asking.
alterative to what ?

I decided to pre-finish the parts before welding in the belief or hope I could make it work, but realise now that pickling/passivation is the only way this can work. So how about the citric acid treatments and is this the same as food grade citric acid which appears to be readily available?

[Gdarc21]

Citric acid may work if you leave it long enough but not let it dry out. I have not tried it for pickling but it works enough for etch tests. Pickling paste is usually the go to though. I think its a matter of what the acid is actually doing and if citric would be strong enough. I think it would be, afterall we used to play around with pickling paste pretty casually. Its not too strong, I wouldnt want it on my car or anything like that though.
If you do give it a go, let us know how it actually goes as a pickling paste.

[tweake]

i'm not sure but i think the citric acid stuff is what works with the electronic cleaner brush.

[gnabgib]

Citric acid may work if you leave it long enough but not let it dry out. I have not tried it for pickling but it works enough for etch tests. Pickling paste is usually the go to though. I think its a matter of what the acid is actually doing and if citric would be strong enough. I think it would be, afterall we used to play around with pickling paste pretty casually. Its not too strong, I wouldnt want it on my car or anything like that though.
If you do give it a go, let us know how it actually goes as a pickling paste.

Ok, I found this. So, it seems Citric acid is not enough for the level of pickling required after welding.

"Citric acid passivation will not remove the low chromium depleted layer underneath the dark oxide surface layer resulting from welding or heat treatment. This requires either pickling, with a solution containing the much stronger hydrofluoric acid, or electropolishing. Removal of the chromium depleted layer is essential for achieving the full corrosion resistance of the grade of stainless steel."

[tweake]

Citric acid may work if you leave it long enough but not let it dry out. I have not tried it for pickling but it works enough for etch tests. Pickling paste is usually the go to though. I think its a matter of what the acid is actually doing and if citric would be strong enough. I think it would be, afterall we used to play around with pickling paste pretty casually. Its not too strong, I wouldnt want it on my car or anything like that though.
If you do give it a go, let us know how it actually goes as a pickling paste.

Ok, I found this. So, it seems Citric acid is not enough for the level of pickling required after welding.

"Citric acid passivation will not remove the low chromium depleted layer underneath the dark oxide surface layer resulting from welding or heat treatment. This requires either pickling, with a solution containing the much stronger hydrofluoric acid, or electropolishing. Removal of the chromium depleted layer is essential for achieving the full corrosion resistance of the grade of stainless steel."

yeah, thats kinda important especially if you or your customer has forked out the extra $$ for 316.

[gnabgib]

"yeah, thats kinda important especially if you or your customer has forked out the extra $$ for 316"

I put these together out of off cuts, it'll only be for internal installation and it is for my own use, but yes also don't like wasting my own time.
Need now to investigate pickling paste.

[tweake]

i use sandvik formula 1 and neutralization paste. i find the neutralization paste handy for safety (small garage) but also it seams to do a better job with it.