Have you used this on your SS?
Citric is easier cheaper and safer.
TIG welded on Thursday and then getting a Hydrofluoric and Nitric Acid bath, have any of you done this?
First question you ought to be asking is why?
I mean to say: What purpose is it you hope to accomplish by invoking a passivation process after welding?
If it is to restore the passive chrome oxide layer you have a more pressing issue which you must address first.
After welding temperatures the surface of SST will have undergone a molecular change.
All (or mostly all) the Chrome in the upper layer of metal will have migrated to the surface and deposited itself at the surface. It does not establish a good bond to the metal so it can be invades and stripped by corrosives.
However, some SST does not do this so dramatically as others. 304 being the most user friendly in that respect.
If you want to address this chrome super deposition issue you need to re heat the metal and anneal it by lowering the temperature slowly over time.
Another anneal for SST is a fast quench in water.
SST and copper are unique in the world of metals in that a fast water quench can anneal them.
To know which anneal you need ( if any) you need to know what the consumable used to weld it was, what the temp it was welded at, whether the weld was done all at once and what grade of SST you started out with.
(sorry to end the sentence with a preposition)
Only after you address the chrome migration between the boundary layers can you then consider whether passivation is an issue.
Remember: SST will instantly produce the passive Chrome oxide layer whenever the chrome at the first mole layer is at 10.2% or higher.
Since all SSt has this percentage it's really all about whether you have changed the molecular structure of the steel or not.
But since it's a pot and since your welder is probably a skilled tradesman (and not a freaking G.D. professional) you are probably golden.
Never let a professional anywhere near you steel. Only tradesmen.
If all you want is to get rid of the rainbow effect use a SST or brass wire brush or some abrasive followed by the SST wire Brush.
Never use a plain steel wire brush.