Following this question, I am trying to understand how/if the choice of acid we might use during the pickling and passivation of certain metals, can influence the severity of hydrogen embrittlement. To my best understanding, all etchants will induce some hydrogen ions into the surface during the etching process. However, some believe Citric acid is a better choice than Nitric acid when it comes to this issue.
I tried doing some research but I can not find any relevant reference who has studied this specifically. So my question is how different acids used for P&P of metals can cause different hydrogen diffusions into the surface? My goal eventually is to find the best etchant to remove the wire EDM recast layer on STAVAX (modified AISI stainless steel series 420).