Aloha, as a former "non-destructive test" technician in the aerospace industry here in SoCal I can verify your "hyd embrittlment" warnings, however most of the things you mention require painting, not parkerizing (another name for the treatment). On my old harleys and trucks the finish your talking about is really just used for aesthetical correctness, it looks right, and on a 100% restoration if it was parkerized, it has to be again. Now if you are dead set on it and it is a small part, and are worried, do what we did in aerospace to parts that are subjected to any type of acid treatment (nital etch) "post bake at 350 degrees F for 2 1/2 hours." This is in fact a mandatory thing to do and is part of the "mil-spec", HAS to be done. after you "pickle them", put them in the oven, this removes any hyd left that the acid may have formed. ALOHA, and go for it!!
