I saw with great interest the posts here about etching your stainless kettles. Not wanting to blow $100 that I spent on my kettle, I asked my brother-in-law, who happens to be a PhD metallurgist and a 30 year specialist in stainless steel. I asked if the battery and vinegar process could cause problems with corrosion on a kettle. This was his reply:
Excellent question. Are you sure you're not a metallurgist? Anyway, yes, probably these etched areas would be prone to corrosion and (worse) might cause your beer to have a metallic taste for the first post-etching batch or two.
Interesting how a little knowledge can be dangerous. A fascinating little idea about how to ruin the very expensive stainless kettle that I have gone to a lot of trouble to make. [Since his company produces stainless steel]
All is not lost! All we need to do is make sure the etched areas have their corrosion resistance restored! We can easily do this with materials found around the home. What I would suggest is soaking a washcloth in lemon juice, laying it on top of the etchings (maybe by turning it sideways), and getting it hot somehow - say, 180 deg. F or thereabouts, so we don't boil the lemon juice off but we have some impetus for the passivation reaction. I guess you could put it in the oven on "low". An hour or two should do it. If it dries out you could just pour some more lemon juice on it. Lime juice would work of course. Or just plain lemons. Nitric acid is normally used, but who has that laying around? Plus it's dangerous.[...]
