I wasn’t speaking to dissimilar metal corrosion, only to corrosion due to the pipes being used as ground. It shouldn’t be significant since current flowing through ground is normally zero (and A.C., not D.C. if there is one).

OTOH, using piping as neutral return would probably yield amusing results.

BTW – I’ve seen the videos of people being hooked up to work on H.T. lines from a helicopter — that takes some serious cojones! Thanks for mentioning that again. And you’re basically right about everything electrical you’ve posted here — are you an EE?