Preventative replacement of alternator?

[80stech]

Very little current is needed, a few milliamps in the case of water heaters and underground gas tanks, larger distances of pipeline gets into amps and the current needs to be impressed, alternator field is a few amps so for sure a factor.
I was told in the old days they used to bury an old car beside the pipeline, connect it and impress a bit of current to make sure it was the car giving off the electrons and being sacrificed and the pipe taking them in.

In the big generators there is so much else going on that the transfer is probably not noticed as much.