>>pipe corrosion

>Will it be? I guess you have AC mains, so there won't be much
>electrolysis.

Pipe corrosion depends a lot on the ground they're stuck in. They can
corrode even if there is no leakage current into them (different ends of a
pipe in grounds with different composition form a galvanic cell - or
battery). The ac leakage into them is usually a small fraction of the
telluric currents (which can be 10's of amps in certain conditions -
think battery with several tens or hundreds of square meters plates). Long
pipes laid in the ground always have provisions to alleviate this problem
at intervals.

I think that normal practice requires a pipe that is used as grounding to
have a shorting bridge mounted across the part that is being repaired.
Such bridges are permanently installed across gas meters and water meters
to avoid the current from interfering with the meters and to allow
changing the meters. I do not know what code covers this.

Peter

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