I have a mild steel pipe (black pipe, NOT zinc plated) water well. My question: is it possible to somehow put a sacrificial anode in an electrolyte contained in a bucket instead of burying it in the ground, which allows zinc to eventually enter and contaminate ground water?
I wonder if a sacrificial anode near the surface could prevent corrosion at the deepest part of your pipe, where the water and wet soil are. Usually, sacrificial anodes are placed fairly close to the item being protected.
It would be worth testing some of the water (that comes up thru the pipe) for pH and corrosivity. If the water is alkaline (hard water), it may not be very corrosive. The oxygen level far below ground would be low, perhaps not enough for rapid corrosion.
Maybe a sacrificial anode is unnecessary.
It's also possible to use magnesium, for example in protection of pipelines. Magnesium will still "contaminate" the soil, but the environmental effect is much less than with zinc or cadmium because magnesium compounds are already common in soil.