On Nov 4, 11:22*pm, "Existential Angst"
wrote:
"TimR" wrote in message

...

I've seen mostly copper inside buildings and have never had a problem
(about 800 locations).

But IIRC copper is anodic to steel, so if the two are connected the
steel pipe should sacrifice itself to protect the copper. *If they
were outside or underground I would guess there could be a problem.

Magnesium, Al, Zn strips would help protect the steel and copper. *Magnesium
stakes are sold for this purpose, and anodic aluminum is found in water
heaters -- altho alum is proly not very effective after its own oxidized
film occurs.

Copper outside form a protective oxide, like alum -- that green patina. *So
copper should be stable outside as well.
--
EA

You don't need to protect the "steel AND copper." The copper is
protected fine by the steel! Nor does the oxidized film have anything
to do with it.

If steel, ductile iron, etc., is connected to copper, you have a
battery. If they are connected again through soil or any other
electrolyte, you have a circuit. Electrons will flow through the
direct connection, ions will flow through the electrolyte connection.
The ferrous metal will corrode while the copper will be protected.

If you look closely at outdoor connections you should see use of
dielectric (insulating) components between valves, meters, etc. to
break this connection. Copper grounding systems inadvertently
connected to natural gas pipes can be a major problem.