This might be just a little off topic, but who better to know about
corrosion than the regulars on wreck.boats.

I have a water intake for my cabin in a fresh water lake. The pump sits
up on shore and the end in the lake is as follows: A 1.25" PVC water
line from the pump out to a point about 20' deep in the lake. This is
attached to a PVC elbow, a 6" section of 1.25" galvanized iron pipe and
a brass check valve and screen.

The check valve is held off the lake bottom with a concrete anchor
(about 50 pounds) cast with a 2' section of galvanized threaded rod
sticking up, to which the 6" pipe section is clamped so the intake
points up.

At the top of the threaded rod, I had attached an eye and a length of
galvanized iron chain leading to a shallow spot where I could use it to
recover the intake if necessary. This contraption has been in the lake
for about 10 years.

The other day, in order to do some maintenance, I located the chain. It
has rusted solid and weakened to the point that I broke it when pulling
on it by hand. This chain was the same stuff I have used with an 8000 lb
winch, so that is pretty seriously degraded.

Does the brass/galvanized iron interface cause this kind of corrosion?
Would the galvanized components survive if I isolate the brass check
valve from the galvanized components with a short PVC section. If not,
what materials are suitable for this kind of environment?

--
Paul Hovnanian
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A physicist is an atom's way of knowing about atoms.
-- George Wald