Gary, It is very difficult, if not impossible to electrically isolate every
component. It is possible to not use copper and brass in salt water. You
should NOT use dissimilar metals without a sacrificial anode and I will
point out that plastic valves are not allowed in engine spaces under Loyds
100A1 and IMO standards, if below the waterline. If however, you have a
plastic boat, you are screwed anyway.
Steve

"Gary" wrote in message
news:FwJVf.188292$B94.140618@pd7tw3no...
My boat has a tee off the sal****er cooling intakes that can act as an
engine driven bilge pump. The tee is copper pipe with the hoses coming up
from the thru hulls. On the leg of the tee is a brass valve that has a
hose that reaches down into the bilge for pumping.

My problem is the corrosion from galvanic action between the copper tee
and the brass valve that controls the bilge suction hose.

Can anyone tell me how to stop the corrosion of the valve? The one I have
in my hand is almost completely pink because the zinc has completely
dissolved.

Ideas?

Gary