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

Brass doesn't need any galvanic corrosion to go bad in salt water and
zinc
won't protect it. The problem is that it is full of zinc which
disappears
leaving it sort of copper Styrofoam. Put in a proper bronze valve.

--

Roger Long

Gary, it takes more than two dissimilar metals in an electrolyte
(sal****er) for galvanic action to occur. The two metals must be
connected electrically, usually by a wire. So unless your copper and
brass fittings are wired together, which obviously they should not be,
they will not generate galvanic currents.

As Roger has pointed out, the brass may be self-corroding.

Chuck




Gary wrote:
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

If the copper pipe is fed directly to the brass valve they are connected
together. Use bronze or possibly plastic if you can find a suitable sea
water rated GRP fitting.

Alec

Gary wrote:
Alec wrote:

If the copper pipe is fed directly to the brass valve they are
connected together. Use bronze or possibly plastic if you can find a
suitable sea water rated GRP fitting.

Alec

The valve is inside the boat and just controls whether the suction from
the bilge is on or not. It is only exposed to salt water on the inside
at one end (as the raw water crosses the tee) normally. I think I'd
like to try a marelon valve in it's place.

Comments?

I'd favor high quality bronze ball valve over marelon. The latter
requires periodic lubrication a couple of times a year. Forget to lube
and it can freeze causing the handle to snap off.

Good bronze valves seem to last forever. YMMV.

Good luck.

Chuck

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

Steve Lusardi wrote:
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.

Agreed.

You
should NOT use dissimilar metals without a sacrificial anode

This surely does not follow from the first sentence. There is a
significant leap of analysis between accepting the near impossibility of
isolating every component and reaching the conclusion that dissimilar
metals should therefore not be used without a sacrificial anode.

Using a sacrificial anode requires that the protected metal be connected
electrically (usually with a wire) to the anode. I think one might even
say that it is very difficult, if not impossible, to electrically bond
every protected component to the anode. But that doesn't suggest that we
should not protect where necessary.

Fortunately, in the case of a metal valve connected to a non-metallic
hose attached to a metal tee, electrical isolation is all but
guaranteed. Unless the valve came into direct contact with the metal
tee, good isolation would be had. The seawater inside the hose does NOT
provide the electrical connection between the tee and the valve required
for galvanic corrosion.

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.

Had to read that a couple of times before I caught on. Good point, Steve.

Chuck

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

Gary wrote:
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
Thanks for all your advice. I replaced the valve with another brass
valve. The bronze ones were twice the size and more than twice the
price and the chap at the store said they wouldn't last twice as long.
At $11, I can afford to change the bilge suction valve every two or
three years.

It is back together.

So you couldn't afford a $22 valve? You need to get out of boating.

Keith wrote:
So you couldn't afford a $22 valve? You need to get out of boating.

If you carefully read my post you would have noted, it was also twice as
big and wouldn't last twice as long. There is more to value than price.

You need to think.