Re: [Amel Yacht Owners] Corrosion in the Seawater Manifold

eric freedman


I had the exact same problem in the exact same place. It must be some stray
AC coming from the pump. However, I am hesitant on grounding the pump. That
would put the stray AC in the whole system. I had a new manifold built out
of stainless steel. In retrospect, I should have the welder make it with a
spare port for a pencil Zinc.

Fair Winds,


Amel Super Maramu #376 Kimberlite


[] On Behalf Of williammelbourne
Sent: Monday, July 21, 2008 4:44 PM
Subject: [Amel Yacht Owners] Corrosion in the Seawater Manifold

I have a general question about corrosion in the seawater manifold.
In May this year the seawater intake manifold on our Super Maramu 2000 (7+
since new, 5 years at sea) developed a leak. The leak occurred at the "tee"
between the main manifold and the smaller pipe that connects to the hose
leading to the
A/C pump. I removed the manifold, and I found serious corrosion inside of
that junction (I
presume from electrolysis). The corrosion appeared to follow the original
solder band at
the junction. However, the corrosion only occurred at the A/C junction, none
was evident
in any of the other four junctions for the two toilets, the anchor wash and
the desalinator.
I repaired the manifold by soldering a slightly oversized short copper
sleeve over the
original A/C pipe. The sleeve fits against the main manifold but it is short
enough to leave
enough room to reconnect the A/C hose onto the original A/C pipe, which was
in good
shape at its downstream end. It seems to work OK, but I worry about the
My question is: Why did this corrosion happen? The manifold has always been
bonded, exactly the way that Chantiers Amel rigged it originally. Our
grounding strap in
the bilge appears to be intact. I haven't done any stray current search yet,
but I will after
hurricane season. It is true that the A/C line gets the most use (a factor
of at least 10
more than the others), and perhaps here is a clue about the cause.
Maybe after 5 years in saltwater, I'm expecting too much from copper. But
the contrast
between the lack of corrosion everywhere inside the manifold other than at
the A/C
junction is at least suspicious. The inside of the A/C junction looked like
Swiss cheese in
miniature, whereas the rest of the manifold looked corrosion-free. I also
note that other
Amels of similar vintage have developed this same leak in the same area of
the manifold.
I have already searched through the Amelyachtowners forum, in particular,
No. 3814, 3813, 3811, 3810, 3809, 3782, 3781, 3780, 3779, 3778, for possible
clues to
this corrosion problem. Although these messages are definitely informative,
I couldn't
find a definite answer to my question.
Any comments? Thanks!
William Melbourne

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