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Subject: Re: Re: TWL: Unzincs
From: Douglas Hoople (doughoople@XXX.XXX)
Date: Wed May 01 2002 - 22:44:53 EDT
Yup, that's right. Reverse the polarity, and the noble metals corrode. It's very disorienting, but true. Nigel Calder's book has a good picture and discussion of this, but I forget which page off the top of my head. Happens when there's stray current, shared ground with three or more boats, or a badly tuned impressed current protection system.
It can happen in a matter of hours or days!
Doug Hoople
M/V Bomar
1963 Stephens Bros. 50 FDMY
Sausalito, CA
A FG boat hauled at my marina last year with large areas surrounding each
and every thru hull which had eaten the paint compleatly off . These areas
were white ish in color and appeared to be a foot or more in dia ..
additionally there was pitting on all bronze underwater fittings - including
thru hulls, shaft, prop, and rudder .. worst I have ever seen .. yet the
zincs appeared to be pretty sound -- which I thought quite odd !
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