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Subject: Re: TWL: Unzincs
From: Douglas Hoople (doughoople@XXX.XXX)
Date: Wed May 01 2002 - 20:45:53 EDT
Hi Jim,
Yours is the first I've seen of the term 'delignification', which is exactly what it is. Nigel Calder and a few other wise guys call it 'alkali attack', which is also exactly what it is. Most people call it 'electrolysis', which it also sorta is, but not really.
When salt water and electrical current interact, the chemical byproduct is an alkaline solution which eats the lignins in the wood, leaving behind raw cellulose fiber and sodium chloride crystals. The more current, apparently, the more alkaline solution is left behind, delignifying ever further.
You mention that, when the zinc was sized down, "the boat measured out fine". Do you remember what you were measuring? Did you actually see a lower voltage reading from the reduction in size? Did your zincs deteriorate at a different rate?
Thanks.
Doug Hoople
M/V Bomar
1963 Stephens Bros. 50 FDMY
Sausalito, CA
Doug,
Maņana had a mild case of what sounds to be your problem. It is called delignification... When he discovered the problem, thankfully early, he removed all but a small zinc on the transom. The boat measured out fine and no more evidence of delignification. Don't know if this helps you or not.
Jim McCorison
M/V Maņana - 38' DeFever, Hull #2
Seattle, WA
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