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Dave Gerr replies . . .
Kim:
Glad you're enjoying
The Masthead
,
and thanks for your thoughts on the
Know It All corrosion question from
the June 2011 issue. You are correct
that poultice corrosion is a serious
problem on aluminum. Poultice cor-
rosion, though, is specifically corro-
sion that takes place when a rela-
tively soft fibrous material is in direct
contact with the aluminum and the
fibrous material retains some water.
This is the case in particular with wet
wood, cloth, carpeting, and such in
contact with aluminum. Here's a
photo of pure poultice corrosion at a
plywood bulkhead in contact with an
aluminum tank. Not good! Note also
that the plywood was cut open with a
hole saw, but the edges of the ply
were not sealed in any way further
enhancing the wood’s ability to ab-
sorb and hold moisture. Not good
either!
Cheers,
Dave Gerr
We Get Mail
continued
Photo: Priscilla Blankenshi
Long-time yard manager, technical writer, author and marine
consultant, Steve D’Antonio has added a highly useful blog to
his website. The goal of the bog is to offer informative de-
tailed and useful technical seamanship and cruising informa-
tion that is designed to make time on the water more enjoy-
able and safer with less hassle. Blog topics are chosen based
on the feedback Steve gets from his clients readers and lec-
ture attendees. Articles cover a wide variety of subjects, with
more being added monthly. Topics range from electrical sys-
tems, fuel filtration and tips on painting aluminum hardware
to properly selecting and installing safety gear. There are also
articles by guest contributors selected for their skills and ex-
perience. They write about everything from a full-time cruising
couple’s wanderings through the Mediterranean and a profes-
sional mariner’s thoughts about maneuvering 900-foot ships,
to hard-won anchoring lessons from a circumnavigator and
former Naval Academy instructor, to name just a few. Here is
brief, introductory example short blog entry:
Ensuring the Longevity of Painted Aluminum Components
April 2011
Military, commercial, scientific and a few recreational vessels
built using aluminum alloy often utilize the un-painted ap-
proach, and with good reason. The next time one passes your
way, take a close look at the US Coast Guard’s heavy-weat
rescue vessel, the venerable 47-foot Motor Life Boat or
MLB. Or, any of their other aluminum response craft includ
the very latest 45-foot Response Boat Medium or RBM, on
which I recently sea trialed (its all electronic control syste
utilizes a joy stick rather than helm wheel, which is perfect
today’s teenage recruits). Check out the paint job on these
aluminum vessels. What you’ll notice is, other than the fa
iar diagonal red-white-and-blue Coastie stripe and bottom
antifoulant, these vessels are un-painted. Although the Co
Guard is well known for its thriftiness, this approach saves
more than simply the cost of the paint. In the long run, it
saves the Coast Guard, and any other aluminum vessel op
tor that follows this paint-free protocol, untold sums in pai
metal maintenance and repair as well as increasing the se
vice life of alloy vessels. Hard to believe? Read on . . .
_________________
Steve D'Antonio
Steve D'Antonio Marine Consulting, Inc.
Sign up for Steve's Marine Systems Excellence blog at:
http://www.stevedmarineconsulting.com/blog/