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On Schooner Stay Nomenclature
(This Issue’s Question is on the Next Page)
The Know It All questions and correct answers are important design tips for students as well
as other marine professionals. We suggest that you file them away for future reference.
The Question Was:
Kevin Ritz, president of Cruising Essentials as well as ABYC west coast representative sent in this conun
drum:
A fleet of well-made aluminum boats–
working in fresh, brackish and salt wa-
ter– virtually all experienced the same
corrosion around the window in the
trunk cabin side. An example is in the
photo at the right.
Can you explain the cause of the corro-
sion?
The Winner Is:
We received nearly a dozen answer to
the June 2011 Know It All question but
only one of them was correct. This was
from Westlawn student Alan Gluyas.
Since Alan is clearly too smart for his
own good, the only option was to honor his now proven status as a brainiac by officially awarding him th
title of Know It All. He should henceforth be addressed as such. Of course, a Westlawn T-shirt, cap and
Know It All certificate is winging its way to our winner.
And the Solution Is:
It is not well know, but most rubber products (including most car and truck tires and most gaskets) cont
carbon black. The carbon black is used as a pigment and as a reinforcing filler. Compounding the carbo
black with rubber improves both tensile strength and wear resistance. The key word, however, is “carbo
Carbon and graphite are the same things and carbon is so noble relative aluminum (and virtually every-
thing else) that even the slightest traces of carbon can cause corrosion issues. Carbon black is, in fact, u
ally more than 97% pure carbon! It shouldn’t be confused with soot, which is usually around 60% carbo
The problem here was carbon black leaching out of the rubber and making contact with the aluminum
through any tiny defect or abrasion in the paint around the gasket. This results is galvanic corrosion of t
aluminum.
Avoid using rubber gaskets for sealing and insulating material on aluminum. Though some rubber prod-
ucts don’t leach the carbon black in sufficient quantity to cause problems, many rubber products can an
do. If you are looking at a corrosion problem around a gasket, grommet or insulating pad on aluminum,
find out if it’s made of rubber. If so, there’s a high likelihood that the carbon black in the rubber is the c
prit and the rubber gasket will need to be discarded and replaced with neoprene or some other material
without carbon black. Neoprene is an excellent gasket and insulating material for use with aluminum.
Thanks to Kevin Ritz, of Cruising Essentials, for passing along this interesting case.
www.cruisingessentials.com