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How
are galvanic corrosion and electrolysis different? B.E., via e-mail
Electrolysis
is the chemical breakdown—otherwise known as corrosion—of
an electrolyte, a liquid that can transfer ions between metals. For example,
when the seawater around your boat undergoes a chemical change, that is
electrolysis. It is also what happens inside your lead-acid battery when
the electrolyte—battery acid—dilutes and is therefore unable
to interact with the lead plates, the chemical reaction necessary to produce
electricity. (Electrolytic corrosion, also known as stray-current corrosion,
is caused by an external electrical current.)
Galvanic
corrosion is the decomposition of one of two metals of different electrical
potential—known as voltage—when they’re immersed in
an electrolyte. A natural battery is formed by two metals—say, a
propeller made of Nibral (an alloy of nickel, bronze, and aluminum) and
a prop shaft made of stainless steel—playing the role of anode and
cathode, when they are immersed in seawater, an excellent current-carrying
liquid. As electrons move from anode to cathode—that is, from the
metal with higher electrical potential (less noble on the galvanic scale)
to the one with the lower potential (more noble on the scale)—the
metal deteriorates. Placing a sacrificial anode made of a metal, such
as zinc, which has a high electrical potential, between the metals in
the circuit will cause the zinc to decompose first and thus save the other
metals.
Need
help with a maintenance problem? Write to Maintenance Q & A, Power
& Motoryacht, 260 Madison Ave., 8th Fl., New York, NY 10016. Fax:
(917) 256-2282. e-mail: ken_kreisler@primediamags.com.
No phone calls, please.
PMY
Tries... Tuf Enuf
I
just tried out a new product on my boat, Tuf Enuf Natural Bilge Cleaner.
Actually, it’s an old product—intro’d in 1993—with
a new logo. Wallace and Sons of St. Augustine, Florida, bottles and sells
the milky stuff that has a citrus scent both intense and Floridian. After
I poured a quart into the bilge of the Scrumpy Vixen, it promptly
began smelling like a freshly peeled orange, thanks to a compound called
d’limonene, which the company says is derived from crushed orange
peels.
What
about the product’s cleaning abilities? I’ve never been one
to keep a spotless bilge, so the Scrump’s nether areas were a tad
grungy. Nor have I ever been one to scrub bilges with brushes and sponges,
so I added a little fresh water and let the mixture slosh around for a
day or so, washing-machine-style. Tuf Enuf removed some grease and grime,
but not all, thereby suggesting that a complete job might call for further
applications.
Since
the company says the mildness of the product makes it safe on fabrics
and the environment, I also tried a little on fiberglass surfaces and
vinyl upholstery inside the wheelhouse. It removed smudges, dirt, and
even rust stains almost instantly. Cost: $9.95 per quart and $29.95 per
gallon.—Capt. Bill Pike
Wallace
& Sons Phone: (800) 223-5969. www.tufenuf.com.
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