Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1882-10-20
u. y. n. BrOOkIyn---Cause % the Rapid
COrrOsiOn OF her sheatbing.


My attention has been drawn to letter from
the regular Washington correspondent Of the
New York Herald in its issue Of the 10th
inst, relative to "Tho Shoathng Of the U. S.
Steamship Brooklyn" which says;
"How to account for the corrosion has been
apuzzle to naval officers. Commodore Walker
chief of the navigation bureau, says that for
some time after the sheathing was put on tho
Brooklyn, at the Brooklyn navy yard, she was
anchored off Wallabout where the large
Brooklyn sewer emptios into the bay. The
cause Of the corrosion of metal which made
il necessary to re.copper the entire bottom, is
traced to the outpouriug Of tho sewer etc.
would suggest for consideration that per
haps the rapid corrosion can be more salts
factorily accounted for, not by the action of
corrosive waters (for il is presumed that dur
ing past years hundreds of vessels have an
chored of Walabout without it being noticed
that their copper sheathng was unusually cor
roded), and was doubtless caused by the sheath
ing not being all of the same quality. Years be-
fore the building Of iron vessels had obtained
prominence, the corrosion of copper sheath
ing by sea water had engaged tho attention Of
scientists and notable among them was Sir
Humphrey Davy. Ibelieve that, if thorough
ly investigated, it will be found as already
suggested, that the sheathing ON the Brooklyn
was not all Of the same quality for, as ad-
mitted by experts and as experience has
shown, it is essential, in order to secure salts
factory wear, that, whatever may be the quail
ity, it should be the same all over the ship,
or else galvanic action will ensue, and certain
sheets will corrode faster than others contig-
uous to them One sheet wears well, others
decay rapidly and when analysed the first
sheet is found impure, in consequence Of
which impure copper has sometimes been rec
mended when il was that one sheet which
induced the rapid corrosion of the others, that
but for il might have worn their presumed
time. We have q very recent and striking in
stance Of eectro-chemcal action in sea water
in the case of the British iron steamer Car
mona. Last month (September) on her pas
sage to Montreal, then in sea way her officers,
happening to look over the stern when she
was pitching heavily, discovered large hole
in her rudder. The explanation given (and
which was undoubtedly correct) was that a
large brass nut at the end Of the propeller
shaft caused galyanc action through sea wa
ter, the iron being disintegrated by degrees
and washing out piecemeal by the force of
the sea. A very slight variation in the COM
position of few sheets will induce electro
chemical action throughout the whole.
1t has also been shown by experiments that
pure, unalloyed copper is more rapidly acted
upon in salt water than that having little
alloy in it and the corroson of pure copper
is still further accelerated when brought in
contact with a negative piece, or alleged cop
per. When it is called to mind that one pound
of silver will (it is said perceptbly affect 10,
600 pounds of copper we realize the effect in
metals Of chemical action; and if an impure
copper is used, and the alloy not homogene-
Gus, with sheets of copper of different com
position, rapid corrosion is explained
Brattleboro, Oct. lG 1852. II. D.