* 
. the average duration now on American ships, is three 
326 On the corrosion of Copper and Silver in Sea-water. 
was employed in the India trade and her sheathing was destroyed 
in August 1849. The copper remaining, weighed 5,810 Ibs. 
Omitting the case of the “Serampore” where the corrosion 
cannot be determined by weight, we have the loss in every one 
hundred parts of metal, for the time of duration,—thus, 
The “Chicora,” twenty-seven months, lost 64°45 per 100 
‘*Hamilton,” twenty-three “ << Oyo me 
“ Carthage,” twenty-one x O35 45 
Allowing the same rate of corrosion and taking the time as 
twenty-seven months for each, 
The “ Chicora” lost - . 64:45 in 100 
Hamilton” - - Be 70-38 “« «& 
“Carthage,” - - “ A3-00 « 
In the cases of the “Hamilton” and “Carthage,” we perceive 
the influence of the different processes of manufacturing the 
sheets, on the durability of the copper. By the operation of 
‘cold rolling,” the surfaces of the sheets are rendered very com- 
pact, and in any corroding solution, they bear a negative relation 
to the metal in the same sheets, between these surfaces. Such 
copper is also always strongly negative to annealed copper in 
acid solutions, until the hardened surfaces are removed, it then 
loses this relation. The ‘“ Hamilton” exhibits the greatest effect 
of sea-water action on the annealed alloy, while in the Carthage, 
the protecting influence of the hardening surface, was exerted 
nearly to the time her copper was removed. 
These observations establish the fact of the rapid corrosion of 
an alloy thus constituted, and show its entire unfitness for sheath; 
ing purposes. 
. The average duration of copper sheathing decreases slightly, 
as the requirement of greater speed in sailing is more urgent. 
Taking one hundred merchant ships, sailing on different oceans, 
years. 
n the point of the kind of corrosion, following the exposure 
of the alloy to sea-water and air, the information obtained in 
these trials, is of a definite character. Part of the sheets rematn- 
ing and an ingot of the copper from smelting a large quanuty, 
were assayed and the results showed that; the same proportion 
only of silver remained, as was originally contained in the alloy: 
The silver alloy therefore, by taking the negative state 1n the 
mass of the metal, hastened its destruction, while its own form 
and condition were such, that it separated as the copper, Was 
corroded. ar ae 4 
For the records of facts and much assistance continued for - 
years, in connection with the subject of copper corrosion, ‘Bem 
indebted to the kindness of my friend, Mr. J. Davis, Jr, Treas- 
urer of the Revere Copper Company. = | ea tet 
1 Pine st, Boston, January 30,1851. ocak glee 
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