Ex Ship's fastenings work: ... Modern analyses have shown, for
example, that while pure copper sheathing releases copper as its toxic
constituents into the water and thereby serves to deter marine growth, it is
also prone to erosion from water-borne debris. While copper has as "fair
erosion resistance" up to 0.9 meters per second (about two knots), alloys
are less susceptible, though there was a problem with what is now called
"de-zincification" as will be seen. Later it was found that the addition of
tin to the product, which then appeared as "Naval brass" (62 percent copper,
37 percent zinc, and 1 percent tin), and "Admiralty brass" (a 70:29:1
alloy), allowed the product to withstand twice that rate of water flow.13
The term "composition metal" resurfaces in this period.14 In
James P. Delgado's analysis of a wreck believed to be that of the famous
Mary Celeste (186185) appears a reference to the American Shipmasters'
Association requiring outer planking to be "fastened with composition or
copper to load lines in addition to the ordinary tree-nail fastenings."
Delgado also quotes the September edition of the New York Sun which
describes a "composition metal that in appearance resembles brass."15
Muntz metal, Yellow metal, Naval brass, and Admiralty brass were
forms that persisted into modern times and with the addition of silicon,
aluminum, iron, and manganese lead to the development of the "high tensile
brasses." Some of these came to be used as fastenings, as will be seen in
the section on modern shipbuilding.
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