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Copper and Copper Alloys |
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Copper
Although copper has a relatively low strength, its electrical and
thermal conductivity make it an appropriate material for some marine
applications. Copper corrodes uniformly at a
low
corrosion rate
in many environments. Copper is subject to metal ion concentration attack and
the corrosion of this alloy is usually reduced within crevices. Copper and
copper alloys are cathodic to steel and many other commonly used alloys. Bronzes.
Bronzes are copper-tin, copper-aluminium, or copper-silicon alloys. Many of
these alloys corrode uniformly at a relatively low rate. Some of the alloys,
particularly Brasses.
Brass is a copper-zinc alloy. Unless the zinc content is below 10% or
inhibitors are added to the alloy, brasses are subject to de-alloying in
immersion service, particularly in seawater. The use of other copper alloys such
as the aluminum bronzes or copper-nickel alloys in lieu of brass is recommended
for most applications where resistance to corrosion in immersion conditions is
important. Copper-Nickel Alloys.
The nickel content of the most common copper-nickel alloys ranges from 10% to
30%. They are most commonly used for heat exchanger tubes. The resistance of the
alloys to velocity attack is good with the limiting velocity for the 10% nickel
alloy being about 8 feet per second and for the 30% nickel alloy being about 20
feet per second. They also have good resistance to low flow conditions. The
alloys
corrode uniformly below their limiting velocities. Both alloys are subject
to metal ion concentration attack and the corrosion of this alloy is usually
reduced within crevices. Beryllium Copper.
Beryllium copper alloys can have very high strengths of up to 200 ksi. They
corrode uniformly at a low rate. Beryllium copper is subject to metal ion
concentration attack and the corrosion of this alloy is usually reduced within
crevices. Beryllium copper is widely used as a spring and electrical contact
material. |
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