  Many
copper alloys were introduced largely because of their excellent resistance
to corrosion by salt-water and salt-laden atmospheres; they have found
also applications where a wear resistance greater than that posessed
by pure copper is required. Thus aluminum bronze, manganese bronze,
aluminium brass, gunmetal, cupro-nickel and 'Monel' are copper alloys
which have long been standard materials for shipbuilding.
In the evolution of warship construction the battleship has been replaced
by the aircraft carrier and vessels such as the Vanguard, the King
George V and the American Missouri have gone for ever. Recently several
new classes of warship have been introduced. These include small commando
carriers and guided missile destroyers which are virtually small cruisers.
Since the Second World War the optimum size of ocean-going liners
on the North Atlantic route has declined slightly and vessels like
the Queen Elizabeth and Queen Mary are no longer built. Nevertheless
in all new construction, both naval and merchant marine, from 2 to
3 percent of the deadweight is in copper and copper alloys.
Ships' propellers in small coastal vessels may be cast iron, but for
warships and the vast majority of merchant vessels, copper alloys,
such as high tensile brass or aluminium bronze, are invariably used.
The propellers of a large ship may weigh up to 20 to 25 tons apiece
(35 tons in the two Queens); and as spare propellers must be carried
on board, this is in more than on sense a heavy item! The very heavy
tailshafts of big ships are usually Admiralty gunmetal (a copper-tin-zinc
alloy in proportions of 88/10/2), and the rudder stocks and massive
propeller cone-nuts are often in the same material.
It is the engine and boiler rooms of a ship where copper and copper
alloys are used to the greatest extent. Marine condenser tubes are
invariably 70/30 cupro-nickel or arsenical aluminium brass, two alloys
which are particularly resistant to the severe corrosive and erosive
effects of rapidly flowing sea-water. The world's first nuclear-powered
merchant ship, Savannah, has more than 30 tons of cupro-nickel condenser
tubes; while the main condensers of the modern liner Empress of Britain
each comprise 5,949 cupro-nickel tubes, with tube-plates and baffles
of naval brass, a copper-zinc-tin alloy (62/37/1). Undoubtedly the
great new Cunarder, now on the drawing board, will follow this practice.
Copper and copper alloys are used for the feed-water, fresh-water
and salt-water cooling systems, for ships' evaporators, low temperature
steam lines and for numerous items of auxiliary equipment such as
pumps, feed heaters, valves and miscellaneous coolers. Among the specific
uses of which have arisen in recent years is the use of aluminium
brass pipes for the large heating coils of oil tankers. Some of these
vessels are giants of up to 100,000 tons with dozens of oil-storage
tanks, and the heating systems are on a corresponding scale.
The electrical equipment in a ship has grown extraordinarily complex
and, as on land, the generators, electric motors, lighting and communications
systems depend almost entirely upon copper and copper alloys for their
operation. With the advent of wireless telegraphy before the first
world war and radar during the second, a considerable amount of space
is now given over to communications equipment, particularly in warships,
where it is standard practice to duplicate vital equipment. This precaution
is not only confined to naval ships; for example, the Empress of Britain
has an emergency system of thirty-five strategic points, each of which
can communicate back to the control room.
Naval ordnance has changed out of all recognition since the brass
cannon of the 16th and 17th Centuries, but if the gun-barrels no longer
contain copper they are fired electrically and considerable use of
copper piping is made for the turret hydraulic systems.
The value of sheathing a ship's bottom in warm waters or polluted
harbours has already been mentioned; but another trouble, to which
all ships both steel and wood are liable, is the perpetual growth
of fouling organisms, such as barnacles, ascidians, small tube-forming
worms and weeds. This can be largely inhibited by covering the underwater
parts with a composition that will poison the layers of sea-water
immediately adjacent. Very many such anti-fouling paints have been
tried, but only two have been found of much value, one including mercury
and the other copper salts.
Small boat design and construction has made spectacular progress during
the past twenty years. Rising standards of living have made it possible
for many people to possess a boat of their own - in USA alone there
are now nearly a million private motor-boats, yachts and other small
craft. Copper alloys such as manganese bronze are used for centre-boards,
rudders and propellers, and naval brass is used for propeller shafts
and miscellaneous deck fittings. Wood is still strongly favoured for
small boats and copper alloys wood screws and nails, generally silicon
bronze, have long been recognized as the most suitable fasteners for
all-wood construction. Many of the screws are now thread-rolled, a
more economical process than screw-cutting since no swarf is formed.
Most of the uses of copper mentioned hitherto in this section have
resulted from careful research and development based on experience
over the centuries, but probably few specific items of equipment have
been so effective or vitally significant as the de-gaussing apparatus
which was hastily improvised during the early part of the last war.
German magnetic mines were then sinking Allied and neutral shipping
indiscriminately at alarming rate. The mines were laid in shallow
waters, even in the Thames Estuary, and detonated magnetically as
soon as the ship's steel hall passed overhead. The resulting uprush
of water usually broke the ship's back. Many ships were sunk and others,
including the battleship Nelson, were damaged by this form of attack.
Fortunately, the counter-measures devised were simple and completely
effective. It was found that by attaching a copper strip around the
hull and passing a current through it the ship's magnetic field was
neutralized and the mines therefore failed to explode. All ships were
subsequently provided with a de-gaussing system and by D-Day 1944
no fewer than 18,000 vessels had been protected in this way. On the
large capital ships a considerable tonnage of copper was required
- the Vanguard, which was completed immediately after the war, required
twenty-eight miles of copper wire weighing 30 tons for the purpose.
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