Page 364 - Introduction to Marine Engineering

Engineering materials 335

Aluminium
Aluminium is a light material which has a good resistance to atmospheric
corrosion. It is usually used as an alloy with small percentages of copper,
magnesium, iron, manganese, zinc, chromium and titanium. It is also
used as a minor alloying element with other metals. Suitable heat
treatment can significantly improve the properties of the alloy.

Copper
Copper has good electrical conductivity and is much used in electrical
equipment. It has a high resistance to corrosion and also forms a
number of important alloys, such as the brasses and bronzes.

Zinc

Zinc has a good resistance to atmospheric corrosion and is used as a
coating for protecting steel: the process is called 'galvanising'. It is also
used as a sacrificial anode material because of its position in the galvanic
series. See the subsection on corrosion later in this Chapter. A number
of alloys are formed using zinc.

Tin

A ductile, malleable metal that is resistant to corrosion by air or water. It
is used as a coating for steel and also in various alloys.

Titanium
A light, strong, corrosion-resistant metal which is used as the plate
material in plate-type heat exchangers. It is also used as an alloying
element in various special steels.

Brass
An alloy of copper and zinc with usually a major proportion of copper,
A small amount of arsenic may be added to prevent a form of corrosion
known as 'dezincification' occurring. Other alloying metals, such as
aluminium, tin and manganese, may be added to improve the
properties.

Bronze
An alloy of copper and tin with superior corrosion and wear resistance
to brass. Other alloying additions, such as manganese, form manganese