Aluminium

Aluminium is a light metal that does not occur naturally in its pure state.

It is normally obtained from bauxite ore. Hot sodium hydroxide solution is used to turn this ore into sodium aluminate, which is dissolved in water and filtered to remove impurities. Subsequent crystallisation of the aluminate forms aluminium hydroxide. This is calcined (annealed) in rotary kilns. Expelling the water leaves alumina, which is reduced to primary aluminium using molten-salt electrolysis.

Aluminium spontaneously develops a thin, firmly adhering oxide layer under a normal atmosphere. This protects the Material underneath against further oxidation (passivation).

Thanks to its excellent durability, aluminium is used to make equipment for use in the food and chemical industries. In concentrated acids (such as hydrochloric or sulphuric acid), however, it dissolves as a base metal with the formation of hydrogen.

Adding small quantities of other Metals results in significant changes to the properties of aluminium. Alloys and wrought alloys with magnesium, silicon, copper, zinc or manganese are the main metals added.

The main areas of application for aluminium and its alloys are automotive engineering, shipbuilding and aircraft construction. It is also used to make pipes, lightweight building materials and structural components.