Aluminium (chemical element with symbol Al) is a metal obtained from an ore called bauxitewhich has been servicing the industry for over 150 years. The name aluminium derives from the Latin alumen.
Being the most abundant metal in the Earth's crust (constitutes approximately 8.5% of theearth’s crust), aluminium was discovered in 1825 in Copenhagen (Denmark), by the physicist Hans Christian Oersted, and in Germany by chemist Friedrich Wöhler.
Aluminium is always combined with different chemical compounds. For example, pure aluminium oxide (Al2O3), also called "aluminium clay", is in the form of corundum. The single crystals of aluminium oxide, stained by the presence of other oxides, are importantgemstones. Among them are the ruby (red), sapphire (blue), the eastern emerald (green) and oriental topaz (yellow).
But of great industrial importance are the huge deposits of bauxite, mineral composed byoxides and hydroxides of aluminium hydrated.
Aluminium is obtained by the electrolysis of molten salt, for which can be used as startingproducts aluminium oxide, bauxite or clay. From these raw materials it is necessary, first, to eliminate impurities such as iron oxide and silica.
The electrolysis of purified aluminium oxide in fusion takes place in sheet iron containers,internally coated with a carbon layer which protects the steel from corrosion and, at the same time, serves as the anode for electrolysis. As cathodes it uses coal blocks.
Aluminium oxide has a very high melting point, therefore it is used for the electrolysis amixture of 80% cryolite (Na3AlF6) and 20% aluminium oxide.
At the temperature that electrolysis is achieved, aluminium is more liquid and dense than theelectrolyte and is, therefore, deposited at the bottom of the container, from where it is then removed and placed in an iron mold in the shape of bars.
With the aspect of silvery gray, aluminium is a light, soft and durable metal. It is not toxic as metal, non-magnetic, nor creates sparks when exposed to friction. It is very malleable (after gold it is the most malleable metal), flexible and suitable for mechanization and casting.
Its light weight, a soft but very resistant consistency, electrical conductivity, corrosion resistance (due to the protective layer of oxide) and low melting point turn aluminium suitable for a multitude of applications.
Aluminium is resistant to atmospheric action and to the attack of dilute acids due to thenatural formation of a layer of insoluble aluminium oxide on its surface, an effect that can be enhanced by anodizing.
Taking into consideration the amount and value of the metal used, the use of aluminiumexceeds the use of any other metal, with the exception of steel. Hence it is a very important material in multiple economic activities.
It has good electrical and thermal conductivity, and therefore, is used in the electrical industry and in the manufacture of kitchen utensils.
Joining small amounts of other metals, very resistant straps are obtained - aladur, duralumin,bondur, hidronálio, silumin, Lantal and mangroves - which have many applications, particularly in shipbuilding.
Aluminium is also used in the construction of cars and airplanes, as well as parts of machines, electrical conductors and blades.
When aluminium is evaporated under vacuum, it forms a coating that reflects both visible light and infrared. This is the most commonly used process for the manufacture of reflectors for automobiles.
On the other hand, since the oxide layer formed prevents deterioration of the coating,aluminium is used for the manufacture of telescope mirrors, instead of silver.
Given its high chemical reactivity it is used, when finely powdered, as a solid fuel for rockets and for the production of explosives.