About aluminium
Aluminium is a light metal belonging to the 3rd main group of the periodic table. Its serial number is 13, its chemical symbol is Al. It is silvery in colour and an oxide layer forms on its surface in seconds after it comes into contact air, which then protects it from further oxidation. It does not colour the flame. Aluminium and its alloys are used in large quantities in industrial processes due to their low density and favourable mechanical properties.
Its history
It was first produced by Ørsted in 1825. The world’s first 1 kg aluminium block was presented at the 1855 World Exhibition in Paris. The silvery piece of metal was called “clay silver” as it was produced from a clay-like ore. At that time, the price of aluminium rivalled that of gold, hence at first jewellery was made from aluminium.
Its properties
Aluminium is soft, cuttable, silver-white. It becomes a grey light metal when crushed into powder. It reacts quickly with the oxygen in the air and is passive due to the aluminium oxide (Al2O3) that protects its surface. It is not attacked by concentrated acids.
It is amphoteric, which means that it is dissolved by alkalis and dilute acids during the formation of aluminates and aluminium salts. If we remove the oxide layer, it reacts with water; by means of which aluminium hydroxide (Al(OH)3) is formed and hydrogen gas is released. The protective oxide layer found on aluminium products is artificially thickened (the process is called anodisation). It is not recommended to scrub aluminium dishes, since without the presence of the protective layer, the aluminium reacts with the oxygen and water content of the air.
Physical properties:
- Its density: 2700 kg/m3,
- Its melting point: 660 °C.
Alloys:
- Main alloys: Cu, Mg, Si addition alloys: Ni, Mn
- Dural alloys(Al-Cu)
- Hydronalium alloys(Al-Mg)
- Silumin alloys(Al-Si)
Scope of usage
- in the form of alloys, for the production of aeroplanes and cars
- as packaging material (aluminium foil, soda cans)
- in powder form
- as a reducing agent for the production of metals
- as a cover paint when mixed with a suitable binder (metallic paints)
- manufacture of electric wires
- production of structural elements (scaffolds, etc.)
- production of metals (aluminothermy)
- due to its resistance, also used in the chemical industry (e.g.: for storing concentrated nitric acid)
- alum
- road signs
