Refinement of aluminium
The material
- Base material of Al = Bauxite and Laterite
- The melting point of pure Al = 658°C
- The specific gravity of aluminium = 2,7 kg / dm3
- With which materials Al is alloyed? = Mainly with Si, Zn, Mn, Mg, Cu
- Al alloys which can be hardened = Al Cu Mg, Al Mg Si, Al Cu Ni, G Al Si Mg
Fortes of the material
- The specific gravity
- High mechanical strength because of suitable alloy forming and thermal treatment
- Corrosion resistance
- High reflecting power
- Good thermal and electric conductivity
- Magnetic neutrality
- High cold working aptitude
Weaknesses of the material
- Low strength and strain limit
- Instability against alkalis and alkaline matters
- Welding and soldering only possible with fluxing agent
- Because of its high affinity to oxygen in the air aluminium forms a thin but dense oxide coating which constructs its space lattice on the aluminium and so protects it against further attacks.
Criteria when galvanizing aluminium
- Aluminium protects itself by a relatively stable oxide coat which must be removed before any galvanic treatment (high affinity to oxygen).
- Aluminium has got a high affinity to react in the alkali as well as in the acidic area and to build up compounds (amphoteric behaviour).
- Because of its position in the electrochemical series of the elements aluminium strongly reacts with other metals, a fact which is important for the corrosion process as well as for the selection of the electrolytes for the galvanic treatment.
- The great number of aluminium qualities which are available requires an indispensable partnership between the producing and the processing companies.