Alloys of aluminium: - Aluminium alloys are alloys of aluminium, often with copper, zinc, manganese, silicon, or magnesum. They are much lighter and more corrosion resistant than plain carbon steel, but not as corrosion resistant as pure aluminium. Bare aluminium alloy surfaces will keep their apparent shine in a dry environment due to the formation of a clear, protective oxide layer. Galvanic corrosion can be rapid when aluminium alloy is placed in electrical contact with stainless steel, or other metals with a more negative corrosion potential than the aluminium alloy, in a wet environment. Aluminium alloy and stainless steel parts should only be used together in water-containing systems or outdoor installations if provision is made for either electrical or electrolytic isolation between the two metals.Aluminium alloy compositions are registered with the Aluminium Association. Many organizations publish more specific standards for the manufacture of aluminium alloy, including the Society of Automotive Engineers standards organization, specifically its aerospace standards subgroups, and the ASTM.
Cast alloys : - The aluminium Association (AA) has adopted a nomenclature similar to that of wrought alloys. British Standard and DIN have different designations. In the AA system, the second two digits reveal the minimum percentage of aluminium, e.g. 150.x correspond to a minimum of 99.50% aluminium. The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot respectively. The main alloying elements in the AA system are as follows:
- 1xx.x series are minimum 99% aluminium
- 2xx.x series copper
- 3xx.x series silicon, copper and/or magnesium
- 4xx.x series silicon
- 5xx.x series magnesium
- 7xx.x series zinc
- 8xx.x series lithium
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