Aluminium is one of the most common metal elements in the earth’s crust, but it is very rarely found in its pure form. Aluminium has an odd combination of high and low reactivity. On one hand it reacts with oxygen, so that it is usually discovered and mined as an oxide or silicate. But this same oxidising property causes it form a protective layer that prevents rusting, at least under reasonable circumstances. Its high reactivity with oxygen prevents it from reacting with water. It is one of the few natural metals immune to rusting with fresh water.
As a building material aluminium is the second most commonly used metal, exceeded only by steel. Though not as strong as steel it is much lighter, meaning the weight to strength ratio is actually quite high. Alloying aluminium improved this strength further, while also improving its other properties.
The most common aluminium alloys are the 5000 series, bonded with magnesium, and the 6000 series, heated treated with magnesium silicone alloys. The 6000 series is quite extrudable, are therefore easily formed into complex shapes. Other aluminium alloys have different properties, optimising heat conductivity, density, malleability, and joining characteristics. Despite the number of variations most of these alloys are still over 90% aluminium, and all have low corrosion and very minimal problems with temperature expansion.
Aluminium cladding is created by coating a base metal with a thin layer of aluminium. This provides all the anti -corrosion advantages of the aluminium, while still giving the strength of the base material. Many architectural components, from windows and flyscreen doors though to pipes and wall structures are made from one of several types of aluminium cladding.