As is made clear in the uses
section, aluminum's corrosion resistance plays a vital role in many of its uses, from packaging, to jumbo jets, and to building and construction work. When exposed to air aluminum forms a 1 nm thick layer of oxide which serves as a brilliant corrosion protector for the metal in most environments.
The effect of oxygen and time on iron, aluminum is not affected like this.
The barrier oxide film is bonded very strongly with the surface, and if it does become damaged it reforms almost immediately in air, maintaining this very high level of protection. This oxide layer changes the properties of the material hugely. Although aluminum is a very reactive metal, in most case this reactivity cannot be seen due to this natural film which prevents the aluminum reacting with other substances.
Unlike in iron where the oxidation of the metal creates substance (rust) damaging to the metal itself, in aluminum the oxide makes the material even more versatile and useful. Aluminum would not be used to the extent that it is in outdoor furniture, gutterings, cars, planes, and on buildings if it couldn't protect itself from the effects of weathering and corrosion. With this layer, it can.
Summary: Aluminum forms an oxide layer when it is exposed to air. This film protects it from the effects of corrosion and stops reactions with other substances. This helps it in its uses in the outdoor world.
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