Anodic oxidation is very widely used for the treatment of aluminium and aluminium alloys. Anodising provides an attractive decorative and protective finish for a wide variety of aluminium components, In the anodising process a thin invisible film of aluminium oxide forms naturally on the surface and provides corrosion protection for the underlying aluminium. Depending upon the initial surface condition, and alloy composition, a bright, semi-bright or matt effect will be obtained. This is known as clear, natural or silver anodising. This anodic film may also be dyed to give a wide range of attractive colour finishes, i.e. Gold, Red, Blue, Green or Black. Because the various dyes are absorbed into the pore structure, the sealed, coloured anodised aluminium is extremely resistant to wear and fading in the sunlight.