With anodising, transparent layers that maintain the metallic lustre are produced electrolytically using a direct current in a bath of sulphuric acid. In addition, the anodised layer can also be coloured using inorganic or organic colouring solutions prior to sealing. With two-step anodisation, formation of the colourless anodised layer is followed by electrolytic colouring in a metallic salt solution. By using special electrolytes for specific alloys, one can use colour anodising to produce a wide range of colours. Thus, with two-step anodisation and special electrolytes one can obtain colours ranging from whitish German silver to black, including light bronze to dark bronze and grey.

Organic coating of aluminium surfaces offers an almost unlimited range of colours. The natural oxide layer is dissolved away together with components that impair adhesion and a conversion coating is then applied. When it comes to the actual colour coating, one differentiates between the batch coating of individual parts, which can be carried out either as a powder or liquid coating, and coil coating in a continuous operation with different lacquer systems and structures.

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