In its natural state, aluminium has a clean and attractive surface with good corrosion resistance. Treating the aluminium surface alters the surface properties and can improve resistance to corrosion and mechanical wear. Different finishes can also be achieved, enhancing the decorative appeal in the final applications.
Anodising is an electrochemical process where the thickness of the naturally occurring oxide layer on the aluminium surface is artificially increased. The process involves lowering the extrusion into an electrolytic bath and connecting the extrusion to a direct current, which then acts as the anode in the circuit. While the natural oxide layer is only 0.02 µm (microns), anodising increases the oxide layer to between 5 and 25µm depending on the product characteristics required. With the anodising process, a wide range of colours are available including bright anodising.
Powder coating offers a virtually unlimited choice of colours and is very durable. The profiles are pre-treated in order to clean and prepare the surface before it is sent through the spray booths where the electro-statically charged powder is sprayed and attracted to the face of the profiles to form an even coating. Once the profiles are coated, it moves through a curing oven that melts the powder to form an even paint coating that adheres to the surface of the profile. The recommended film thickness is 60 µm (microns).
Screen printing and the use of protective foils are other methods of surface treatment. Mechanical brushing, polishing and barrel processing are examples of mechanical surface treatments.