Even before surface treatment, the appearance and surface quality of extruded aluminium profiles is perfectly satisfactory for many applications. Thanks to good corrosion resistance, surface treatment is rarely necessary simply to provide corrosion protection. However, there are many other reasons for treating the surfaces of profiles. Examples of attributes that can be changed by surface treatment include:
– surface structure
– corrosion resistance
– wear resistance
– electrical insulation
Surfaces do not always need treatment after extrusion. Load-bearing structures and machine parts are examples of products where the surface quality is satisfactory without any treatment.
Maintenance – cleaning
The anodic oxide layer has good corrosion resistance in most environments. With the proviso that the surface is cleaned, anodised profiles are virtually maintenance-free. The surface cleans easily in both water with a little neutral detergent and in white spirits. Although solvents do not affect aluminium, strong alkaline solutions should be avoided.
Resistance to corrosion, discoloration and abrasion increases with layer thickness.
As the anodic oxide layer has poor cold formability, forming should take place before anodising. Cutting and drilling can be carried out after anodising but the exposed surfaces will, of course, be untreated. Welding is to be carried out before anodising.