Anodic oxidation ("anodising") is a process for creating an oxidic protective layer on aluminium or titanium. This process does not actually apply a protective layer on the material, but creates a thin oxide layer by converting the top metal layer.
The conversion is done after chemical preparation (degreasing, corroding) by means of electrolysis. Hydrogen and water are created at the cathode, whereas at the anode, aluminium is oxidised to aluminium oxide. The result is a thin layer of 5-25 µm, which ensures good protection against corrosion and wear resistance.
Depending on the oxidation conditions and the choice of electrolyte, aluminium alloys of various grades of hardness can be created, which can be used for corrosion protection or decorative purposes.