Plasma electrolytic oxidation

It is similar to anodizing, but it employs higher potentials, so that discharges[1] occur and the resulting plasma modifies the structure of the oxide layer.

This process can be used to grow thick (tens or hundreds of micrometers), largely crystalline, oxide coatings on metals such as aluminium, magnesium[2] and titanium.

Because they can present high hardness[3] and a continuous barrier, these coatings can offer protection against wear, corrosion or heat as well as electrical insulation.

In conventional anodizing, this layer of oxide is grown on the surface of the metal by the application of electrical potential, while the part is immersed in an acidic electrolyte.

It is electrically connected, so as to become one of the electrodes in the electrochemical cell, with the other "counter-electrode" typically being made from an inert material such as stainless steel, and often consisting of the wall of the bath itself.