Plasma electrolytic oxidation (PEO), microarc oxidation (MAO), is an electrochemical surface treatment process carried out in metals like Aluminium, Magnesium, Titanium ,Tantalum and their respective alloys to form a hard oxide coatings on metal surface by immersing in an electrolyte.

This is a form of anodizing, but it employs higher voltage, so that an arc occurs around the component and which is in plasma state resulting in the formation of the oxide layer.
In this process, greater thickness to even an extent of milli-meter range can be achieved and is largely crystalline in structure.

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Since these coatings exhibits very high hardness over the surface these coatings can offer protection against wear, corrosion or heat as well as electrical insulation.
Alloys containing higher amount of Silicon do not promote greater coating properties.

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