PLASMA OXIDATION

Plasma electrolytic oxidation (PEO), also known as electrolytic plasma oxidation (EPO) or microarc oxidation (MAO), is an electrochemical surface treatment process for generating oxide coatings on metals. It is similar to anodizing, but it employs higher potentials, so that discharges 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 and titanium. Because they can present high hardness and a continuous barrier, these coatings can offer protection against wear, corrosion or heat as well as electrical insulation.

surface coatings formed through plasma electrolytic oxidation can offer 2-4x more hardness than hard anodizing or steel, and provide increased wear resistance..

Plasma electrolytic oxidation (PEO), also known as micro-arc oxidation (MAO), is a bath-based method of producing ceramic layers on the surface of light alloys. PEO surface coatings are characterised by their wear resistance, corrosion resistance and thermal and chemical stability. The method is suitable for alloys of high aluminium, magnesium and titanium composition, but can also be applied to other metals such as zirconium, tantalum, niobium, hafnium and cobalt.

1. Development of harder ceramic phases (including crystallisation)
2. Chemical passivity – most PEO ceramics are chemically inert
3. Incorporation of elements from the electrolyte into the ceramic to give different properties
4. Reduced stiffness gives high adhesion under mechanical strain or thermal cycling
5. Crack-free edges

It is an electrochemical surface treatment process for generating oxide coating on metals. It employs higher potentials, so that discharges occur and the resulting plasma modifies the structure of the oxide layer. This process can be used to grow thick largely crystalline oxide coating on metals. Because they can present high hardness and a continuous barrier these coatings can offer protection against wear, corrosion or heat as well as electrical insulation. The coating is a chemical conversion of the substate metal into its oxide and grows both inwards and outwards from the original metal surface. Because it grows inward into the substrate, it has excellent adhesion to the substrate material. A wide range of substrate alloys can be coated, including all wrought aluminum alloys and most cast alloys, although high levels of silicon can reduce coating quality.