page_title: Plasma electrolytic oxidation
hierarchical_section_title: Plasma electrolytic oxidation
caption_attribution_description: This is an SEM micrograph of a typical PEO coating showing characteristic surface morphology: there are many small (~20 micron diameter), overlapping, volcano-like eruptions onto the surface, indicating the local melt flow which occurs during the process.
context_page_description: Plasma electrolytic oxidation, also known as electrolytic plasma oxidation or microarc oxidation, 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, 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.
  The coating is a chemical conversion of the substrate 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 metal. 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.
context_section_description: 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.
  The coating is a chemical conversion of the substrate 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 metal.  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.
caption: A typical PEO surface on aluminium, as viewed in an SEM.
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