Process of formation of the structure and composition of MAO-coatings on aluminum alloys

The investigations of the formation of the surface layer during microarc oxidation are performed. The results of experimental studies on determination of the structure and composition of the oxide coatings on aluminum alloys are presented. The studies revealed that as a distinct of the existing ideas about the initial stages of micro-arc oxidation the “barrier layer” grows unevenly over the area of a sample and the clear boundary between pre-spark and spark regimes of the process. The uneven growth of the “barrier layer” is associated with a different distribution of the electric field on the surface of the sample and the concentration of the electrolyte components. According to the used electrolyte the inner coating layers composed mainly of alumina, and the outer layers contain components formed by the electrolyte thermochemical transformation.