Composition and adhesion of protective coatings on aluminum

The composition, structure and homogeneity of oxide coatings formed by the microarc oxidation (MAO) method on aluminum alloy surfaces and possessing significant hardness and heat-resistance up to 870°C were investigated. On the basis of experimental data obtained by X-ray analysis, EPMA, XPS methods, the conclusions about oxide layers composition formations were made. The presence of finely dispersive aluminum oxide as a main component in the coating composition provides the hardness and heat-resistance of the layer obtained on the aluminum. This layer has a significant adhesion to aluminum substrate. The model ideas concerning construction and reasons of formation of thin friable top layer have been suggested.