Thin Al2O3 Coatings produced by electrochemical method, subjected to thermo-chemical treatment

Abstract

The article presents the effect of the anodizing parameters, as well as the thermo-chemical treatment, of Al2O3 layers produced on an aluminum alloy on the characterization of structure, geometrical structure of the surface (SGS), the thickness of the oxide layers, the phase composition, and their microhardness. The oxide layers were produced by the method of direct current anodizing in a three-component electrolyte. Then, thermo-chemical treatment was carried out in distilled water and aqueous solutions of sodium dichromate and sodium sulphate. The anodizing parameters and compounds for the thermo-chemical treatment were selected on the basis of Hartley’s plans. The research showed the effect of anodizing parameters on the thickness of the Al2O3 layers and the increase in the thickness of the layers as a result of the thermo-chemical treatment. The research showed a significant increase in the microhardness of the layers as a result of thermo-chemical treatment and its influence on the phase composition of Al2O3 layers. A significant influence of the thermo-chemical treatment on the geometrical structure of the surface was also found.