Formation of Coatings by Mixed Aluminum and Manganum Oxides on AL25 Alloy

CZU 541.13; 621.35

The features of the cast aluminum alloy AL25 plasma electrolytic oxidation are investigated. It is shown that the variation in the nature as well as in the ratio of the electrolyte components concentrations allows forming mixed oxides, which include both the main matrix material and the dopant. An increase in the cover thickness and manganese oxide content is achieved by homogenizing the processed surface due to the simultaneous formation of mixed oxides and removal of the alloying component from the surface layers. The current density intervals are determined to ensure a uniform distribution of elements in the coating and a high efficiency of the Faraday and thermochemical reactions. It was established that the stoichiometric oxygen index in oxides MnO_x is in the interval x = 1.71–1.87. Testing of the synthesized oxide systems in model reactions of the carbon oxide (II) oxidation to CO₂ showed that the temperature of ignition and complete conversion is as for the platinum catalysts.

Keywords: AL25 alloy, plasma electrolytic oxidation, metal oxide system, manganese oxides, catalytic activity.