Comparative Study of Mechanical and Tribological Properties of Alumina Coatings Formed on 5754 Aluminium Alloy under Various Conditions

Abstract

In this paper we present the results of the comparative study of the performance of two sulfuric and oxalic anodizing process already retained, based on the superposition of the surface responses. For this purpose two Doehlert experimental designs with three variables (temperature, current density, sulphuric acid concentration) and other three variables (temperature, current density, oxalic acid concentration) were realized. Three responses were studied, namely: growth rate, Vickers microhardness, wear rate after friction test of the anodic oxide layer. A comparative study based on the surface responses was carried out. Compared with the sulphuric acid bath, it was found that the oxalic acid bath affords low growth rates, high wear resistance and high microhardness but less ductile layers. The observed mechanical properties of the oxide layers can be related to their morphology revealed by the scanning electron microscopy and optical observations and their chemical composition determined by the glow-discharge optical emission spectroscopy.