Abstract:The effects of anodizing conditions (electrolyte, current density and temperature) on the friction coefficient and Vickers microhardness of anodic oxide layers formed on Al 5754 and Al 1050A substrates were investigated. The studied properties were examined using DELTALAB HVS-1000 Vickers microhardness tester and rotating pin on disc tribometer. It was established that the highest microhardness (>HV 400) and the lowest friction coefficient (<0.4) were obtained with the oxalic acid addition of 10 g/L at high current density of 3 A/dm2 and low temperature of 5 °C. The presence of oxidized Mg through the anodic oxide layer formed on Al 5754 was examined using glow-discharge optical emission spectroscopy (GDOES). The MgO was found to act negatively on the mechanical property of the layer. Finally, the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM) were used to characterize the anodic layer before and after friction tests. It is found that the wear mechanism is related to many aspects of the initial morphology, chemical composition of the layer (C, S and Mg), porosity and internal stress.

Key words: aluminium alloy; anodization; friction coefficient; microhardness; dry sliding friction; surface characterization