Improving the Anti-Corrosion and Anti-Wear Performance of Anodic Coating on the Surface of AA 5052 via Hydro-Thermal Treatment

Abstract

Hydro-thermal technology had been used to improve the anti-corrosion and anti-wear performance of anodizing coating on the surface of aluminium alloys. The micromorphology of the coating has been studied by SEM and results proved the coating had a compact structure. The element in the substrate had been characterized by EDS and results proved Fe had redissolved to the Al substrate. The crystalline structure of the coating had been studied by XRD and results proved the anodic coating could be transformed into η-, p- and γ-alumina. The electrochemical properties had been researched using an electrochemical workstation; results proved after the coating had been treated by hydro-thermal technology, its anti-corrosion properties could be improved. At the hydro-thermal temperature of 400 ℃, its open circuit voltage and impedance reached −0.46 V and 160 kΩ × cm2, respectively. The hardness of the coating had to be measured with an HVS-100 micro-hardness tester, with results proving that, after the hydro-thermal treatment, the hardness of the coating increased to 150 HV. The friction coefficient of the coating had been studied using a ball-on-disk tester, and the results proved it decreased to 0.46. The MMW-2 scratch tester had been used to measure the adhesion between the coating and substrate; results proved the coating had better adhesion with the substrate. The thermal conductivity of the coating had been studied by a heat conduction coefficient measurement device; results proved that it reached 11.2 W/m × K at a hydro-thermal temperature of 400 ℃, far higher than that of organic coating.