Effect of Corrosion on The Microstructure of Anodized Aluminum

Abstract: Effect of corrosion on microstructure of aluminium alloy was investigated. Three unanodized and three anodized samples were used for the experiment. The result shows the microstructure of the control specimen has the structure of α-Al (white) and has a Zn-Al-Cu inter-metallic phase which shows CuAl2 embedded in the Aluminium-Zinc solid solution. The structure of the anodized Alloy shows much finer grains, which indicate an increase in the strength and hardness of the Alloy, since the size of the grains influence the mechanical properties of a material. This implies that anodizing helps to improve the mechanical properties. Micrograph of the unanodized specimens (Al-Zn-Cu-Mg) subjected to corrosion test shows dark portions distributed in the Al-matrix which represent the corrosion products. It also implies that the Al-Alloy in the 1.0M HCl corroded more than that in 1.0M NaOH solution. It means that anodizing helps to reduce the corrosion effects in both acidic and basic medium.