| Magnesium alloys, the lightest metal structural material in use, have been widely applied in automotive, electronic and aeronautical industries because of a number of desirable features, such as high specific strength, high specific stiffness, damping characteristic and recycled easily. However, their applications are limited severely for their low corrosion resistance. For the moment, it is quite urgent and significant to search an environment-friendly anodizing process of magnesium alloy, and improve its anti-corrosion property in the industrial application of magnesium alloy.An magnesium alloy anodizing process based on an environmentally friendly electrolyte bath has been studied in this paper. The anodizing process can form a better anti-corrosive anodized film on magnesium alloy. The effects of different processing parameters on anodizing of magnesium alloys were also studied. At the same time, the mechanisms on the formation of anodic film as well as the corrosion and protection properties of anodized samples were studied.Different films were formed by changing the processing parameter using constant current anodizing method. The properties of the films were determined by EIS and potentiodynamic polarization method. The investigation show that when the applied current density is 10mA·cm-2, the anti-corrosion properties of ZK60 magnesium increase with the anodization time at first, it is the best when the anodization time is 40min, but if the anodization time was longer than 40min, the corrosion resistance of the film decrease. The effect of current density on the properties of the films are also considered, When the current density is less than 20mA·cm-2, the corrosion resistances of the films increased with current density, but when it exceeds 20mA·cm-2, the corrosion resistances of the anodized films begin to decrease with current density. The properties of the anodizing films formed on different magnesiums is different, even when the other conditions are the same, and the magnesium itself has an obviously effect on the anodized films.The effect of the electrolyte solution on the protective property of the film was also investigated. Orthogonal tests was applied to select an optimum solution, and the results showed the optimum bath can improved the corrosion resistance of ZK60 magnesium obviously, and the film formed in the optimum bath shows superior corrosion resistance than that formed by the traditional HAE process. Microstructure and composition of films were examined by SEM, XRD and EDS. The cohesion tests showed that the anodizing films had excellent cohesion. The corrosion resistance of both blank sample and anodized samples were determined by neutral salt immersion test and EIS to study their corrosion mechanisms. |
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