Study on Anodic Oxidation Technology and Corrosion Resistance of Aluminum Silicon Alloy
|Keywords||aluminum silicon alloy anodic oxidation corrosion resistance electrochemical test|
Aluminum silicon alloy has many excellent performances, such as smaller density, higher intensity. The corrosion sensitivity of alloy will be beincreased by adding silicon and magnesium. The alloy will be eroded at atmosphere environment. In this paper, the sulfuric acid anodic oxidation has been selected. The process of surface pretreatment is optimized according to studying the effects of degreasing, alkaline cleaning, desmutting on the film mass. Based on the anode oxidation mechanism, the effects of craft parameters, electrolyte concentration, electrolyte temperature, oxidation current density, oxidized time, additive and post-sealing treatment on the oxide film’s quality was discussed. The corrosion resistance of oxide film was qualitative analysed by mensurating AC impedance chart and polarization curve. Considering the ornament performance and corrosion resistance of oxide film, the optimal craft parameter could be obtained ultimately.The morphology, component, microstructure of anodic oxide films are characterized by SEM, XRD and EDS. The results showed that the anodic film is composed of amorphous alumina and has compact and homogeneous surface. Potassium dichromate dropping test, sodium hydroxide dropping test and 240 hour’s neutral salt spray fogtest (NSS) were applied to anodic oxide film, the results indicate that the films which are prepared under the optimum oxidization process conditions were of the resistance to acid, alkali and salt. Electrochemical behavior of anodic oxide films in NaCl solution was studied by means of electrochemical impedance spectroscopy (EIS) and polarization curves. The results revealed that the film after sealing has the better corrosion resistance and the film’s corrosion resistance is relative to the chloride concentration of the NaCl solution.