Study On Coloring Process And Corrosion Resistance Of Aluminum Silicon Alloy

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, CrO3surface coloring has been selected. The process of surface pretreatment is optimized according to studying the effects of degreasing, alkaline cleaning, acid wash, desmutting on the film mass. Based on the anode oxidation mechanism and electrolytic coloring mechanism, the effects of craft parameters, electrolyte concentration, electrolyte temperature, coloring current density, oxidized coloring 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,micro structure of anodi coxide coloring films are characterized by SEM, EDS. The results showed that the coloring anodic film is composed of amorphous alumina and Cr(Ⅵ) and has compact and homogeneous surface. Potassium dichromate dropping test, alkaline cauterization, acide cuaterizationa and NaCl cuaterization to coloring 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.