Effect of titanium sol on sulfuric-citric acids anodizing of 7150 aluminum alloy

The corrosion resistance of 7150 aluminum alloy was improved by anodizing treatment in a mixed solution of sulfuric-citric acids with titanium sol. Scanning electron microscope (SEM), coating mass test, neutral salt spray, Electrochemical Impedance Spectroscopy (EIS) and Tafel plot are used to characterize the anodic film. The expose time in salt spray test no pitting appearing is extended from less than 280 h to over 336 h with titanium sol as additive in sulfuric-citric acids electrolyte. The results of EIS show that the resistance of barrier layer with 5 mL/L titanium sol added into electrolyte solution was two orders of magnitude higher than it without titanium sol. It is revealed that the addition of titanium sol improves the compactness of the barrier layer and the corrosion resistance of the anodic film.