Synergistic effect of rare earth salt and organic acid in the anodization of aluminum in phosphoric acid

The effect of rare-earth element (cerium salt) and organic acid (citric acid) on the anodic oxide film obtained in phosphoric acid and their synergistic mechanism in the anodizing process were studied. The results show that the synergistic effect of cerium salt and citric acid in anodization of phosphoric acid can reduce surface defects, improve its microstructure and properties of the anodic oxide film. With the analysis of EDAX and XPS, the hydroxide of cerium salt was deposited on the film surface. It is deduced that cerium salt takes part in the formation of oxide film directly on the synergistic effect of citric acid.