Influence of silica sol particle behavior on the magnesium anodizing process with different anions addition

Abstract

Combining the processes of colloid chemistry and electrochemistry the anodic films were made in electrolytes with silica sol addition. Two basic electrolytes 1 M NaOH + 10 vol.% silica sol and 1 M Na 2SiO 3 +10 vol.% silica sol were chosen to investigate the silica sol particle behavior during the anodizing process. The anodic films were prepared separately in the two basic electrolytes with various Na 2CO 3 or Na 3PO 4 additions at 2 A/dm 2, 20 °C for 10 min. The micro-images and element contents of the specimen were characterized by SEM and EDS. The results showed that some cracks appeared on the films by adding PO 4 3− in both of the two basic electrolytes. And the films became compact and uniform with the addition of CO 3 2− in Na 2SiO 3 basic solution. Moreover, the film average thickness decreased with adding anions. It can be confirmed that the sol particle adsorbing behavior in the solution was influenced by the amount of anions' charges, size and structure.