Kinetics of the Formation and Dissolution of Anodic Aluminum Oxide in Electrolytes Based on Sulfuric and Selenic Acids

Abstract

Measurements were made to study the kinetics of the formation and dissolution of porous anodic aluminum oxide in electrolytes based on sulfuric and selenic acids at temperatures from 0 to 30°C. It was shown that there is a significant difference in the kinetics of the dissolution of anodic aluminum oxide at the bottom of the pores during its formation and throughout the walls of the porous structure after the termination of the anodizing. In the anodizing of aluminum in 2.0 M H2SO4 in kinetic mode, the apparent activation energy of the dissolution of anodic aluminum oxide at the bottom of the pores is 53.2 ± 1.8 kJ/mol, whereas in the chemical dissolution of the walls of the porous structure, this quantity is 83.3 ± 2.1 kJ/mol. The observed difference in the dissolution kinetics predicts the increase in maximum accessible thickness of the porous anodic aluminum oxide film with decreasing electrolyte temperature.