Barrier type anodic oxides on aluminum-magnesium (Al-Mg) alloy in nonaqueous electrolyte solution are found to feature some excellent characteristics. Surface micro roughness is found by far less than that grown in aqueous electrolyte solution. Moisture outgassing from the barrier anodic oxides is very much limited. Even at elevated temperature, the barrier anodic oxides develop no heat cracks. They feature outstanding resistance to corrosive process gases. Anodization of Al-Mg alloys in nonaqueous electrolyte solution will be promising surface passivation of the semiconductor vacuum chambers. Copyright The Electrochemical Society.