In the electrodeposition of aluminum (Al) from non-aqueous electrolytic baths, the contamination of the baths by water has been suspected to adversely influence the electrodeposition. In this study, we carried out the electrodeposition of Al from dimethylsulfone-AlCl3 baths containing various amounts of water to quantify the effect of water. Al deposits with uniform, smooth surfaces were obtained from the baths containing <180 ppm water, whereas deposits with dark, rough surfaces were electrodeposited from the baths containing >320 ppm water. A decrease in the current efficiency and an increase in the impurity content of the Al deposits were also observed with increasing water content of the baths. The measurement of the water content of the bath heated at 110 ℃ under an inert atmosphere revealed that the water content decreased with an increase in the duration of heating, indicating that the water could be eliminated through vaporization from the bath. The recovery of the current efficiency was confirmed by heating the bath for >24 h.
