Effect of moisture concentration on electrodeposition of aluminum in dimethylsulfone

The influence of moisture on Al electrodeposition was investigated in 23.3 mol% AlCl 3 –DMSO 2 bath at 403 K. Cyclic voltammetry measurement and electrodeposition at constant current were carried out in baths containing 67–174 ppm moisture. The deposits obtained under 40 mA cm −2 for 1 h was characterized in terms of their surface appearance, surface microstructure, and cross section in SEM observation, XRD analysis and surface hardness, and film thickness (current efficiency). In addition, NMR spectroscopy was used to clarify the effect of moisture on the relative abundance of Al(DMSO 2 ) 3 3+ and AlCl 4 − species in the bath. When the AlCl 3 –DMSO 2 bath was kept at 403 K in the glove box, its moisture content decreased gradually up to 5 h, and increased between 6 and 72 h with the elapse of heating time. A high current efficiency of c.a. 100% was observed, the low surface hardness was improved, and the surface was uniform for Al deposits obtained after 5 and 6 h or drying when the abundance of Al(DMSO 2 ) 3 3+ was relatively high.