ELECTRODEPOSITION OF TITANIUM-ALUMINUM ALLOYS IN THE LEWIS ACIDIC ALUMINUM CHLORIDE-1-ETHYL-3-METHYLIMIDAZOLIUM CHLORIDE MOLTEN SALT

摘要

The chemical and electrochemical behavior of titanium was examined in the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl_3-EtMelmCl) molten salt at 353.2 K. Dissolved Ti(Ⅱ), as TiCl_2, is stable in the 66.7-33.3 m/o composition of this melt, but shows a slight tendency to disproportionate in the 60.0-40.0 m/o melt. At low current densities, the anodic oxidation of Ti(0) does not lead to dissolved Ti(Ⅱ), but to an insoluble passivating film of TiCl_3. At high current densities or very positive potentials, Ti(0) is oxidized to Ti(Ⅳ); however, the electro-generated Ti(Ⅳ) vaporizes from the melt as TiCl_4(g). The electrodeposi-tion of Ti-Al alloys was investigated at Cu rotating wire electrodes. Ti-Al alloys containing up to ～ 19 a/o titanium could be electrodeposited from saturated solutions of Ti(Ⅱ) in the 66.7-33.3 m/o melt at low current densities, but the titanium content of these alloys decreased as the reduction current density was increased. The pitting potentials of these electrodeposited Ti-Al alloys exhibited a positive shift with increasing titanium content comparable to that observed for alloys prepared by sputter deposition.