Conductivities of AlCl₃/ionic liquid systems and their application in electrodeposition of aluminium

Solubilities and conductivities of anhydrous AlCl₃ in six kinds of ionic liquids (ILs) were measured. Among the six kinds of ILs [bmim] Cl, [bmim] Br, [bmim] BF₄, [bmim] PF₆, [emim] [EtSO₄] and [bmim] [HSO₄], anhydrous AlCl₃ could be dissolved in the first five kinds but was hardly dissolved in [bmim] [HSO₄]. The results showed that the nominal solubilities of AlCl₃ in ILs increased in the order of [bmim] [HSO₄] < [bmim] PF₆ < [emim] [EtSO₄] < [bmim] BF₄ < [bmim] Cl < [bmim] Br. Conductivities of the AlCl₃/ILs systems depended apparently on the nominal molar ratio of AlCl₃ to ILs. The conductivities of AlCl₃/[bmim] Cl, AlCl₃/[bmim] Br and AlCl₃/[bmim] PF₆ systems had a similar tendency as a function of the nominal molar ratio, that is, as the molar ratio was increased, conductivities increased first and then decreased, with the maximum conductivity obtained at approximately 0.9:1, 1.0:1 and 0.5:1, respectively. Conductivities of the AlCl₃/[bmim] BF₄ exhibited a dentate change and decreased with the molar ratio of AlCl₃ to [bmim] BF₄ increasing in general. With the increasing of the anhydrous AlCl₃ amount in [emim] [EtSO₄], conductivity of AlCl₃/[emim] [EtSO₄] monotonically decreased. AlCl₃/[brnim] Cl system was chosen as the electrolyte for the electrodeposition of Al. Preliminary experimental results showed that dense, adherent and homogeneous Al coatings could be electrodeposited on stainless steel by means of constant potential technique and the surface coverage was quite satisfactory.