Electrochemistry of titanium and the electrodeposition of Al-Ti alloys in the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride melt

• Published in: Journal of the Electrochemical Society 2003-04, Vol.150 (4), p.C234-C243
• Main Authors: TSUDA, Tetsuya, HUSSEY, Charles L, STAFFORD, Gery R, BONEVICH, John E
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Electrodeposition, electroplating; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1554915

The chemical and electrochemical behavior of titanium was examined in the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl sub 3 -EtMeImCl) molten salt at 353.2 K. Dissolved Ti(II), as TiCl sub 2 , was stable in the 66.7-33.3% mole fraction (m/o) composition of this melt, but slowly disproportionated in the 60.0-40.0 m/o melt. At low current densities, the anodic oxidation of Ti(0) did not lead to dissolved Ti(II), but to an insoluble passivating film of TiCl sub 3 . At high current densities or very positive potentials, Ti(0) was oxidized directly to Ti(IV); however, the electrogenerated Ti(IV) vaporized from the melt as TiCl sub 4 (g). As found by other researchers working in Lewis acidic AlCl sub 3 -NaCl, Ti(II) tended to form polymers as its concentration in the AlCl sub 3 -EtMeImCl melt was increased. The electrodeposition of Al-Ti alloys was investigated at Cu rotating disk and wire electrodes. Al-Ti alloys containing up to approx =19% atomic fraction (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 Al-Ti alloys exhibited a positive shift with increasing titanium content comparable to that observed for alloys prepared by sputter deposition.