Mechanism of the Electrolytic Deposition of Titanium

Abstract

ONE of the commercial methods of manufacturing pure titanium metal involves the high-temperature electrolysis of either K₂TiF₆, TiCl₄ or TiCl₃ in a molten alkali halide eutectic. Several such processes have been in operation for some time, and certain details of the preparative techniques have been published¹. The mechanism of these electrolytic methods has, however, remained in doubt. Of the two possibilities, (1) primary deposition of a titanium ion, complex or otherwise, on to a suitable cathode, or (2) secondary deposition where the titanium species are reduced by electrolytically produced alkali metal, the latter has seemed more probable because of the amorphous nature of the resultant titanium. It is true that fairly large dendritic crystals of titanium are produced during the electrolysis, but such dendrites are also found in the commercial preparation of titanium where TiCl₄ is reduced with liquid sodium. The current–voltage relations observed during electrolysis are also in keeping with a predominantly secondary process.