The anodic behaviour of titanium carbide in sulphuric acid solutions

Abstract

Recent studies on the corrosion and passivation of titanium carbide layers prepared by chemical vapour deposition (CVD), and of titanium carbide single crystals, in aqueous sulphuric acid solutions at 23°C are summarised, together with experiments to test the feasibility of polishing titanium carbide anodically in methanolic solutions. In aqueous 2 N H 2SO 4, corrosion starts at 0.8 V (standard hydrogen electrode) with the formation of TiO 2+, Ti 3+ acting as an intermediate. The onset of passivation is observed at 1.0 V, the surface becoming progressively covered with the hydrated oxide TiO 2.H 2O. At potentials above 1.8 V, dissolution of this oxide is apparent and TiO 2 2+ passes into solution. For the anodic polishing of TiC, the best results were obtained under potentiostatic conditions in a 1 M or 2 M solution of H 2SO 4 in methanol within the range of 1.7 to 4.0 V (saturated mercurous sulphate electrode). Alternatively, a constant current density of 1 A cm -2 may be used. In the polishing region, CO 2, Ti(IV) and Ti(VI) have been identified as products.