Corrosion Behavior and Passive Film Characteristics Formed on Ti, Ti[sub 3]SiC[sub 2], and Ti[sub 4]AlN[sub 3] in H[sub 2]SO[sub 4] and HCl

We report on the chemical and electrochemical corrosion of Ti, and in HCl and solutions. The chemical corrosion of under conditions similar to those used industrially for the electrolysis of HCl (15% HCl, 65°C) is significantly better than that of pure Ti, indicating that it could be a promising substrate for dimensionally stable anodes. The enhanced resistance is attributed to the formation of a thin, passivating -based layer. The same layer protects during its anodic oxidation. After a 4 day period, during which the rate of growth of the -based layer is initially high, but then slows to a steady rate of about is established, which translates to a Ti dissolution rate of Analysis of Mott-Schottky plots and electrochemical impedance spectra show that the passive films that form onto Ti and in 1 M HCl and at room temperature are n-type semiconductors dominated by space-charge capacitances. The films forming on have significantly lower space-charge-layer thicknesses and higher donor densities than those that form on Ti. Preliminary results for indicate that the passive film formed is a p-type semiconductor. © 2004 The Electrochemical Society. All rights reserved.