ANODIC-OXIDATION OF TITANIUM CARBIDE IN SULFURIC-ACID-SOLUTIONS STUDIED BY ELLIPSOMETRIC TOMOGRAPHY

Tomographical in situ measurements on titanium carbide, anodically pol arized (in 5 N H2SO4 solution at potential of 0.2 V), shows a rapid (n early linear) increase in the oxygen concentration in the surface oxyc arbide layer at the initial stage of polarization. During further pola rization, the formation of oxycarbide is impeded by slow diffusion, wh ich becomes the limiting stage of the process when the individual tita nium oxide phase forms over the titanium oxycarbide. The oxycarbide an d the oxide films on the TiC surface cause its passivity and high corr osion resistance within a potential range from free corrosion to oxidi zing decomposition. Spectral ellipsometric tomography in the mode of m onitoring the wavelength of the sounding radiation seems to be promisi ng for studying heterogeneous conductive surface systems of similar ty pe.