Morphological changes of sputter-deposited TiN films in 0.1 M sulphuric acid have been followedin situwith scanning force microscopy at different potentials. Disappearance of small structures was observed with increasing potential up to 1.2 V. A further increase of potential above 1.5 V resulted in growth of larger grains. Two passivation peaks at about 0.6 and 1.2 V, respectively, were recorded for the TiN films. The passivating layers formed at these two passivation peaks were characterized by x-ray photoelectron spectroscopy. At the lower passivation peak, titanium suboxides or oxynitrides were detected, whileTiO2was formed at potentials above 1.2 V.