Abstract. Titanium dissolution and passivation were studied in NaOH aqueous solution using open-circuit potential, potentiodynamic and potentiostatic techniques. Potentiodynamic data showed that the active-passive transition involves active metal dissolution followed by formation of a poorly conducting passive oxide film that passivates the electrode. The critical current density varied with pH as dlogI>j/I>SUB>m/SUB>/dpH=-0.098 in the pH range 11.0014.00, while the passivation potential is changed according to the following two features: at pH10.5513.00, dI>E/I>SUB>m/SUB>/dpH=-0.06V; and at pH13.5014.00, dI>E/I>SUB>m/SUB>/dpH=-0.40V. The apparent activation energy, E*, was calculated from the slope of the Arrhenius plot and was found to be 12.6kJmol1. Current-time transients showed that the growth of titanium oxide passive film is a diffusion-controlled process. XPS measurements indicated that the passive oxide film consists mainly of TiO2 and a mixture of suboxides of Ti2O3 and TiO.