The kinetics of open circuit growth of an oxide film on zirconium electrode in NaN 3 solution of various concentrations was investigated using potential and capacitance measurements. The protective oxide film formed in azide solutions was found to thicken with time in two steps, the rate of oxide growth was found to decrease as the azide concentration increased. The corrosion behaviour of the electrode was characterized by ac impedance measurements to obtain detailed information about the effect of azide ion concentration on the electrical properties of the Zr electrode surface. The impedance response for the metal-metal oxide-electrolyte system was modeled with a transfer function. The potentiodynamic oxidation of Zr was also studied as a function of the azide ion concentration. The polarization curves showed the peak-shaped activeto-passive transition and the corrosion rate was found to increase with increase of azide ion concentration. The activation energy of corrosion was calculated according to Arrhenius plot and found to be 14.5 kJ mol À1 . The polarization results in azide solutions were compared to those obtained in solutions of different halide ions, namely, F À , Cl À , Br À and I À ions. The rate of corrosion was found to decrease in the order Br À > Cl À > F À , I À > azide. Opposite to the behaviour in azide solutions, the halide ions do not show the activepassive transition.