Anodic and cathodic processes of the system on (30% Ir) in comparison with Ti/Pt electrodes were examined. The anodic Cl2 evolution follows the same scheme on both the electrodes but electrodes undergo a marked passivation for , whereas the passivation on electrodes is important only at overvoltages higher than 0.5V. Such a difference in passivation is noted also in the cathodic process: on electrodes in fact, at low overvoltages, the process follows the scheme due to the higher catalytic activity of the surface.