Anodic and cathodic processes of the Cl2/Cl− system on Ti/Pt-Ir (30% Ir) in comparison with Ti/Pt electrodes were examined. The anodic Cl2 evolution follows the same scheme on both the electrodes [FORMULLA OMITTED] but Ti/Pt electrodes undergo a marked passivation for ηan > 0.2V, whereas the passivation on Ti/Pt-Ir electrodes is important only at overvoltages higher than 0.5V. Such a difference in passivation is noted also in the cathodic process: on Ti/Pt-Ir electrodes in fact, at low overvoltages, the process follows the scheme [FORMULLA OMITTED] due to the higher catalytic activity of the surface. © 1969, The Electrochemical Society, Inc. All rights reserved.