The influence of the aging time of RuO2 and TiO2 sols used for the preparation of (40% RuO2 + 60% TiO2)/Ti anodes by the sol-gel procedure on the electrochemical properties and behavior for the chlorine evolution reaction of obtained anodes was studied. The electrochemical (active) surface area of the anode coatings was examined by cyclic voltammetry. The electrocatalytic activity and stability of obtained anodes for the chlorine evolution reaction were investigated by polarization measurements and accelerated stability test. The dependence of electrochemical properties of obtained activated titanium anodes on RuO2 and TiO2 sol particle size was established. (C) 2000 Elsevier Science Ltd. All rights reserved.