Polyaniline (Pani) films Were frown potentiodynamically on Pt electrodes in 0.1 M aniline/0.5 M acid (H2SO4 Or HClO4), or in a 0.1 M aniline/0.5 hi acid/0.2 M salt containing an alkaline cation, between -0.25 and 0.69 V vs. SCE. A series of films were grown at a sweep rate of either 0.1 V s(-1) or 0.002 V s(-1) only for the first cycle, followed by 0.1 V s(-1) for the remaining cycles up to a constant anodic charge of 40 mC cm(-2). Changes in the morphology, as well as in the electrical properties of the films as a function of the initial potential perturbation and the alkaline cation in the electrolyte were followed, respectively, by SEM images and electrochemical impedance spectroscopy measurements. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.