Using the electrochemical oxidation of monomers: pyrrole,aniline and pyrrole-aniline mixture of different compositions in aqueous solutions containing dopant anions as supporting electrolyte, the polymeric conductive films of polypyrrole and polyaniline and also, the composite films of polypyrrole-polyaniline were electrodeposited on the Co67Cr29W4 alloy electrode Surface The electrochemical properties of the obtained modified electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that the mechanism of the redox process is complex and may be governed by the diffusion of the electrolyte. It was observed that the cobalt based. alloy substrate had a considerable effect on the electrochemical activity of the polypyrrole and polyaniline films and that because in the presence of polymeric film. anodization of these modified electrodes resulted in formation of an oxides complex film and polymeric: layers simultaneously This is consistent With a galvanic interaction between the polymer and the cobalt-chromium based alloy substrate. giving rise to oxidation of cobalt, chromium and tungsten and reduction of the polymer (C) 2009 Elsevier B.V. All rights reserved.