In the present study potentiodynamic polarisation curves were obtained for carbon and stainless steel in contact with 3% sodium chloride aqueous solution saturated with air in order to evaluate the capacity of polyaniline in the emeraldine oxidation state to protect the surface against corrosion processes. A high stability of the PAni films was observed with a gain of the corrosion potential around 270 mV more positive in the substrate covered with PAni than in the case without it. Corrosion of steel could be prevented using the conducting polymers as a protective layer.