Polypyrrole/PW 12O 40 3− hybrid material was electrosynthesised on carbon steel electrodes in acetonitrile medium. The coatings obtained were characterised by Electrochemical Impedance Spectroscopy (EIS). On free-standing polypyrrole films the electrical response was mainly due to ion–ion charge transfer resistance, with a value of 175 Ω cm 2. A value of 2 × 10 −5 S/cm was determined for the hybrid material conductivity. A charge transfer resistance about 7000 Ω cm 2 was obtained due to steel/oxide interface. Corrosion tests showed an important improvement in the protection against corrosion when the carbon steel electrodes were coated by these polymeric films.