Electrodeposition of sulfonated polypyrrole (SPPy) on 304-stainless steel (SS) was achived in fluorosulfonic acid (FSO3H)/acetonitrile medium using potentiostatic techniques. Adherent and homogeneous SPPy films were obtained. The corrosion behavior of stainless steel with sulfonated PPy coatings in 0.5 M hydrochloric acid solutions, were investigated by potentiodynamic polarization technique, open circuit potential-time curves and electrochemical impedance spectroscopy technique (EIS). It was found that the sulfonated PPy prepared in the presence of 10 mM FSo(3)H (SPPy)1 could provide much better protection than sulfonated PPy prepared in the presence of 50 mM FSo(3)H (SPPy)2. Polarization results showed that (SPPy)1 inhibits the pitting corrosion of SS while EIS measurement shows that both coating gives protection efficiency of greater than 90% after 48 h of immersion time in corrosive test solution. (c) 2005 Elsevier B.V. All rights reserved.