Electrochemical synthesis of polyaniline (PANI) was achieved on Ni plated (1 mum) mild steel (MS/Ni) and unplated mild steel (MS). The synthesis was carried out under cyclic voltammetric conditions from 0.1 M aniline containing oxalic acid solution. AC impedance spectroscopy (EIS) and anodic polarization curves were used to evaluate the corrosion performance of PANI coated and uncoated electrodes in 3.5 % NaCl. It was observed that Ni plating reduced drastically the corrosion rate of mild steel and exhibited an efficient barrier property on MS. However, the porosity of nickel plating increased for longer periods. It was found that polymer film decreased the porosity of Ni coating by catalyzing the passivation of this layer with time and that PANI top coat could provide significant protection efficiency to MS/Ni electrode. While PANI coated mild steel (MS/PANI) showed a protection property against the attack of corrosive products. Its lifetime was limited for extended periods. It was found out that corrosion resistance of Ni plating with PANI top coat (MS/Ni/PANI) was higher for much longer periods with respect to the one observed for mild steel. (C) 2004 Elsevier B.V. All rights reserved.