Polypyrrole modified nickel coating on mild steel

Electrochemical synthesis of polypyrrole (PPy) film was achieved on mild steel (MS) which has been previously coated with various thicknesses of nickel coatings. Electrodeposition of nickel coating on MS was carried out galvanostatically and the PPy top coating was synthesized by using cyclic voltammetry technique, in monomer containing oxalic acid solutions. The corrosion performances of single nickel coating (with different thicknesses from 0.5 to 4 μm) and PPy top coated nickel coatings have been investigated, in 3.5% NaCl solution. For this aim, electrochemical impedance spectroscopy (EIS) and anodic polarization curves were used. It was shown that the PPy modified nickel coatings could provide much better protection for mild steel, for longer periods when compared to single nickel coating. The polymer film exhibited simple physical barrier behaviour on top of Ni layer and hindered the attack of corrosive species. It was also shown that the polymer film enhanced the protection efficiency and life time of nickel layer, by accelerating and stabilizing the formation of protective oxide layer.