Polypyrrole films on nickel-plated copper

Polypyrrole (PPy) film was synthesized on nickel-plated copper electrodes, from monomer containing 0.2 M ammonium oxalate solution. The thickness of galvanostatically deposited nickel layer was 2 μm, while ∼0.80 μm thick polymer film was obtained by using cyclic voltammetry technique. The protective behavior of PPy modified nickel coating has been investigated, against copper corrosion in 3.5% NaCl solution. For this aim, ac impedance spectroscopy, the anodic polarization curves and open circuit potential-time (Eocp-t) diagrams were utilized. It was shown that PPy modified nickel coating could provide important protection to copper for considerable periods, in such aggressive medium. The thin polymer film constituted a physical barrier on top of nickel layer against the attack of corrosive environment for a certain period. Also, it was found that the thin PPy film could increase the protection efficiency and lifetime of nickel coating, by its catalytic behavior on formation of NiO layer.