Effects of nitrate ions on the electrochemical synthesis and behavior of polypyrrole films

Effects of nitrate ions on the properties of polypyrrole films electrodeposited in phosphoric acid medium on 304 stainless steel were studied. The presence of nitrate ions enhances the process of oxidation by moving the oxidation potential of monomers toward more cathodic values and increases the current density of oxidation and reduction peaks while it has no effect on the morphology of the films. It is worth mentioning that nitrate ions have doped the formed films as proven by Infrared spectroscopy. Polarization curves and electrochemical impedance spectra performed in 3% NaCl solutions have shown that the doping of polymer films with nitrate ions improves the pitting corrosion resistance of the stainless steel and also increases the ageing time of polypyrrole coating.