Effect of solvents on the preparation and corrosion protection of polypyrrole

To clarify the effect of solvents with different donor number (DN) on the preparation and corrosion protection ability of polypyrrole (PPy) films, PPy were firstly synthesized in water or acetonitrile or nitromethane solutions containing NaClO4 + pyrrole by a potentiostatic method. The corrosion protection performances of these films with stainless steel as a substrate were investigated by open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy in 1 M H2SO4. Results indicated that all PPy films showed spherical structure in scanning electron microscopy photograph and corrosion protection ability. Particularly, PPy prepared in nitromethane solutions performed the best due to the lowest DN value. Nitromethane had the weakest interaction with the intermediates of pyrrole polymerization which results in the smallest particles, the most compact accumulation, the highest conductivity and the longest conjugated chain.