Coatings of Conducting Polymers for Corrosion Protection of Mild Steel

The investigation of electrochemical behavior of different conducting polymers, polythiophene (PTh), polypyrrole (PPy) and polyterthiophene (PTTh) on a mild steel (MS) electrode were done. Moreover, the combinations of the conducting polymers PTh and PPy was investigated. The synthesis of all polymeric coatings was done by the cyclic voltammetry technique. The electrochemical impedance spectroscopy (EIS) measurements were used to evaluate the corrosion performance of coated mild steel by different polymers in 0.5 M of different acid solutions (HCl, HClO4, H2C2O4, H3PO4 and HNO3). The protection of all polymeric coatings against corrosion of the substrate was promising and the bilayer coating PPy/PTh gave the best protection efficiency in all used acids. The order of efficiency for the different coatings in HCl and HNO3 solutions was MS/PPy/PTh > MS/PPy > MS/PTTh > MS/PTh but the order in HClO4, H3PO4 and H2C2O4 solutions was MS/PPy/PTh > MS/PTTh > MS/PPy > MS/PTh.