The electrochemical copolymerization of pyrrole and bithiophene on stainless steel in the presence of SDS in aqueous medium and its anticorrosive performance

For the first time, the electrosynthesis of poly(pyrrole-co-bithiophene) copolymers (P(Py-co-BT) I, II, III) was carried out using the potentiostatic technique on stainless steel (SS) electrode from aqueous oxalic acid solutions containing fixed concentration of bithiophene (BT) and different concentrations of pyrrole (Py) in the presence of sodium dodecylsulfate (SDS). Corrosion protection behaviors of these copolymer-coated steels were investigated in 3.5% NaCl solution by potentiodynamic polarization, Tafel test technique and electrochemical impedance spectroscopy (EIS). Among the protective copolymer coatings, the P(Py-co-BT) II, which was obtained from polymerization solution containing 0.025 M Py, exhibited the best protection against corrosion. Hence, only this copolymer was characterized by cyclic voltammetry, FT-IR, UV–vis, conductivity measurement and differential scanning calorimetry (DSC) by comparing with those of the polybithiophene (PBT) and polypyrrole (PPy) homopolymers. It was determined that this polymer was the polypyrrole-based copolymer. The incorporation of BT units into PPy chains not only increased dry conductivity but also developed the toughness of polymer.