Influence of electrochemically prepared poly(pyrrole-co-N-methyl pyrrole) and poly(pyrrole)/poly(N-methyl pyrrole) composites on corrosion behavior of copper in acidic medium

Poly(pyrrole-co-N-methyl pyrrole) copolymer and poly(pyrrole)/poly(N-methyl pyrrole) bilayer composites were electrochemically synthesized on copper by cyclic voltammetry from aqueous solution of 0.3 M oxalic acid and 0.1 M monomer. Synthesis of copolymers were performed with different monomer feed ratios (pyrrole:N-methyl pyrrole, 8:2, 6:4, 5:5, 4:6 and 2:8) and in order to determine the copolymer, which has the best corrosion performance, anodic polarization was applied to copolymer coated samples. It was found that the performance of coatings was strongly dependent to the monomer feed ratio and the copolymer synthesized with 8:2 concentration ratio showed the most protective property compared to others. Bilayer of poly(pyrrole)/poly(N-methyl pyrrole) was also synthesized to compare the anticorrosive properties. Polymer films were characterized by ATR-FTIR spectroscopy and SEM techniques. Corrosion behavior of polymer composites was investigated in 0.1 M H2SO4 solution by anodic polarization and electrochemical impedance spectroscopy. Different approaches such as phase angle at high frequency and areas under Bode plots were used to evaluate corrosion performances of the coatings. Copolymer and bilayer coatings were found to have higher protection effect than single polypyrrole coatings. Moreover, bilayer coating exhibited better protection efficiency than copolymer coating against corrosion of copper when the obtained results were compared.

► We synthesized poly(pyrrole-co-N-methyl pyrrole) on copper from oxalic acid solution.
► We synthesized PPy/PNMPy bilayers on copper.
► We characterized copolymer and bilayer films.
► We examined corrosion performance of copolymer and bilayer films in H2SO4 solution.
► Copolymer synthesized with 8:2 monomer feed ratio has the best corrosion performance.