Electropolymerization of poly(N-methylaniline) on mild steel: Synthesis, characterization and corrosion protection

Poly(N-methylaniline) (PNMA) coatings on a steel disc electrode have been successfully electrodeposited from N-methylaniline (NMA) in aqueous oxalic acid solution using potentiodynamic, potentiostatic and galvanostatic techniques. For the potentiodynamic synthesis, formation of the PNMA coatings was found to be strongly dependent on the upper potential limits and scan rates. Smooth and strongly adherent PNMA coatings were obtained under potentiodynamic conditions during sequential scanning of the potential region between −0.5 and 1.0 V, at a scan rate of 10 mV s−1. The PNMA coatings were characterized by cyclic voltammetry, FT-IR and UV-Vis spectroscopy and SEM techniques. It was shown that NMA converts the iron(III) species to iron(II) chemically, causing a decrease in the current value corresponding to the electrochemical conversion (repassivation). The corrosion behavior of steels covered by polymer was investigated by anodic potentiodynamic polarization technique and the Tafel test. The corrosion resistance of the PNMA coated steel was found to be considerably higher and the corrosion rate was much slower than that of bare steel.