Polyaniline, poly(N-methylaniline) and poly(aniline-co-N-methylaniline) coatings on stainless steel

Polyaniline (PANI), poly(N-methylaniline) (PNMA) and poly(aniline-co-N-methylaniline) (PANI-co-PNMA) coatings were synthesised on stainless steel (SS) surface (AISI 316) in two different supporting solutions, oxalic acid and sulphamic acid. PNMA and PANI-co-PNMA films failed to be synthesised in sulphamic acid solution. Homo-and copolymer films were achieved as homogenous and adherent structures as shown in scanning electron images. Electrochemical corrosion properties of homo-and copolymer films were investigated in 3.5% NaCl solution by electrochemical techniques including a potentiodynamic method and ac impedance spectroscopy. Potentiodynamic studies proved that the PNMA coating had a better electroactive structure in comparison with homo-and copolymer coatings. The results showed that homo- and copolymer coatings exhibited an effective barrier property on a SS electrode and a remarkable anodic protection to the substrate for a longer exposure time. A superior corrosion protection property was obtained by PNMA coating by providing enhanced catalytic efficiency for the formation of protective oxide layers on the metal surface.