Corrosion protection of mild steel by electroactive polyaniline coatings

The ability of polyaniline (PANi) to act as a protective coating for mild steel corrosion in saline and acid was investigated by electrochemical impedance spectroscopy. The impedance behaviour is best explained by a mediated redox reaction in which PANi passivates the metal surface and reoxidizes itself by dissolved oxygen. The effectiveness of such a process, which also provides the repassivation of damaged films, is greater in acids. The performance of PANi is further enhanced by the presence of a top coat to increase the diffusional resistance for the corrosion species.