Suppression of cathodic reactions on aluminum alloy 2024-T3 using polyaniline coating systems

The mechanism by which poly(aniline)-poly(methyl-methacrylate) (PANI/PMMA) blends inhibit cathodic reactions on aluminum alloy AA2024-T3 was discussed. The three mechanisms by which PANI coatings act as a corrosion inhibition system were also discussed. In the first case, the open-circuit potential (OCP) of the metal substrate is raised to a level at which the formation of a protective oxide on the surface occurs. In the second case, where once the PANI component of the blend is reduced, it releases its counteranion which complexes with metal ions released from the metal surface, forming an insoluble salt. In a third mechanism, the PANI component of the coating raises the OCP of the interface to values where cathodic reactions are kinetically hindered.