Effect of polypyrrole conformational rearrangement on Al alloys corrosion protection

Polypyrrole (PPy) films were galvanostatically synthesized on 6082-T6 and 2024-T3 Al alloys. Experiments based on Otero’s Electrochemically Stimulated Conformational Relaxation (ESCR) model were used to investigate PPy re-oxidation kinetics as a function of polymer compaction. Chronoamperograms after pre-polarization at different cathodic potentials for various times were recorded in LiClO4/propylene carbonate solution. Physico-chemical parameters such as compaction coefficient, closing potential and diffusion parameter were used to characterize the relaxation and diffusion controlled processes of PPy films. All indicate that conformational rearrangements depend mainly on polymer structure, governed in turn by substrate nature. However, experiments in aggressive NaCl solution have confirmed the importance of the redox process dynamics on the protection performance of PPy against Al alloy degradation. Galvanic coupling has been confirmed to be the main factor for effective corrosion protection of Al 2024 by Ppy.