Processable polyaniline-HCSA/poly(vinyl acetate-co-butyl acrylate) corrosion protection coatings for aluminium alloy 2024-T3: A SVET and Raman study

Scanning vibrating electrode technique (SVET) analysis of processable polyaniline-HCSA/poly(vinyl acetate-co-butyl acrylate) coated on to aluminium alloy 2024-T3 exhibited strong interaction between the polymer coating and the underlying metal. A scribed defect in the coating surface resulted in rapid oxidation of the exposed metal within a coating defect while the overlying polymer coating underwent both reduction and dedoping. Under the conditions investigated no protective oxide was observed to form. Raman spectroscopy of the polymer surface confirmed that dedoping was the dominant process which was accompanied by a clear reduction of the emeraldine salt form of the coating to the leucoemeraldine base form within the defect. This coating/metal interaction was observed to be dependant of the proximity to an artificial defect, initially yielding a more reduced material in close proximity to the coating defect, providing evidence of an electrochemical interaction between the polyaniline co-polymer system rather than a barrier effect.