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Polyaniline and nanoparticle containing anodic films for corrosion protection of 2024T3 aluminium alloy

Abstract Anodic alumina films containing polyaniline and TiO2 or ZrO2 nanoparticles were electrochemically synthesised on an AA2024T3 aluminium alloy in a single step anodising process carried out in oxalic acid electrolyte containing aniline and nanoparticles. The morphology and composition of the films were examined by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The resultant coatings, with a thickness of ∼2·5 μm, presented a polyaniline and nanoparticle rich layer in the near surface region, with a thickness in the range of 150–250 nm. The electrochemical polarisation curves revealed that the TiO2 containing films provide improved corrosion protection to the AA2024T3 aluminium alloy, showing a passive current density two orders of magnitude lower than the films with ZrO2 nanoparticles and the films without nanoparticles. The improved corrosion protection offered by the TiO2 nanoparticle containing coatings is attributed to the presence of the nanoparticle rich layer formed on the outer part of the coating, which acts as a barrier layer that blocks the pores of the anodic alumina film.