Polystyrene/TiO₂Nanocomposite Coatings To Inhibit Corrosion of Aluminum Alloy 2024-T3

Polystyrene (PS)/TiO2 nanocomposite coatings (PNCC) with extremely high TiO2 nanoparticle loadings (42 vol %) generated by capillary rise infiltration were applied for the first time on AA2024-T3 aluminum alloy for corrosion protection. The corrosion behavior of the coatings in 3.5 wt % NaCl aqueous solution was evaluated. Microscopic morphology, X-ray diffraction, energy dispersive spectroscopy, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) testing were performed to evaluate the corrosion behavior of PNCCs across immersion time as compared to the bare and PS-coated Al alloy specimens. It showed PNCCs exhibited better corrosion protection of Al alloy than the pure PS coating. The thickness ratio of the PS layer to the TiO2 layer in PNCCs before annealing had an effect on the microstructure and corrosion behavior of PNCCs. When the PS/TiO2 layer thickness ratio was smaller than the porosity of the TiO2 layer (0.58), PS partially filled the voids of the TiO2 layer, generating a less dense PNCC; when the PS/TiO2 layer thickness ratio was close to the porosity of the TiO2 layer, PS completely filled the pores of the TiO2 layer, generating a dense PNCC with the same thickness as the TiO2 layer. When the PS/TiO2 layer thickness ratio was larger than the porosity of the TiO2 layer, PS completely filled the interstices of the TiO2 layer, generating a dense and thinner PNCC; however, a residual PS layer underlying was observed. The results demonstrated that the PNCC whose PS/TiO2 layer thickness ratio was close to the porosity of the TiO2 layer showed the best corrosion protection of Al alloy among all the coatings in the 3.5 wt % NaCl aqueous solution.

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