Electropolymerized PANI-TiO2 composite coatings for enhanced corrosion resistance of AA6060 aluminum alloy in saline environments

Abstract

Corrosion of aluminum alloys remains a major industrial concern, particularly in aggressive chloride-rich environments encountered in automotive, aerospace, and marine applications. AA6060 aluminum alloy, widely recognized for its excellent formability, strength-to-weight ratio, and versatile structural performance, is especially vulnerable to localized corrosion and pitting due to inherent limitations of its native passive oxide layer. Herein, the corrosion protection of AA6060 aluminum alloy was significantly enhanced through electropolymerization of polyaniline (PANI) composite coatings reinforced with titanium dioxide (TiO 2 ) nanoparticles. Coatings were synthesized by cyclic voltammetry using an electrolyte containing sulfuric acid, oxalic acid, aniline monomer, and dispersed TiO 2 nanoparticles. Comprehensive electrochemical investigations, including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS), demonstrated superior corrosion resistance for the composite-coated alloy compared to the bare substrate. Notably, the PANI–TiO 2 coating exhibited significantly elevated polarization resistance (R p ) values, which increased from approximately 4.5×10 3 Ω cm 2 (uncoated alloy) to 7.9×10 4 Ω cm 2 upon coating. Correspondingly, the corrosion current density (i corr ) decreased by nearly four orders of magnitude, indicating suppression of corrosion processes. Surface and structural analyses (SEM-EDX, XRD, FTIR) confirmed the coating’s compositional integrity, morphological stability, and effective barrier characteristics even after 48 h immersion in 3.5 wt.% NaCl solution. The excellent corrosion inhibition performance of the PANI–TiO 2 composite coating is attributed primarily to robust physical barrier effects and electrochemical passivation, providing effective protection for AA6060 alloy in aggressive chloride-containing environments.