Enhancement of the shielding/passivation dual functions of PANI-SSA/epoxy composite coatings by rGO for long-term anti-corrosion of Al alloy

Abstract

Conductive polymers have attracted significant attention in the field of anti-corrosion coatings due to their unique passivation effects on certain metal substrates. In this work, a sulfosalicylic acid doped polyaniline (PANI-SSA)/reduced graphene oxide (rGO)/epoxy (P-r/EP) composite coating was proposed for the long-term anti-corrosion of Al alloys. The strategic introduction of rGO not only enhances the passivation ability of PANI-SSA but also improves the barrier effect of the composite coatings to the corrosive media. The results indicate that the addition of rGO reduces the defects of the composite coatings and improves the compactness of the composite coatings. Additionally, rGO exhibits outstanding electrical conductivity, facilitating the connection of PANI-SSA to form passivation networks in the local area of the composite coatings, thereby fully passivating the Al substrate to form a homogeneous and continuous oxide film. The P-r_0.5/EP composite coating exhibits the most durable anti-corrosion performance with the |Z|_0.01 Hz value of 5.55 × 10⁹ Ω⋅cm² after 360 days of immersion, achieving an optimal balance between oxide film formation and the shielding performance of the composite coatings. Consequently, the P-r/EP composite coatings achieve a sustained passivation effect on the Al substrate and show broad potential for long-term anti-corrosion.