Polyaniline sulfate nanoparticles as an alternative to zinc phosphate in alkyd anticorrosive coatings

Purpose This study aims to synthesize polyaniline sulfate nanoparticles (PANI sulfate NPs) and evaluate their effectiveness as environmentally friendly anticorrosive pigments for alkyd-based protective coatings as an alternative to conventional zinc phosphate inhibitors. Design/methodology/approach PANI sulfate NPs were synthesized via a template-free in situ chemical oxidative polymerization method. The prepared NPs were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy with EDX. The synthesized NPs were incorporated into alkyd primer formulations and applied onto mild steel panels with a dry film thickness of 105 ± 5 µm. The coatings were evaluated according to ASTM standard methods for physicomechanical properties, chemical resistance, adhesion and corrosion resistance through seawater immersion testing. Findings The obtained results demonstrated that coatings containing PANI sulfate NPs exhibited excellent anticorrosive performance comparable to or superior to coatings formulated with zinc phosphate. The PANI sulfate-based coating showed high rust resistance (grade 9), low scribe failure (2 mm) and minimal blistering after prolonged seawater immersion exposure. In addition, the incorporation of PANI sulfate NPs significantly improved adhesion and maintained excellent hardness, flexibility, impact resistance, gloss stability and chemical resistance. The enhanced protection performance was attributed to the synergistic barrier effect, strong interfacial adhesion and passivation capability of the conductive polyaniline NPs, which effectively suppressed the penetration of corrosive species and reduced electrochemical corrosion reactions. Originality/value This work demonstrates the successful use of PANI sulfate NPs as an efficient and low-cost alternative to conventional zinc phosphate anticorrosive pigments in alkyd coating systems. The prepared nanostructured coatings combine improved mechanical durability with superior corrosion protection, highlighting their potential for advanced environmentally friendly protective coating applications.