Gum Arabic-Assisted Polyaniline Nanofillers for Improving Anticorrosion Performance of Waterborne Epoxy Coatings

The agglomeration of polyaniline (PANI) nanofillers in waterborne resins substantially reduces the long-term corrosion resistance of the resins. In this study, we use gum arabic (GA), a biological macromolecule, as a green stabilizer to prepare aqueous dispersions of GA-PANI nanofillers via chemical oxidative polymerization. The highly dispersed GA-PANI nanofillers are incorporated into waterborne epoxy (WEP) matrix and sprayed onto Q235 steel surface. The results show that the GA-PANI nanofillers exhibit excellent dispersion, stability, and compatibility in WEP, as evidenced through transmission electron microscopy and scanning electron microscopy of the cross-sectional morphology, water-absorption tests, and coating adhesion tests. An electrochemical test indicates that the 3.0 wt % GA-PANI/WEP coating displays remarkable corrosion resistance, with the value of impedance modulus in the low-frequency region (|Z|_0.01Hz) remaining at 3.372 × 10⁷ Ω cm² after 60 days of immersion in a 3.5 wt % NaCl solution. This value is almost 1 order of magnitude higher than that of WEP. An X-ray photoelectron spectroscopy test confirms the presence of a corrosion product component on the coating/steel interface. Moreover, the GA-PANI nanofillers extend the penetration route of corrosive species and provide favorable adhesion and anodic protection.