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

Abstract

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.