Anticorrosive Behavior of a Novel Ternary RGO–ZnO–PANI Nanocomposite-Reinforced Epoxy Coating on Mild Steel in Marine Environment

In this study, a novel corrosion-resistant reduced graphene oxide (RGO)–ZnO–polyaniline (PANI) nanocomposite is successfully synthesized by decorating ZnO nanorods onto RGO via ultrasonication, followed by PANI wrapping and incorporated into the epoxy matrix through the solution blending method. Coating morphology, chemical structure, thermal stability, and wettability are analyzed through field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and contact measurements. Among all coatings (EP, EP/RGO, EP/RGO–ZnO, and EP/RGO–ZnO–PANI), the EP/RGO–ZnO–PANI coating exhibits the smoothest surface, highest thermal stability, and enhanced hydrophobicity. The anticorrosive behavior of mild steel (MS) coated with epoxy-based nanocomposite coatings is evaluated using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy, and salt spray tests. PDP results display that the EP/RGO–ZnO–PANI coating provides the highest corrosion protection efficiency (99.98%) in a 3.5 wt% NaCl solution. Electrochemical impedance spectroscopy (EIS) and salt spray tests (ASTM B117) analysis confirms superior long-term corrosion resistance of the ternary composite coating over 45 days immersion in 3.5% NaCl and 1000 h exposure to 5 wt% NaCl, respectively, compared to other coatings. These findings suggest that the synthesized ternary composite is a potential candidate for corrosion protection applications.