Graphene–Nickel Oxide–Polyaniline Ternary Nanocomposite-Embedded Epoxy Coating on Mild Steel for Corrosion Protection

The present work addresses the synthesis and application of graphene-based ternary nanocomposite for anticorrosion performance to protect mild steel in an accelerated corrosive environment. The chemically-functionalized graphene-nickel oxide (Gr-NiO)-PANI ternary nanocomposite is synthesized by the hydrothermal reduction of graphene oxide (GO) and nickel salt in the presence of urea, followed by interfacial wrapping of Gr-NiO by in situ grown polyaniline (PANI). The transmission electron microscopic images reveal the wrapping of Gr-NiO by PANI in the Gr-NiO-PANI ternary nanocomposite. The spectroscopic analyses (Fourier transform infrared and Raman) suggest the multiple interactions between Gr-NiO and interfacially grown PANI in Gr-NiO-PANI. The thoroughly blended Gr-NiO-PANI ternary nanocomposite into epoxy matrix via interfacial interactions provides uniform coating (thickness: 87 ± 6 μm) on mild steel and increases the hardness by 160%. The corrosion inhibition performance of PANI, Gr-PANI, and Gr-NiO-PANI nanocomposites in epoxy coating is probed based on electrochemical and salt spray measurements in a 3.5% NaCl solution. The Gr-NiO-PANI in the epoxy coating substantially enhances the total impedance and protects the underneath mild steel. The salt spray tests further corroborate the electrochemical results and demonstrate substantial enhancement in corrosion inhibition by Gr-NiO-PANI nanocomposite with no sign of corrosion even after 10 days, revealing its potential to mitigate corrosion of mild steel-based structural and engineering installations.