Graphene loaded with corrosion inhibitor cerium (Ⅲ) cation for enhancing corrosion resistance of waterborne epoxy coating: Physical barrier and self-healing

Abstract

Tannic acid (TA) was self-assembled with graphene (Gr) via π-π interaction. Then green corrosion inhibitor cerium (Ⅲ) cation (Ce3+) was loaded on graphene sheets through a reversible complexation with tannic acid which is depending on pH value, enabling the release of Ce3+ in an acid environment. Characterization methods including fourier transform infrared spectroscopy (FT-IR), raman spectroscopy, transmission electron microscope (TEM), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) mapping verified the successful preparation of Gr-TA and Gr-TA-Ce3+ hybrid materials. Electrochemical impedance spectroscopy (EIS) results of bare steel in the Gr-TA-Ce3+ extract showed the self-healing of Gr-TA-Ce3+ nanofillers which increased the impedance modulus at 0.01 Hz by one order of magnitude compared with bare steel. Waterborne epoxy coating doped with Gr-TA-Ce3+ material exhibited significant barrier performance originated from shielding property of graphene nanosheets against corrosive mediums and efficient self-healing capacity derived from the protective film formed by cerium cations. Electrochemical impedance spectroscopy results manifested that coating doped with Gr-TA-Ce3+ material maintained impedance modulus at 0.01 Hz of ~2.90 × 107 Ω.cm2 after immersion in 3.5 wt% sodium chloride solution for 60 days, two orders of magnitude higher than neat epoxy coating.