Designing a dual barrier-self-healable functional epoxy nano-composite using 2D-carbon based nano-flakes functionalized with active corrosion inhibitors

Graphene oxide (GO) nanosheets were in-situ functionalized via polypyrrole (POP) nanoparticles using ammonium persulfate and afterward doped with sodium molybdate (GPM) and finally incorporated into the epoxy resin for achieving a nano-composite coating with dual barrier and self-healing properties. The synthesized nanoparticles were characterized by field-emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), and thermal gravimetric analysis (TGA) techniques. The release mechanism of the inhibitors from the GPM was investigated in both solution and coating phases. In addition, the modified coatings were tested electrochemically using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization as well as the pull-off test, cathodic disbonding, and salt spray. Results from FE- SEM /EDS, FT-IR, TGA, and XRD investigations supported the successful synthesis of the GPM complex and molybdate adsorption on the surface of GP. Electrochemical measurements revealed that the release of MoO4−2 from GPM resulted in the creation of a compact protective layer on the steel surface, enhanced inhibitive ability, and a low corrosion rate (1.41 A cm−2). It was shown that the charge transfer resistance of the bare steel sample in the blank solution enhanced from 2360 Ω cm2 to 8530 Ω cm2 in the presence of GPM after 1 h immersion time. The epoxy coating's ability to prevent corrosion was also improved by the GPM nanoparticles, reaching 99%.