Enhancement of the active/passive anti-corrosion properties of epoxy coating via inclusion of histamine/zinc modified/reduced graphene oxide nanosheets

This research introduces a green/novel route for preparation of an epoxy system with bi-functional active/passive anti-corrosion properties via inclusion of modified/reduced graphene nanoparticles. For the first time, the reduced nanosheet (RGO) with the barrier-inhibitive activities was prepared using bioactive reductant based on histamine. Also, zinc cations were loaded onto RGO sheets by two sequence based (RGO-Hist-Zn-I nanosheet) and in-situ based (RGO-Hist-Zn-II nanosheet) approaches. Characterization of the synthesized RGOs using X-ray photoelectron spectroscopy, field emission-scanning electron microscopy, transmittance electron microscopy, ultraviolet-visible and inductively coupled plasma techniques approved the precision of graphene oxide reduction via histamine and zinc cation's chemical adsorption. The performance of the RGO nanosheets was investigated by electrochemical impedance spectroscopy, potentiodynamic polarization, salt spray, pull off adhesion, cathodic disbondment (CD) and energy dispersive X-ray spectroscopy analyses. The results clarified that the epoxy coating reinforced with RGO-Hist-Zn-I provided the best anti-corrosion performance (log |Z|10 mHz = 9.73 Ω cm2 after 60 days immersion in NaCl solution), self-healing property (liberation of histamine and zinc cations from the nanocomposite bulk to the scratch region after 8 h immersion), adhesion to steel surface (lowest adhesion loss, i.e. 14.2% after 38 days of immersion and CD resistance (ca. 4.7 mm).