Designed a novel EP + GO/ZRC + GO coating with bilayered structure for enhancing corrosion resistance of steel substrate

Highlights: • Both epoxy zinc-rich coating and graphene-based coating own their advantages and shortages. • Five coatings with bilayered structure were designed and fabricated. • Anticorrosion mechanism of the coatings was clarified. The study aimed to provide an effective way to combine the advantages of both the zinc-rich epoxy coating and the graphene-based coating. Herein, we introduce ZRC + GO/EP + GO and EP + GO/ZRC + GO coatings with bilayered structure. In addition, the bilayered ZRC, ZRC + GO and EP + GO coatings were also fabricated to comparatively investigate the anticorrosion mechanisms of the coatings. In order to obtain better dispersion of GO in waterborne coatings, ionic liquid (1-aminoethyl-3-methylimidazolium bromide) was successively grafted on GO, which was confirmed by XPS, Raman and FT-IR results. The results obtained from electrochemical impedance spectroscopy (EIS) and salt spray test proved that the as-prepared EP + GO/ZRC + GO coating presented superior corrosion protection which was derived from the synergistic effect of barrier property and cathodic protection endowed by the special bilayered structure of the coating. Besides, SEM, EDS and XRD results of the coating-exfoliated steel substrates also revealed the steel substrate coated by EP + GO/ZRC + GO was not obviously corroded at the end of the immersion.