Enhanced corrosion resistance of zinc-rich epoxy anti-corrosion coatings using graphene-Fe2O3 and HEDP

The presence of the block of conductive pathways, and the low utilization of zinc powders in coatings are severe challenges for the traditional zinc-rich coatings in practice application. In this paper, we use reduced graphene oxide (rGO), ferric oxide (Fe2O3) and 1-hydroxy ethylidene-1,1-diphosphate (HEDP) to design a ternary nano-composite for zinc-rich epoxy coatings with long-term anticorrosion performance. The results show that the zinc-rich coatings containing the optimal amount of 1.5 wt% rGO-Fe2O3-HEDP exhibit the most pronounced improvement in corrosion resistance performance due to the combination of three components with synergistic effect. Its cathodic protection is extended to 40 days, and the corrosion current density (Icorr) is 7.8 x 10-9 A cm-2 after 60-day immersion, which decreases by two orders of magnitude compared with that of the pure zinc coating. The rGO-Fe2O3-HEDP plays an important role in inhibition of corrosion-promoting effect of graphene, conducting connective path of zinc particles and substrate, physical shieling, activation of zinc particles, and self-repairing, due to the well-disperse and moderate conductivity of rGO based composite, superior coordination of HEDP with zinc and ferrous ions. The possible anticorrosion mechanism is also proposed. Therefore, this work provides a novel research perspective to solve the traditional heavy-duty zinc-rich anticorrosive coatings in the industry.