Morphology and charge effect of ZnO nanostructures on the performance of anticorrosion coatings

Corrosion as an unresolved problem causes irreversible damage to steel structures worldwide that even rigorously intensifies in marine aggressive environments. In the last decade, the essential inclusion of zinc oxide (ZnO) in marine protective coatings has been prominent for corrosion and biofouling mitigation as an alternative to toxic coating constituents. Towards the development of highly efficient marine coatings, we explored the morphology and charge effect on anticorrosion performance for various ZnO nanostructures (nanoparticles (NPs), nanowires (NWs), nanoflakes (NFs), and javelin-like (Jav)) possessing a range of surface charge between -3.81 and +30.43 mV. These ZnO nanostructures with different surface charges combined with negatively charged graphene oxide (GO) nanoflakes as ionic barrier in a self-polishing rosin-based biopolymer matrix were examined. Among the tested coatings, Rosin/GO/ZnO Jav showed the best performance with an impedance modulus |Z| 0.01Hz of 5.93 × 10 7 Ωcm 2 , and a significantly reduced corrosion rate of 9.95 × 10 -9 mmpy (millimetres per year), compared to the bare sample's |Z| 0.01Hz value of 892.32 Ωcm 2 and corrosion rate of 3.78 × 10 -2 mmpy. The excellent performance is attributed to the better electrostatic interaction between ZnO Jav and GO in suspension posing superior film formation ability regulated by the high surface charge (-44.23 mV) and javelin-like morphology of ZnO in the coating matrix. This simple and effective formulation with selective structural variation of ZnO nanostructures may thus be an excellent finding for marine protective coatings.