Effects of graphene oxide content on corrosion resistance and mechanical performance of zinc-rich epoxy coatings under different corrosive environments

Steel structures exposed to harsh marine environments and intense ultraviolet (UV) radiation frequently encounter corrosion challenges. In this paper, five zinc-rich epoxy coating/steel substrate specimens with varying graphene oxide (GO) contents (0, 0.1, 0.3, 0.5, and 0.7 wt.%) were designed to evaluate their corrosion resistance and mechanical performance under dry-wet cycling (DWC) and UV dry-wet cycling coupling (UVDWC) conditions. Surface morphology was initially characterized using electron microscopy, while scanning electron microscopy (SEM) provided microstructural analysis of coating porosity. The corrosion protection capability was assessed through open circuit potential (OCP) measurements and electrochemical impedance spectroscopy (EIS). Mechanical evaluation consisted of three-point bending tests for elastic modulus determination and tensile testing combined with digital image correlation (DIC) to characterize interfacial bonding properties through fracture strength, fracture toughness, and interfacial shear strength analyses. The results demonstrated that the enhancement effect of GO on both corrosion resistance and mechanical properties of the coating/steel substrate system initially increased and then decreased with increasing GO content. The optimal performance was achieved at 0.3 wt.% GO content, where the composite system exhibited maximum corrosion resistance and mechanical properties. However, it was found that exposure to UV radiation compromised the enhancement effect of GO, indicating that environmental conditions may influence its enhancement efficacy.