Improved UV Stability and Corrosion Resistance of Epoxy Zinc-Rich Coatings with Reduced Zinc Content via Graphene–Zinc Composite Networks

The study aims to enhance the comprehensive protective performance of epoxy zinc-rich coatings with reduced zinc content under ultraviolet aging and salt spray corrosion conditions. Although traditional high-zinc coatings provide cathodic protection, they often develop pore defects and exhibit poor adhesion, which limits their application in environmentally friendly and efficient protection systems. To address this issue, graphene with different loadings was introduced to construct a graphene–zinc composite network possessing both conductive and shielding functions. The effects of graphene content on coating structure and corrosion protection were investigated using XRD, FTIR, SEM, and electrochemical measurements. The results showed that adding 0.8 wt % graphene significantly improved the coating compactness, adhesion, and flexibility, reducing the corrosion current density from 2.88 × 10–6 A·cm–2 to 2.19 × 10–8 A·cm–2 while maintaining high impedance after 1440 h of salt spray exposure. Graphene formed a stable conductive pathway and a two-dimensional barrier structure at the epoxy–zinc interface, which promoted uniform electron transfer between zinc particles and sustained cathodic protection while effectively blocking UV radiation and electrolyte penetration-induced interface degradation. The study demonstrates that the graphene–zinc composite network, through the combined effects of electrical conductivity, shielding barrier, and corrosion product sealing, significantly delays the aging and failure processes of low-zinc systems and provides a scientific basis and engineering guidance for the design of durable low-zinc protective coatings.