The antagonistic impact of filler conductivity effect on its dimensional barrier performance in anticorrosion coatings

This study focuses on the antagonistic effect between the dimensional barrier and electrical conductivity of reduced graphene oxide (rGO) in epoxy anti-corrosion coatings. By regulating hydrothermal reduction conditions, rGO with tailored sheet size and conductivity was prepared and incorporated into epoxy coatings. The microstructures, electrochemical behavior, and long-term anti-corrosion performance were systematically investigated. Results demonstrate that the corrosion resistance is determined by the competition between dimension effect and conductivity effect. MZrE-rGO₁₂₀ and MZrE-rGO₁₄₀ show poor protection due to the negative dimension effect caused by agglomeration and insufficient barrier. MZrE-rGO₁₈₀ exhibits accelerated local corrosion owing to the detrimental conductivity effect that induces severe micro-galvanic corrosion. In contrast, MZrE-rGO₁₆₀ achieves an optimal antagonistic balance, presenting the highest impedance, lowest porosity, and weakest corrosion propagation. After 30 days of immersion and 900 h of salt spray, MZrE-rGO₁₆₀ still exhibits superior long-term durability.