Enhanced Corrosion Resistance of Waterborne Epoxy Coatings by High-Entropy Layered Double Hydroxides/Graphitic Carbon Nitride Fillers.

Two-dimensional nanomaterials exhibit excellent physical barrier properties, which can effectively enhance the corrosion resistance of waterborne epoxy coatings. Herein, we report a facile strategy for preparing a multi-component synergistic anti-corrosion coating, where two-dimensional graphitic carbon nitride (g-C3N4) and high-entropy layered double hydroxides (HE-LDHs) are integrated into a waterborne epoxy matrix via magnetic-ultrasonic synergistic dispersion. The resulting HE-LDHs/g-C3N4-epoxy coating exhibits exceptional corrosion resistance for Q235 steel. Electrochemical impedance spectroscopy (EIS) and polarization curves showed that when the mass ratio of g-C3N4 to HE-LDHs was 1:1, the resulting coating (PCN-LDH-1.0) maintained a coating resistance of 5.48 × 105 Ω·m2 after 28 days of immersion in 3.5% NaCl solution, which was five orders of magnitude higher than that of pure waterborne epoxy coating. Meanwhile, the corrosion current density was reduced by four orders of magnitude, from 5.83 × 10-1 A·m-2 to 1.68 × 10-5 A·m-2. After 30 days of salt spray testing, no rust, blistering or adhesion loss was observed on the coating surface. These enhanced performances by addition of g-C3N4 and HE-LDHs were attributed to the combined effects of the tortuous diffusion pathways. Additionally, the PCN-LDH-1.0 coating retained excellent mechanical properties, including a pencil hardness of 3H and the highest adhesion grade. This study provides a facile method for preparing high-performance waterborne anti-corrosion coatings.