Carbon-Dot-Assisted Mg–Al-Layered Double Hydroxide Dispersion in Waterborne Epoxy Coating with Enhanced Corrosion Protection

Owing to the uniqueness of their structure, remarkable specific surface area, and exceptional impermeability, two-dimensional layered nanomaterials (including graphene, hBN, MXene, LDH, and nanoclays) broadly act as reinforcing fillers to optimize the effectiveness of organic coatings in corrosion prevention. constituting the primary influence on coating performance is the state of their dispersion within the polymer matrix. Herein, a simple, exfoliation-friendly, and cost-effective method is reported for synthesizing functional LDH-Cdot nanohybrids for metal anticorrosion. A 3 nm carboxyl-rich carbon dot (Cdot) was prepared via pyrolysis and introduced into the LDH galleries, where it adsorbed onto LDH to form LDH-Cdot nanohybrids. Compared with pure LDH, LDH-Cdot exhibits a significantly improved water dispersion. By incorporation of the LDH-Cdot nanocomposite into a waterborne epoxy matrix, a corrosion-resistant coating featuring a controlled thickness of around 53 μm was successfully constructed. EIS results demonstrated that the impedance modulus at 0.01 Hz decreased in the sequence LDH-Cdot epoxy > LDH epoxy > pure epoxy. Notably, the |Z|0.01 Hz value of the LDH-Cdot epoxy coating was still retained at 4.05 × 108 Ω·cm2 following 90 days of immersion. Findings from LEIS and corrosion product analyses indicated that carbon dots anchored onto LDH are capable of coordinating with metal ions, which facilitates passivation layer formation and effectively slows corrosion kinetics.