Novel Lignin-Functionalized Waterborne Epoxy Composite Coatings with Excellent Anti-Aging, UV Resistance, and...

Developing high-performance lignin anti-corrosive waterborne epoxy (WEP) coatings is conducive to the advancement of environmentally friendly coatings and the value-added utilization of lignin. In this work, a functionalized biomass waterborne epoxy composite coating is prepared using quaternized sodium lignosulfonate (QLS) as a functional nanofiller for mild carbon steel protection. The results showed that QLS has excellent dispersion and interface compatibility within WEP, and its abundant phenolic hydroxyl, sulfonate, quaternary ammonium groups, and nanoparticle structure endowed the coating with excellent corrosion inhibition and superior barrier properties. The corrosion inhibition efficiency of 100 mg L^-1 QLS in carbon steel immersed in a 3.5 wt% NaCl solution reached 95.76%. Furthermore, the coating maintained an impedance modulus of 2.29 × 10⁶ Ω cm² (|Z|_0.01 Hz) after being immersed for 51 days in the high-salt system. In addition, QLS imparted UV-blocking properties and thermal-oxygen aging resistance to the coating, as evidenced by a |Z|_0.01 Hz of 1.04 × 10⁷ Ω cm² after seven days of UV aging while still maintaining a similar magnitude as before aging. The green lignin/WEP functional coatings effectively withstand the challenging outdoor environment characterized by high salt concentration and intense UV radiation, thereby demonstrating promising prospects for application in metal protection.