Effect of lignin incorporation on the performance of epoxidized soybean oil biobased coatings for corrosion protection

This study reports a fully bio-based, UV-cured anti-corrosion coating developed by mixing epoxidized soybean oil (ESO) and lignin. Rheology and photorheology revealed stable viscosity and high UV reactivity, while Fourier Transform Infrared spectroscopy showed high epoxy group conversion. The coatings exhibited robust thermal stability (as determined by thermogravimetric analysis) and valuable surface properties, including high pencil hardness, excellent adhesion, good solvent resistance, and tunable contact angle. Electrochemical impedance spectroscopy measurements acquired in 3.5 wt%. NaCl electrolyte demonstrated that lignin remarkably improves barrier protection, whereas unmodified ESO films offer little protection against corrosion in a harsh saline environment. Field Emission Scanning Electron Microscopy analysis of coated steel after corrosion tests further confirmed the good corrosion resistance of the coatings. These findings demonstrate a sustainable route to high- performance, eco-friendly corrosion protection.