Novel One‐Step Synthesis of Bio‐Polyol From Tung Oil‐Based FAME Using CMBSA‐Si Catalyst at Ambient Temperature and Its Characterization DFT and Application in Anticorrosion Coating

Chloride‐induced corrosion of mild steel reinforcement remains a major challenge in reinforced concrete structures. In this study, a bio‐based polyol was synthesized from tung oil‐derived fatty acid methyl ester (FAME) using a heterogeneous CMBSA‐Si catalyst under ambient‐temperature conditions without external heating. The synthesized polyol was subsequently utilized for the preparation of polyurethane coatings based on methylene diphenyl diisocyanate (MDI) and isophorone diisocyanate (IPDI) systems. The structural and chemical properties of the synthesized polyol were confirmed by FT‐IR, 1 H NMR, 13 C NMR, HR‐MS, TGA, and hydroxyl value analysis, while computational studies further verified the conversion of FAME into polyol. The prepared coatings were evaluated using FT‐IR, TGA, SEM‐EDAX, gloss, hardness, adhesion, flexibility, Taber abrasion, salt spray, cathodic disbondment, and contact‐angle analyses. Comparative studies revealed improved corrosion resistance, adhesion, and durability for the polyol‐based polyurethane coatings. Density functional theory (DFT) calculations at the B3LYP/3‐21G level were performed to investigate the electronic properties of FAME, polyol, MDI, IPDI, and their complexes. The polyol‐MDI and polyol‐IPDI systems exhibited lower HOMO–LUMO energy gaps, higher dipole moments, and favorable intermolecular interactions, which correlated with the coating performance observed experimentally. Overall, this work presents an ambient‐temperature route for tung oil‐derived polyurethane coatings with enhanced anticorrosion performance.