In this study, we will be discussing the effect of isocyanate on the anti-corrosive property of the mild steel by the co-polymerizationof urethane with benzoxazine, which was synthesized from eugenol, glycine ethyl ester and paraformaldehyde.Monomer was characterized by proton, carbon NMR, Fourier Transform-IR and Ultraviolet- visible techniques. Similarly, the co-polymer was also characterized by Fourier Transform-IR and Ultraviolet- visible techniques. The polymerization process was conducted on the mild steel surface by dip-coating of the benzoxazine with isocyanate hardener in three ratios i.e., 60%, 80%, 100% and cured in a muffle furnace. Then, the coated mild steel was investigated for the anti-corrosive property using Polarization and Electrochemical Impedance Spectroscopy.The results show that the rise in the amount of isocyanate hardener on the metal surface will elevate the corrosion inhibition efficiency. The morphological studies and elemental analysis performed by using SEM- EDAX. The hydrophobicity of the copolymer was investigated by usual ASTM-D570 methods like water absorption and Gel absorption studies. The theoretical studies DFT was also performed to support the anti-corrosive property of the synthesized monomer and its copolymer in terms of the band gap, electrophilicityfactors.