This study focuses on the synthesis and characterization of a new epoxy resin, Tetraglycidyl orthophenyl diamine (TGOPDA), as an effective corrosion inhibitor for C38 carbon steel in 1 M HCl. The structure of TGOPDA was confirmed using Fourier transform infrared spectroscopy. The corrosion inhibition and adsorption behavior of TGOPDA were evaluated through weight loss measurements, thermodynamic/kinetic parameters, and electrochemical techniques (Open Circuit Potential, Potentiodynamic Polarization, and Electrochemical Impedance Spectroscopy). Surface morphology was analyzed using SEM/EDX, and computational tools such as DFT, RDF, MC, and MD simulations were employed to understand the adsorption mechanism. The results showed that TGOPDA significantly improved the corrosion inhibition of C38 steel, achieving a protection rate of about 95.27% at 5 mM. The adsorption followed the Langmuir isotherm, and TGOPDA formed a protective barrier film on the steel surface, as confirmed by SEM and EDX studies. Computational investigations further validated the formation of a corrosion-protective barrier.This study focuses on the synthesis and characterization of a new epoxy resin, Tetraglycidyl orthophenyl diamine (TGOPDA), as an effective corrosion inhibitor for C38 carbon steel in 1 M HCl. The structure of TGOPDA was confirmed using Fourier transform infrared spectroscopy. The corrosion inhibition and adsorption behavior of TGOPDA were evaluated through weight loss measurements, thermodynamic/kinetic parameters, and electrochemical techniques (Open Circuit Potential, Potentiodynamic Polarization, and Electrochemical Impedance Spectroscopy). Surface morphology was analyzed using SEM/EDX, and computational tools such as DFT, RDF, MC, and MD simulations were employed to understand the adsorption mechanism. The results showed that TGOPDA significantly improved the corrosion inhibition of C38 steel, achieving a protection rate of about 95.27% at 5 mM. The adsorption followed the Langmuir isotherm, and TGOPDA formed a protective barrier film on the steel surface, as confirmed by SEM and EDX studies. Computational investigations further validated the formation of a corrosion-protective barrier.