Present study is designed for the synthesis, characterization and corrosion inhibition behavior of two diamine aromatic epoxy pre-polymers (DAEPs) namely, N¹,N¹,N²,N²-tetrakis (oxiran-2-ylmethyl) benzene-1,2-diamine (DAEP1) and 4-methyl-N¹,N¹,N²,N²-tetrakis (oxiran-2-ylmethyl) benzene-1,2-diamine (DAEP2) for carbon steel corrosion in acidic medium. Synthesized DAEPs were characterized using spectral (Nuclear magnetic resonance (¹H NMR) and Fourier transform infrared-attenuated total reflection (FTIR-ATR)) techniques. Viscosity studies carried out at four different temperatures (20–80 °C) increase in temperature causes significant reduction in their viscosities. The anticorrosive properties of DAEPs differing in the nature of substituents, for carbon steel corrosion in 1 M HCl solution was evaluated using several experimental and computational techniques. Both experimental and computational studies showed that inhibitor (DAEP2) that contains electron releasing methyl (-CH₃) showed higher protectiveness as compared to the inhibitor (DAEP1) without substituent (-H). Electrochemical results demonstrate that DAEPs act as reasonably good inhibitors for carbon steel in 1 M HCl medium and their effectiveness followed the sequence: DAEP2 (92.9%) > DAEP1 (91.7%). The PDP results show that the diamine aromatic epoxy pre-polymers molecules (DAEPs) act as mixed type inhibitors. Electrochemical study was also supported using scanning electron microscopy (SEM) method were significant improvement in the surface morphology of inhibited (by DAEPs) metallic specimens was obtained. Results derived from computational density functional theory (DFT) and molecular dynamics (MD) simulationsand studies were consistent with the experimental results derived from SEM, EIS and PDP electrochemical studies. Adsorption of the DAEPs obeyed the Langmuir adsorption isotherm model.

Epoxy polymer, namely, decaglycidyl pentamethylene dianiline of phosphorus (DGPMDAP) was synthesized in three steps. The synthesis of epoxy polymer DGPMDAP was investigated by nuclear magnetic resonance spectroscopy, rheological analysis, scanning electron microscope (SEM), stationary and transient electrochemical methods (PDP and EIS), respectively. The rheological properties of composite (DGPMDAP/MDA/TiO2) without and with different percentages of titanium dioxide (0%, 5%, 10% and 15%) increase with both the increase in frequency and with rate of load of titanium dioxide. Besides, SEM micrographs shows a good dispersion of the titanium dioxide charge in the composite (DGPMDAP/MDA/TiO2) elaborated. The results of PDP show that epoxy polymer DGPMDAP acts as mixed type inhibitor and reaches maximum corrosion inhibition efficiency reaches 92 % at 10-3 M. Besides, EIS results indicate that DGPMDAP act as good inhibitor for carbon steel in 1 M HCl solution and its efficiency reaches 91 % at 10-3 M of DGPMDAP. Furthermore, the adsorption of DGPMDAP on carbon steel surface obeyed Langmuir isotherm.