Epoxy resins and their zinc composites as novel anti-corrosive materials for copper in 3% sodium chloride solution: Experimental and computational studies

This study reports the evaluation of the anticorrosive performance of two macromolecular aromatic epoxy resins (ERs), namely, tetra glycidyl of ethylene dianiline (TGEDA) and hexaglycidyl Tris (p-ethylene dianiline) phosphoric triamide (HGEDPAT) and their polymer composite reinforced with Zinc for copper corrosion in 3% NaCl using the computational and experimental analyses. Electrochemical results showed that HGEDAPT cured with methylene dianiline (MDA) showed better protection efficiency with optimum corrosion current density (i_corr) value of 2.0 μ cm⁻² and the polarization resistance (R_p) value of 17.00 kΩ·cm² than that of TGEDA-MDA having i_corr value of 2.4 μ cm⁻² and the R_p value of 15.24 kΩ·cm². The anti-corrosive effect of TGEDA-MDA and HGEDAPT-MDA was evaluated in the presence of 5% zinc (Zn). Experimental results demonstrate that the presence of 5% of zinc in TGEDA-MDA and HGEDAPT-MDA formulations significantly enhanced their protection ability. The anticorrosive effect of the different formulations followed the order: ER1 (TGEDA-MDA) (potentiodynamic polarization (PDP); 90% and electrochemical impedance spectroscopy (EIS) 92%) < ER2 (HGEDAPT-MDA) (PDP; 92% and EIS 93%) < ER3 (TGEDA-MDA-5%Zn) (PDP; 96% and EIS 97%) < ER4 (HGEDAPT-MDA-5%Zn) (PDP; 97% and EIS 98.5%). Density functional theory (DFT) study revealed that ER1 and ER2 interact with the metallic surface using donor-acceptor interactions in which electron rich centers acted as most favorable sites for the interactions. Molecular dynamics (MD) simulations studies suggest that ER1 and ER2 acquire the flat or horizontal orientations and their orientations on metallic surface are largely influenced by the presence of zinc. Different experimental and computational studies are in good agreement.