Highly functionalized epoxy macromolecule as an anti-corrosive material for carbon steel: Computational (DFT, MDS), surface (SEM-EDS) and electrochemical (OCP, PDP, EIS) studies

In present study, a tetra-functionalized aromatic epoxy pre-polymer namely, 4,4′-oxybis(N,N-bis(oxiran-2-ylmethyl)aniline) (AA2) was synthesized and established as corrosion inhibitor for carbon steel corrosion in 1 M HCl medium. The prepolymer was characterized by proton nuclear magnetic resonance (¹H NMR) and Fourier-transform infrared spectroscopy (FT-IR) spectral techniques and its inhibition property was demonstrated using electrochemical open circuit potential (OCP), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS), surface scanning electron microscopy (SEM) analysis coupled with energy dispersive spectroscopy (EDS) analysis and computational density functional theory (DFT) and molecular dynamic (MD) simulations methods. Electrochemical studies demonstrate that AA2 acts as sensibly good inhibitor for carbon steel in 1 M HCl medium and showed highest efficiency of as high as 91.3% at 10^{− 3} M. The PDP results show that AA2 behaves as predominantly cathodic type of inhibitor. SEM analysis coupled with EDS showed that AA2 forms surface protective films and isolates the metal from aggressive solution. DFT studies suggest that both neutral as well as cationic forms of the AA2 strongly interact with metallic surface using two aromatic and four oxirane rings. Molecular dynamic simulations (MDS) study showed that AA2 adsorb strongly on metallic surface using their electron rich centers and acquires the parallel or flat orientation. Outcomes of the experimental (SEM-EDS, OCP, EIS and PDP) and computational (DFT and MDS) studies were in excellent concurrence.