Correlation between experimental and theoretical approaches in the performance of new epoxy resin as an effective corrosion inhibitor for mild steel in acid pickling bath

Abstract

In this work, a new epoxy resin named 2,3,5,6-tetraglycidyloxy-4-(3,4,5-triglycidyloxy)-6-(glycidyloxymethyl)tetrahydro-2H-pyran-2-yloxyhexanal (OER) was synthesized and characterized using FTIR spectroscopic techniques. The corrosion inhibiting performance of mild steel in a 1 M HCl corrosive medium was evaluated through electrochemical techniques, including potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) measurements. The topological analyses of the surface were performed using scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy (SEM/EDS). Theoretical calculations (DFT and MD simulation) were employed to confirm the obtained results. For the three electrochemical techniques, the inhibitory efficiencies of the OER product increased with the concentration, reaching their peak values at a concentration of 10–3 M (95.32% for PDP, 94.78% for EIS, and 92.31% for EFM). Additionally, the PDP method indicated that the inhibitor acted as a mixed-type inhibitor with anodic dominance in a 1 M HCl medium. The increase in temperature leads to a slight decrease in the inhibitory effectiveness of mild steel in 1 M HCl medium in the presence of 10–3 M of OER. This inhibitor exhibited chemical type adsorption, occurring according to the Langmuir approach. The SEM/EDS analyses specifically highlighted the corrosion inhibiting properties of the OER inhibitor. Theoretical methods provided molecular-level information by determining the natures of the active centers that contributed to the effectiveness of the OER inhibitor, as well as the nature of the bonds occurring between the OER molecules and the steel surface.