Synthesis, structural analysis and corrosion inhibition application of a new indazole derivative on mild steel surface in acidic media complemented with DFT and MD studies

Abstract

A great deal of consideration has been given to the development of new compounds having diverse functionality. In this report, a new indazole derivative bearing a nitro group, namely 2-(3-chloro-5-nitro-1H-indazol-1-yl) acetic acid (CNIA) was synthesized, characterized, and used as corrosion inhibitor for mild steel (MS) in 1.0 M HCl. A full characterization of the prepared compound was performed using single‐crystal XRD, FT-IR, and UV–vis measurements; its corrosion inhibition properties were experimentally evaluated by potentiodynamic polarization (PDP) curves as well as electrochemical impedance spectroscopy (EIS) measurements, and theoretically by Density Functional Theory (DFT) and molecular dynamics (MD) simulations. Scanning electron microscope (SEM) was used to examine the morphology of the corroded metal surface before and after the inhibition. The findings demonstrated that the application of CNIA significantly reduced the corrosion rates of MS. The corrosion inhibition ability of the synthesized compound was also identified at a lower concentration in all experiments, reaching a maximum of 89 % at 10−3 mol/L. The results of potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) confirmed that CNIA could be categorized as a mixed type inhibitor with an increased polarization resistance at higher concentrations. Langmuir's adsorption isotherm was found to fit the adsorption of CNIA molecules on the MS surface. SEM photographs showed obvious less-corroded morphologies in the presence of the CNIA as compared to untreated MS surface. Theoretical calculations were proposed to explain the mechanism of the inhibition effect and found that it is due to the donor/acceptor properties of the inhibitor and its parallel disposition over the steel surface. The present compound could be a promising corrosion inhibitor for mild steel in HCl solutions, and showed a corrosion inhibition property that is superior to similar compounds.