Exploring the potential role of pyrazoline derivatives in corrosion inhibition of mild steel in hydrochloric acid solution: Insights from experimental and computational studies

Iron and its alloys are commonly used materials in petroleum refining facilities. However, poor corrosion resistance is always a disturbing problem for these industries. Herein, we demonstrated the utility of two pyrazoline derivatives (PYRs), namely, 2-(4-(4,5-dihydro-3-(4-methoxyphenyl)-1H-pyrazol-5-yl)phenoxy)acetic acid (PYR-1) and 2-(4-(4,5-dihydro-3-p-tolyl-1H-pyrazol-5-yl)phenoxy)acetic acid (PYR-2) for enhancing mild steel (MS) resistance in 1.0 M HCl using chemical, electrochemical, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and computational techniques. Weight loss measurements revealed that the optimum concentration of inhibitors is 5 mM. The maximum inhibition efficiencies (based on electrochemical results) were obtained 94% and 88% for PYR-1 and PYR-2, respectively. Pyrazolines retard corrosion at room temperatures and show high inhibition efficiency at higher temperatures, (above 90% at 333 K). XPS results showed that these compounds could effectively inhibit acid attack through physical and chemical adsorption on the metal surface. PYRs adsorption onto the steel surface follows Langmuir adsorption model. Electrochemical results revealed that the new compounds could exhibit excellent corrosion inhibition performance and displayed mixed-type inhibition. The performances of inhibitor films and the potential mechanisms were also investigated theoretically using MD simulation, radial distribution function (RDF), mean square displacement (MSD) and free volume theory. The present results will be helpful to uncover the versatile importance of pyrazoline compounds in the corrosion inhibition process.