New pyrazole compounds as a corrosion inhibitor of stainless steel in 2.0 M H2SO4 medium: Electrochemical and theoretical insights

Abstract

The present paper examines the adsorption of two novel heterocyclic compounds of the pyrazole derivatives, namely, Ethyl 1-amino-3-(2-chlorophenyl)-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b] phthalazine-2 carboxylate (Py-1) and Ethyl 1-amino-5,10-dioxo-3-(p-tolyl)-5,10-dihydro-1H-pyrazolo[1,2-b] phthalazine-2-carboxylate (Py-2) against the oxidation of stainless steel in 2.0 M H2SO4. The EIS and PDP demonstrate that the inhibitory properties of both compounds under investigation grow with concentration. Inhibition efficiencies of Py-1 and Py-2 followed the order: 90.9% (Py-2) < 96.7% (Py-1). the intensity-potential curves show that Py-1 &Py-2 imparted high resistance and acted as anodic type inhibitors. According to the Langmuir Isotherm adsorption model, the tested inhibitors have been deposited on the stainless-steel surface. The impedance diagrams also include two semicircles, the first of which was linked to the development of protective inhibitor films and the second to the process of charge transfer. SEM/EDX analyses were performed to describe the chemical makeup of the layer that had formed on the steel's surface. Theoretical studies, such as MD simulation and DFT, have helped to better elucidate the understanding of the process of corrosion inhibition.