Corrosion inhibition and substituent impact of newly synthesized 1,3,4-oxadiazole derivatives on mild steel in acidic media: Electrochemical and quantum chemistry insights

Abstract

Organic inhibitors are commonly used to protect steel and its alloys from corrosion in acidic aqueous environments. This study evaluates the corrosion inhibition performance of two novel 1,3,4-oxadiazole derivatives 5-(6-chloropyridin-3-yl)-N-(2,6-difluorophenyl)-1,3,4-oxadiazol-2-amine (OXDA1) and 5-(6-chloropyridin-3-yl)-N-(2,6-dimethylphenyl)-1,3,4-oxadiazol-2-amine (OXDA2) on mild steel in 1 M HCl solution. The investigation employed Weight Loss (WL), Electrochemical Impedance Spectroscopy (EIS), and Potentiodynamic Polarization (PDP) methods to assess their anticorrosive properties. Weight loss measurements were conducted at various inhibitor concentrations (10⁻³–10⁻⁵ M) at 308 K. At the optimal concentration (10⁻³ M), OXDA1 exhibited an inhibition efficiency of 88.66 %, whereas OXDA2 achieved 95.02 %. Kinetic and thermodynamic analyses indicated that both OXDAs derivatives undergo physicochemical adsorption on the mild steel surface, functioning as mixed-type inhibitors. Their adsorption behavior followed the Langmuir adsorption isotherm. Theoretical studies (DFT and MD simulations) corroborated experimental findings, identifying reactive inhibitor sites and adsorption mechanisms on mild steel. Experimental and theoretical data led to a proposed inhibition mechanism, demonstrating the compounds’ significant efficacy in mitigating corrosion under acidic conditions.