Novel oxadiazoles derivatives as promising corrosion inhibitors for mild steel in an acidic environment: An experimental and theoretical investigation

Four new oxadiazole derivatives designated by the symbols OXDA5, OXDA6, OXDA7, and OXDA8 were synthesized and tested as inhibitors of corrosion for mild steel in 1 M HCl solution. Their molecular structures were validated by FT-IR spectroscopy, 13C NMR, and 1H NMR. weight loss (WL) and Electrochemical measurements (PDP, and EIS) revealed that every substance functions as a proficient mixed type inhibitor, with OXDA5 showing the highest efficiency of 91.50 % (WL), 92.92 % (PDP), and 90.24 % (EIS) at 10⁻³ M. The adsorption of these molecules adhered to the Langmuir isotherm, with negative ΔG°ads values signifying spontaneity and both physical and chemical adsorption interactions. Surface analyses (MEB, EDS, XPS) confirmed the formation of a protective film, in agreement with electrochemical data. DFT, molecular dynamics simulations, and Radial Distribution Function (RDF) analysis supported experimental findings, clarifying the electronic structure and adsorption behavior of the inhibitors. These findings underscore the potential of oxadiazole derivatives as effective corrosion inhibitors for mild steel in acidic environments.