Inhibition performances of spirocyclopropane derivatives for mild steel protection in HCl

The use of green and environmentally friendly substances is a contemporary scientific challenge and a key task for today's specialists in chemistry and technology-related fields. In this context, this research work involves the study of two new compounds named 1-benzoyl-2-(3,4-dimethoxyphenyl)-6,6-dimethyl-5,7-dioxaspiro [2.5]octane-4,8-dione (2-MPOD) and 1-benzoyl-6,6-dimethyl-2-(3,4,5-trimethoxyphenyl)-5,7-dioxaspiro [2.5]octane-4,8-dione (3-MPOD). The two compounds were synthesized and their inhibition properties for mild steel (MS) corrosion in 1.0 M HCl were first evaluated by means of experimental methods such as electrochemical impedance spectroscopy (EIS), weight loss (WL), in addition to potentiodynamic polarization (PDP) techniques, and also utilizing quantum chemistry studies and molecular dynamics (MD) simulations. For a description of the impact of molecules on the MS surface, the X-ray photoelectron spectroscopy (XPS) and scanning electron microscope equipped with an energy-dispersive spectrometer (SEM-EDS) have been performed. 2-MPOD and 3-MPOD were confirmed to be effective inhibitors in acidic solution and the highest resistance was achieved at 10-3 M concentration and 303 K. The adsorption of inhibitors on MS has been linked to both physical and chemical processes. The adsorption is in accordance with the Langmuir isotherm model. Quantum mechanical calculation results suggest that π-electrons in the aromatic ring and the lone-pair electrons in the methoxy group contribute to enhanced adsorption onto iron surface, leading to effective corrosion inhibition.