Experimental and theoretical insights into Oxalis corniculata L. extract as a sustainable and eco–friendly corrosion inhibitor for carbon steel in acidic environments

In this work, Oxalis corniculata L. was effectively extracted as a corrosion inhibitor for carbon steel in 1 mol L−1 hydrochloric acid (HCl). Oxalis corniculate L. extract (OCLE) was produced by grinding, distilling with ultrapure water, and drying. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP), and potential of zero charge (PZC) were used to test the performance of the OCLE. The corrosion inhibition behavior of OCLE was microscopically characterized by scanning electron microscopy (SEM). OCLE contains monosaccharide molecules identified by high–performance liquid chromatography (HPLC). Moreover, quantum chemical (QC) calculations and molecular dynamics (MD) simulation results showed that OCLE contains monosaccharide molecules that can form adsorption films on carbon steel through O and N to inhibit corrosion. Electrochemical experimental results showed that the corrosion inhibition efficiency increased with concentration and decreased with increasing temperature. At 298 K, the corrosion inhibition efficiency of 500 mg/L OCLE was 93.68%. The adsorption of OCLE on the carbon steel substrate was under the Langmuir adsorption isotherm, which was mixture adsorption. This study provides new ideas for inhibiting metal corrosion and provides theoretical support for the application of eco–friendly corrosion inhibitors.