Going green: Stachys scardica H. leaves extract derived from supercritical CO2 extraction as an effective corrosion inhibitor for mild steel in 1 M HCl media

In this study, an extracted Stachys scardica Hayek leaves in the Eastern Region of Kosovo is used to enhance its value as a mild steel corrosion inhibitor in 1 M HCl medium. The electrochemical experiments indicate that the extract provides excellent corrosion protection, with a highest value of ≈ 92% in the inhibitor at a concentration of 600 mg/L. The potentiodynamic polarization plots show that the extract has a mixed response, reducing the strongly the current density in the presence of 600 mg/L inhibitor. The “inhibitor” molecules of SSH extract follows the Langmuir adsorption isotherm, with an adsorption energy of −15.29 kJ/mol due to interaction with the metals surface. Density functional theory, molecular dynamic, and monte Carlo theoretical investigations corroborate earlier experimental findings. The analysis of the radial distribution function from the Molecular dynamic trajectory provides compelling evidence of a prominent peak occurring at a distance of < 3.5 Å. The observed robust adsorption is primarily driven by the favorable interaction between the inhibitor's oxygen atoms and the metal surface, emphasizing the significance of this specific molecular interaction in facilitating the adsorption process.