Electrochemical and computational study of a weed based inhibitor for mild steel corrosion in an acidic medium

The development of effective green corrosion inhibitors for the descaling of corroded industrial gas pipelines has been very challenging. Cosmos sulphureus plant contains rich phytochemicals that can inhibit corrosion on mild steel. The study aims to assess the corrosion inhibition efficacy of Cosmos sulphureus , a widespread weed, employing electrochemical and computational studies. FTIR spectroscopic analysis revealed the major functional groups present in the extract molecules. The electrochemical impedance spectroscopic results indicated an increase in charge transfer resistance and a decrease in double-layer capacitance on adding the extract to the corrosive solution, indicating the plant’s ability to protect the metal. Potentiodynamic polarization studies indicated that the plant extract functions as a mixed-type inhibitor. The decrease in corrosion current from 3.83E-04 A cm − 2 to 2.77E-05 A cm −2 and the maximum inhibition efficiency of 92.77% confirmed its efficacy as a corrosion inhibitor. The Nyquist and Tafel plots exhibited similar trends. The scanning electron microscopic images confirmed the formation of a protective layer of the plant extract. Further, computational simulations of the major phytoconstituents displayed favorable values of quantum chemical parameters. The Fukui indices and local philicities suggested the electron-rich centers for adsorption on the metal surface. The adsorption energy values from Monte Carlo studies suggested plausible adsorption. The corroboration of experimental and computational results revealed the corrosion inhibition ability of Cosmos sulphureus for mild steel in an acidic medium.