Contribution to the corrosion inhibition of aluminum in 1 M HCl by Pimpinella Anisum extract. Experimental and theoretical studies (DFT, MC, and MD)

Corrosion inhibition of aluminum in 1 M hydrochloric acid solution by aqueous extract of Pimpinella anisum was studied using linear polarization, electrochemical impedance spectroscopy (EIS) and Density Functional Theory (DFT). Pimpinella Anisum plant was used. The results show an excellent performance of the aqueous extract as a corrosion inhibitor for aluminum. The inhibition efficiency was found to increase with increasing concentration of Pimpinella Anisum aqueous extract. The electrochemical measurements showed that the Pimpinella Anisum extract acts as a mixed-type inhibitor. The inhibition is due to adsorption of the extract molecules on the aluminum surface according to the Langmuir adsorption isotherm. DFT calculations and MD simulations were used to explain the adsorption mode on the metal surface and to determine the adsorption centers of this inhibitor. DFT, MC, and MD calculations show a strong adsorption interaction between the extract molecules and the metal surface. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) study confirmed that the corrosion inhibition of aluminum occurs through adsorption of the extract's molecules on the metal surface. The theoretical calculations are in good agreement with the experimental results.