Ferula hermonis Plant Extract as Safe Corrosion Inhibitor for Zinc in Hydrochloric Acid Solution

The efficiency of Ferula hermonis plant extract, as inhibitor for zinc (Zn) corrosion in a 1 M HCl solution, has been tested by mass loss (ML), electrochemical measurements (potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) procedures), in addition to surface examination analysis. The outcomes indicated that F. hermonis extract showed good efficiency to Zn corrosion, and displayed high inhibition efficiencies. The maximum inhibition efficiency approached 90.6% at 300 ppm extract. The adsorption isotherm of extract on the Zn surface was found to follow Langmuir adsorption isotherm. Thermodynamic parameters were determined and discussed. Also, the inhibition efficiency (%IE) was found to increase as the concentration of extract increases, and depressed as the temperature rises. The morphology of the surface of uninhibited and inhibited Zn was examined by Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDX) and ultraviolet–visible spectroscopic (UV). Biological effect of the extract was studied. The results indicated that there is a protective film formed by extract on the Zn surface that protects it from dissolution in the acid media. The outcomes of the applied chemical and electrochemical techniques are in good agreement.