Some Natural Additives as Corrosion Inhibitors for Zinc in Acetic Acid Media

The inhibition effect of some plant extracts, namely Vulgaris Thymus (VT), Cuminum Cyminum, (CC), Hibiscus Subdariffa (HS), Feungreek Seeds(FS) on the corrosion of zinc in 2M CH3COOH solution has been investigated using weight loss , pH measurement and electrochemical measurements. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor and with decreasing temperature. The adsorption of these inhibitors on the zinc surface obeys Langmuir isotherm. Some activated thermodynamic parameters were calculated. The variation of the open circuit potential of zinc electrode with time in 2M CH3COOH shows that Ecorr is shifted with time in the cathodic direction, i.e. to more negative values before return to the positive direction attainment quaisteady states. But the addition of these extract, the potential is shifted initially to more positive values then returned to negative values with time by increasing concentration of the additive extracts is recorded in comparison with blank.