Abstract: The amino acid, cystein was examined as an inhibitor for zinc in 0.5N HCl was using weight loss and potentiodynamic polarization studies. Corrosion parameters such as inhibition efficiency, corrosion rates, corrosion potential and corrosion current were evaluated. The inhibition efficiency was found to increase with increase in the inhibitor concentration. The adsorption of the inhibitor on the zinc surface followed Temkin adsorption isotherm.