The efficiency of methionine (MTI) as a non-toxic corrosion inhibitor for copper in 0.5 M HCI has been studied by using cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Methionine has shown limited inhibiting properties for copper corrosion in 0.5 M HCl. The presence of Zn2+ ions increases the inhibition efficiency to 92%. Results obtained from potentiodynamic polarization and impedance measurements are in good agreement. The adsorption of methionine on copper surface follows Langmuir isotherm. The adsorption free energy of methionine on copper (similar to-26 kJ mol(-1)) reveals a strong physical adsorption of the inhibition on the copper surface. (C) 2008 Elsevier B.V. All rights reserved.