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The corrosion protection of copper by cysteine in aerated 0.5 M H2SO4 solution at open circuit corrosion potential (Ecorr) was evaluated by electrochemical methods (potentiodynamic polarization and impedance spectroscopy (EIS) measurements). Thethermodynamic parameters were discussed. Cysteine is readily available, environmentally-friendly, non-toxic for human beings and contains many heteroatoms. This molecule is therefore a good candidate as a corrosion inhibitor. The Inhibition efficiencies evaluated using different methods are in a good agreement and were averagely above 97% at10-3 M. The voltammetric measurements indicated that the cysteine acts as mixed type inhibitor, but hinders essentially cathodic reactions. Changes in impedance parameters are indicative of the adsorption of cysteine on the copper surface which obeys Langmuir-type adsorption isotherm. This study was completed by surface characterizations through scanning electron microscopy (SEM) and in-situ Raman spectroscopy.Surface observation shows that the addition of cysteine has improved considerably the surface morphology of the copper electrodeFinally, the in situ Raman spectra corroborate the formation of a complex between copper and cysteine in an acidic medium as deduced from impedance measurements.