Corrosion inhibition of phenylalanine (phe) and its its cobalt complex(Co-phe) were evaluated using electrochemical polarization and electrochemical impedance spectroscopy (EIS) for mild steel in 0.1 M H2SO4 solution. The results indicate that the compounds inhibit the corrosion of mild steel in H2SO4 solutions and the extent of inhibition increases with inhibitor concentration and decreases with temperature. The order of inhibition efficiency obtained was Co-phe > phe. The adsorption characteristics of the inhibitor were approximated by Langmuir isotherm. Morphological study of the carbon steel electrode surface was undertaken by scanning electron microscope (SEM).