The corrosion and passivation behaviors of alloys with different Cu-Ni ratios were investigated in acidic sulfate solutions. The corrosion rate was calculated and the corrosion inhibition process was investigated using different amino acids as corrosion inhibitors. For these investigations conventional electrochemical techniques and electrochemical impedance spectroscopy (EIS) were used. Fitting of the experimental impedance data to theoretical values enables understanding of the corrosion inhibition mechanism and the suggestion of a suitable electrical model to explain the behavior of the alloys under different conditions. The investigation of the electrochemical behavior of alloys before and after the corrosion inhibition processes has shown that some amino acids like lysine have promising corrosion inhibition efficiency at very low concentrations. A model for the electrode/electrolyte interface during the corrosion inhibition processes was suggested and the validity of the model for the explanation of the corrosion inhibition phenomena was discussed.