The oxidation behavior of Ni-50%Co alloy has been investigated in Li + K carbonate melt by electrochemical impedance spectroscopy and cyclic voltammetry. Equivalent circuits have been worked out by simulating the impedance data, and the results are used to explain the oxidation kinetics. In the overall process of oxidation, the slowest step is the diffusion of metal ions through the metal oxide layer. Lithiation reaction is observed at the second potential plateau region as judged from the values of the resistance element of the oxide layer determined from impedance measurement. From the cyclic voltammetry the peak corresponding to this reaction is also observed. In a Ni-50%/Co, the diffusion of Li+ ion from the carbonate melt into the oxide layer causes further oxidation of Coo into LiCoO2.