Electrochemical behavior of nickel in HNO3 and the effect of chloride ions

The electrochemical behavior of nickel in HNO3 solutions of varying concentrations was examined using the cyclic voltammetry and potentiodynamic anodic polarization techniques. The anodic branch of the cyclic voltammogram is characterized by one anodic dissolution peak and a passivation region before oxygen evolution. The cathodic branch shows only one cathodic reduction peak corresponding to the reduction of HNO3. Analysis of the anodic polarization data shows features of both reversible and irreversible reactions pointing to the complexity of the system. Cl- ions enhance the active dissolution of nickel in HNO3 due to the adsorption on the bare metal surface and cause destruction of the passive film and initiation of pitting corrosion.