抄録
Electrochemical study of nickel has been made in LiCl-KCl eutectic melt containing nitrate, with regard to the electrochemical estimation of the corrosion rate.
The experiments were made under argon atmosphere at 500°C. In the absence of nitrate ion, the anodic polarization of nickel yielded a well defined Tafel line with a slope of 90 mV/decade. In the presence of nitrate ion, the cathodic polarization curves exhibited a limiting current, which was proportional to the concentration of nitrate. The limiting current was attributed to the diffusion controlled reduction of nitrate ion. With increasing concentration of nitrate, the corrosion potential shifted to the noble direction by 67 mV/decade of mol%, and the corrosion rate increased.
The behaviour was fully explained by the superposition of the anodic dissolusion of nickel and the diffusion limited reduction of nitrate, based on the mixed potential theory. Therefore, the corrosion rate was found to be controlled by the diffusion of nitrate. It was also found that the corrosion rate estimated by the polarization resistance methode was consistent with that estimated from the weight loss.
