Corrosion Electrochemical Behavior of Nickel in Molten Lithium and Potassium Chlorides Containing Additives of Substances of Various Chemical Origins

Electrochemical diagnostics is carried out for nickel electrodes in the LiCl-KCl eutectic melt containing up to 0.2 wt % Li2O, 10 vol % O-2, and 2% LaCl3 at 500 degrees C in an inert argon atmosphere. Both silver chloride and lithium dynamic electrodes are used as reference electrodes. The latter is certified by thermodynamic analysis and recording of cyclic voltammograms along with the potential decay curves under the chronopotentiometric conditions for which the following most optimum parameters of the galvanostatic pulse are selected: a pulse duration of 4 s at a current density of 0.6 A/cm(2). Under these conditions, the stability time of a lithium dynamic reference electrode is 59.5 +/- 1.2 s. The electrochemical diagnostics of a nickel-molten salt electrolyte system with artificially added oxygen-containing impurities affecting the redox potential of the corrosion-active medium is carried out. The introduction of oxygen anions into the system shifts the nickel potential to the cathodic region, which decreases the corrosion activity of the medium. An increase in the oxygen concentration in the system shifts the nickel potential to the anodic region, indicating a more aggressive salt medium. The addition of lanthanum chloride to the melt affects the potential only if the system contains O-2, which is due to their interactions. The corrosion potentials of nickel obtained at both the silver chloride and lithium dynamic reference electrodes correlate to each other. This fact allows one to extend the applicability of the lithium dynamic reference electrode to any halide melts, including fluoride ones.