Pump Oxygen Electrode-ysz In Cryolite Molten Salt Corrosion Behavior

Inert anode, which is environmentally friendly for aluminum electrolysis, can greatly reduce the production cost, cut down the energy consumption, increase the production capacity. Its development and application in industry has vital significance for environment and economy. With the aim of developing a new inert anode for the aluminum electrolysis, a new type of anode, pumping-oxygen electrode, was prepared with ZrO₂-Y₂O₃ solid electrolyte (YSZ). The corrosion and electrolysis behaviors of YSZ in cryolite molten salt were investigated in details by the principles of physical chemistry. XRD, SEM/EDS, AAS, XRF and metallographic analysis, and experimental apparatuses such as high temperature bench-scale cells were adopted to study the characteristics of the technique. The main conclusions can be summarized as follows:a) YSZ eroded badly in molten cryolite salt in the absence of external electric field. The solubility of Y and Zr from YSZ in melts is 0.0775, 0.285% at 960℃, respectively. While the exterior configurations of YSZ were destroyed completely by molten cryolite salt. And the corrosion depth reached 33～58 mm·y^-1.b) The apparent activation energy of 3^#YSZ in corrosion reaction is 176.67kJ·mol^-1. While the apparent activation energy of 4^#YSZ is 136kJ·mol^-1 in the presence of external electric current. The corrosion rate of YSZ could be enhanced by decreasing the alumina content in molten salts, increasing the temperature and the content of Y₂O₃.c) YSZ shows good corrosion-resistive ability to molten cryolite salt in the presence of external electric current. The exterior configurations was almost intact after 26.5h of experiment in the melts, and the corrosion depth decreased to 13～30mm·y^-1 under the experimental condition.d) There are electric and chemical potential differences on both sides of YSZ in the presence of electric current. The potential differences and the anodic process during dual interface lead to the embarrassment of the dissolution of YSZ in molten cryolite salt.e) The conductivity of YSZ at high temperature reached 0.0451S·cm^-1. In electrolysis experiment with YSZ anode and carbon cathode, the decomposition voltage in cryolite-alumina melt is about 1.5V, which is lower than the theoretical decomposition voltage 2.0V. Both of aluminum produced by the anode and oxygen generated in the cathode are detected. It illustrates that the result is satisfactory.