Correlation Between Corrosion Rate and Electrochemical Parameters of Anode Process on the Metallic Electrode in Molten Oxyfluorides

Using metallic anodesAnode enables oxygen evolution during the aluminum reductionAluminum reduction in electrolysis cellsElectrolysis cell with vertical electrodes. Although they are considered non-consumable compared to carbon ones, they tend to corrode in molten fluorideMolten fluoride media, and the corrosionCorrosion products end up in aluminumAluminum as impurities. The big challenge for the industry is finding the best conditions (anodeAnode and bath composition, temperature, and current density) that provide the lowest corrosion rateCorrosion rate. The most reliable way to characterize the corrosion rateCorrosion rate is to perform an electrolysisElectrolysis test and determine the mass of anodeAnode components in the produced aluminumAluminum. This methodMethod is highly time- and resource-demanding. This paper investigates the connection between the electrochemical parameters of the anodeAnode process, which can be measured in minutes, and the results of long-term electrolysisElectrolysis tests. Several parameters, such as exchange currentExchange current density on clean and oxidized surfacesSurface, were studied in the low-temperature KF-NaF-AlF3-Al2O3 melt at 800 °C. A linear dependency between exchange currentsExchange current and corrosion rateCorrosion rate was found.