Dynamic Corrosion Tests of 12Kh18N10T in the LiCl–2 wt % Li2O Melt at 650°C

The corrosion processes that occur in structural materials in high-temperature apparatuses with a significant volume of molten salt mixtures are caused by the complex hydrodynamic conditions induced by the temperature gradients in different parts of an installation, the presence of gaseous reaction products, and other technological factors that set a molten salt electrolyte in motion, along with chemical and electrochemical factors. It is advisable to conduct both static and dynamic corrosion experiments to substantiate the choice of structural materials for the apparatuses used in the pyrochemical processing of spent nuclear fuel from fast neutron reactors. This work investigates the influence of forced convection of the LiCl–2 wt % Li2O melt with a specified linear velocity from 4 to 16 mm/s on the degradation of 12Kh18N10T steel. Corrosion tests for 100 and 1000 h are performed at a temperature of 650°C in an inert argon gas atmosphere with a water content of less than 0.1 ppm and an oxygen content of less than 10 ppm. When the rotation speed of a sample increases, the degradation rate is found to increase significantly (from 0.018 to 0.094 g/(m2 h)). When the rotation speed of steel samples increases, a Cr–Fe phase and FeO form on their surface, and LiFeO2 and LiCrO2, which form as a result of corrosion exposure under natural convection and at a speed of up to 8 mm/s, have not been detected. Corrosion tests for 1000 h under forced convection conditions (medium movement speed is 16 mm/s) do not lead to a significant increase in the corrosion rate (0.059 g/(m2 h)) compared to the values obtained in a static isothermal medium (0.052 g/(m2 h)). Electron probe microanalysis analysis indicates the presence of a near-surface layer with a predominant content of oxygen and chromium.