Experimental apparatus for studying the corrosion of materials in high-temperature liquid sodium for nuclear and solar thermal research - corrosion analysis of sodium exposed 316 L stainless steel at 650 °C

With the growing interest in testing liquid metals, such as sodium, for nuclear or concentrated solar power applications, two new experimental apparatuses were designed and custom-built to conduct static and dynamic corrosion testing. These apparatuses aid in characterizing high temperature sodium compatibility with structural alloys, under controlled conditions. The static system design offers several advantages, including effective sodium vapor management, controlled oxygen levels, and the ability to conduct long-term corrosion testing of multiple samples at temperatures up to 760 °C. The dynamic test loop is designed to allow for continuous testing up to 800 °C, cycling testing with a heating/cooling capacity of 8 kW, impurity control and monitoring via a cold trap and plugging meter. To demonstrate the utility of the static testing system, corrosion of 316 L Stainless Steel alloy in liquid sodium containing 3 ppm and high oxygen levels was investigated at 650 °C for 340–504 h and compared to the literature. After exposure, the samples were characterized by scanning electron microscopy coupled with energy dispersive x-ray spectroscopy. In agreement with the literature, our results show a significant reduction in corrosion damage under low-oxygen conditions and confirm the functionality of the designed test apparatus for sodium corrosion investigations in static systems. The dynamic system is operational, but yet to be deployed for corrosion tests.