The corrosion mechanism of elemental sulfur on iron-chromium alloys in thermal energy storage systems

High-temperature thermal energy storage is known as a low-cost and large-scale energy storage solution. Elemental sulfur has been proposed in recent years as an alternative thermal storage medium to provide lower storage costs and higher thermal stability than conventional molten salt storage materials. However, the corrosion issue of elemental sulfur at high temperatures is non-negligible. In this study, we investigated the sulfur corrosion mechanism on iron-chromium alloys in closed containers from 300 to 500 degrees C. The results show that increasing the chromium content in the alloy could increase the corrosion activation energy, thereby effectively decreasing the corrosion rate. In comparison to liquid sulfur, sulfur vapor has a lower corrosion rate at 300 degrees C due to the low vapor pressure, but a higher corrosion rate at temperatures above 400 degrees C. Among all selected stainless-steel materials, SUS 329J4L has the largest corrosion resistance to both liquid sulfur and sulfur vapor and a relatively fair cost. Corrosion tests with a 500-h duration are then performed to further prove the feasibility of selected alloys for a long-term operation and to elucidate how sulfur corrosion rate varies with the test duration.