Role of nitrogen in the cover gas over molten lithium hydride on corrosion of type 304L stainless steel containment

Nitrogen contamination of the nominal argon-30% hydrogen cover gas over molten lithium hydride dramatically influences corrosion of type 304L stainless steel containment. Compared to 0% nitrogen, 15% nitrogen in the cover gas changes the primary corrosion mechanism from nickel leaching to chromium leaching and increases weight loss and intergranular penetration of 304L by at least an order of magnitude at 800 C. At 715 C, weight loss and intergranular penetration are about a factor of 3 greater than at 800 C for the 15% nitrogen cover gas. Cover gas contamination with 0.5% nitrogen accelerates weight loss about 15% compared to the nitrogen-free experiment at 800 C and the 304L containment material experiences nickel and chromium leaching. It was postulated that nitrogen and lithium penetrate grain boundaries to form a soluble precipitate incorporating chromium that accelerates corrosion in the presence of nitrogen. ((orig.))