Electrochemical nitriding of type 316 stainless steel (316SS) in molten fluoride salt (LiF-KF, FLiK) containing Li(3)N was investigated. Formation of chromium nitride CrN and iron nitride alpha-Fe(x(x>8))N was confirmed. Cyclic voltammogram measurements and electrolysis treatment were carried out using an Al-Li alloy reference electrode at 873K. After potentiostatic treatment at 1.0V vs. Li/Li(+) for 100 min, the specimen was characterized by SEM, XPS, EPMA, and XRD. SEM observation revealed that the initially smooth surface changed into a rugged structure covered by a wrinkle structure about 1-2 mu m in width after electrolysis. XPS analysis revealed that chromium nitride (CrN) was selectively formed at the surface layer. According to the EPMA analysis, the treatment promoted nitrogen diffusion from the surface to a depth of 35 mu m. CrN was formed from the surface to a depth of 2 mu m. It was determined that iron nitride alpha-Fe(x(x>8))N was formed from there to a depth of 35 mu m as an inside diffusion layer, but neither Fe(2)N nor Fe(4)N was detected. Formation of CrN and alpha-Fe(x(x>8))N was also confirmed by XRD measurement and XPS analysis. The formation of chromium nitride and iron nitride was discussed in terms of thermodynamics. (C) 2011 Elsevier Ltd. All rights reserved.