Corrosion behavior of ion nitrided stainless steels containing Mo

Corrosion behavior of ion nitrided stainless steels (SS) containing Mo was investigated by electrochemical methods. The morphologies of ion nitrided s tainless steel were analyzed using optical microscopy and scanning electron microscopy (SEM). Pitting corrosion resistance is improved remarkably in the case of ion nitr ided SS containing 4.05 mass% Mo at 653 It for 30 h because Mo acts to form a protective surface layer against Cl- ion and nitrited film such as Fe4N formed on the surface at low nitriding temperature. In the case of ion nitr iding at 823 K, the pit nucleation rate and the number of pit decreased as the Mo content increased owing to retardation of the nucleation and growth of chromium carbide or nitride at the grain boundaries.