The role of nitrogen and molybdenum in the corrosion of stainless steels

This work deals with the role of nitrogen and molybdenum in corrosion and passivation of high N-bearing stainless steels(>0.35%N). Nitrogen exists as atomic nitrogen, nitric oxide, nitro-oxyanions(NOx-) and N-H species, not nitride in the passive film. Because of its high mobility, the enriched atomic nitrogen can act as a reservoir. Mo exists as metallic molybdenum, molybdenum oxide, and molybdate.; Mo makes molybdate ion and nitrogen makes nitro-oxyanions and ammonium ion. These oxyanions can be formed by a 'solid state reaction' in the passive film even at low electrode potential because excess OH. and NH4+/NH3 are formed in the passive film. Then, oxyanions in the passive film could be soluble in part, and some ions have been detected in the anolytes. Also, nitro-oxyanions may be reduced and then ammonium ion can be easily detected both in the film and in the solution.