Synergistic effect of Ni and N on improvement of pitting corrosion resistance of high nitrogen stainless steels

Abstract

The pitting corrosion resistance of Fe18Cr10Mn(0·33–0·69)N, Fe18Cr10Mn1Ni(0·33–0·84)N, and Fe18Cr10Mn0·35N(0–3)Ni alloys were investigated. The pitting potential increased as the N content increased in both Fe18Cr10Mn(0·33–0·69)N and Fe18Cr10Mn1Ni(0·33–0·84)N alloys. The rise in the pitting potential was more pronounced in Fe18Cr10Mn1Ni(0·33–0·84)N alloys than in Fe18Cr10Mn(0·33–0·69)N alloys. However, it was found that Ni alone had no effect on the pitting corrosion resistance of Fe18Cr10Mn0·35N based alloys. Thus, it was concluded that the alloyed N worked synergistically with Ni to promote the pitting corrosion resistance in Fe18Cr10Mn based alloys. Analyses of passive films of Fe18Cr10Mn(0·33–0·69)N and Fe18Cr10Mn1Ni(0·33–0·84)N alloys revealed that N was incorporated into the passive film, with N enriched at the film/metal interface. However, the alloyed N increased the Cr cation fraction in passive films of Fe18Cr10Mn1Ni(0·33–0·84)N alloys, whereas N decreased in that of Fe18Cr10Mn(0·33–0·69)N alloys. This difference was considered as the reason for the synergistic effect between N and Ni in Fe18Cr10Mn based alloys.