Corrosion of low-temperature nitrided molybdenum-bearing stainless steels

Abstract Austenitic stainless steels with up to 6.1 wt.% Mo were nitrided at 425 °C and examined in 0.1 M Na 2 SO 4 without and with chlorides at pH 3.0 and 6.5. Nitrided steels exhibited an increased resistance to pitting, but at pH 3.0 they had a decreased resistance to general corrosion. After corrosion at pH 3.0 surface films contained chromium nitrides and oxides of Mo, Cr and Fe. It is proposed that the improved pitting resistance of nitrided steels is associated with the initially accelerated dissolution which leads to the accumulation of corrosion resistant CrN and of oxidised steel components.