Pitting corrosion characteristics of sintered Type 316 L stainless steel: relationship between pores and MnS

In Type 316 L stainless steel fabricated from gas-atomized powder via spark plasma sintering, lack-of-fusion pores and MnS inclusions were identified as possible pitting initiation sites. Through potentiodynamic polarization with different working electrode areas, the distribution density of the identified pit initiation sites was compared with that of sites found on wrought Type 316 L stainless steel. Surface observations of the sintered Type 316 L after polarization suggest that pitting corrosion was initiated at a location where both MnS and pores existed. By reducing the porosity and removing MnS, the roles of pores and MnS inclusions in the initiation of pitting corrosion were investigated.