Artificial MnS Inclusions in Stainless Steel: Fabrication by Spark Plasma Sintering and Corrosion Evaluation by Microelectrochemical Measurements

Spark plasma sintering was used to fabricate type 304L stainless steel specimens containing artificial manganese sulfide (MnS) inclusions, and a microelectrochemical technique was used to characterize the pit initiation behavior at the MnS. A 200 μm square electrode area that included an artificial MnS particle was potentiodynamically polarized in 0.1 M NaCl, and the electrode surface was observed in situ by optical microscopy. The anodic dissolution of the MnS particle was observed in the passive region of the stainless steel. The pit occurred at the boundary between the particle and the steel matrix after the particle dissolved slightly. The dissolution potential and pit initiation behavior at the artificial MnS particles in the sintered stainless steel were confirmed to be similar to those at MnS inclusions in commercial stainless steels.