Cerium addition to CaS inclusions in stainless steel: Insolubilizing water-soluble inclusions and improving pitting corrosion resistance

Abstract Pit initiation behavior at Ce-added and Ce-free CaS inclusions in Type 304 L stainless steel was investigated by microelectrochemical measurements. Stainless steel specimens containing artificial Ce-added and Ce-free CaS inclusions were fabricated by spark plasma sintering. The pit initiation resistance at the Ce-added CaS inclusions was higher than that at the Ce-free CaS inclusions. The surface of the Ce-free CaS inclusions largely dissolved during immersion in 0.1 M NaCl, while a large part of the Ce-added CaS inclusions remained undissolved. Thermodynamic calculation showed that CeS is less soluble than CaS.