Effects of misch metal on the formation of non-metallic inclusions and the associated resistance to pitting corrosion in 25% Cr duplex stainless steels

The addition of up to 0.067 wt.% misch metal in 25% duplex stainless steel led to a decrease in the size and surface density of (Mn, Cr, RE)-oxysulfides and an increase in the resistance to pitting corrosion. Pitting corrosion was initiated in the interface between the matrix and (Mn, Cr, RE)-oxysulfides. The resistance to pitting corrosion of the alloys was mainly affected by the shape and number of (Mn, Cr, RE)-oxysulfides per unit area rather than the area fraction of the non-metallic inclusions.