Quantitative analysis of initiation site of pitting corrosion on type 304 austenitic stainless steel

The initiation site of pitting corrosion on type 304 stainless steel was quantitatively analysed using an automatic inclusion analyser and electron backscatter diffraction. In a sample anodically polarised at 0.43 VSSE, the fraction of stable pits initiated from inclusions was only 23 %. Pits initiated from sites other than inclusions probably initiated from grain boundaries, strain-induced martensite and scratches. In mixed inclusions of MnS and oxides, the probability of pit initiation increased with the S concentration. The Ti concentration had no effect on the probability of pit initiation, suggesting that whether Ti exists as TiO2 or TiN is important.