Effect of phosphorous on intergranular corrosion of 310 stainless steel at transpassive potential

Komatsu, Atsushi ; Motooka, Takafumi; Igarashi, Takahiro  ; Ueno, Fumiyoshi  ; Yamamoto, Masahiro 

The effect of phosphorous on intergranular corrosion of 310 stainless steel at transpassive potential was investigated. High purity 310 stainless steel containing 270 ppm phosphorous with different heat treatments was polarized at transpassive potential. Intergranular corrosion depth was measured by SEM observation, and grain boundaries were observed using 3D atom probe. Intergranular corrosion became severe in heat treated sample to enhance phosphate precipitation. 3D atom probe measurement revealed that grain boundary of high dissolution rate had phosphorous and chromium concentration layer of less than 10 nm thick. On the other hand, grain boundary of low dissolution rate had no concentration layer of phosphorous. From these results, it is suggested that intergranular corrosion of 310 stainless steel at transpassive potential is related to phosphorous and chromium concentration layer.