Correlation between intergranular corrosion and impurities of extra high purity austenitic stainless steels

Ioka, Ikuo  ; Suzuki, Jun; Motooka, Takafumi; Kiuchi, Kiyoshi; Nakayama, Jumpei*

An intergranular corrosion is an important degradation mechanism of austenitic stainless steels for use in a nuclear fuel reprocessing plant. The intergranular corrosion is caused by the segregation of impurities to grain boundaries. An extra high purity austenitic stainless steel (EHP) was developed with conducting the new multiple refined melting to suppress the impurities less than 100ppm. The intergranular corrosion behavior of EHP alloys added various impurities was examined in boiling nitric acid solution with highly oxidizing ions. A multi regression analysis was performed using the obtained data. The degree of influence of the impurities on intergranular corrosion was shown from the analysis. The influence on corrosion rate became small in order of B, P, Si, C, S and Mn. There is little effect of Mn on corrosion rate of EHP-SSs in case of 10000appm or less.