In-situ measurement of solution electrical conductivity within crevice of stainless steels in high temperature water

Soma, Yasutaka   ; Kato, Chiaki   ; Ueno, Fumiyoshi  

Stress corrosion cracking (SCC) on stainless steels have been recognized as one of the most important corrosion-related failure in light water reactors. Many researches have been pointed out that the SCC advances under altered solution chemistry condition at the crack tip region compared to the bulk pure water. However, little works have been done to clarify degree of the alteration as function of bulk water condition, geometrical factor, and time. In this work, we carried out in-situ measurement of solution electrical conductivity within crevice of stainless steels. To create crevice specimen, a couple of stainless steel plate was fixed with bolts and nuts. Small sensors were imbedded into the crevice plate at three different positions with different crevice gaps. The crevice specimen with sensors was exposed to 288C water with pressure of 8 MPa, dissolved oxygen concentration of 32 ppm. The solution electrical conductivity at the crevice gap of 6e-5 m was almost same to that of bulk pure water. At the crevice position with 1e-5 m gap, the maximum conductivity value was nearly 1000 times higher than that of bulk water and that is equivalent to decrease in pH of 3 from the neutral value. This indicates, if the crevice gap was narrow enough, local acidification occurred at the tip of the crevice.