Experimental and modeling study on ion concentration behavior in metal crevices in high-purity water

Soma, Yasutaka   ; Komatsu, Atsushi ; Igarashi, Takahiro  

In our previous study, we reported that Cl ions penetrating stainless steel crevices do not dissipate by diffusion, even in high-purity water (i.e., conductivity remains stable), likely due to electrochemical reactions inside and outside the crevice. This study further analyzes ion behavior by experimentally and computationally investigating ion concentration drivers in high-purity water. Results show that, at 50C, the crevice conductivity of SUS316L stainless steel reached 100 S/cm (100-1000 times bulk water). Modeling suggests this is due to metal cations and hydroxide ions from dissolved oxygen reduction. The dissolution rate was estimated at 10nA/cm.