2020 Volume 69 Issue 2 Pages 40-48
In order to clarify the relationship between crevice corrosion behavior of SUS304 and the pH in crevice（pHc）, simultaneous measurement of pH in crevice by semiconductor chemical sensor at potentiostatic polarization.
The pH measured by the sensor is not influenced by the metal ion and shows the value reflecting［ H＋］ and γH＋.
When crevice corrosion is always progressing by potentiostatic polarization, among the metal ions dissolved in the crevice, mainly in the hydrolysis reaction of Cr3＋ or formation of chloride complex ions, the entire crevice part becomes extremely low pH environment with pHc＜0.0.
On the other hand, when polarization by two-step potentiostatic polarization, the amount of metal dissolved in the crevice decreases depending on the second potential（E2）, and finally, eventually leading to re-passivation.
In the case of this study, the re-passivation pH after crevice corrosion progression was 2.5 to 3, and the repassivation potential was about 80 mV, which gave high engineering significance.
