Visualisation of chlorides in corroded crevice of a stainless steel by using the radioisotope Cl-36

Aoki, So  ; Abe, Yosuke  ; Abe, Hiroshi*; Watanabe, Yutaka*; Yamamoto, Masahiro*

The objective of this study was to visualise chlorides in corroded crevice of a stainless steel by using the radioisotope Cl-36 as a tracer. Chlorides in the corroded crevice were successfully visualised by imaging the luminescence of the imaging plate due to beta rays emitted by Cl-36 adhering to the corroded crevice. In the 72-hour corrosion test, the luminescent areas roughly coincided with the corroded areas on the test surface, suggesting that chlorides were concentrated in the corroded areas inside the crevice. In the test in which the specimen was left in pure water for 360 hours after the 72-hour corrosion test, the area of the luminescent areas was smaller than the corroded areas of the test surface, but high luminance areas were observed locally. SEM observations showed that the crevice corrosion had propagated deeply in such areas. These results suggest that the propagation of crevice corrosion did not stop under this test conditions.