TY - JOUR
T1 - NH4 + generation
T2 - The role of NO3 − in the crevice corrosion repassivation of type 316L stainless steel
AU - Aoyama, Takahito
AU - Sugawara, Yu
AU - Muto, Izumi
AU - Hara, Nobuyoshi
N1 - Funding Information:
This work was partially supported by the Center of World Intelligence Project for Nuclear S&T and Human Resource Development by the Ministry of Education, Culture, Sports, Science and Technology of Japan. This research was supported by JSPS KAKENHI grant Number JP17H01331.
Publisher Copyright:
© The Author(s) 2019.
PY - 2019
Y1 - 2019
N2 - The role of NO3 − in the repassivation of crevice corrosion of Type 316L stainless steel was investigated. In crevice corrosion tests, the solution was changed from 1 M NaCl to NaCl- NaNO3. NO3 − led to complete repassivation, and after potentiostatic polarization in 2 M KNO3, NH4 + was detected in the crevice solution by ion chromatography analysis. Repassivation of the crevice corrosion was found to take place in two steps. In the first step, the estimated current density inside the crevice gradually decreased from ca. 5 mA cm−2 to ca. 5 μA cm−2. After that, the current density suddenly decreased to less than 0.1 μA cm−2. From the potentiodynamic polarization in acidic solutions simulated inside the crevice (pH 0.2) and in situ observations of the crevice corrosion morphology, the first step was thought to be generated by the suppression of active dissolution by NO3 −. It would appear that the generation of NH4 + results in a pH increase and the further suppression of active dissolution, and then repassivation occurs.
AB - The role of NO3 − in the repassivation of crevice corrosion of Type 316L stainless steel was investigated. In crevice corrosion tests, the solution was changed from 1 M NaCl to NaCl- NaNO3. NO3 − led to complete repassivation, and after potentiostatic polarization in 2 M KNO3, NH4 + was detected in the crevice solution by ion chromatography analysis. Repassivation of the crevice corrosion was found to take place in two steps. In the first step, the estimated current density inside the crevice gradually decreased from ca. 5 mA cm−2 to ca. 5 μA cm−2. After that, the current density suddenly decreased to less than 0.1 μA cm−2. From the potentiodynamic polarization in acidic solutions simulated inside the crevice (pH 0.2) and in situ observations of the crevice corrosion morphology, the first step was thought to be generated by the suppression of active dissolution by NO3 −. It would appear that the generation of NH4 + results in a pH increase and the further suppression of active dissolution, and then repassivation occurs.
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U2 - 10.1149/2.0501910jes
DO - 10.1149/2.0501910jes
M3 - Article
AN - SCOPUS:85073202635
VL - 166
SP - C250-C260
JO - Journal of the Electrochemical Society
JF - Journal of the Electrochemical Society
SN - 0013-4651
IS - 10
ER -