This study explores the effect of thiosulfate on the metastable pitting of UNS S30403 in 0.6M chloride solution. A significant decrease in the pitting potential was found in 0.6M chloride solution after 0.03M thiosulfate addition. Chronoamperometry was used to study the metastable pitting behavior of UNS S30403. Specimens were polarized at -0.1V and 0V vs. SCE. By analyzing the frequency and peak current distribution of the metastable pits, it was found that thiosulfate promotes both metastable pitting frequency and growth. A turning point was found on the log Ipeak vs. cumulative frequency curve, which may correspond to the size of the pit at which reduced sulfur species start to facilitate pitting.

Subject
Anions, Pits, Electric current, Ions, Potentiostatic polarization, Repassivation, Repassivation potentials, Sodium chloride, Chloride solutions, Sodium chloride solution, Thiosulfate, Pitting, Chlorides
Keywords:
metastable pitting, thiosulfate, pit initiation, repassivation
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2015
Association for Materials Protection and Performance (AMPP)
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