title: Pitting of steam-generator tubing alloys in solutions containing thiosulfate and sulfate or chloride.
abstract: The pitting of nuclear steam generator tubing alloys 600, 690 and 800 was studied at 60 °C using dilute thiosulfate solutions containing excess sulfate or (for Alloy 600) chloride. A potentiostatic scratch method was used. In sulfate solutions, all alloys pitted at low potentials, reflecting their lack of protective Mo. The alloys demonstrated the most severe pitting at a sulfate : thiosulfate concentration ratio of ∼40. Alloy 600 pitted worst at a chloride : thiosulfate ratio of ∼2000. The results are interpreted through the mutual electromigration of differently charged anions into a pit nucleus, and differences in the major alloy component.
authors.affiliation: University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Toronto, Canada. roger.newman@utoronto.ca a.carcea@utoronto.ca lianwei.zhang@utoronto.ca.
authors.forename: William
authors.initials: W
authors.lastname: Zhang
authors.forename: Anatolie G
authors.initials: AG
authors.lastname: Carcea
authors.forename: Roger C
authors.initials: RC
authors.lastname: Newman