Low-temperature stress corrosion cracking of alloy 601 in thiosulfate and chloride solutions

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Corrosion

DOI:https://doi.org/10.5006/1.3283963· OSTI ID:305362

Gonzalez-Rodriguez, J G ^[1]; Salinas-Bravo, V M ^[2]; Martinez-Villafane, A ^[3]

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1. U.A.E.M., Cuernavaca (Mexico). Facultad de Ciencias Quimicas e Ingenieria
2. I.I.E., Cuernavaca (Mexico)
3. CIMAV, Chihuahua (Mexico)

The stress corrosion cracking (SCC) susceptibility of unsensitized and sensitized alloy 601 (UNS N06601) was studied in sodium thiosulfate (Na{sub 2}S{sub 2}O{sub 3}) and sodium chloride (NaCl) solutions using slow strain rate testing (SSRT). Specimens were tested in the as-received condition (mill-annealed) after solution annealing at 1,050 C for 30 min and after solution annealing and sensitizing for 2, 5, 24, or 772 h at 700 for 30 min. Environments included Na{sub 2}S{sub 2}O{sub 3} and NaCl at different concentrations ranging from 0.01 M to 1.0 M at 25 C and 95 C. Double-loop electrochemical potentiokinetic reactivation (DL-EPR) tests in 0.01 M sulfuric acid (H{sub 2}SO{sub 4}) + 0.001 M potassium thiocyanate (KSCN) and immersion tests in boiling 25% nitric acid (HNO{sub 3}) solution were used to evaluate the effect of heat treatment on the degree of sensitization (DOS) and on intergranular corrosion (IGC) of alloy 601. In all environments tested, the unsensitized alloy was immune to SCC and showed only ductile failure. The alloy sensitized for 24 h showed the highest degree of susceptibility to SCC in 0.1 M Na{sub 2}S{sub 2}O{sub 3}, followed by the alloys sensitized for 72, 5, and 2 h, followed by the as-received and solution-annealed alloys. Except for the other times of sensitization, ductility for the specimen sensitized for 24 h was always lower at 25 C than at 95 C. The modified Huey and the DL-EPR tests also revealed the highest susceptibility to IGC for specimens sensitized for 24 h. This susceptibility did not change as Na{sub 2}S{sub 2}O{sub 3} concentration decreased from 0.5 M to 0.01 M, but ductility decreased as solution pH was increased from 3 to 7. Addition of NaCl to Na{sub 2}S{sub 2}O{sub 3} did not have a clear effect on susceptibility to SCC of the sensitized alloy since ductility sometimes increased but at other times decreased.

• Sponsoring Organization: USDOE
• OSTI ID: 305362
• Journal Information: Corrosion, Journal Name: Corrosion Journal Issue: 1 Vol. 55; ISSN 0010-9312; ISSN CORRAK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRACKS
ELECTROCHEMISTRY
NICKEL BASE ALLOYS
NITRIC ACID
SODIUM CHLORIDES
STRAIN RATE
STRESS CORROSION
SULFURIC ACID
THIOCYANATES
THIOSULFATES