Electrochemical and metallurgical aspects of stress corrosion cracking of sensitized Alloy 600 in simulated primary water containing sulfur contamination

Conference · Tue Jan 01 04:00:00 EST 1985

OSTI ID:6467767

Bandy, R; Kelly, K

The stress corrosion cracking (SCC) of sensitized Alloy 600 was investigated in aerated solutions of sodium thiosulfate containing 1.3% boric acid. Results indicate that in the borated thiosulfate solution containing 7 ppM sulfur, 5 ppM lithium as lithium hydroxide is sufficient to inhibit SCC in U-bends. The occurrence of inhibition seems to correlate to the rapid increase of pH and conductivity of the solution as a result of the lithium hydroxide addition. In the slow strain rate tests in the borated solution containing 0.7 ppM lithium as lithium hydroxide, significant SCC is observed at a sulfur level of 30 ppB, i.e., a lithium to sulfur ratio of 23. In a parallel test in 30 ppB sulfur level but without any lithium hydroxide, the SCC is more severe than that in the lithiated environment. In the constant load test on a specimen held initially at a nominal stress near the yield strength of the material, cracks continue to grow until fracture during controlled, progressive dilution of the bulk solution, leading to final lithium concentration of 1.5 ppM and sulfur concentration (as thiosulfate) of 9.6 ppB i.e., a lithium to sulfur ratio of about 156, although lithium hydroxide retards the rate of crack propagation to some extent. The crack growth rate is strongly influenced by the electrochemical potential which is primarily governed by the local crack tip chemistry.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6467767
• Report Number(s): BNL-NUREG-37001; CONF-850902-8; ON: TI86002510
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALKALI METAL COMPOUNDS
ALLOYS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CORROSION
CRACK PROPAGATION
HYDROGEN COMPOUNDS
HYDROXIDES
INCONEL 600
INCONEL ALLOYS
IRON ALLOYS
LITHIUM COMPOUNDS
LITHIUM HYDROXIDES
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
OXYGEN COMPOUNDS
STRESS CORROSION
THIOSULFATES