Review of IGA, IGSCC and wastage of Alloys 600 and 690 in high-temperature acidified solutions
- Materials Engineering Associates, Inc., Lanham, MD (United States)
A program has been recently completed (1) to better quantify the susceptibility of Alloy 600 and 690 steam generator (SG) tubing materials to intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC) in acid solutions of the types that could concentrate in steam generator crevices, and (2) to establish the effectiveness of various remedial measures achieved through chemical additions to the secondary side coolant. The main test method was the exposure of stressed C-rings and expanded capsules of SG tubing to acid chloride and sulfate environments of various pH levels, temperatures, and applied potentials. Following these exposures, crack lengths were measured on metallographic cross-sections of the C-rings, and wastage rates were calculated from weight loss, surface area and time. Test solutions were based on varying concentrations of sulfate and chloride species, with other contaminants added to some tests. The temperature dependence of the pH of the acidified solutions was calculated using the EPRI-developed MULTEQ computer program. High-temperature pH levels ranged from values of 2.5 to 5.8, the latter being the pH of neutral water at 315 C, which is the nominal test temperature. Various accelerating and inhibiting factors were evaluated. Wastage of all the tested materials has been found to be a function of pH{sub 315 C} and sulfate content. Intergranular stress-corrosion cracking (IGSCC) did occur at pH{sub 315 C} values less than about 4.0. However, in solutions with high sulfate concentrations, the amount of wastage overwhelmed the crack growth rate, and IGSCC was not detected. Tests with zinc oxide added showed that wastage and cracking were reduced over a wide range of temperatures.
- OSTI ID:
- 409739
- Report Number(s):
- CONF-9510292--; ISBN 1-57570-008-4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
CORROSION
CORROSION INHIBITORS
CRACK PROPAGATION
EXPERIMENTAL DATA
INCONEL 600
INCONEL 690
INTERGRANULAR CORROSION
MITIGATION
PH VALUE
PWR TYPE REACTORS
SECONDARY COOLANT CIRCUITS
STEAM GENERATORS
STRESS CORROSION
WATER CHEMISTRY
WATER TREATMENT