Inhibitory effect of boric acid on intergranular attack and stress corrosion cracking of Alloy 600 in high temperature water
- Central Research Inst. of Electric Power Industry, Tokyo (Japan). Komae Research Lab.
- Kyushu Electric Power Co., Inc., Fukuoka (Japan). Research Lab.
The inhibitory effect of boric acid on the Intergranular Attack and Stress Corrosion Cracking (IGA/SCC) propagation behavior of steam generator (SG) tubing was studied under accelerated test conditions. Based on the analysis results of stress intensity factors at IGA/SCC crack tips, the notched C-ring tests were carried out to evaluate the effect of stress intensity and boric acid on the IGA/SCC crack propagation. The A.C. impedance measurement and Auger electron spectroscopy (AES) were also conducted to clarify the inhibitory effect of boric acid. Notched C-ring test results indicated that IGA/SCC crack velocity of alloy 600 increased gradually with increasing stress intensity factor in the range 4 to about 26 MPa{center_dot}m{sup 1/2}, which might be loaded on the IGA/SCC crack tips of actual SG tubes under PWR secondary conditions. Adding boric acid slightly retarded the crack velocity in both all volatile treatment (AVT) water and caustic solutions. IGA/SCC crack velocities were lower in nearly neutral solutions than in alkali or acidic solutions. Furthermore, A.C. impedance studies showed that the polarization resistances of oxide films formed in boric acid solutions were higher than those of films formed in acidic and alkali solutions. AES analysis revealed that boron content in the oxide films formed in acidic solution containing boric acid was lowest. Good agreement was obtained between the IGA/SCC inhibitory effect of boric acid and the formation of the stable oxide films containing boron.
- OSTI ID:
- 99552
- Report Number(s):
- CONF-950304-; TRN: 95:019163
- Resource Relation:
- Conference: Corrosion `95: National Association of Corrosion Engineers (NACE) international annual conference and corrosion show, Orlando, FL (United States), 26-31 Mar 1995; Other Information: PBD: 1995; Related Information: Is Part Of Corrosion/95 conference papers; PB: 5788 p.
- Country of Publication:
- United States
- Language:
- English
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