Kinetics and Mechanism of Columbium Alloy Corrosion In Superheated Steam
Journal Article
·
· Corrosion (Houston)
Binary Nb-V alloys were studied in detail and were observed to follow initially low powe rate laws varying from quartic to parabolic behavior. A rate transition occured after longer exposures to a linear rate law that was associated with spalling and cracks in the oxide films. The corrsion product was shown to be different from that formed in air or oxygen for Nb-3.5 5V and was a complex unknown phase. An increase in V content to 10 at % enabled beta-Nb/ sub 2/O/sub 5/ to form with the unknown phase, and NbO/sub 2/ also formed as a third phase on Nb-15V. A change oxide morphology was noted a V increased from 3.5 to 8.9 at. %. The activation energy for corrosion, 13 kcal/ mol, was the sanme for binary Nb-V alloys, which formed either the unknown oxide phase or NbO/ sub 2/ at temperatures below 482 un. Concent 85% C, and was considerably less than that for O diffsion in Nb/sub 2/O/sub 5/ containing 1 mole % V/sub 2/O/sub 5/ . The apparent diffsion-controlled process and low corrosion activation energy strongly suggest oxide grain boundary diffusion as a rate-limiting step during the pretransition period. Oxygen contamination of the substrate occurred readily, the tolerance for O decreasing with increasing V. (P.C.H.)
- Research Organization:
- General Electric Co., Pleasanton, Calif.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-020417
- OSTI ID:
- 4730505
- Journal Information:
- Corrosion (Houston), Journal Name: Corrosion (Houston) Journal Issue: 4 Vol. 19; ISSN 0010-9312
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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