Aqueous chemistry of lithium hydroxide and boric acid and corrosion of Zircaloy-4 and Zr-2.5Nb alloys
- Ontario hydro, Toronto, Ontario (Canada). Research Division
- Chalk River Labs., Chalk River, Ontario (Canada)
The chemistry of the aqueous solution, surface chemistry of zirconium oxide (ZrO{sub 2}), and the physical structure of the corrosion film have to be considered for an understanding of the mechanism of corrosion of zirconium alloys in aqueous solutions. Based on information available in all these areas, the authors are proposing a model for oxide growth on Zircaloy-4 fuel cladding and Zr-2.5Nb pressure tube material, in lithium hydroxide (LiOH) solutions with and without added boric acid (H{sub 3}BO{sub 3}). Corrosion exposures were at 360 C and were short term of four-day duration. Concentration of lithium covered the range 0.7 to 3,500 ppm and boron was added at 300, 600 and 1,200 ppm. Weight gain, Fourier Transform InfraRed (FTIR) spectroscopy, and Secondary ion Mass Spectrometry (SIMS) were used to characterize the oxide films. Potentiodynamic polarization measurements were made in separate tests at 315 C. The chemistry of LiOH-H{sub 3}BO{sub 3} system at 300 to 360 C was evaluated from the ionization constants of water, LiOH, and H{sub 3}BO{sub 3}. There is no simple relationship between pH and corrosion. In the absence of boron acceleration in corrosion, in these short-term tests, is observed at concentrations >350 ppm Li for Zircaloy-4 and at >60 ppm Li for Zr-2.5Nb. According to the model proposed for oxide growth, the corrosion behavior can be classified into two categories: (1) growth of post-transition type films under acceleration conditions where solution had access into the oxide and (2) growth of pre-transition films under non-acceleration conditions where the solution had not gained access into the oxide.
- OSTI ID:
- 55662
- Report Number(s):
- CONF-930611-; ISBN 0-8031-2011-7; TRN: 95:012907
- Resource Relation:
- Conference: 10. international symposium on zirconium in the nuclear industry, Baltimore, MD (United States), 21-24 Jun 1993; Other Information: PBD: 1994; Related Information: Is Part Of Zirconium in the nuclear industry: Tenth international symposium. ASTM STP 1245; Garde, A.M.; Bradley, E.R. [eds.]; PB: 818 p.
- Country of Publication:
- United States
- Language:
- English
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