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| Mechanism of LiOH aqueous solution accelerating corrosion rate of zircaloy--4 |
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| 上海大学 |
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Cite this article:
;. Mechanism of LiOH aqueous solution accelerating corrosion rate of zircaloy--4. Chin J Mater Res, 2004, 18(3): 225-231.
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Abstract Autoclave experiments in different water chemistry were conducted to clarify the
degradation behavior of zircaloy--4 corroded in LiOH aqueous solution. It was
found that the compressive stress and the tetragonal zirconia ($t$--ZrO$_{2}$)
contents in oxide films formed in different media were different; when specimens
were exposed in LiOH and KOH solutions with same concentration, the penetration
depth is shallower and the intensity of K$^{+}$ is weaker than those of Li$^{+}$,
and the penetration depth of OH$^{-}$ corroded in KOH solution is also shallower than
that corroded in LiOH solution. Based on the results, it is suggested that the
growth of oxide films is a process of OH$^{-}$ diffusing from outside of oxide
into metal/oxide interface and reacting with zirconium to form ZrO$_{2}$ and
hydrogen. It is easy for Li$^{+}$ to diffuse into oxide film because of small radius
when specimen was exposed in LiOH aqueous solution, so more OH$^{-}$ would
diffuse into oxide film deeply. The reaction between adequate OH$^{-}$ and
oxygen vacancies in the $t$--ZrO$_{2}$ would promote the transformation from
$t$--ZrO$_{2}$ to monoclinic zirconia ($m$--ZrO$_{2}$). The transformation would
bring some cracks in the oxide, which relaxed the compressive stress in the
oxide, degraded the protective ability of oxide films and caused an enhancement
of corrosion rate of zircaloy--4 alloy.
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Received: 19 July 2004
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