Abstract

Three zirconium alloys (Zry-4, Zry-2, and NDA) were corrosion tested at 633 K in pure water and in mixed gas of Ar and oxygen. In both environments, their corrosion rate showed cyclic changes. The time and the weight gain at the transition point changed with their corrosion resistance. In the pure water corrosion test, one test cycle was 600 h, and the cumulative total test duration was as much as 7200 h. After each test cycle, the weight changes and the hydrogen contents were analyzed. The hydrogen pick-up ratio was calculated for each test cycle based on the weight change and the increase of the hydrogen content. The calculated hydrogen pick-up ratios were not constant. They showed periodic changes. In the pre-transition region, the corrosion rate showed a gradual decrease; however, the calculated hydrogen pick-up rate gradually increased. After the transition, in contrast to the increase in the corrosion rate, the calculated hydrogen pick-up rate decreased. The changes of the corrosion rate and the calculated hydrogen pick-up rate for the test interval exhibited an inverse relationship. Transmission electron microscopy (TEM), scanning TEM, energy dispersive x-ray (EDX) spectroscopy, and electron diffraction (ED) pattern analysis of the oxide/metal interface showed the existence of an interface layer that consists of distorted ZrO2 and a sub-oxide. Before the transition, the interface layer was clearly observed. On the other hand, the interface layer disappeared after the transition. The cyclic changes in the corrosion rate were closely related to the interface barrier layer at the oxide/metal interface. The interface layer suppresses the corrosion rate, and the degradation of its barrier property increases the corrosion rate. By comparing the morphology of the oxide/metal interface between the water corrosion samples and the mixed gas oxidation samples, it can be seen that the generated hydrogen in the oxide may have two opposite effects. One is to stabilize the interface layer and to suppress the transport of the oxygen ion, and the other is to degrade the interface layer at the transition and accelerate the generation of the uniform oxide. The effect of the chemical composition on the properties of the oxide-metal interface and the mechanism of the corrosion transition will be discussed.

References

1.
Yilmazbayhan
,
A.
,
Motta
,
A. T.
,
Comstock
,
R. J.
,
Sabol
,
G. P.
,
Lai
,
B.
, and
Cai
,
Z.
, “
Structure of Zirconium Alloy Oxides Formed in Pure Water Studied With Synchrotron Radiation and Optical Microscopy: Relation to Corrosion Rate
,”
J. Nucl. Mater.
 0022-3115 https://doi.org/10.1016/j.jnucmat.2003.08.038, Vol.
324
,
2004
, pp.
6
22
.
2.
Motta
,
A. T.
,
Yilmazbayhan
,
A.
,
Comstock
,
R. J.
,
Partezana
,
J.
,
Sabol
,
G. P.
,
Lai
,
B.
, and
Cai
,
Z.
, “
Microstructure and Growth Mechanism of Oxide Layers Formed on Zr Alloys Studied with Micro-Beam Synchrotron Radiation
,”
14th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1467, Stockholm, Sweden,
ASTM International
,
West Conshohocken, PA
,
2004
, pp.
205
232
.
3.
Yilmazbayhan
,
A.
,
Breval
,
E.
,
Motta
,
A. T.
, and
Comstock
,
R. J.
, “
Transmission Electron Microscopy Examination of Oxide Layer Formed on Zr Alloys
,”
J. Nucl. Mater.
 0022-3115 https://doi.org/10.1016/j.jnucmat.2005.10.012, Vol.
349
,
2006
, pp.
265
281
.
4.
Garzarolli
,
F.
,
Seidel
,
H.
,
Tricot
,
R.
, and
Gros
,
P.
, “
Oxide Growth Mechanism on Zirconium Alloys
,”
9th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1132, Kobe, Japan,
ASTM International
,
West Conshohocken, PA
, pp.
395
415
.
5.
Beie
,
H. J.
,
Mitwalsky
,
A.
,
Garzarolli
,
F.
,
Ruhmann
,
H.
, and
Sell
,
H. J.
, “
Examinations of the Corrosion Mechanism of Zirconium Alloys
,”
10th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1245, Baltimore, MD,
ASTM International
,
West Conshohocken, PA
,
1994
, pp.
615
643
.
6.
Bauer
,
K.
,
Garzarolli
,
F.
,
Ruhmann
,
H.
, and
Sell
,
H. J.
, “
Electrochemical Examinations in 350°C Water with Respect to the Mechanism of Corrosion-Hydrogen Pickup
,”
12th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1354, Toronto, Canada,
ASTM International
,
West Conshohocken, PA
,
2000
, pp.
836
852
.
7.
Wadman
,
B.
,
Lai
,
Z.
,
Andren
,
H. O.
,
Nystrm
,
A. L.
,
Rudling
,
P.
, and
Petterson
,
H.
, “
Microstructure of Oxide Layers Formed During Autoclave Testing of Zirconium Alloys
,”
10th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1245, Baltimore, MD,
ASTM International
,
West Conshohocken, PA
,
1994
, pp.
579
598
.
8.
Anada
,
H.
, and
Takeda
,
K.
, “
Microstructure of Oxides on Zircaloy-4, 1.0Nb Zry-4 and Zry-2 Formed in 10.3Mpa Steam at 673K
,”
11th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1295, Garmish-Partenkirchen, Germany,
ASTM International
,
West Conshohocken, PA
,
1996
, pp.
35
54
.
9.
Nanikawa
,
S.
, and
Etoh
,
Y.
, “
The Effect of Oxide Microstructure on Kinetic Transition in Out-of-Pile Steam Corrosion Test for Zircaloy-2 and Zircaloy-2
,”
J. Nucl. Sci. Technol.
 0022-3131, Vol.
38
, No.
6
,
2001
, pp.
420
428
.
10.
Bossis
,
P.
,
Lelievre
,
G.
,
Barberis
,
P.
,
Iltis
,
X.
, and
Lefebvre
,
F.
, “
Multi-Scale Characterization of the Metal-Oxide Interface of Zirconium Alloys
,”
12th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1354, Toront, Canada,
ASTM International
,
West Conshohocken, PA
,
2000
, pp.
918
945
.
11.
Nanikawa
,
S.
,
Etoh
,
Y.
,
Shimada
,
S.
,
Kubo
,
T.
,
Ito
,
K.
, and
Harada
,
H.
, “
Correlation Between Characteristics of Oxide Films Formed on Zr Alloys in BWRs and Corrosion Performance
,”
12th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1354, Toront, Canada,
ASTM International
,
West Conshohocken, PA
,
2000
, pp.
815
835
.
12.
Dobler
,
U.
,
Knop
,
A.
,
Ruhmann
,
H.
, and
Beie
,
H. J.
, “
On the Initial Corrosion Mechanism of Zirconium Alloy: Interaction of Oxygen and Water with Zircaloy at Room Temperature and 450°C Evaluated by X-Ray Absorption Spectroscopy and Photoelectron Spectroscopy
,”
10th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1245, Baltimore, MD,
ASTM International
,
West Conshohocken, PA
,
1994
, pp.
644
662
.
13.
Nishino
,
Y.
,
Krauss
,
A. R.
,
Lin
,
Y.
, and
Gruen
,
D. M.
, “
Initial Oxidation of Zirconium and Zircaloy-2 With Oxygen and Water Vapor at Room Temperature
,”
J. Nucl. Mater.
 0022-3115 https://doi.org/10.1016/0022-3115(95)00194-8, Vol.
228
,
1996
, pp.
346
353
.
14.
Morant
,
C.
,
Sanz
,
J. M.
,
Galan
,
L.
,
Soriano
,
L.
, and
Rueda
,
F.
, “
An XPS Study of the Interaction of Oxygen
,”
Surf. Sci.
 0039-6028 https://doi.org/10.1016/0039-6028(89)90156-8, Vol.
218
,
1989
, pp.
331
345
.
15.
Gonzalex
,
C. O. D.
, and
Garcia
,
E. A.
, “
An X-Ray Photoelectron Spectroscopy Study of the Surface Oxidation of Zirconium
,”
Surf. Sci.
 0039-6028 https://doi.org/10.1016/0039-6028(88)90438-4, Vol.
193
,
1988
, pp.
305
320
.
16.
Grandjean
,
A.
, and
Serruys
,
Y.
, “
Metal and Oxygen Mobilities during Zircaloy-4 Oxidation at High Temperature
,”
J. Nucl. Mater.
 0022-3115 https://doi.org/10.1016/S0022-3115(99)00036-7, Vol.
273
,
1999
, pp.
111
115
.
17.
Bossis
,
P.
,
Pêcheur
,
D.
,
Hanifi
,
K.
,
Thomazet
,
J.
, and
Blat
,
M.
, “
Comparison of the High Burn-Up Corrosion on M5 and Low Tin Zircaloy-4
,”
14th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1467, Stockholm, Sweden,
ASTM International
,
West Conshohocken, PA
,
2004
, pp.
494
525
.
18.
Hatano
,
Y.
,
Sugisaki
,
M.
,
Kitano
,
K.
, and
Hayashi
,
M.
, “
Role of Intermetallic Precipitates in Hydrogen Transport Through Oxide Films on Zircaloy
,”
12th International Symposium on Zirconium in the Nuclear Industry
, ASTM STP 1354, Toront, Canada,
ASTM International
,
West Conshohocken, PA
,
2000
, pp.
901
917
.
19.
Takeda
,
K.
,
Harada
,
M.
,
Ishii
,
Y.
, and
Miyazaki
,
A.
, “
Effect of Metallographic Factor on Hydrogen Pick-up Properties of Zircaloy-2
,”
J. Nucl. Sci. Technol.
 0022-3131, Vol.
43
, No.
9
,
2006
, pp.
984
990
.
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