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| EFFCTS OF pH AND Cl− CONCENTRATION ON THE CORROSION BEHAVIOR OF COPPER IN BORIC ACID BUFFER SOLUTION |
| WANG Changgang, DONG Junhua, KE Wei, CHEN Nan |
State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences,
Shenyang 110016 |
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Cite this article:
WANG Changgang DONG Junhua KE Wei CHEN Nan. EFFCTS OF pH AND Cl− CONCENTRATION ON THE CORROSION BEHAVIOR OF COPPER IN BORIC ACID BUFFER SOLUTION. Acta Metall Sin, 2011, 47(3): 354-360.
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Abstract The strategy for disposal of high–level radioactive waste in china is to enclose the spent nuclear fuel in sealed metal canisters which are embedded in bentonite clay hundreds meters deep in the bed–rock. The choice of container material depends largely on the redox conditions and the aqueous environment of the repository. One of the choices for the fabrication of waste canisters is copper, for it is thermodynamically stable under the saline, anoxic conditions over the large majority of the container lifetime. For this advantage, some other countries (Canada, Sweden) have selected copper as the material of nuclear waste container. However, in the early aerobic phase of the geological disposal the corrosion of copper could take place, and the corrosion behavior of copper would be influenced by the complex chemical conditions of groundwater markedly. Regularly, in atmosphere environment the semiconductor passive film which is constructed by Cu2O would generate on the surface of copper. On the one hand, the Cu2O film could protect copper from corrosion. On the other hand, the formation of Cu2O film is necessary to maintain the propagation of crack during the stress corrosion cracking. Therefore, the study of the effect of water chemistry conditions on the stability of Cu2O passive film makes great sense for the general corrosion and stress corrosion cracking of copper. For copper and copper alloy, Cl− is a highly aggressive ion. Lots of cases of failure and corrosion behavior of copper and copper alloy in Cl− environment have been studied. The immersion of Cl− would affect the semconductor properties of Cu2O, therefore, we focused on the effect of pH and Cl− concentration on the corrosion behavior and semiconductor properties of Cu2O in this paper. The polarization behavior of Cu electrodes and the stability of passive film Cu2O in boric acid buffer solution have been investigated respectively by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and semiconductor capacitance method (Mott–Schottky method). The results showed that the destruction and dissolutioof the passive film Cu2O happened in the conditions of low pH and high Cl− concentration. The semconductor character of passive film changed from p–type into n–type in the solution with high Cl− concentration, so that Cl− is more likely to enter the passivfilm and take complex reaction wth Cu+, which could destroy thpassive film and accelerate corrosion. The passive film Cu2O is more steady in the condition of high pH and low Cl− concentration.
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Received: 31 August 2010
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| Fund: Supported by National Natural Science Foundation of China (No.51071160) |
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