硼酸缓冲溶液中pH值和Cl^-浓度对Cu腐蚀行为的影响

来源期刊：金属学报2011年第3期

论文作者：王长罡 董俊华 柯伟 陈楠

文章页码：354 - 360

关键词：高放废物地质处置； Cu₂O钝化膜； 稳定性； 电化学阻抗谱 (EIS)； Mott-Schottky方法

Key words：geological disposal of high level radioactive waste； Cu₂O passive film； stability； electrochemical impedance spectroscopy (EIS)； Mott-Schottky method

摘    要：在硼酸缓冲溶液中,采用动电位极化、电化学阻抗谱(EIS)和半导体电容分析方法分别研究了Cu电极的极化行为及其表面人工Cu₂O钝化膜的化学稳定性.结果表明,低pH值、高Cl^-浓度均造成Cu₂O钝化膜的破坏和溶解.高Cl^-浓度时,Cu₂O钝化膜的半导体性质由p型转变为n型,使Cl^-更容易进入钝化膜与Cu⁺络合,并破坏钝化膜从而加速腐蚀.高pH值、低Cl^-浓度有利于Cu₂O钝化膜稳定.

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 semiconductor 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 dissolution of the passive film Cu₂O happened in the conditions of low pH and high Cl^- concentration.The semiconductor 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 passive film and take complex reaction with Cu⁺,which could destroy the passive film and accelerate corrosion.The passive film Cu₂O is more steady in the condition of high pH and low Cl^- concentration.