Effects of temperature and pH on the electrochemical behaviour of alloy 600 in simulated pressurized water reactor primary water

JOURNAL OF NUCLEAR MATERIALS

卷:528

Article

Yang, Jie¹  Li, Yanhui²  Macdonald, Digby D.¹ 

[1] Univ Calif Berkeley, Dept Nucl Engn, Berkeley, CA 94720 USA

[2] Xi An Jiao Tong Univ, Sch Energy & Power Engn, Key Lab Thermofluid Sci & Engn MOE, Xian 710049, Shaanxi, Peoples R China

关键词: Alloy 600;    Temperature;    pH;    Passive film;    Anodic potentiostatic polarization;    Mott-Schottky analysis;    EIS;    Mixed potential model;   

DOI  :  10.1016/j.jnucmat.2019.151850

来源: Elsevier

【 摘 要 】

The effects of temperature and pH on the electrochemical properties of Alloy 600 were studied in oxygenated borate buffer solutions by the measurements of open circuit potential (OCP), anodic potentiostatic polarization, Mott-Schottky analysis (MSA), and electrochemical impedance spectroscopy (EIS). At each temperature and pH, the stabilized anodic passive current density was independent of the formation potential, and the slope of the M - S plot for the passive film formed at +0.3 Vocp (OCP + 0.3 V) is positive, indicating that the passive films formed on Alloy 600 have n-type semiconductor character. With increasing temperature (in each solution), the OCP and the impedance modulus decreased, while the passive current density and the defect density calculated from MSA increased, indicating a significant reduction in corrosion resistance. With the increase in pH value, the passive current density decreased, the absolute value of impedance increased slightly, revealing a slight increase in corrosion resistance. According to the optimization of Mixed Potential Model (MPM) on the experimentally measured EIS data for Alloy 600 at OCP and +0.3 Vocp, a series of fundamental parameters related to the micro-characteristic of passive film were extracted. In the barrier layer of the passive film, the concentration of cation interstitials is much higher than that of anion vacancies, indicating that the former was a dominant defect. With increasing temperature, the linear increase in the defect density and film thickness resulted in a linear increase of the anodic current density. However, with increasing pH, the decrease of defect density and the slight increase of film thickness caused a linear reduction in anodic current density. Elevated temperature has a more significant deterioration effect on the corrosion resistance of Alloy 600 than the increased pH value. Additionally, all the kinetics parameters describing the generation of cation interstitials and oxygen vacancies at the substrate/film were obtained. (C) 2019 Elsevier B.V. All rights reserved.

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