物理化学学报 >> 2015, Vol. 31 >> Issue (3): 467-475.doi: 10.3866/PKU.WHXB201501053

电化学和新能源 上一篇    下一篇

690合金在300 ℃含硫模拟碱性水化学中的腐蚀行为

夏大海1,2,3, LUO Jing-Li2   

  1. 1. 天津大学材料科学与工程学院, 天津 300072;
    2. Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 2V4, Alberta, Canada;
    3. 天津市材料复合与功能化重点实验天津, 天津 300072
  • 收稿日期:2014-11-21 修回日期:2014-12-31 发布日期:2015-03-06
  • 通讯作者: 夏大海, LUO Jing-Li E-mail:dahaixia@tju.edu.cn;luoj@ualberta.ca
  • 基金资助:

    加拿大原子能公司资助项目

Corrosion Behavior of Alloy 690 in Simulated Alkaline Water Chemistries Containing Sulfur at 300 ℃

XIA Da-Hai1,2,3, LUO Jing-Li2   

  1. 1. School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China;
    2. Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 2V4, Alberta, Canada;
    3. Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072, P. R. China
  • Received:2014-11-21 Revised:2014-12-31 Published:2015-03-06
  • Contact: XIA Da-Hai, LUO Jing-Li E-mail:dahaixia@tju.edu.cn;luoj@ualberta.ca
  • Supported by:

    The project was supported by the Atomic Energy of Canada Limited (AECL).

摘要:

690 合金作为压水堆核电站蒸汽发生器传热管的一种关键材料, 其在碱性环境下还原态硫导致的钝化膜的腐蚀退化是引发应力腐蚀开裂的关键原因之一. 本文采用动电位极化曲线, 结合扫描电镜(SEM)、俄歇能谱(AES)、二次离子飞行时间质谱(ToF-SIMS)研究了690合金在300 ℃模拟碱性水化学中的腐蚀行为, 并分析了硫代硫酸根与硫酸根对钝化膜特性的影响. 实验结果表明: 300 ℃碱性溶液中690合金表面钝化膜为外层的多孔层与内层的紧密层组成的双层结构, 所加入的硫酸盐种类对690合金的耐蚀性有较大影响; 硫代硫酸根使690合金钝化电流密度增加, 过钝化电位降低, 即钝化膜的耐蚀性降低; 此外, 硫代硫酸根使钝化膜中的Cr含量降低而Ni 含量提高, 硫代硫酸根会在合金表面电化学还原成为更低价态的硫进入钝化膜, 使钝化膜中的硫化物增多也是导致钝化膜防护性能变差的原因; 而硫酸根与钝化膜的作用较弱, 对钝化膜的影响较小.

关键词: 690合金, 钝化膜, 碱性, 硫代硫酸根, 硫酸根

Abstract:

Alloy 690 is one of the steam generator (SG) tubing materials in pressurized water reactors (PWR). The degradation of this alloy in alkaline solutions containing reduced sulfur is one of the main causes of stress corrosion cracking. In this study, the corrosion behavior of Alloy 690 in simulated alkaline crevice chemistry at 300 ℃ was investigated using polarization curves, scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Studying the effect of thiosulfate and sulfate on the properties of the passive film formed on Alloy 690 showed that the film formed at 300 ℃ was composed of an outer porous layer and an inner compact layer, and that the ion species presented in chloride solutions had a significant impact on the corrosion behavior of the alloy. The addition of thiosulfate increased the passive current density, decreased the transpassive potential, and therefore lowered the corrosion resistance. The presence of thiosulfate also led to a decrease in Cr levels and an increase in Ni levels in the passive layer. The thiosulfate can reduce sulfur at the film surface and enter into the film, causing an increased sulfide content in the film which decreases the corrosion resistance. However, experiments using sulfate had no obvious effect on film degradation as the ion had minimal interaction with the film.

Key words: Alloy 690, Passive film, Alkaline, Thiosulfate, Sulfate

MSC2000: 

  • O646