物理化学学报 >> 2013, Vol. 29 >> Issue (05): 1003-1012.doi: 10.3866/PKU.WHXB201302251

电化学和新能源 上一篇    下一篇

高温高压喷射湍流区中X70管线钢CO2腐蚀电化学特征

蔡峰1, 柳伟1, 樊学华2, 张晶1, 路民旭1   

  1. 1 北京科技大学新材料技术研究院, 北京 100083;
    2 中国石油集团工程设计有限责任公司北京分公司, 北京 100085
  • 收稿日期:2012-11-13 修回日期:2013-02-25 发布日期:2013-04-24
  • 通讯作者: 柳伟 E-mail:weiliu@ustb.edu.cn
  • 基金资助:

    国家重大科技专项经费(2008ZX05026-003-04)资助

Electrochemical Corrosion Behavior of X70 Pipeline Steel in Turbulence Zone under Jet Impingement at High Temperature and High Pressure CO2 Environment

CAI Feng1, LIU Wei1, FAN Xue-Hua2, ZHANG Jing1, LU Min-Xu1   

  1. 1 Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, P. R. China;
    2 Beijing Branch of China Petroleum Engineering Co., Ltd., Beijing 100085, P. R. China
  • Received:2012-11-13 Revised:2013-02-25 Published:2013-04-24
  • Supported by:

    The project was supported by the National Science & Technology Major Project of China (2008ZX05026-003-04).

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摘要：

采用高温高压环路喷射装置并结合腐蚀微电极技术, 开展了湍流区中X70 管线钢CO2腐蚀实验. 利用扫描电镜对不同实验时间的试样表面腐蚀产物微观形貌进行了观察和分析, 并进行了湍流区原位电化学测试和分析. 结果表明, 湍流区中X70 钢的CO2腐蚀电化学特征与其表面所覆盖腐蚀产物膜层变化密切相关. 实验12 h内, 湍流区中X70钢表面从最初的基体与腐蚀产物共存, 转变为由疏松且不完整的膜层覆盖的特征. 实验12 h 后, 试样表面出现内外两层腐蚀产物膜, 内层膜堆垛致密, 外层膜疏松多孔, 同时湍流区中高切应力导致外层腐蚀产物脱落, 材料表面逐渐被完整致密的内层膜覆盖, 这是腐蚀速率持续下降的主要原因. 电化学结果表明, 实验12 h 内, 湍流区中X70 钢的腐蚀电位Ecorr和线性极化电阻Rp不断下降; 电化学阻抗谱由高频容抗弧、中频容抗弧和低频感抗弧组成, 膜层电阻Rf缓慢增加, 电荷传递电阻Rt不断下降, 双电层电容Cdl和膜层电容Cf迅速下降; 12 h后, 腐蚀产物膜层对基体材料保护性随喷射时间延长逐渐增强, Ecorr和Rp逐渐增大, 电化学阻抗谱中低频感抗弧逐渐收缩并在48 h 时消失, 最后转变为双容抗特征, Rf、Rt和Cdl随时间迅速增大, Cf趋于稳定.

关键词: CO2腐蚀, 湍流区, 腐蚀电化学, 腐蚀形态, X70管线钢

Abstract:

The corrosion behavior of X70 pipeline steel in the turbulent zone was investigated in situ with a micro-electrode technique using loop jet impingement under high temperature and high pressure CO2 environment. The morphology of the corrosion product formed on the surface and corrosion behavior of X70 steel after different periods were investigated by scanning electron microscopy and in situ electrochemical methods, respectively. The electrochemical behavior of X70 steel was closely related to the evolution of corrosion scales on the steel surface. The surface of the steel changed gradually from the presence of both substrate and corrosion product to loose, porous corrosion scales during the first 12 h. After 12 h, the corrosion scales were mainly composed of inner and outer scales. Because of the effect of high wall shear stress in the turbulent zone, the porous, less-protective outer scale was thinned and then removed from the steel surface. Consequently, the surface was increasingly covered by the compact inner scale, which decreases the corrosion rate of the steel considerably. Correspondingly, during the first 12 h, the corrosion potential Ecorr and linear polarization resistance Rp of the sample decreased continuously. Meanwhile, electrochemical impedance spectroscopy (EIS) exhibited high- and medium-frequency capacitive loops and a low-frequency inductive loop. Analysis of EIS revealed that the resistance Rf of the corrosion film increased slowly and charge transfer resistance Rt decreased steadily, while the double-layer capacitance Cdl and corrosion film capacitance Cf decreased rapidly. After 12 h, the protectiveness of the corrosion scales improved with time, and thus the Ecorr and Rp increased. As the inductive component weakened with time and finally disappeared at 48 h, EIS changed to double capacitive loops. The Rf, Rr, and Cdl increased quickly. Furthermore, the Cf stabilized.

Key words: CO2 corrosion, Turbulent zone, Corrosion electrochemistry, Corrosion morphology, X70 pipeline steel