时间、pH和Cl^-对既成膜管线钢腐蚀电化学行为的影响

Effects of Time,pH and Cl^- Concentration on Electrochemical Corrosion Behavior of Filmed Pipeline Steels

采用极化曲线和EIS技术研究了时间、pH和Cl-对既成膜管线钢X65和X70腐蚀电化学行为的影响。结果表明,两种既成膜管线钢的电化学阻抗谱均由高频容抗和低频感抗组成,含两个时间常数;各条件下形成的既成膜覆盖度较高但致密性不好,发生进一步活性溶解有限;时间、pH和Cl-对腐蚀电化学行为的影响与既成膜的特性密切相关,当成膜充分且无内应力破裂时,既成膜X70钢比X65更难发生进一步腐蚀,且对Cl-浓度变化不敏感。

Polarization curves and electrochemical impedance spectroscopy （EIS）were used to study the effects of time,pH and Cl^-concentration on electrochemical corrosion behavior of filmed X65 and X70 steels.The investigation indicated that Nyquist diagrams of both the filmed pipeline steels included a high frequency capacitive loop and a low inductive arc,implying two time constants.The coverage of film formed under different conditions was extremely good,but its density was poor,and the occurrence of its further active dissolution was limited.Effects of time,pH and Cl^- concentration on corrosion electrochemical behavior were closely related to the film characteristics,the filmed X70 steel with a full and none stress rupture film would be more difficult to suffer further corrosion and was less sensitive to Cl^- concentrations than X65.