X80管线钢在西北盐渍土壤模拟溶液中的电化学腐蚀行为

Electrochemical Corrosion Behavior of X80 Pipeline Steel in Simulated Solution of Northwest Saline Soil

采用电化学测试、扫描电镜观察、表面能谱分析及X射线衍射等方法研究了原始态(焊态)与650℃×3 h退火态X80管线钢在西北盐渍土壤模拟溶液中的电化学腐蚀行为与机理,分析了退火处理及腐蚀时间等因素对X80管线钢极化曲线的影响。结果表明:退火态X80管线钢的耐蚀性远低于原始态的,这主要与组织发生改变有关;随着浸泡时间的延长,两种状态X80管线钢的腐蚀倾向是先增大后减小,腐蚀速率呈现出先减小再增大的趋势,但总的腐蚀速率呈增大趋势,点蚀敏感性增加,其阴极过程均为氧的去极化反应;腐蚀产物主要由FeOOH(表层)和Fe3O4(内层)组成,Cl-浓度对X80管线钢的腐蚀起主导作用。

The electrochemical corrosion behavior and mechanism of original state （welded state） and tempered state （650 ℃ for 3 h） X80 pipeline steel were investigated in a simulated solution of northwest saline soil by using electrochemical measurements, SEM, EDS and XRD. Effects of anneal treatment and corrosion time on the polarization curves were anlyzed. The results show that the change of microstructure caused the corrosion resistance of annealed state X80 pipeline steel was far lower than that of original state. The corrosion tendency both first increased and then decreased with the increasing corrision time. The corrosion rates first, decreased then increased, but the general corrosion rates and pitting sensitivity for both original and heat-treated steels increased with increasing exposure time. The cathodic process was dominated by the oxygen activation control. The corrosion product consisted of FeOOH （surface layer） and Fe3O4 （inner layer）. The content of Cl^- dominated the corrosion severity.