X80管线钢在库尔勒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 Ku' erle Soil

X80管线钢在油气输送中广泛使用,而对其在土壤溶液的腐蚀情况研究尚不够系统、深入。为此,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,研究了原始态与退火处理态的X80管线钢在库尔勒土壤模拟溶液中的电化学腐蚀行为与机理,分析了热处理和腐蚀时间等因素对X80钢极化曲线的影响。结果表明,退火态X80钢的耐蚀性低于原始态,这主要与X80钢的组织因热处理而发生改变有关;随浸泡时间的延长,两种状态X80钢总的腐蚀倾向均增加,但原始态时的腐蚀速率呈增大-减小-增大趋势,退火态时的腐蚀速率则呈增大趋势;腐蚀产物主要由FeOOH(表层)和Fe3O4(内层)组成,而腐蚀产物膜的完整性和致密性影响了X80钢表面的腐蚀行为与过程,使管线钢表面的局部腐蚀破坏程度增加。研究还发现C l-对X80钢的腐蚀起主导作用。

The electrochemical corrosion behavior and mecha-nism of X80 pipeline steel in simulated solution of Ku' erle soil were investigated bv making use of electrochemical measurement, scan-ning electron microscopic observation, energy dispersive spectrome-tric analysis, and X-ray diffraction analysis. At the same time, the effects of heat treatment and corrosion time on the polarization curves of the pipeline steel were analyzed. Results show that the annealed X80 steel has poorer corrosion resistance than the as-prepared X80 steel, due to the change of microstructure by annealing. Both the as -prepared and annealed X80 steel had similar corrosion tendency. Namely, their corrosion became increasingly severe with extendingtime of corrosion. The as-prepared X80 steel was dominated by in-crease, decrease, and again increase of corrosion rate with extending corrosion time, but the annealed one was dominated by simple in-crease of corrosion rate therewith. The corrosion products are com-posed of Fc(X)H ( surface layer) and Fe3O4(inner layer). The inte-grality and compactness of the corrosion product film had significanteffects on the corrosion behavior and process, and localized corrosion damage of X80 steel. Moreover, the content of C1- in the solution dominated the corrosion severity.