某集气站集输管线腐蚀机理及腐蚀速率预测方法研究

发布时间：2018-11-18 20:11

【摘要】：本文在对国内外集输管线腐蚀调研的基础上,通过20#钢集输管线的失效分析及室内电化学测试,明确其腐蚀失效的主控因素及腐蚀机理,并对其在工况环境中的腐蚀速率进行预测。结果表明:溶解氧是造成该管线腐蚀失效的主要原因,管道内介质中Cl-含量较高、耐蚀合金元素含量较低及化学元素分布不均匀也促进了失效管线的腐蚀。在CO_2和CO_2+O_2两种腐蚀条件下,20#钢的电化学腐蚀为阴极活化控制;微量溶解氧的存在并未对腐蚀电位产生较为显著的影响,但显著促进了阴极反应,自腐蚀电流密度增大。在反应初始阶段,20#钢在CO_2和CO_2+O_2两种腐蚀条件下都存在三个时间常数,随着腐蚀时间的延长,高频端容抗弧增大,低频端感抗弧减小,48h后试样表面已经形成完整的腐蚀产物膜覆盖,低频端感抗弧消失,仅出现容抗弧,腐蚀产物膜的保护性显著增强,极化电阻急剧增大,腐蚀速率降低。腐蚀速率预测结果表明:温度升高对钢的电化学反应的促进作用要强于腐蚀产物膜的保护作用,腐蚀速率增加;低分压CO_2对钢的腐蚀速率影响较小,而微量溶解氧的存在促进了钢的阴极反应,随着溶解氧含量增加,腐蚀速率增大。在集输工况条件下,20#钢的室内模拟平均腐蚀速率为0.0357mm/a,其与预测结果较为吻合。
[Abstract]:Based on the investigation of corrosion of gathering pipeline at home and abroad, the main controlling factors and mechanism of corrosion failure of 20 # steel gathering pipeline are determined through failure analysis and indoor electrochemical test. The corrosion rate in the operating environment is predicted. The results show that dissolved oxygen is the main reason for the corrosion failure of the pipeline. The high content of Cl- in the medium, the low content of corrosion resistant alloy elements and the uneven distribution of chemical elements in the pipeline also promote the corrosion of the failure pipeline. Under the conditions of CO_2 and CO_2 O _ 2 corrosion, the electrochemical corrosion of 20 # steel is controlled by cathodic activation. The presence of trace dissolved oxygen had no significant effect on the corrosion potential, but significantly promoted the cathodic reaction and increased the corrosion current density. In the initial stage of the reaction, there are three time constants for 20 # steel under CO_2 and CO_2 O _ 2 corrosion conditions. With the increase of corrosion time, the capacitive reactance arc at the high frequency end increases and the inductance arc at the low frequency end decreases. After 48 hours, a complete corrosion product film was formed on the surface of the sample, and the low frequency inductive arc disappeared, only the capacitive reactance arc appeared, the protection of the corrosion product film increased significantly, the polarization resistance increased sharply, and the corrosion rate decreased. The results of corrosion rate prediction show that the effect of increasing temperature on the electrochemical reaction of steel is stronger than that of the protective effect of corrosion product film, and the corrosion rate increases. Low partial pressure CO_2 had little effect on the corrosion rate of steel, while the presence of trace dissolved oxygen promoted the cathodic reaction of steel, and the corrosion rate increased with the increase of dissolved oxygen content. The average indoor simulated corrosion rate of 20 # steel is 0.0357 mm / a, which is in good agreement with the predicted results.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG172

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