天然气管道破损内涂层局部腐蚀规律研究

发布时间：2018-05-26 19:28

  本文选题：天然气管道 + 破损内涂层　； 参考：《西南石油大学》2017年硕士论文

【摘要】：天然气管道涂覆内涂层不仅能够提高输量,而且具有相应的防腐效果。环氧内涂层大量应用于国内外天然气管道中。但是,国内外普遍采用的内腐蚀直接评估方法(ICDA)不能适用于这类内涂层天然气管道,同时国内外针对内涂层局部破损天然气管道的内腐蚀机理及规律研究较少。因此,开展天然气管道破损内涂层的局部腐蚀规律研究,可为内涂层天然气管道的内腐蚀直接评估方法的建立及内涂层改性方案的制定提供依据。根据实际天然气管道工程概况,确定了腐蚀实验试样采用X80管线钢/环氧内涂层体系。在系统分析了实际天然气管道工程内检测数据分布规律的基础上,合理确定了环氧内涂层的典型破损尺寸。从金属电化学腐蚀的热力学和动力学理论出发,筛选出了温度、压力和Cl-浓度为影响破损内涂层处金属腐蚀的主要环境因素。基于微区扫描测试系统(Tafel极化曲线/EIS/SKP)、动态反应釜与腐蚀产物测试平台(SEM/EDS),研究了不同破损尺寸、温度、压力和Cl-浓度下的破损环氧内涂层的局部腐蚀规律,确定了相应的宏观与微观参数、特征,提出了减小内涂层破损可能性的氧化石墨烯(GO)改性方案并评价了其防腐效果。通过研究得到的主要结论如下:(1)破损内涂层为宽缝时(3mm× 1mm),破损内涂层处的金属处于开放的腐蚀环境中,电荷转移更容易进行,金属腐蚀过程持续发生。(2)温度越高,破损内涂层处的金属腐蚀速率比相同温度下无涂层X80裸钢越快。EIS结果表明20℃、30℃时电极反应受扩散过程控制。SEM结果表明10℃时生成的腐蚀产物结构较稀松;而30℃时,虽然腐蚀产物增多且致密,但可能形成了氯化物复盐,导致腐蚀产物部分溶解,金属基底重新裸露。(3)管道压力从1MPa变化至8MPa的过程中,H_2O和腐蚀介质的传输动力增大,加快了内涂层剥离失效,破损内涂层处的腐蚀电流密度是无涂层X80裸钢的2～2.5倍,金属基底腐蚀更严重。SEM结果表明8MPa下腐蚀产物表面存在较大孔洞,这些孔洞将成为腐蚀介质向金属基体表面扩散的通道,从而为点蚀或坑蚀发生提供了条件。(4)在0.05mol/LNaCl浓度下,X80管线钢/破损环氧内涂层体系的局部腐蚀行为最活跃。EIS结果表明Cl-浓度越高,溶液导电性越好,离子交换越容易,金属腐蚀受扩散过程控制的时间越早。SKP扫描结果表明随着浸泡时间的延长,界面两侧的电势差由约520mV增大至900mV,局部腐蚀向涂层内部转移的趋势明显。(5)提出了氧化石墨烯(GO)内涂层改性方案,GO的存在使得改性内涂层具有更高的硬度和抗划伤性能,并且能够有效阻隔H_2O和Cl-向涂层内部渗透,将金属腐蚀活动限制在破损涂层处并形成一层较厚的保护膜。
[Abstract]:The inner coating of natural gas pipeline can not only increase the quantity of transportation, but also have the corresponding anticorrosive effect. Epoxy coating is widely used in natural gas pipelines at home and abroad. However, ICDAA, which is widely used at home and abroad, can not be applied to this kind of inner coating natural gas pipeline. At the same time, there are few researches on the internal corrosion mechanism and law of the internally coated local damaged natural gas pipeline at home and abroad. Therefore, the study on the local corrosion law of damaged inner coating of natural gas pipeline can provide the basis for the establishment of direct evaluation method of internal corrosion of inner coating natural gas pipeline and the formulation of modification scheme of inner coating. According to the general situation of natural gas pipeline engineering, X80 pipeline steel / epoxy inner coating system was determined. Based on the systematic analysis of the distribution of testing data in natural gas pipeline engineering, the typical damaged size of epoxy coating is reasonably determined. Based on the thermodynamic and kinetic theory of electrochemical corrosion of metals, temperature, pressure and Cl-concentration were selected as the main environmental factors affecting metal corrosion in damaged inner coatings. Based on the Tafel polarization curve / EIS / SKP and the dynamic reactor and corrosion product testing platform, SEM / EDSU, the local corrosion behavior of damaged epoxy coatings with different damage sizes, temperatures, pressures and Cl-concentration was studied. The corresponding macro and micro parameters and characteristics were determined. The modification scheme of graphene oxide (GOO) to reduce the possibility of internal coating damage was put forward and its anticorrosive effect was evaluated. The main conclusions obtained from the study are as follows: (1) when the damaged inner coating is a wide seam, the metal in the damaged inner coating is in an open corrosion environment, the charge transfer is easier, and the corrosion process of the metal continues to occur at a higher temperature. The results of EIS show that the electrode reaction at 20 鈩，

本文编号：1938631