掺海水输送对海底管道结垢及腐蚀行为的影响

Effects of Seawater⁃Mixed Transportation on Scaling and Corrosion Behavior of the Submarine Pipeline

为了保障管道流动安全,明确管道掺海水输送方案的结垢及腐蚀风险,针对我国南海海域某油田现场的实际工况,分析了掺入海水后水质结垢倾向的变化,并模拟垢层沉积状态,开展了腐蚀模拟评价实验。利用失重法测试平均腐蚀速率,利用扫描电子显微镜及能谱仪进行腐蚀形态观察和腐蚀产物分析,并结合激光共聚焦显微镜观察基体表面腐蚀形态,探究了海水掺入对管线钢结垢腐蚀的影响。通过开展原位电偶腐蚀实验,探究了垢层沉积对管线钢腐蚀电化学行为的影响。结果表明:海底管道中海水的掺入比例及海水中腐蚀性离子的种类、含量影响海管输送系统的结垢风险。垢层的形成,一方面使管道内壁整体的腐蚀倾向有所减小;另一方面,沉积的垢层在基体表面不均匀分布改变基体表面电位状态,构成局部电偶电池,促进局部腐蚀坑的萌生与发展。

In order to ensure the safety of pipeline flow and clarify the scaling and corrosion risks of seawater⁃mixed pipeline transportation scheme,the change of water scaling tendency after adding seawater was analyzed based on the actual on⁃site working conditions of an oil field in South China Sea,and the deposition state of scale layers was simulated to carry out corrosion simulation evaluation experiment.To study the effects of adding seawater on the scaling corrosion of pipeline steel,the average corrosion rate was tested by weight loss method,the scanning electron microscope and energy dispersive spectrometer were employed to observe the corrosion morphology and analyze the corrosion products,and the surface corrosion morphology of the substrate was observed by a laser confocal microscope.Meanwhile,in⁃situ galvanic corrosion exper⁃iments were carried out to investigate the effect of scale deposition on the electrochemical behavior of pipeline steel corrosion.Results showed that the proportion of seawater in the submarine pipeline and the type and content of corrosive ions in the seawater affected the scaling risk of the submarine pipeline transportation system.On the one hand,the formation of the scale layer reduced the overall corrosion tendency of the inner wall of the pipeline;on the other hand,the uneven distribution of the deposited scale layer on the surface of the substrate changed the potential state of the substrate surface,formed a local galvanic battery and thus promoted the emergence and development of local corrosion pits.