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目的 研究在H2S/CO2酸性环境中,不同溶解氧浓度对低合金管材点蚀形成和发展的影响.方法 通过模拟酸性油田环境,利用高温高压设备及常温常压设备来进行腐蚀失重试验,测试出腐蚀速率,并通过扫描电镜对腐蚀产物的形貌及点蚀坑的形貌尺寸进行分析.结果 溶解氧对腐蚀产物的影响较明显,对腐蚀产物膜的破坏较大.溶解氧存在时,腐蚀产物在基体的覆盖量减少,产物膜的厚度减小,实验表面都出现不同尺寸的点蚀坑.溶解氧分压在0.1 MPa时,点蚀现象较明显,L245NCS表面点蚀坑的直径约为0.4 mm,而L290试样表面点蚀坑的直径约为0.25 mm.结论 在H2S/CO2共存的腐蚀环境中,溶解氧的加入使碳钢更容易发生点蚀.随溶解氧浓度的增加,碳钢的均匀腐蚀速率增加明显,同时,溶解氧浓度越高,腐蚀产物在基体上的覆盖越少.加上溶解氧本身氧化能力较高的原因,使得腐蚀电位容易达到点蚀电位临界值,造成点蚀的形成.点蚀一旦形成就与周围致密层保护区域形成“小阳极-大阴极”加速腐蚀体系,形成较深的点蚀坑.

The work aims to study the effect of different dissolved oxygen concentration on the pitting formation and development of in low alloy tubes in H2S/CO2 acidic environment.Corrosion rate was tested by performing corrosion weight loss experiment using high-temperature & pressure apparatus and normal pressure & temperature in simulated corrosion environment.Morphology of corrosion products and size of pitting pits were analyzed by using SEM.The dissolved oxygen had obvious effects on the corrosion products and produced great damage to the corrosion product film.The corrosion products covered on the substrate reduced,the product film thickness decreased and different sizes of pitting pits were found on the surface when the dissolved oxygen was present.The pitting phenomenon was obvious at the dissolved oxygen partial pressure of 0.1 MPa.The diameter of the pitting pits on the surface of L245NCS was nearly 0.4 mm and L290 0.25 mm.The addition of dissolved oxygen leads to pitting of carbon steel easily in the H2S/CO2 corrosion environment.Uniform corrosion rate increases significantly and corrosion products covered on the substrate decreased as the dissolved oxygen concentration increases.Due to the favorable oxidizability of dissolved oxygen,pitting corrosion potential may easily reach potential critical value and lead to the formation of pitting.Once pitting is formed,it will constitute a "small anode-large cathode" accelerated corrosion system along with the surrounding dense layer,thus producing deeper pitting pits.