CO₂分压对N80钢腐蚀影响的研究

Study on the Effect of CO₂ Partial Pressure on the Corrosion of N80 Steel

为获得CO2分压对N80钢腐蚀的影响规律,提高对N80钢油气管线的腐蚀防护效果。应用高温高压釜实验装置,采用挂片对比试验方法,借助扫描电镜手段,研究了不同CO2分压条件下,N80钢挂片腐蚀产物膜表面形貌、腐蚀产物膜下金属基体表面形貌、挂片横截面腐蚀产物膜特点以及挂片腐蚀速率和挂片表面腐蚀产物膜生长特点。随着CO2分压的增加,挂片表面产生的腐蚀产物膜由薄到厚,由平滑到粗糙;腐蚀速率逐渐增加,且存在峰值腐蚀速率;腐蚀产物膜生成初期,生成过程不均匀,导致局部腐蚀或者蚀斑;腐蚀产物膜存在内、中间、外3层结构,由内到外逐层减薄;内层与中间层结合较差,内层与外层之间存在明显的空隙,易发生严重局部腐蚀。输送含CO2油气管线的腐蚀防护,关键是在投产初期抑制局部腐蚀的发生,一旦腐蚀产物膜均匀发展,将对管线产生较好的防护。

In order to obtain the influence rule of partial pressure of CO2 on corrosion of N80 steel and improve the corrosion protection effect of N80 steel oil and gas pipeline. With the aid of scanning electron microscope, the effect of CO2 partial pressure on the temperature and pressure of CO2 was studied, the surface morphology of corrosion product film on N80 steel hangers, the surface morphology of metal substrate under the corrosion product film, the characteristics of corrosion product film on Cross section of hangers, the corrosion rate of hangers and the growth characteristics of corrosion product film on hangers surface. With the increase of the partial pressure of CO2, the corrosion product film on the surface of the hanging plate changes from thin to thick, from smooth to rough, the corrosion rate increases gradually with the existence of peak corrosion rate, and the formation process of the corrosion product film is not uniform at the initial stage, there are three layers in the corrosion product film, which are inner, middle and outer layers, and thin from the inner layer to the outer layer, the inner layer and the middle layer combine badly, there is obvious gap between the inner layer and the outer layer, and serious local corrosion occurs easily. The key to the corrosion protection of oil and gas pipelines containing CO2 is to restrain the local corrosion at the beginning of operation.