添加Cr和RE对碳钢抗CO_(2)腐蚀性能的影响

The Effect of Adding Cr and RE on the CO_(2)Corrosion Resistance of Carbon Steel

为研究添加Cr和稀土(RE)对碳钢抗CO_(2)腐蚀性的影响,采用25Mn2、1Cr和1CrRE钢使用高压釜模拟了井下腐蚀环境下的腐蚀行为。使用光学显微镜、扫描电子显微镜以及配套的能谱仪、X射线衍射仪对3种钢的腐蚀膜进行分析。结果表明,在碳钢中添加1Cr能够降低腐蚀速率23%,而在1Cr钢中添加RE又能提高40%抗CO_(2)腐蚀性能。研究发现,腐蚀膜主要由FeCO_(3)和少量FeOOH以及内层点状Fe_3C构成。25Mn2和1Cr钢腐蚀膜呈双层结构,但1CrRE钢腐蚀膜为三层结构,且Cr元素在界面处富集。研究认为,腐蚀膜中的增碳现象是由于Fe_(3)C与碳酸发生反应导致。稀土使得FeCO_(3)晶面间距减小,利于FeCO_(3)晶体生长的更为致密,但阻碍了离子传输,一方面利于抗CO_(2)腐蚀,另一方面也使得1CrRE钢的腐蚀膜呈三层结构。

In order to sludy the elect of adding Cr and rare earth(RE)on the CO_(2)corrosion resistance of carbon steel.25Mn2.1Cr and ICrRE steels were used to simlate the comosion behavor under the downhole comsion enyronment in autocave,"he coosion fims on the three kinds of steels were analyzed by optical microscope,scanning elecron microscope,energy spectrometer and X-ray dilractometer.Resuls showed that adding 1Cr to carbon steel could reduce the corsion rate by 23%,and ading RE to 1Cr steel could inerease the corrosion resistanee of CO_(2)by 40%6.It was found that the corrosion film was mainly composed of FeCO_(3)and a small amount of Fe0OH,as well as doted Fe,C in the iner layer.Additionally,the corosion films of 25Mm2 and 1Cr steel had a two-layer structure,but the corrosion films of 1CrRp steel had a three-laver structure with the Cr element enrichment at the interace.Research suggested that the carbon pickup phenomenon ohserved in the corsion flm was caused by the reaction belween Fe_(3)C and carbonic acid,furthermore,rare earths reduced the spacing belween FeCO_(3)crvstal planes,which facilitated the denser grwth of Fec0,crvstals and hindered ion transport,On the one hand.thev wer benelicial for CO_(2)corrosion resistance,and on the other hand,they also made the corosion film of 1CrRE steel appear in a three-layer structure.