辽河油田土壤中溶解氧对X70管线钢腐蚀的影响

Effect of Dissolved Oxygen on Corrosion of X70 Pipeline Steel in Liaohe Oilfield

目的降低腐蚀对油气管线运行的危害。方法通过控制溶液中不同通氮时间,获得不同溶解氧浓度的辽河油田土壤模拟溶液,利用交流阻抗技术和动电位极化技术研究不同的溶解氧浓度对X70管线钢在模拟溶液中电化学腐蚀行为的影响,并结合金相显微镜对管线钢表面的腐蚀形貌进行表征,以阐明该条件下不同浓度溶解氧对管线钢腐蚀行为的作用机制。结果在该环境下,X70钢的腐蚀机理为阳极溶解机制。随着溶解氧含量的不断降低,电极极化电阻变大,腐蚀电流密度明显减小,此时,电极表面点蚀坑数量也变少,点蚀坑的直径变小,金属腐蚀速率显著下降。当溶解氧质量浓度为10.0 mg/L时,试件的腐蚀速率最大,腐蚀现象最明显。当溶解氧质量浓度从10.0 mg/L降低至0.3 mg/L时,金属电极表面生成了一层以Fe CO3为主的腐蚀产物膜,产物膜明显抑制了腐蚀反应的进行,对X70钢起到保护作用,此时试样腐蚀现象最不明显。结论溶解氧浓度的不同导致了X70管线钢电极表面产物膜形态的不同,从而影响了该环境下金属的电化学腐蚀行为。

The work aims to reduce the harm of corrosion on operationoil and gas pipelines.In the soil simulation solution of Liaohe Oilfield,soil simulation solution with different dissolved oxygen concentration was obtained by controlling different nitrogen pass-through time in the solution.The influence of different dissolved oxygen concentrations on electrochemical corrosion behavior of X70 pipeline steel in soil simulation solution of Liaohe Oilfield was studied by AC impedance technology and potentiodynamic polarization technology.In order to clarify the mechanism of the different concentrations of dissolved oxygen on the corrosion behavior of pipeline steel,the corrosion morphology of the pipeline steel surface was characterized with a metallographic microscope.In such environment,the corrosion mechanism of X70 steel was anodic dissolution mechanism.With the continuous decrease of dissolved oxygen content,the polarization resistance of the electrode becamelarger and the corrosion current density decreased.At this time,the number of pits on the surface of the electrode also decreased,the pit diameter became smaller,and the metal corrosion rate droppedsignificantly.When the dissolved oxygen concentration was 10.0 mg/L,the corrosion rate of the specimen was the largest,and the corrosion phenomenon was most obvious.When the dissolved oxygen content reduced from 10.0 mg/L to 0.3 mg/L,a layer of corrosion product mainly containing FeCO3 was formed on the surface of the metal electrode.The product film significantly inhibited the corrosion reaction and protected the X70 steel.At this time,the corrosion of the sample wasthe least obvious.The difference in dissolved oxygen concentration leads to different morphologiesof the product film on the surface of the X70 pipeline steel electrode and then affects the electrochemical corrosion behavior of the metal in the environment.