基于试验的天然气集输管道失效性机理分析

Failure Analysis of Natural Gas Gathering Pipeline Based on Experiments

为分析天然气集输管道的腐蚀失效行为,确定集输管线腐蚀形貌特征与产物成分,查明其腐蚀失效特征、腐蚀类型及失效机理。管道失效性分析以试验研究为主要手段,通过表面宏观测量分析管道内壁的腐蚀部位及宏观特征,开展材料力学性能、显微硬度、化学成分、金相分析等试验检测管道材质。对腐蚀穿孔处取样,采用扫描电镜(scanning electron microscopy,SME)进行微观形貌分析,结合能谱分析(energy dispersive spectroscopy,EDS)和X射线衍射(X-ray diffraction,XRD)技术对腐蚀产物作进一步物相分析。结果表明:管样失效处基体化学成分和材料力学性能符合国家标准要求,金相组织正常。管道钢L245在高矿化度水环境下发生CO_(2)腐蚀,形成疏松、多孔且带裂纹的簇状腐蚀产物,腐蚀产物主要成分为FeCO_(3)和Fe_(2)O_(4),腐蚀产物膜与金属基体结合强度低,流体介质冲刷发生剥离并加速金属溶解和腐蚀性物质扩散,形成具有自催化的电化学腐蚀。

The corrosion failure behavior of a natural gas gathering and transportation pipeline was examined.The corrosion morphology characteristics and product composition of the pipeline were also determined,as were the corrosion failure characteristics,corrosion types,and failure mechanism.The failure analysis of pipeline was made by taking an experimental research as the primary means.The corroded parts and macroscopic features of the inner wall of the pipeline ware analyzed through macroscopic surface measurement.The pipeline materials was tested,such as mechanical properties,microhardness,chemical composition and metallographic analysis.Scanning electron microscopy(SME)was used to analyze the morphology of the corrosion products.Energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD)were used to analyze the phase of the corrosion products.The results show that the matrix s chemical composition and mechanical properties meet the national standard and the typical metallographic structure.CO_(2)corrosion occurred in pipeline steel L245 in a high salinity water environment,forming loose,porous,cracked corrosion products in clusters.The main components of the corrosion product are FeCO_(3)and Fe_(2)O_(4).Due to the low bonding strength between the corrosion product film and the metal matrix,it is easy to strip under the action of the erosion of the fluid medium,accelerating the dissolution of metal and the diffusion of corrosive substances,and forming electrochemical corrosion with autocatalytic effect.