Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation.The welding reinforcement height(WRH)can induce locally micro-turbulent flow field,which aggravates local...Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation.The welding reinforcement height(WRH)can induce locally micro-turbulent flow field,which aggravates local corrosion of welded joints.A high wall shear stress(WsS)experimental setup was established to conduct the online electrochemical corrosion test.The influence of WRH sizes on local corrosion of welded joints was studied at different flow rates.The electrochemical signals of the local corrosion of X80 welded joints at different flow rates were monitored in real time using electrochemical impedance spectroscopy and wire beam microelectrode.In addition,the corrosion products composition and properties were analyzed.The results show that the micro-turbulent flow fields induced by the WRHs can enhance ion mass transfer near the welded joints.The corrosion products on the WRH surface also present different microscopic morphologies at different flow rates.In strong flow fields,the locally enhanced wsS can peel off the dense corrosion product partially,leading to the electrochemical distribution of large cathode and small anode,which accelerates the occurrence and development processes of the local corrosion of welded joints.The scientific guidelines for the corrosion protection of long-distance oil and gas pipelines can be potentially provided.展开更多
In this study, the microstructure evolution and corrosion resistance in O. 5 M Na2CO3 - 1 M NaHCO3 solution of X80 high-deformability （ X8OHD ） pipeline steel coarse-grained heat-affected zone （CGHAZ） with several...In this study, the microstructure evolution and corrosion resistance in O. 5 M Na2CO3 - 1 M NaHCO3 solution of X80 high-deformability （ X8OHD ） pipeline steel coarse-grained heat-affected zone （CGHAZ） with several heat input levels were investigated. It is shown that the microstructure of CGHAZ changes from bainite ferrite to granular bainite as the heat input increasing. In addition, the corrosion resistance and the stability of passive film of base material are better than those of CGHAZ with several heat input levels. Too small or too big heat input is inadvisable and better corrosion resistance of CGHAZ is attained when heat input is 30 kJ/cm.展开更多
The occurrence and development mechanism of internal local corrosion has always been a controversial topic,and especially under flow conditions.In this paper,an improved high shear force loop was experimentally used,a...The occurrence and development mechanism of internal local corrosion has always been a controversial topic,and especially under flow conditions.In this paper,an improved high shear force loop was experimentally used,and local flow field is induced by simulating corrosion defects on the surface of X80 pipeline steel specimens.The characteristics of corrosion products deposited on the surface of specimens in CO2-saturated NACE solution were investigated by means of electrochemical impedance spectroscopy(EIS),scanning electron microscopy(SEM),X-ray diffraction(XRD),and energy dispersive spectrometry(EDS).The 3D micromorphology of the corrosion test surface after remove the corrosion scale used to measure the size of localized corrosion pit.Under the influence of local defects,the wall shear stress(WSS)and turbulent kinetic energy of local flow fields enhanced significantly,and pressure fluctuations in local flow field were induced.The results showed that the characteristics of surface corrosion products varied with flow velocity.The corrosion scales formed in various regions of specimens with defects exhibited different surface micro-morphologies and chemical compositions.Overall,these data offer new perspectives for better understanding the mechanisms behind local corrosion.展开更多
The stress corrosion cracking （SCC） behavior of welded X80 pipeline steel in simulated Ku＇erle soil solution was studied by means of electrochemical impedance spectroscopy （EIS） and slow strain rate tests （SSRT...The stress corrosion cracking （SCC） behavior of welded X80 pipeline steel in simulated Ku＇erle soil solution was studied by means of electrochemical impedance spectroscopy （EIS） and slow strain rate tests （SSRT）. The microstructure of the welded steel was observed by optical microscopy （OM）. It is demonstrated that the microstructure of the weld metal consists of acicular ferrite and grain boundary ferrite, while that of heat affected zone （HAZ） is a mixture of acicular ferrite and bainitic ferrite micro- constituents. The microstructure of the base steel is composed of ferrite and pearlite. The anodic dissolution of X80 pipeline steel in simulated Ku＇erle soil solution could be enhanced and the SCC sensitivity increased with the increase of CO2 partial pressure. The SCC mechanism of X80 pipeline is a mixing mechanism of hydrogen embrittlement combined with anodic dissolution, and the hydrogen embrittlement plays a leading role. The higher SCC sensitivity of the weld metal was attributed to the metallurgical transformation, local hardening and residual stress.展开更多
基金support from the National Natural Science Foundation of China(Nos.52206199,42176209,51979282,and 41676071)the Natural Science Foundation of Shandong Province(No.ZR2021MD064).
文摘Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation.The welding reinforcement height(WRH)can induce locally micro-turbulent flow field,which aggravates local corrosion of welded joints.A high wall shear stress(WsS)experimental setup was established to conduct the online electrochemical corrosion test.The influence of WRH sizes on local corrosion of welded joints was studied at different flow rates.The electrochemical signals of the local corrosion of X80 welded joints at different flow rates were monitored in real time using electrochemical impedance spectroscopy and wire beam microelectrode.In addition,the corrosion products composition and properties were analyzed.The results show that the micro-turbulent flow fields induced by the WRHs can enhance ion mass transfer near the welded joints.The corrosion products on the WRH surface also present different microscopic morphologies at different flow rates.In strong flow fields,the locally enhanced wsS can peel off the dense corrosion product partially,leading to the electrochemical distribution of large cathode and small anode,which accelerates the occurrence and development processes of the local corrosion of welded joints.The scientific guidelines for the corrosion protection of long-distance oil and gas pipelines can be potentially provided.
基金This work was supported by The National Natural Science Foundation of China （No. 51271099）.
文摘In this study, the microstructure evolution and corrosion resistance in O. 5 M Na2CO3 - 1 M NaHCO3 solution of X80 high-deformability （ X8OHD ） pipeline steel coarse-grained heat-affected zone （CGHAZ） with several heat input levels were investigated. It is shown that the microstructure of CGHAZ changes from bainite ferrite to granular bainite as the heat input increasing. In addition, the corrosion resistance and the stability of passive film of base material are better than those of CGHAZ with several heat input levels. Too small or too big heat input is inadvisable and better corrosion resistance of CGHAZ is attained when heat input is 30 kJ/cm.
基金supported by the National Natural Science Foundation of China with(No.51774314)Natural Science Foundation of Shandong Province with grant number(No.ZR2018MEM002)the Fundamental Research Funds for the Central Universities(No.19CX05001A)for financial support。
文摘The occurrence and development mechanism of internal local corrosion has always been a controversial topic,and especially under flow conditions.In this paper,an improved high shear force loop was experimentally used,and local flow field is induced by simulating corrosion defects on the surface of X80 pipeline steel specimens.The characteristics of corrosion products deposited on the surface of specimens in CO2-saturated NACE solution were investigated by means of electrochemical impedance spectroscopy(EIS),scanning electron microscopy(SEM),X-ray diffraction(XRD),and energy dispersive spectrometry(EDS).The 3D micromorphology of the corrosion test surface after remove the corrosion scale used to measure the size of localized corrosion pit.Under the influence of local defects,the wall shear stress(WSS)and turbulent kinetic energy of local flow fields enhanced significantly,and pressure fluctuations in local flow field were induced.The results showed that the characteristics of surface corrosion products varied with flow velocity.The corrosion scales formed in various regions of specimens with defects exhibited different surface micro-morphologies and chemical compositions.Overall,these data offer new perspectives for better understanding the mechanisms behind local corrosion.
基金supported by the National Natural Science Foundation of China (No.50771053)
文摘The stress corrosion cracking （SCC） behavior of welded X80 pipeline steel in simulated Ku＇erle soil solution was studied by means of electrochemical impedance spectroscopy （EIS） and slow strain rate tests （SSRT）. The microstructure of the welded steel was observed by optical microscopy （OM）. It is demonstrated that the microstructure of the weld metal consists of acicular ferrite and grain boundary ferrite, while that of heat affected zone （HAZ） is a mixture of acicular ferrite and bainitic ferrite micro- constituents. The microstructure of the base steel is composed of ferrite and pearlite. The anodic dissolution of X80 pipeline steel in simulated Ku＇erle soil solution could be enhanced and the SCC sensitivity increased with the increase of CO2 partial pressure. The SCC mechanism of X80 pipeline is a mixing mechanism of hydrogen embrittlement combined with anodic dissolution, and the hydrogen embrittlement plays a leading role. The higher SCC sensitivity of the weld metal was attributed to the metallurgical transformation, local hardening and residual stress.
