Study On Flow Corrosion Behavior Of X100 Pipeline Steel In Simulated Formation Water

In the oil and gas industry,corrosion has become the main mechanism of pipeline failure,resulting in huge economic losses.Among the commonly used oilfield pipes,X100 steel has the advantages of high strength,good pressure resistance and low cost,which is bound to be used in large quantities in the future.In the oil and gas field transportation,the relative motion between the surface of the substrate and the medium will not only cause electrochemical reaction,but also the fluid dynamics factor has an important influence on the corrosion of the material.However,there is less corrosion in X100 steel in the flow system.Therefore,studying the electrochemical corrosion of X100 steel in flowing media is of great significance to reveal the mechanism of flow corrosion process and promote the application of X100 steel.In this paper,through the design and fabrication of the flow corrosion test device,using the dynamic potential polarization curve and AC impedance spectroscopy technology,combined with the numerical simulation of the system flow field,the factors such as Clconcentration,temperature,time,flow rate and impact angle are studied for the X100 pipeline.The effect of corrosion behavior of steel.The following main conclusions are drawn:(1)The change of Cl~- concentration does not affect the mechanism of the anode-anode reaction of the potentiodynamic polarization curve.With the increase of Cl~- concentration,the corrosion rate of the medium under static conditions increases first and then decreases due to the accumulation of corrosion products.However,in the flowing state,the self-corrosion current Icorr increases continuously,and the charge transfer resistance Rct decreases indicating that the increase of Cl~- concentration has a significant acceleration effect on the corrosion of X100 steel.(2)When the temperature range is between 40 ? and 55 ?,the medium state has no effect on the corrosion rate of X100 steel,and it increases with the increase of temperature.The charge transfer resistance Rct decreases with the increase of temperature.At the same temperature.The corrosion rate in the flowing state is slightly higher than the corrosion rate in the static state,but there is not much difference in the difference.At the same temperature,the charge transfer resistance Rct in the flowing state is higher than the charge transfer resistance Rct in the stationary state,and the difference is large.(3)In the time range of 0~8h,with the increase of time,the self-corrosion current Icorr of X100 steel decreases first and then increases,and the charge transfer resistance Rct increases first and then decreases;the self-corrosion current Icorr in the flow state first After increasing,the corrosion rate increases first and then decreases.And at the same time,the corrosion rate in the flowing state is much higher than the corrosion rate in the static state,indicating that the flow will aggravate the corrosion of the sample.(4)When the flow rate is changed between 0.5m/s and 2.0m/s,X100 steel is controlled by activation,its electrochemical impedance spectrum is a semicircular shape,and the radius is gradually reduced,and the charge transfer resistance Rct is continuously reduced.And the boundary layer of the surface is widened,the resistance of the ions in the medium to the surface of the X100 pipeline steel is reduced,and the self-corrosion current Icorr is increased.(5)The change of impact angle does not affect the mechanism of the anode-anode reaction of the potentiodynamic polarization curve.As the impact angle increases,the self-corrosion current Icorr decreases,the charge transfer resistance Rct increases,and the corrosion rate decreases.At different fluid impact angles,there are different flow fields and flow rates on the electrode surface.At the minimum impact angle,the electrode surface has the maximum flow velocity and shear stress.