Study On Corrosion Of X100 Pipeline Steel In Produced Water Containing CO₂

CO2 corrosion problem has a significant effect on the safe production of transmission projects.Using high-strength pipeline steels can increase transportation efficiency as well as reduce construction costs because of the improved mechanical properties.China's large-scale engineering application of pipeline steel is X80 at this stage,and X100 will be the next one,so the studies on corrosion of X100 in CO2-containing environments can guide production.Most of the studies on the corrosion behavior of pipeline steels are carried out under static condition or in adjustable speed reactors.There is a big gap in the actual working conditions of pipeline steels.In this paper,the self-constructed corrosion experiment system was used to simulate real working condition of pipeline steel.The effect of temperature and flow rate on the corrosion of X100 in the saturated CO2 produced water was studied through electrochemical methods and corrosion product analysis methods.The experimental results under simulated real working conditions are compared with that under common conditions.Common experiment was conducted in constant temperature water bath and magnetic stirred kettle.In this paper,X100 corrosion behavior under different experimental conditions of C,40,60,and 65°C was studied.The results show that the environment has a great influence on the corrosion current of X100.The corrosion current at 60°C under common conditions is 185?A /cm2 while it is about 1518?A /cm2 under simulated conditions.When just immersed,the corrosion resistance of X100 decreases with the increase of temperature.when immersed for 24 hours under common conditions,the corrosion resistance is best in 60°C because of the complete protective corrosion product film.Under the simulated conditions,corrosion resistance first decreases and then increases with increasing temperature.The corrosion products are mainly Fe CO3 and Fe3 C.The corrosion resistance is worst at 60°C because the corrosion product film is greatly damaged due to erosion.Product film is more dense in higher temperature.In this paper,the corrosion behavior of X100 at flow rates of 0.2m/s,0.4m/s,and 0.6m/s at 60°C was studied.The results show that: the flow rate have a great influence on the X100 corrosion under the simulated conditions.The corrosion current was 666?A/cm2 at 0.2m/s and 2152 ?A/cm2 at 0.6m/s.Under common conditions,the corrosion resistance of X100 shows a tendency to increase with flow rate because higher flow rate is beneficial to the formation of protective corrosion product film.Under simulated condition,the corrosion resistance of X100 decreases with the increase of the flow rate because the stronger destructiveness to corrosion product film.Corrosion product composition and structure is almost same when the flow rate is different.Based on the parameters obtained in above experiments,Comsol are used to analyze the effect of flow rate on corrosion.Considering the effects of flow field and mass transfer,the distribution of flow and material in the pipeline was obtained.Results shows that there was a sudden change near the bend section,and the nonuniformity of flow field and material distribution in the pipeline decreases with the increase of the flow rate.Considering material transfer and chemical reactions to establish a mechanism-based simulation model.Results show that the corrosion rate decreases and then increases with the increase of the flow rate.The distribution of flow field and material near the bend section of the pipeline is the main reason to accelerate corrosion.Based on experimental and simulation results,we suggest that temperature should be set to deviate from 60°C,and the flow rate can be appropriately increased depending on the situation.