Study On Mechanism And Monitoring Of Corrosion In The CO₂ Continuous Medium Along The Pipeline Steel

The corrosion of the N80 and 20#pipeline steel in the saturated CO₂ environment was investigated by using the high temperature and high pressure reactor and the electrochemical testing equipments.Through the real-time monitoring of the Iron ion concentration,using the artificial current accelerated simulation method of the local corrosion,it could be found out that the relationship between the Iron ion concentration and the corrosion of the pipeline steel was in different situations,which provided the data support for the corrosion process of the pipeline steel through the change of Iron ion concentration monitoring in the saturated CO₂environment.Regardless of the liquid of the pipeline steel in a stationary state or in a flow state,the iron ions concentration was very high at the beginning of the corrosion,and decreased rapidly and decreased over a long period of time after the corrosion enters stable.If there was local corrosion inside the pipeline,the iron ion concentration in the entire pipe would rise again,and became stabilized after a period of time.And the rate of the change of the iron ion concentration at the local corrosion location was linearly related to the linearity at the pipe outlet.In addition,the effect of the enriched Iron ion in the pipeline steel in the solution of the saturated CO₂ environment was studied through the electrochemical simulation.The results showed that the corrosion product film is produced by the local particle deposition,covering,destruction and re-deposition.The enrichment of the Iron ion in the solution would slow down the corrosion of pipeline steel.With the increase of the Iron ion concentration and the corrosion time,the reaction of the electrode was inhibited.With the increase of the Iron ion concentration and the extension of the corrosion time,the electrode reaction would be inhibited.The Iron ion could inhibit the cathodic reaction and promote the formation of the corrosion product film.Moreover,with the continuous corrosion,the corrosion products filmed on the substrate surface will become more remarkable.