Study On Corrosion Behavior Of Two New Cr-containing Steels In CO₂ Environment

The drilling and production process of the modern oil and gas industry is accompanied by a large amount of CO₂,CO₂ dissolved in water to form carbonic acid,which causes severe CO₂ corrosion to oil well steel tubes and gathering pipeline.Chromium can significantly increase the CO₂ corrosion resistance of materials and reduce the occurrence of local corrosion.The 1Cr4Ni2P steel and the 0Cr13Ni2P steel produced by a domestic steel plant have the characteristics of high strength and superior cost,and have a wide application prospects in the field of oil and gas development.However,there are few studies on the CO₂ corrosion behavior of these two new chromium-containing steels.Therefore,the corrosion behavior of these two kinds of Cr-containing steels in CO₂environment is studied in this paper,so as to provide the necessary theoretical basis for their application in the development of oil and gas fieldsThis article mainly focuses on 1Cr4Ni2P steel and 0Cr13Ni2P steel,using electrochemical testing technology to study the effects of chlorine ion,temperature and dissolved oxygen in CO₂ Environment,and analysis its corrosion mechanism.Comparing its corrosion resistance with other several Cr-containing steels of the same grade.At the same time,the chemical composition and morphology of the corrosion products were analyzed using modern analytical methods such as XPS and SEM.The conclusions obtained are as follows:?1?1Cr4Ni2P steel produces active dissolution in NaCl solution of saturated CO₂.Its anodic electrochemical impedance spectroscopy consists of high frequency capacitive arc and low frequency inductive arc,its cathodic electrochemical impedance spectroscopy consists of two segments of resistance arc.Its corrosion process is controlled by the cathode reaction,and the cathode reaction is the reduction reaction of H₂CO₃ and HCO₃^-.With the increase of temperature,the corrosion rate,anode and cathode reaction rate of1Cr4Ni2P steel increased.With the increase of Cl^-concentration of solution,the corrosion rate and anode reaction rate of 1Cr4Ni2P steel f increase first and then decrease,and the cathode reaction rate decreases.The presence of dissolved oxygen cannot change the electrochemical impedance spectrum,but leads to the occurrence of oxygenation reaction,leading to a significant increase in the anode reaction rate and the cathode reaction rate.?2?The potentiodynamic polarization curves of 0Cr13Ni2P steel in chloride/CO₂solution all directly enter the passivation zone.The addition of CO₂ cannot change the electrochemical impedance spectrum,but increases the corrosion rate.With the increase of Cl^-concentration,the pitting sensitivity of 0Cr13Ni2P steel increases,and the corrosion rate increases first and then decreases.With the increase of temperature,the pitting sensitivity of 0Cr13Ni2P steel increases,the electrochemical impedance spectroscopy?EIS?features remain unchanged,but the charge transfer resistance decreases first and then increases,leading to a first increase and then a decrease in the corrosion rate.?3?The passive film formed on 0Cr13Ni2P in chloride/CO₂ solution displayed an n-p semi-conductive character,and consists of Cr₂O₃ and Fe₂O₃.With the increase of the potential and the prolongation of the time,the donor density/acceptor density of the passivation film decreases,and the protective performance of the passivation film increases.?4?The corrosion resistance of 1Cr4Ni2P steel is similar to that of domestic 3Cr-2under the simulated 110°C corrosion environment in Changqing Oilfield,and superior to domestic 3Cr-1 and imported 3Cr.In simulated formation water,the corrosion resistance of 0Cr13Ni2P steel is superior to that of common 13Cr steel,and inferior to that of Super13Cr.In the completion fluid,the corrosion resistance of 0Cr13Ni2P steel is similar to that of common 13Cr,and inferior to that of Super 13Cr.