Research Progress on the Mechanism of Oxidative Carburization Corrosion and Coating Protection of Steels Served at High-temperature CO2 Environment
Steel is widely used as various structural components owing to its excellent properties,such as high strength and heat resistance;however,it usually faces severe corrosion problems during service.CO2 corrosion is a common cause of corrosion failure in steel applications.However,a systematic summary of the corrosion behavior of steel in high-temperature CO2 environments is lacking.Therefore,in this study,the current oxidation and carburization mechanisms of steel in high-temperature CO2 environments are summarized,and the effects of temperature,pressure,and other gas impurities in the service environment on the corrosion mode and mechanisms are reviewed.Typically,the CO2 corrosion behavior of steel manifests as carbonation corrosion generated after it is dissolved in water.However,in high-temperature environments,CO2 can directly oxidize the steel surface,which is generally accompanied by carburization,significantly decreasing the mechanical and corrosion resistance of steel.In this case,the composition and structure of the oxide layer are strongly affected by the Cr content in the steel;thus,the corrosion resistance of steel is generally determined by the Cr content.Naturally,Cr2O3 oxide layers are formed in steels with a Cr content higher than 12wt.％during oxidation,resulting in better resistance to oxidation and carburizing.Increased temperature and pressure can generally aggravate the CO2 corrosion of steel.Therefore,an increased temperature can increase the thickness of the Cr2O3 layer,and the increased pressure mainly affects the carburizing behavior of steels.However,the influence of gas impurities,such as O2,H2O,and SO2,on the CO2 corrosion of steel changes with the type of steel and the service environment.Meanwhile,the development of existing CO2 corrosion models,types of coatings resistant to CO2 corrosion,and their protective effects are discussed.Most models were developed based on experimental results in which the oxidation or carburizing kinetics showed a parabolic trend.Although these models can predict the thickness of the oxide layer and the depth of carburizing,they fail to accurately predict the corrosion life of steel subjected to simultaneous oxidation and carburizing.In addition,CO2 in a flowing state under actual working conditions accelerates the corrosion rate of the steel and causes the oxidation layer to fall off.Therefore,developing models that simultaneously cover the interaction of oxidation and carburizing or consider the erosion caused by the CO2 flow,especially the CO2 flow containing oxide particles,is necessary in the future.To improve the service life of steel in high-temperature CO2 environments,Al,Cr,and other coatings are often prepared to improve the oxidation and carburizing resistance of steel.However,the mechanical properties of coated steels and coatings in a corrosive environment also significantly impact their corrosion behavior,and further study is required.In addition,Ni-based coatings often exhibit better corrosion resistance than other coatings.Therefore,Ni-based alloys are generally used as the main component of steel coatings.However,the high cost of Ni-based coatings limits their widespread applications.For this purpose,the introduction of nanoparticles and effective control of the coating composition and structure based on simulation calculations to improve the mechanical properties and corrosion resistance of coatings hold great promise in coating composition selection.Moreover,improving the adhesion strength and interface stability between the coating and the steel matrix is important to ensure the protective effect of the coatings.This requires the exploration of preparation techniques to improve the uniformity and density of the coating effectively.In such case,this study can not only point out the shortcomings of existing studies and the development direction of future studies,but also provide a comprehensive theoretical basis for the selection of anti-CO2 corrosion protection techniques in high temperature environment and the evaluation of long-term safety service life for steel.
CO2 corrosioncorrosion mechanisminfluence factorprediction modelcoating protection
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