Galvanic Corrosion And Inhibition Mechanism Of N80 Carbon Steel-13Cr Stainless Steel Under Supercritical CO₂ Conditions

The rapid development of industries consume a large amount of fossil energies,and the massive emissions of carbon dioxide have caused serious global climate problems.The applications of Carbon Capture and Storage?CCS?technology and CO₂ Enhanced Oil Recovery?CO₂-EOR?technology not only decrease the emissions of CO₂ but also make rational use of the emitted CO₂.However,the injection of CO₂ in CO₂-EOR technology would cause serious corrosion of carbon steel pipelines,as well as galvanic corrosion between carbon steel and stainless steel in the supercritical CO₂?SC-CO₂?environment,which would cause great security risks.Therefore,it is of great theoretical significance and practical value to study the galvanic corrosion behavior between carbon steel and stainless steel in SC-CO₂ environment and the inhibitive effects of inhibitors on the galvanic corrosion.In this thesis,N80 carbon steel and 13Cr stainless steel were selected as the materials.The galvanic corrosion behavior and mechanism between N80 carbon steel and 13Cr stainless steel in SC-CO₂ environment and the inhibitive effects of inhibitors on the galvanic corrosion were investigated by weight loss,in situ electrochemical measurements and surface analysis.The main contents are as follows:?1?A setup for in situ electrochemical and weight loss were designed to study the galvanic corrosion behavior between N80 carbon steel and 13Cr stainless steel under SC-CO₂ environment.The influence of fluid flow on the galvanic corrosion was investigated by comparing the difference under static and dynamic?2 m/s?conditions.The results show that N80 carbon steel acts as anode and 13Cr stainless steel acts as cathode in the galvanic system in SC-CO₂ containing formation water.When coupled with 13Cr stainless steel,the galvanic effect leads to formation of less protective FeCO3 film on the carbon steel surface and accelerates the corrosion of N80 carbon steel.The galvanic effect also weakens the corrosion resistance of 13Cr stainless steel.In addition,due to the compact corrosion product film gradually formed on the N80 carbon steel surface,the corrosion rate of N80 carbon steel whether coupled with 13Cr stainless steel or not,the galvanic current density and galvanic effect between N80 carbon steel and 13Cr stainless steel decrease with corrosion time.Moreover,the fluid flow improves the corrosion rate of N80 carbon steel and weakens the corrosion resistance of 13Cr stainless steel.Meanwhile,FeCO₃ film formed on the surface of carbon steel under dynamic conditions is earlier but the film is less protective,which also leads to earlier positive shift of the coupled potential and rapid reduction of galvanic current density.The fluid flow also increases the galvanic current density and enhances the galvanic effect.?2?The inhibitive effects of imidazoline?IM?,1-butyl-2-thiobenzyl benzimidazole?BTBBI?and lauric acid?LA?inhibitors on the galvanic corrosion of N80 carbon steel and13Cr stainless steel under dynamic?2 m/s?conditions were studied.The results show that all these three inhibitors can effectively inhibit the corrosion of N80 carbon steel as mixed-type inhibitors with predominant anodic effectiveness whether N80 carbon steel is coupled or not,but the galvanic effect reduces the inhibitive effects of IM,BTBBI and LA on N80 carbon steel.Among these three inhibitors,IM has the highest inhibition efficiency for the galvanic corrosion of N80 carbon steel and maintain high inhibition efficiency during the corrosion process,and the corresponding galvanic current density is also minimum.N80 carbon steel suffers from slight corrosion in the solution with IM,but severe pitting corrosion occurs in the solutions with BTBBI or LA.The corrosion rate and pitting corrosion are most serious in the solution with LA,and the pitting corrosion is promoted by galvanic effect.Hence the inhibitive effects of these three inhibitors on galvanic corrosion between N80 carbon steel and 13Cr stainless steel follow the order of IM>BTBBI>LA.