超临界CO2环境中温度和流速对N80碳钢腐蚀行为的影响

Effects of Temperature and Flow Velocity on the Corrosion Behavior of N80 Carbon Steel in Supercritical CO2 Environment

目的研究超临界CO2环境中温度和流速对N80碳钢腐蚀行为的影响,探讨N80碳钢在超临界CO2环境中的腐蚀机制。方法利用高压釜进行失重和电化学测试,同时利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)进行腐蚀形貌观察和腐蚀产物成分分析。结果当温度为40℃时,腐蚀速率最小,电化学阻抗随时间延长持续减小,此条件下并没形成FeCO3保护膜。升高温度导致腐蚀初期的腐蚀速率明显增大,然而腐蚀某个时刻后,电化学阻抗突然增大,意味着FeCO3保护膜的形成。温度越高,腐蚀24 h后的阻抗越大,产物膜越致密,保护性越好。另外,腐蚀失重速率随流速的增加而增大,电化学测试也表明流速越大,阻抗越小,腐蚀电流密度越大。SEM形貌分析表明,流体流动破坏了FeCO3膜的致密度,降低了其对N80碳钢基体的保护作用。结论尽管升高温度加速了N80碳钢的腐蚀,但却有利于保护性FeCO3膜的形成。温度越高,FeCO3膜越致密。流体流动破坏了保护性FeCO3膜的致密性,加速了N80碳钢腐蚀。

This work aims to study the effects of temperature and flow velocity on the corrosion behavior of N80 carbon steel in supercritical CO2 environment and explore the corresponding corrosion mechanism by weight loss and electrochemical measurements.Furthermore,the corrosion morphology of N80 carbon steel was observed by scanning electron microscope(SEM)and the composition of corrosion product was analyzed by X-ray diffraction(XRD),respectively.The results indicated that the weight loss corrosion rate was smallest at 40℃.Meanwhile,the impedance decreased continuously with the prolongation of time,suggesting that no protective FeCO3 film was formed at 40℃.Although increasing temperature enhanced the weight loss corrosion rate in the initial period,the impedance suddenly increased at a certain time at higher temperatures,which indicates the formation of protective FeCO3 film.The higher the temperature,the larger the impedance after corrosion for 24 h,and the denser and more protective corrosion product film.In addition,weight loss corrosion rate increased with the increase of flow velocity.Electrochemical tests also showed that the higher flow velocity,the smaller impedance and the larger corrosion current density.Moreover,SEM surface morphology confirmed that the fluid flow destroyed the compactness of FeCO3 film and then reduced its protective effect for N80 carbon steel substrate.As a conclusion,although increasing temperature aggravates the corrosion of N80 carbon steel in the initial period,it facilitates the formation of protective FeCO3 film.Moreover,the higher the temperature,the denser the FeCO3 product film.The fluid flow destroys the compactness of protective FeCO3 film and thus accelerates the corrosion of N80 carbon steel.