| CHEN Yufan,LIN Xueqiang,SUN Jianbo,SUN Chong,XU Xuexu,PANG Bo,CHEN Hui.Effect of Flow Rate on Corrosion Behavior of N80 Steel in a Multivariate Thermal Fluid Environment[J],53(10):124-133 |
| Effect of Flow Rate on Corrosion Behavior of N80 Steel in a Multivariate Thermal Fluid Environment |
| Received:July 12, 2023 Revised:November 14, 2023 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2024.10.009 |
| KeyWord:N80 steel flow rate CO2-O2 coexistence multicomponent thermal fluid in-situ electrochemistry corrosion behavior |
| Author | Institution |
| CHEN Yufan |
China University of Petroleum East China, Shandong Qingdao , China |
| LIN Xueqiang |
China University of Petroleum East China, Shandong Qingdao , China |
| SUN Jianbo |
China University of Petroleum East China, Shandong Qingdao , China |
| SUN Chong |
China University of Petroleum East China, Shandong Qingdao , China |
| XU Xuexu |
China University of Petroleum East China, Shandong Qingdao , China |
| PANG Bo |
China University of Petroleum East China, Shandong Qingdao , China |
| CHEN Hui |
Shenzhen Polytechnic University, Guangdong Shenzhen , China |
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| Abstract: |
| In order to study the corrosion characteristics of N80 steel under different flow rate conditions in the environment of injecting multiple thermal fluids, and to explore the influence and mechanism of flow rate changes on the corrosion behavior of N80 steel, this article used a self-made high-temperature and high-pressure multiphase flow erosion corrosion loop device to simulate the environment of injecting multiple thermal fluids with different flow rates (0, 0.5, 1.0, 2.0 m/s). The corrosion simulation experiment was conducted in a corrosion testing section, and the average corrosion rate of N80 steel at different flow rates was measured by the weightlessness method. At the same time, in-situ electrochemical testing was conducted under the same conditions in the electrochemical testing section. Scanning electron microscope (SEM) and diffraction of X-rays (XRD) were used to analyze the phase composition and surface morphology of corrosion products of N80 steel after corrosion at different flow rates. The results indicated that the average corrosion rate of N80 steel in the multi element hot fluid environment increased with the increase of flow rate. The flow rate affected the diffusion and mass transfer of O2, the distribution of near surface ions, and the magnitude of wall shear force, leading to changes in the characteristics of the corrosion product film and inducing varying degrees of corrosion of the substrate. At 0 m/s, the corrosion product was composed of FeCO3 and a small amount of Fe2O3, which was a single-layer film structure, and the bond between it and the steel substrate was relatively tight, and the corrosion was uniform. Within the range of 0.5-2.0 m/s, the types of corrosion products increased, which mainly composed of FeCO3, Fe2O3, and small amounts of FeO (OH). The film layer showed a double-layer structure. The outer layer was an iron oxide film, which was reddish brown in color and had weak binding force with the inner layer film, making it easy to be detached. The inner layer was similar to the product film at 0 m/s. The macroscopic morphology showed that there were bubbles in the gaps between the inner and outer film layers, and the number of bubbles increased with the increase of the flow rate. After removing surface corrosion products, it was found that local corrosion occurred below the bubbles. In addition, the in-situ electrochemical results showed that as the flow rate increased, the anode slope increased, while the cathode slope decreased. The outer corrosion product film resistance Rf1, charge transfer resistance Rct, and diffusion resistance W showed a decreasing trend. Therefore, the above experimental results indicate that the increase in flow velocity accelerates the diffusion and mass transfer process of O2, causing the corrosion electrochemical control step to change from cathodic oxygen diffusion process to anodic dissolution process. Additionally, the protective FeCO3 film thickness on the sample surface decreases, leading to a decrease in the protective properties of the product film. Furthermore, Fe2+ is more easily oxidized to form Fe3+, and local FeCO3 is oxidized to Fe2O3, thus damaging the integrity of the inner film and causing localized corrosion. |
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