| WANG Haoqian,WANG Dan,HOU Zhengyu,LIANG Shoucai,ZHANG Xiaolong,XIE Fei.Effect of Parallel Magnetic Field on Corrosion Behavior of Pipeline Steel with V-type Flaws[J],53(2):78-87 |
| Effect of Parallel Magnetic Field on Corrosion Behavior of Pipeline Steel with V-type Flaws |
| Received:September 06, 2022 Revised:June 14, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.02.007 |
| KeyWord:parallel magnetic field corrosion X70 steel V-type flaws Ku'erle soil |
| Author | Institution |
| WANG Haoqian |
School of Petroleum and Natural Gas Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
| WANG Dan |
School of Petroleum and Natural Gas Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
| HOU Zhengyu |
Liaohe Oil Field of CNPC, Liaoning Panjin , China |
| LIANG Shoucai |
Liaohe Oil Field of CNPC, Liaoning Panjin , China |
| ZHANG Xiaolong |
Liaohe Oil Field of CNPC, Liaoning Panjin , China |
| XIE Fei |
School of Petroleum and Natural Gas Engineering, Liaoning Petrochemical University, Liaoning Fushun , China |
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| Abstract: |
| The corrosion behavior of X70 pipeline steel with V-type corrosion flaws in Ku'erle simulated soil solution was investigated using a parallel magnetic field. The weight loss technique was used to calculate the corrosion rate of X70 pipeline steel with V-type corrosion flaws under varying parallel magnetic field intensities. The corrosion morphology and corrosion products inside and outside the V-groove were analyzed with a metal electron microscopy and an X-ray photoelectron spectroscopy (XPS), and the relative content of each corrosion product was analyzed. The corrosion current density of X70 pipeline steel with V-type corrosion flaws under different parallel magnetic field intensities was analyzed by the AC impedance technique, and the equivalent circuit diagram was fitted by the potentiodynamic polarization technique to analyze the resistance in the reaction process. With the increase of magnetic field intensity, the corrosion rate gradually accelerated. However, the parallel magnetic field had different effects on the corrosion outside and inside the V-groove. The corrosion current density without a magnetic field was 6.83 μA/cm2, the polarization resistance was 1 197.78 Ω. The corrosion product was Fe2O3. When the magnetic field intensity was 10 mT, the corrosion current density in the V-groove was 5.221μA/cm2, the polarization resistance was 1 718.59 Ω, and the corrosion product was Fe3O4; while the corrosion current density outside the V-groove was 7.88 μA/cm2, the polarization resistance was 811.14 Ω, and the corrosion product was Fe2O3. However, with the increase of the magnetic field intensity, the corrosion current density outside the V-groove gradually increased, and the polarization resistance gradually decreased. The relative content of corrosion product Fe2O3 increased and the relative content of Fe decreased. The corrosion current density in the V-groove gradually decreased, the polarization resistance gradually increased, and the relative content of corrosion product Fe2O3 decreased. The corrosion product changed to Fe3O4 at 40 mT and FeO at 70 mT. In addition to it anyway, corrosion morphology illustrated that, compared with no magnetic field, the corrosion pit outside the V-groove increased dramatically when the parallel magnetic field was applied, while the corrosion pit inside the V-groove became smaller. With increasing magnetic field intensity, the number of corrosion pits outside the V-groove grew from a small number at 10 mT to a substantial number at 40 mT, and the individual size of the corrosion pits steadily increased from 40 mT to 70 mT. This was because when the magnetic field acted on the surface of the V-groove, due to its uneven surface, the magnetic field would form a magnetic field gradient force at the V-groove, by attracting paramagnetic substances, the force would repel diamagnetic substances to move inside and outside the groove, thus affecting the corrosion process. The existence of a parallel magnetic field accelerates the external corrosion of the V-groove and inhibits the internal corrosion of the V-groove. With the increase of magnetic field intensity, the promotion and inhibition of magnetic field on the corrosion of pipeline steel are enhanced. The research results in this paper have a certain reference value for understanding the corrosion failure behavior of pipeline steel under a magnetic field. |
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