| YANG Yong,RAN Wen-shen,LI Lin-tao,SUN Ming,HE Xiao-gang.Effect of Magnetic Field on AC Corrosion Behavior of Pipeline Steel in Simulated Yingtan Soil Solution[J],52(5):189-196, 225 |
| Effect of Magnetic Field on AC Corrosion Behavior of Pipeline Steel in Simulated Yingtan Soil Solution |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.05.018 |
| KeyWord:magnetic field X52 pipeline steel AC stray current corrosion behavior simulated Yingtan soil solution |
| Author | Institution |
| YANG Yong |
China Special Equipment Inspection and Research Institute, Beijing , China |
| RAN Wen-shen |
China Special Equipment Inspection and Research Institute, Beijing , China |
| LI Lin-tao |
China Special Equipment Inspection and Research Institute, Beijing , China |
| SUN Ming |
China Special Equipment Inspection and Research Institute, Beijing , China |
| HE Xiao-gang |
Beijing Special Equipment Inspection and Testing Research Institute, Beijing , China |
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| Abstract: |
| Alternating current (AC) interference can cause serious corrosion of oil and gas pipelines and thus cause accident. Magnetic flux leakage (MFL) internal detection is currently the most effective and widely used nondestructive technology for detecting metal damage in oil and gas pipelines. The purpose of this study is to explore the effect of magnetic field on the corrosion behavior of X52 pipeline steel caused by AC stray current, mainly including corrosion rate, corrosion potential, polarization current, corrosion products and corrosion morphology. In order to more realistically simulate the actual situation of the magnetic field generated by the magnetized pipeline, a 10 mm-wide ring was cut from a ϕ219 mm×6 mm pipe, and 650 turns of insulated copper wire (with a copper core diameter of 0.82 mm) were wound, and a slot was cut into the ring to embed the test sample. During the experiment, a 2 A direct current was applied to the insulated copper wire to simulate the magnetization of the sample, and the magnetic field intensity that was calculated was 1.9 kA/m. Open circuit potential, polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and weight loss tests were used to study the effect of the magnetic field generated by the magnetized oil and gas pipelines on the AC corrosion behavior of the X52 pipeline steel in simulated Yingtan soil solution. The applied magnetic field made the AC corrosion potential move negatively and then positively, increased the AC amplitude potential, increased the polarization current, decreased the reaction interface capacitance, increased the charge transfer impedance and increased the average AC corrosion rate, had a certain effect on the morphology of corrosion products, but basically had no effect on the corrosion morphology. Compared with the case of a direct application of a magnetic field that was perpendicular or parallel to the working surface of an electrode in most studies, the magnitude of the leakage magnetic field that acted on the electrochemical reaction in this study depended on the strength of the magnetic field loaded in the ring and the surface roughness of the sample (equivalent to numerous tiny defects) or the size and shape of the defects. The Loren magnetic force could increase the diffusion rate of solution particles, thereby reducing the Fe2+ concentration at the electrode/solution interface and the thickness of interfacial diffusion layer, and eventually increasing the corrosion rate. In a nonuniform magnetic field, the magnetic field gradient force caused paramagnetic ions in a non-uniform magnetic field to move to the high magnetic induction intensity region and the diamagnetic ions to move to the low magnetic induction intensity region. The magnetic field gradient could inhibit local corrosion in corrosion pits to a certain extent because magnetic induction intensity and magnetic field gradient in corrosion pits were higher than other areas. The conclusions of this paper indicate that the evaluation standard of AC stray current corrosion of oil and gas pipelines tested by in-line inspections based on the magnetic flux leakage (MFL) principle should be improved. |
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