Study of Electrochemical Corrosion Behavior on X70 Natural Gas Pipeline Steel under CO2 System

HAN Xiaolong, WANG Yi, WU Xin, ZHANG Ji

doi:10.16577/j.issn.1001-1560.2024.0105

Materials Protection >

2024 , Vol. 57 >Issue 5: 83 - 89

DOI: https://doi.org/10.16577/j.issn.1001-1560.2024.0105

Study of Electrochemical Corrosion Behavior on X70 Natural Gas Pipeline Steel under CO₂ System

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(Karamay Fucheng Natural Gas Co.，Ltd.，Karamay 834008，China)

HAN Xiaolong( 1986-)，Undergraduate Course，Bachelor's Degree，Research Focus: Oil and Gas Recovery，Tel.: 15809908371，E-mail: 2559793306@ qq.com

Received date: 2023-02-16

Revised date: 2023-05-24

Accepted date: 2023-06-24

Online published: 2024-05-31

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Abstract

The electrochemical corrosion behavior of X70 pipeline steel under four different CO₂ pressures was investigated by electrochemical test methods and scanning electron microscope analysis, based on the simulated environment of the extracted water of natural gas transmission pipeline in an oilfield of Xinjiang. Results showed that in simulated extracted water solutions with high chloride ion content, the electrochemical impedance spectra(EIS) and polarization curves indicated that the corrosion of X70 steel specimens became increasingly severe with increasing CO₂ pressure(0.5, 1.0, 2.0, 3.0 MPa). The results of the loss-in-weight experiments showed that the corrosion rate of the X70 steel specimens increased with increasing CO₂ pressure, with a maximum corrosion rate of 2.573 9 mm/a at a pressure of 3 MPa. In addition. the XRD results indicated that the corrosion products were mainly FeCO₃. The SEM results showed that the pitting on the surface of the specimen became increasingly severe with increasing CO₂ pressure, and the surface of the specimen became increasingly rough. These results were attributed to the effect of high pressure CO₂ and pitting exacerbated by high Cl^- concentrations. Hence, it could be found that high CO₂ and Cl^- had a serious damaging effect on X70 pipeline steel. This work provided reference and guidance for the prevention of this type of corrosion.

Key words： X70 steel; natural gas pipelines; carbon dioxide corrosion; pitting; chloride ions

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HAN Xiaolong, WANG Yi, WU Xin, ZHANG Ji . Study of Electrochemical Corrosion Behavior on X70 Natural Gas Pipeline Steel under CO₂ System[J]. Materials Protection, 2024 , 57(5) : 83 -89 . DOI: 10.16577/j.issn.1001-1560.2024.0105

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