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Damage Evolution of Pipeline API X52 Steel with Different Coating Conditions under Cathodic Protection in Soil and NS4 Solutions

Li, Ximing
http://rave.ohiolink.edu/etdc/view?acc_num=akron1406291563

Abstract Details

2014, Master of Science in Engineering, University of Akron, Chemical Engineering.
The susceptibility of pipeline to soil corrosion is always minimized by imposing an insulating barrier or coating at the pipe surface, and protection is enhanced by cathodic protection (CP) using either a sacrificial anode bed or an impressed current in case there are some defects or holidays on the coating surface. However, disbonding and/or delamination of the coating can still result in serious localized corrosion, because the cathodic current cannot penetrate under a delaminated coating and the uncovered sites become susceptible to localized corrosion. This work aims to identify and characterize the damage evolution of pipeline with intact and defect coal tar coating under cathodic protection in soil or NS4 solution, measured by electrochemical impedance spectroscopy (EIS). The transmission line model (TLM) was used to simulate the EIS results and to verify the proposed damage evolution. The results demonstrated that in soil, for the pipeline with intact coal tar coating, the assumed process, corresponding to three stages, would be adsorption of water and soil particles to the surface of the coating and water and ions to the interior coating, diffusion of water and ions to the interface of coating and steel, and relatively saturated electrolyte in the interface before the steel suffers corrosion. In soil, for pipe with defect coating, corrosion products were initially formed at the coating holiday. After long term exposure the mass transfer mechanism became the dominant process, as opposed to diffusion, due to the corrosion product covering the holiday surface that increased the impedance. For intact coating in homogeneous NS4 solution, the first two stages were detected: there was water uptake within the coating layer and the impedance decreased with time due to the damage evolution of each element forming the electrochemical cell. For defect coating in NS4 solution, impedance decreased over time until corrosion products covered the holiday surface, after which impedance increased over exposure time.
Homero Castaneda-Lopez, Dr. (Advisor)
Scott Lillard, Dr. (Committee Member)
Hongbo Cong, Dr. (Committee Member)
97 p.
Chemical Engineering
pipeline; coating; electrochemical impedance spectroscopy; transmission line model; equivalent circuit; damage evolution

Recommended Citations

Citations

  • Li, X. (2014). Damage Evolution of Pipeline API X52 Steel with Different Coating Conditions under Cathodic Protection in Soil and NS4 Solutions [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1406291563

    APA Style (7th edition)

  • Li, Ximing. Damage Evolution of Pipeline API X52 Steel with Different Coating Conditions under Cathodic Protection in Soil and NS4 Solutions. 2014. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1406291563.

    MLA Style (8th edition)

  • Li, Ximing. "Damage Evolution of Pipeline API X52 Steel with Different Coating Conditions under Cathodic Protection in Soil and NS4 Solutions." Master's thesis, University of Akron, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1406291563

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.