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Mechanistic Study of Under Deposit Corrosion of Mild Steel in Aqueous Carbon Dioxide Solution

Huang, Jin
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1385569495

Abstract Details

2013, Doctor of Philosophy (PhD), Ohio University, Chemical Engineering (Engineering and Technology).
Silica sand is produced from geological formations that contain hydrocarbons and has the potential to be transported with extracted oil and gas along pipeline transmission systems. Consequently, the presence of sand is a significant challenge to production in the oil and gas industry. A particular threat is so called under deposit corrosion, which is refers to accelerated corrosion processes that develop underneath the deposit. Such accelerated corrosion processes may cause leakage of pipelines or result in catastrophic failure without control and prevention. Therefore, it is important to understand the mechanisms of under deposit corrosion. In this dissertation, possible mechanisms of CO2 corrosion of mild steel under sand deposits are proposed and evaluated. Both uniform corrosion processes and localized corrosion were studied. Electrochemical experiments were conducted with and without corrosion inhibitor to examine the effect of silica sand deposits on CO2 corrosion of mild steel. A simple and reliable method for testing of localized under deposit corrosion was developed and verified. It was established that in a solution free of corrosion inhibitor, both anodic and cathodic reactions are retarded by the sand deposit. The presence of the sand also caused a water chemistry difference between deposit covered areas and adjacent uncovered surface regions. This water chemistry difference resulted in a higher solution pH on the steel surface and promoted iron carbonate formation, which acted as a further mass transfer barrier for diffusion. A mechanistic electrochemical model was developed which was able to capture the characteristic features of the effect of sand deposits and was capable of predicting the under deposit corrosion rate. In the study of under deposit corrosion in inhibited environments, three uniform corrosion inhibitors were tested. The effects of environmental factors such as pH and temperature in conjunction with deposit particle size and porosity on inhibition were evaluated. The effect of sand deposit on inhibition mechanisms of different types of corrosion inhibitors were proposed and examined. It was found that general depletion of surfactant inhibitor (imidazoline type) by adsorption on the silica sand surface was not the critical factor that causes inhibition failure in under deposit CO2 corrosion. Slow diffusion of inhibitor through the porous sand deposit layer was also not the limiting factor in cases where inhibition failed. Localized corrosion in the form of pitting was identified in under deposit corrosion and related to the inability of the inhibitor to protect the steel surface in the crevices immediately underneath individual sand particles. These pits rapidly propagated due to galvanic effects, eventually merging and causing a high rate of attack underneath sand deposits.
Srdjan Nesic (Advisor)
Michael Prudich (Committee Member)
Kevin Crist (Committee Member)
Howard Dewald (Committee Chair)
Michael Jensen (Committee Co-Chair)
234 p.
Chemical Engineering
CO2 Corrosion; pipeline; under deposit; silica sand; mechanisms; localized corrosion; pitting; corrosion inhibitor; imidazoline; thiosulfate

Recommended Citations

Citations

  • Huang, J. (2013). Mechanistic Study of Under Deposit Corrosion of Mild Steel in Aqueous Carbon Dioxide Solution [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1385569495

    APA Style (7th edition)

  • Huang, Jin. Mechanistic Study of Under Deposit Corrosion of Mild Steel in Aqueous Carbon Dioxide Solution. 2013. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1385569495.

    MLA Style (8th edition)

  • Huang, Jin. "Mechanistic Study of Under Deposit Corrosion of Mild Steel in Aqueous Carbon Dioxide Solution." Doctoral dissertation, Ohio University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1385569495

    Chicago Manual of Style (17th edition)

ohiou1385569495
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© 2013, all rights reserved.
This open access ETD is published by Ohio University and OhioLINK.