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Coating Disbondment, Cathodic Protection, Pitting Corrosion, Near-neutral pH Stress Corrosion Cracking, Pipeline Steel

Eslami, Abdoulmajid

Supervisor and department: Chen, Weixing Chemical and Materials Engineering Eadie, Reginald Chemical and Materials Engineering

Examining committee member and department: Chen, Weixing Chemical and Materials Engineering Wang, Xiaodong Mechanical Engineering Elliot, Janet Chemical and Materials Engineering Luo, Jingli Chemical and Materials Engineering Revie, Winston Canmet Materials Technology Laboratory Eadie, Reginald Chemical and Materials Engineering

Department: Department of Chemical and Materials Engineering

Specialization:

Date accepted: 2012-09-26T10:41:59Z

Graduation date: 2012-09

Degree: Doctor of Philosophy

Degree level: Doctoral

Abstract: This research is aimed at understanding near-neutral pH SCC initiation under disbonded coatings of pipeline steels, and the effect of different environmental and operational factors on crack initiation. Understanding near-neutral pH stress corrosion cracking SCC could answer many of the primary questions on crack initiation of SCC which have not yet been answered. It could also assist the development of effective mitigative measures dealing with thousands of kilometer of pipelines containing this form of cracking, in addition to preventive action for future pipeline installations. Near-neutral pH SCC usually occurs under polyethylene tape PE tape coated pipelines, at locations where the coating becomes disbonded and-or damaged. Ground water can then penetrate under the damaged-disbonded coating, become trapped and form a suitable environment for corrosion and cracking. Despite extensive studies on this topic the details of crack initiation mechanisms in addition to the exact role of environmental and operational factors on crack initiation are not thoroughly understood. Most previous laboratory tests have been done in aggressive loading conditions and ignored the effect of coatings and cathodic protections CP. In order to simulate the conditions responsible for crack initiation, a novel testing setup capable of simulating the synergistic effects of coating disbondment, cathodic protection and cyclic loading was implemented. Using this setup and long term laboratory tests near-neutral pH SCC initiation mechanisms and the effect of some environmental and operational factors on crack initiation were investigated. It was found that near-neutral pH SCC initiation does not necessarily occur in near-neutral pH environments as commonly believed. Depending on the level of CP and CO2 in the underground environment, different localized environments with varying pH values from near-neutral to high values above 10 can form under the disbonded coatings. This significantly affected the corrosion and near-neutral pH SCC initiation mechanisms. These investigations brought out new findings about the effect of environment and operations on near-neutral pH SCC initiation.

Language: English

DOI: doi:10.7939-R3K99N

Rights: Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.





Author: Eslami, Abdoulmajid

Source: https://era.library.ualberta.ca/


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University of Alberta Near-neutral pH Stress Corrosion Crack Initiation under Simulated Coating Disbondment by Abdoulmajid Eslami A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctoral of Philosophy in Materials Engineering Department of Chemical and Materials Engineering ©Abdoulmajid Eslami Fall 2012 Edmonton, Alberta Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only.
Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the authors prior written permission. To Prophet Muhammad, the Messenger of Peace and Mercy. Abstract This research is aimed at understanding near-neutral pH SCC initiation under disbonded coatings of pipeline steels, and the effect of different environmental and operational factors on crack initiation.
Understanding near-neutral pH stress corrosion cracking (SCC) could answer many of the primary questions on crack initiation of SCC which have not yet been answered.
It could also assist the development of effective mitigative measures dealing with thousands of kilometer of pipelines containing this form of cracking, in addition to preventive action for future pipeline installations. Near-neutral pH SCC usually occurs under polyethylene tape (PE tape) coated pipelines, at locations where the coating becomes disbonded and-or damaged. Ground water can then penetrate under the damaged-disbonded coating, become trapped and form...





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