University of Cambridge
The Electrochemistry of Corrosion Inhibitors in the Oil and Gas Industry
Abstract
dc:description.abstractFor corrosion control in the petroleum industry the use of acid corrosion inhibitors is a necessity. In particular alkynol inhibitors are used in protecting oilfield steels. A future business need is the development of these inhibitors so that they may safely be pushed to higher operating temperatures, higher pressures, more sour oilwell conditions, and longer exposure times which is a present continuing trend. For these reasons improving the efficiency of inhibitors is paramount. Second, there is also a trend towards greener inhibitors that exhibit lower toxicity or at least improve the health and safety profiles of the toxic inhibitors in present use. The aim of this research is then two-fold, to address these two particular business drivers. A specific acid corrosion inhibitor, 4-ethyl-1-octyn-3-ol with a surfactant was found to display a mixed-type of inhibition which was more effective at higher temperatures. The inhibitor formulation commercially used in excess, was found to be susceptible to cause pitting in the underlying HS80 steel substrate which was identifiable through chronoamperometry as transient occurrences of noise. The mechanism leading to this is suggested to be violent microscopic ruptures of an overlying polymeric film that exposes regions of the underlying steel surface to corrosive attack. This polymer film was found to be persistent: as long as the established coating was not damaged the total inhibitor volume could be decreased after an initial film forming step and retain the same level of protection to the underlying steel substrate. This observation has the potential to represent a significant cost-saving as well as reducing the total amount of toxic chemicals that require handling. Given the centrality of the polymer film in imparting protection, key experiments on a dry coated specimen found the film to be roughly 3.5 nm to 10 nm thick and conductive to electrons. The polymer film could be perturbed and manipulated from the passage of electrons through it and this finding was leveraged to produce a program of polarisation scans directly onto the steel substrate which optimised the inhibitor film efficiency resident on it, providing an almost one order of magnitude improvement in corrosion protection at 83 ⁰C.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2022
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Choda, Varun
- Advisor dc:contributor.advisor
-
- Burstein, Gordon
Subjects
dc:subject × 7Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.73827
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/326369