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A surface analytical chemistry approach to copper corrosion and its inhibition with benzotriazole derivatives in oil-filled power transformers

A surface analytical chemistry approach to copper corrosion and its inhibition with benzotriazole derivatives in oil-filled power transformers
A surface analytical chemistry approach to copper corrosion and its inhibition with benzotriazole derivatives in oil-filled power transformers
In this thesis is discussed the possible application of surface analytical chemistry techniques to the study of copper corrosion and its inhibition in insulating oils. In particular, the techniques investigated were X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SSIMS). XPS was used, in combination with energy-dispersive spectroscopy (EDX), to study the formation and migration of the corrosion by-product copper sulfide on both copper conductors and paper insulation, as a consequence of their exposure to corrosive insulating oils. Its surface atomic sensitivity allowed the study of the influence of variables such as concentration of corrosive species, oxygen, time and copper-paper proximity on the corrosion process. This ultimately led to the formulation of a new bifurcated mechanism to explain how copper sulfide might contaminate the insulating system of power transformers filled with corrosive oils. Additionally, XPS could also be used to study the inhibitor layer formed by the benzotriazole derivative Irgamet®39 on copper immersed in oil. The corrosion inhibitor was detected as a local enrichment of nitrogen on copper substrates, solely induced by the presence of its surface-active tolyltriazole moiety. Remarkably, it was possible to identify a correlation between the amount of corrosion inhibitor present in the oil and that effectively protecting copper, while estimating the thickness of the protection layer and the optimal amount of corrosion inhibitor to be used in real-life applications. SSIMS was used to increase the understanding of the copper inhibition process in oil by means of tolyltriazole. Thanks to its surface molecular sensitivity it was possible to obtain a new insight on the surface chemistry of the inhibitor, while investigating the effect of local temperature changes on the metal coverage and its stability under vacuum with the help of ion imaging. Moreover, it was also possible to estimate the energy of desorption of the tolyltriazole molecules from the copper surface. Finally, SSIMS ion imaging was shown to be a potentially valuable asset in forensic investigations, being able to track the distribution of corrosion inhibitor and by-products in decommissioned or failed power transformers.
Facciotti, Marco
4c7dc014-3d52-4fdb-98f2-867f81b3447b
Facciotti, Marco
4c7dc014-3d52-4fdb-98f2-867f81b3447b
Brown, Richard
21ce697a-7c3a-480e-919f-429a3d8550f5

(2015) A surface analytical chemistry approach to copper corrosion and its inhibition with benzotriazole derivatives in oil-filled power transformers. University of Southampton, Chemistry, Doctoral Thesis, 212pp.

Record type: Thesis (Doctoral)

Abstract

In this thesis is discussed the possible application of surface analytical chemistry techniques to the study of copper corrosion and its inhibition in insulating oils. In particular, the techniques investigated were X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SSIMS). XPS was used, in combination with energy-dispersive spectroscopy (EDX), to study the formation and migration of the corrosion by-product copper sulfide on both copper conductors and paper insulation, as a consequence of their exposure to corrosive insulating oils. Its surface atomic sensitivity allowed the study of the influence of variables such as concentration of corrosive species, oxygen, time and copper-paper proximity on the corrosion process. This ultimately led to the formulation of a new bifurcated mechanism to explain how copper sulfide might contaminate the insulating system of power transformers filled with corrosive oils. Additionally, XPS could also be used to study the inhibitor layer formed by the benzotriazole derivative Irgamet®39 on copper immersed in oil. The corrosion inhibitor was detected as a local enrichment of nitrogen on copper substrates, solely induced by the presence of its surface-active tolyltriazole moiety. Remarkably, it was possible to identify a correlation between the amount of corrosion inhibitor present in the oil and that effectively protecting copper, while estimating the thickness of the protection layer and the optimal amount of corrosion inhibitor to be used in real-life applications. SSIMS was used to increase the understanding of the copper inhibition process in oil by means of tolyltriazole. Thanks to its surface molecular sensitivity it was possible to obtain a new insight on the surface chemistry of the inhibitor, while investigating the effect of local temperature changes on the metal coverage and its stability under vacuum with the help of ion imaging. Moreover, it was also possible to estimate the energy of desorption of the tolyltriazole molecules from the copper surface. Finally, SSIMS ion imaging was shown to be a potentially valuable asset in forensic investigations, being able to track the distribution of corrosion inhibitor and by-products in decommissioned or failed power transformers.

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Published date: October 2015
Organisations: University of Southampton, Chemistry

Identifiers

Local EPrints ID: 387346
URI: http://eprints.soton.ac.uk/id/eprint/387346
PURE UUID: 0c3d8890-5170-43af-80b8-8861dff0cf2e
ORCID for Richard Brown: ORCID iD orcid.org/0000-0003-0156-7087

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Date deposited: 18 Feb 2016 12:48
Last modified: 06 Jun 2018 13:01

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Contributors

Author: Marco Facciotti
Thesis advisor: Richard Brown ORCID iD

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