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Title: A surface analytical chemistry approach to copper corrosion and its inhibition with benzotriazole derivatives in oil-filled power transformers
Author: Facciotti, Marco
ISNI:       0000 0004 5916 7876
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2015
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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.
Supervisor: Brown, Richard Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available