Control of Magnesium Alloy Corrosion through the Use of Engineered Intermetallics

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dc.contributor.advisor Robinson, M. J.
dc.contributor.advisor Impey, Susan A. Pidcock, Andrew 2015-06-01T09:19:18Z 2015-06-01T09:19:18Z 2014-12
dc.description.abstract The low density and high relative strength of Mg alloys means they can offer engineering benefits over steels or Al alloys. However, the susceptibility of Mg alloys to corrosion has limited their exploitation and restricted their use to more benign environments. An Mg-Al intermetallic surface layer is a good candidate for a robust corrosion protection method. This work demonstrates their development by using a novel ionic liquid electroplating process to deposit Al on to Mg substrates that when heat treated diffuses to form discrete intermetallic layers. Examination of three Mg-Al-Zn alloys showed that the amount Mg-Al intermetallic phases in their microstructures was linked to the quantity of Al they contained. Subsequent self-corrosion measurements using electrochemical impedance spectroscopy demonstrated that their performance was connected to the amount of intermetallic present, and in particular the strength of the micro-galvanic couples generated between the anodic and cathodic phases. Measurements of the self-corrosion behaviour of manufactured samples of the Mg-Al intermetallics confirmed that they could provide significant improvements, but it was acknowledged that their noble nature compared to an Mg substrate would encourage galvanic corrosion if a surface layer was damaged. As such the galvanic activity of the Mg-Al-Zn alloys and Mg-Al intermetallics was compared against a pure Mg standard using zero resistance ammetry and the resistance box technique. Galvanic models of alloy self-corrosion and a damaged intermetallic surface layer were also used to assess the potential problem. These measurements demonstrated that the intermetallics could act as strong cathodes, but further discussion on the nature of the behaviour suggested means by which galvanic corrosion might self-limit or self-repair. The galvanic corrosion experiments also revealed how the combination of current flow and a solution saturated with Mg2+ ions could lead to the formation of a highly protective Mg(OH)2 film with promising characteristics. en_UK
dc.language.iso en en_UK
dc.publisher Cranfield University en_UK
dc.rights © Cranfield University 2014. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. en_UK
dc.subject Aluminium en_UK
dc.subject electroplating en_UK
dc.subject microstructure en_UK
dc.subject EIS en_UK
dc.subject galvanic en_UK
dc.title Control of Magnesium Alloy Corrosion through the Use of Engineered Intermetallics en_UK
dc.type Thesis or dissertation en_UK
dc.type.qualificationlevel Doctoral en_UK
dc.type.qualificationname PhD en_UK

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