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XANES study of chemistry of localised corrosion in artificial pits of 316L stainless steel and titanium

Monir, Mehdi (2012)
Ph.D. thesis, University of Birmingham.

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Abstract

X-ray absorption near edge structure (XANES) experiments on artificial pits of 316L stainless steel were carried out to study the oxidation state and speciation of alloying elements in the pit solution. It was confirmed that the oxidation states of Fe, Cr and Ni are 2+, 3+ and 2+, respectively. Ni(H\(_2\)O)\(_6\)\(^{2+}\) was found to be the main solution species through the pit with no evidence of any Ni-Cl complexes. However, for iron and chromium, hexa-aquo ions (Fe(H\(_2\)O)\(_6\)\(^{2+}\) and Cr(H\(_2\)O)\(_6\)\(^{3+}\)) were found near the pit mouth with chloro complexes close to the dissolving metal surface.
The chemistry of molybdenum species in artificial pits of 316L stainless was investigated and the molybdenum oxidation state was found to be 3+. There was no evidence of any Mo(VI) polymolybdates, which have previously been proposed to explain the beneficial effects of Mo on the corrosion resistance of 316L stainless steel. High resolutions measurements did not detect any different molybdenum species adjacent to the salt film.
XANES measurements on titanium artificial pits showed a presence of TiCl\(_4\), titanium oxides (rutile and anatse) and metal fragments that were generated during the electrochemical dissolution process. X-ray fluorescence and XANES were also carried out to study the titanium distribution and species in human tissues extracted from the vicinity of failed knee, BAHA (bone-anchored hearing aid) and dental implants. Metal fragments and titanium oxides (rutile and anatase) were found in the tissues. In addition, XANES was carried out on neutrophil cells that had been cultured in the presence of anatase. In one case, a spectrum of rutile was found, suggesting the cells may be able to convert anatase to rutile.

Type of Work:Ph.D. thesis.
Supervisor(s):Davenport, Alison and Rayment, Trevor
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Subjects:T Technology (General)
TA Engineering (General). Civil engineering (General)
TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:3258
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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