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Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte

Geraint Williams Orcid Logo, Nick Birbilis, Hamilton McMurray

Faraday Discussions, Volume: 180, Pages: 313 - 330

Swansea University Authors: Geraint Williams Orcid Logo, Hamilton McMurray

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DOI (Published version): 10.1039/c4fd00268g

Abstract

The early stages of localised corrosion affecting magnesium (Mg) surfaces when immersed in aqueous sodium chloride (NaCl) solutions involves the propagation of dark regions, within which both anodic metal dissolution and cathodic hydrogen evolution occur. For nominally “pure” Mg, these dark areas ca...

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Published in: Faraday Discussions
ISSN: 1359-6640 1364-5498
Published: 2015
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URI: https://cronfa.swan.ac.uk/Record/cronfa21191
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fullrecord <?xml version="1.0"?><rfc1807><datestamp>2021-01-14T12:55:37.0232620</datestamp><bib-version>v2</bib-version><id>21191</id><entry>2015-05-07</entry><title>Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte</title><swanseaauthors><author><sid>0d8fc8d44e2a3c88ce61832f66f20d82</sid><ORCID>0000-0002-3399-5142</ORCID><firstname>Geraint</firstname><surname>Williams</surname><name>Geraint Williams</name><active>true</active><ethesisStudent>false</ethesisStudent></author><author><sid>56fc1b17ffc3bdf6039dc05c6eba7f2a</sid><firstname>Hamilton</firstname><surname>McMurray</surname><name>Hamilton McMurray</name><active>true</active><ethesisStudent>false</ethesisStudent></author></swanseaauthors><date>2015-05-07</date><deptcode>MTLS</deptcode><abstract>The early stages of localised corrosion affecting magnesium (Mg) surfaces when immersed in aqueous sodium chloride (NaCl) solutions involves the propagation of dark regions, within which both anodic metal dissolution and cathodic hydrogen evolution occur. For nominally &#x201C;pure&#x201D; Mg, these dark areas can either take the form of discs which expand radially with time, or filiform-like tracks which lengthen with time. For Mg surfaces which display disc-form corrosion features in concentrated NaCl electrolyte, a transition to filiform corrosion (FFC) is observed as the concentration is decreased, indicating ohmic constraints on radial propagation. A similar effect is observed when Mg specimens of different iron impurity are immersed in a fixed, high concentration NaCl solution, where disc-form corrosion is observed on samples having &#x2265;280 ppm Fe, but FFC predominates at &#x2264;80 ppm Fe. An in situ scanning vibrating electrode technique (SVET) is used to determine current density distributions within the propagating corrosion features. Cathodic current density values of between &#x2212;100 and &#x2212;150 A m&#x2212;2 measured in central areas of disc-like features are sufficient to sustain the radial growth of a local anode at the perimeter of the discs. However, for high purity Mg specimens (&#x2264;80 ppm Fe), cathodic current densities of &#x2212;10 A m&#x2212;2 or less are measured over FFC affected regions, indicating that linear propagation arises when there is insufficient cathodic current produced on the corroded surface to sustain radial growth. The results are consistent with surface control of localised corrosion propagation in concentrated electrolyte, but ohmic control in dilute, lower conductivity NaCl solution.</abstract><type>Journal Article</type><journal>Faraday Discussions</journal><volume>180</volume><journalNumber/><paginationStart>313</paginationStart><paginationEnd>330</paginationEnd><publisher/><placeOfPublication/><isbnPrint/><isbnElectronic/><issnPrint>1359-6640</issnPrint><issnElectronic>1364-5498</issnElectronic><keywords/><publishedDay>31</publishedDay><publishedMonth>8</publishedMonth><publishedYear>2015</publishedYear><publishedDate>2015-08-31</publishedDate><doi>10.1039/c4fd00268g</doi><url>http://dx.doi.org/10.1039/c4fd00268g</url><notes/><college>COLLEGE NANME</college><department>Materials Science and Engineering</department><CollegeCode>COLLEGE CODE</CollegeCode><DepartmentCode>MTLS</DepartmentCode><institution>Swansea University</institution><apcterm/><lastEdited>2021-01-14T12:55:37.0232620</lastEdited><Created>2015-05-07T05:24:18.6933460</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Engineering and Applied Sciences - Materials Science and Engineering</level></path><authors><author><firstname>Geraint</firstname><surname>Williams</surname><orcid>0000-0002-3399-5142</orcid><order>1</order></author><author><firstname>Nick</firstname><surname>Birbilis</surname><order>2</order></author><author><firstname>Hamilton</firstname><surname>McMurray</surname><order>3</order></author></authors><documents/><OutputDurs/></rfc1807>
spelling 2021-01-14T12:55:37.0232620 v2 21191 2015-05-07 Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte 0d8fc8d44e2a3c88ce61832f66f20d82 0000-0002-3399-5142 Geraint Williams Geraint Williams true false 56fc1b17ffc3bdf6039dc05c6eba7f2a Hamilton McMurray Hamilton McMurray true false 2015-05-07 MTLS The early stages of localised corrosion affecting magnesium (Mg) surfaces when immersed in aqueous sodium chloride (NaCl) solutions involves the propagation of dark regions, within which both anodic metal dissolution and cathodic hydrogen evolution occur. For nominally “pure” Mg, these dark areas can either take the form of discs which expand radially with time, or filiform-like tracks which lengthen with time. For Mg surfaces which display disc-form corrosion features in concentrated NaCl electrolyte, a transition to filiform corrosion (FFC) is observed as the concentration is decreased, indicating ohmic constraints on radial propagation. A similar effect is observed when Mg specimens of different iron impurity are immersed in a fixed, high concentration NaCl solution, where disc-form corrosion is observed on samples having ≥280 ppm Fe, but FFC predominates at ≤80 ppm Fe. An in situ scanning vibrating electrode technique (SVET) is used to determine current density distributions within the propagating corrosion features. Cathodic current density values of between −100 and −150 A m−2 measured in central areas of disc-like features are sufficient to sustain the radial growth of a local anode at the perimeter of the discs. However, for high purity Mg specimens (≤80 ppm Fe), cathodic current densities of −10 A m−2 or less are measured over FFC affected regions, indicating that linear propagation arises when there is insufficient cathodic current produced on the corroded surface to sustain radial growth. The results are consistent with surface control of localised corrosion propagation in concentrated electrolyte, but ohmic control in dilute, lower conductivity NaCl solution. Journal Article Faraday Discussions 180 313 330 1359-6640 1364-5498 31 8 2015 2015-08-31 10.1039/c4fd00268g http://dx.doi.org/10.1039/c4fd00268g COLLEGE NANME Materials Science and Engineering COLLEGE CODE MTLS Swansea University 2021-01-14T12:55:37.0232620 2015-05-07T05:24:18.6933460 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering Geraint Williams 0000-0002-3399-5142 1 Nick Birbilis 2 Hamilton McMurray 3
title Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte
spellingShingle Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte
Geraint Williams
Hamilton McMurray
title_short Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte
title_full Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte
title_fullStr Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte
title_full_unstemmed Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte
title_sort Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte
author_id_str_mv 0d8fc8d44e2a3c88ce61832f66f20d82
56fc1b17ffc3bdf6039dc05c6eba7f2a
author_id_fullname_str_mv 0d8fc8d44e2a3c88ce61832f66f20d82_***_Geraint Williams
56fc1b17ffc3bdf6039dc05c6eba7f2a_***_Hamilton McMurray
author Geraint Williams
Hamilton McMurray
author2 Geraint Williams
Nick Birbilis
Hamilton McMurray
format Journal article
container_title Faraday Discussions
container_volume 180
container_start_page 313
publishDate 2015
institution Swansea University
issn 1359-6640
1364-5498
doi_str_mv 10.1039/c4fd00268g
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Materials Science and Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Materials Science and Engineering
url http://dx.doi.org/10.1039/c4fd00268g
document_store_str 0
active_str 0
description The early stages of localised corrosion affecting magnesium (Mg) surfaces when immersed in aqueous sodium chloride (NaCl) solutions involves the propagation of dark regions, within which both anodic metal dissolution and cathodic hydrogen evolution occur. For nominally “pure” Mg, these dark areas can either take the form of discs which expand radially with time, or filiform-like tracks which lengthen with time. For Mg surfaces which display disc-form corrosion features in concentrated NaCl electrolyte, a transition to filiform corrosion (FFC) is observed as the concentration is decreased, indicating ohmic constraints on radial propagation. A similar effect is observed when Mg specimens of different iron impurity are immersed in a fixed, high concentration NaCl solution, where disc-form corrosion is observed on samples having ≥280 ppm Fe, but FFC predominates at ≤80 ppm Fe. An in situ scanning vibrating electrode technique (SVET) is used to determine current density distributions within the propagating corrosion features. Cathodic current density values of between −100 and −150 A m−2 measured in central areas of disc-like features are sufficient to sustain the radial growth of a local anode at the perimeter of the discs. However, for high purity Mg specimens (≤80 ppm Fe), cathodic current densities of −10 A m−2 or less are measured over FFC affected regions, indicating that linear propagation arises when there is insufficient cathodic current produced on the corroded surface to sustain radial growth. The results are consistent with surface control of localised corrosion propagation in concentrated electrolyte, but ohmic control in dilute, lower conductivity NaCl solution.
published_date 2015-08-31T03:25:06Z
_version_ 1763750870917316608
score 11.017731

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