Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt
Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2007-2008. The processes of generalized and localized corrosion induced at a cobalt electrode polarized in slightly alkaline aqueous media (pH 7-10) have been investigated using electrochemical methods and surface analysis tec...
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ftunivlavalcorp:oai:corpus.ulaval.ca:20.500.11794/19283 2024-06-23T07:52:04+00:00 Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt Gallant, Danick Pézolet, Michel Simard, Stéphan 2018-04-12T21:37:45Z xxix, 307 f. application/pdf https://hdl.handle.net/20.500.11794/19283 eng eng 24755 http://hdl.handle.net/20.500.11794/19283 TC-QQLA-24755 http://purl.org/coar/access_right/c_abf2 QD 3.5 UL 2007 G163 Cobalt -- Corrosion Cobalt -- Alliages -- Corrosion Cobalt -- Électrométallurgie Couches d'oxyde -- Spectre thèse de doctorat COAR1_1::Texte::Thèse::Thèse de doctorat 2018 ftunivlavalcorp https://doi.org/20.500.11794/19283 2024-05-27T23:52:33Z Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2007-2008. The processes of generalized and localized corrosion induced at a cobalt electrode polarized in slightly alkaline aqueous media (pH 7-10) have been investigated using electrochemical methods and surface analysis techniques. In buffer solutions of H2C03/HCO,/CO^ at near neutral pH (7-8), particularly aggressive corrosion phenomena have been observed. The presence of carbonic acid in solution, as well as the high solubility of the CoO oxide, were identified as being responsible for the accelerated metal dissolution. However, the addition of a low concentration of phosphate species to the corrosive environment allows an important inhibition of cobalt dissolution under the form of the Co(CO,)2_ soluble complex. Potentiodynamic experiments have shown the efficiency of benzotriazole to inhibit the active dissolution of cobalt in slightly alkaline media. Using a novel approach to obtain the SERS effect (Surface-Enhanced Raman Scattering) directly from a massive cobalt electrode, the interaction mode of benzotriazole with the metal surface has been determined. Neutral benzotriazole molecules, first chemisorbed under cathodic polarization, are thereafter deprotonated at the zero charge potential of the System. As a result, a thin polymer-like [Co(II)(BTA)2-H20]„ film, insoluble and highly protective, is found on the electrode surface. This passive film restrains the access of chemical species known to be aggressive to the active sites of the electrode. In a situation of incomplete surface coverage by benzotriazole, cobalt species which originate from further dissolution processes, are preferentially complexed to deprotonated benzotriazole species present in the bulk solution. Such a mechanism contributes to the formation of the [Co(II)(BTA)2H20]„ film. To avoid degradation of cobalt through the initiation of localized corrosion induced by chloride ions, a protection method based on the passivation of the metal has been developed. It ... Doctoral or Postdoctoral Thesis Carbonic acid Université Laval: CorpusUL |
institution |
Open Polar |
collection |
Université Laval: CorpusUL |
op_collection_id |
ftunivlavalcorp |
language |
English |
topic |
QD 3.5 UL 2007 G163 Cobalt -- Corrosion Cobalt -- Alliages -- Corrosion Cobalt -- Électrométallurgie Couches d'oxyde -- Spectre |
spellingShingle |
QD 3.5 UL 2007 G163 Cobalt -- Corrosion Cobalt -- Alliages -- Corrosion Cobalt -- Électrométallurgie Couches d'oxyde -- Spectre Gallant, Danick Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt |
topic_facet |
QD 3.5 UL 2007 G163 Cobalt -- Corrosion Cobalt -- Alliages -- Corrosion Cobalt -- Électrométallurgie Couches d'oxyde -- Spectre |
description |
Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2007-2008. The processes of generalized and localized corrosion induced at a cobalt electrode polarized in slightly alkaline aqueous media (pH 7-10) have been investigated using electrochemical methods and surface analysis techniques. In buffer solutions of H2C03/HCO,/CO^ at near neutral pH (7-8), particularly aggressive corrosion phenomena have been observed. The presence of carbonic acid in solution, as well as the high solubility of the CoO oxide, were identified as being responsible for the accelerated metal dissolution. However, the addition of a low concentration of phosphate species to the corrosive environment allows an important inhibition of cobalt dissolution under the form of the Co(CO,)2_ soluble complex. Potentiodynamic experiments have shown the efficiency of benzotriazole to inhibit the active dissolution of cobalt in slightly alkaline media. Using a novel approach to obtain the SERS effect (Surface-Enhanced Raman Scattering) directly from a massive cobalt electrode, the interaction mode of benzotriazole with the metal surface has been determined. Neutral benzotriazole molecules, first chemisorbed under cathodic polarization, are thereafter deprotonated at the zero charge potential of the System. As a result, a thin polymer-like [Co(II)(BTA)2-H20]„ film, insoluble and highly protective, is found on the electrode surface. This passive film restrains the access of chemical species known to be aggressive to the active sites of the electrode. In a situation of incomplete surface coverage by benzotriazole, cobalt species which originate from further dissolution processes, are preferentially complexed to deprotonated benzotriazole species present in the bulk solution. Such a mechanism contributes to the formation of the [Co(II)(BTA)2H20]„ film. To avoid degradation of cobalt through the initiation of localized corrosion induced by chloride ions, a protection method based on the passivation of the metal has been developed. It ... |
author2 |
Pézolet, Michel Simard, Stéphan |
format |
Doctoral or Postdoctoral Thesis |
author |
Gallant, Danick |
author_facet |
Gallant, Danick |
author_sort |
Gallant, Danick |
title |
Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt |
title_short |
Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt |
title_full |
Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt |
title_fullStr |
Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt |
title_full_unstemmed |
Étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt |
title_sort |
étude spectroélectrochimique de la corrosion du cobalt en milieux faiblement alcalins : base de la compréhension des mécanismes de corrosion des alliages de cobalt |
publishDate |
2018 |
url |
https://hdl.handle.net/20.500.11794/19283 |
genre |
Carbonic acid |
genre_facet |
Carbonic acid |
op_relation |
24755 http://hdl.handle.net/20.500.11794/19283 TC-QQLA-24755 |
op_rights |
http://purl.org/coar/access_right/c_abf2 |
op_doi |
https://doi.org/20.500.11794/19283 |
_version_ |
1802643265797750784 |