Titre : Comportement des rouilles vertes carbonatées et sulfatées
Année : 2007
Auteur(s) : Antony H. Legrand L. Chaussé A.
Abstract : Les rouilles vertes (RV) sont des composés hydroxydes doubles lamellaires de formule
générale [FeII
(1-x)FeIII
x(OH)2]x+.[x/nAn-.mH2O]x- (avec An- : CO3
2-, SO4
2-, Cl-…). Elles
interviennent dans les processus de corrosion des aciers [1], le cycle biogéochimique du fer
[2] et peuvent être utilisés comme composés actifs dans certains procédés de dépollution [3].
Le caractère ferreux-ferrique qu’elles présentent, leur confère potentiellement le double rôle
de donneur et d’accepteur d’électrons et les positionne, par conséquent, au centre des
processus d’oxydoréduction impliquant l’élément fer.
La littérature comporte quelques études du comportement en oxydation des rouilles vertes ;
ces études concernent principalement des suspensions mises en aération, et les résultats
reportés indiquent la possibilité d’obtenir différents composés ferriques finaux selon les
conditions expérimentales, ce qui semble suggérer l’intervention de différents mécanismes.
En revanche, aucune étude sur le comportement en réduction n’était reportée,
vraisemblablement du fait de la difficulté à imposer des conditions de réduction à ces
suspensions.
Nous utilisons au laboratoire, des films minces de composés purs, synthétisés par voie
électrochimique ou chimique, sur divers substrats [4, 5]. Des électrodes ainsi constituées sont
particulièrement bien adaptées pour l’étude des processus rédox ; en effet, une perturbation
oxydante ou réductrice peut facilement être appliquée au composé par imposition d’un
potentiel ou courant appropriés. De même, cette approche permet de coupler in-situ les
mesures électrochimiques avec d’autres techniques d’analyse comme la microbalance à quartz
et le microRaman.
La présente communication reporte des résultats obtenus au cours d’études de l’oxydation et
de la réduction de films minces de rouilles vertes carbonatée et sulfatée [6]. Les mesures
gravimétriques in-situ ont été exploitées pour préciser la nature des transformations rédox (à
l’état solide ou via la solution). Ces résultats ont été complétés par des analyses ex-situ par
MEB, FTIR en mode réflection-absorption et DRX.
A partir de nos travaux et des données déjà existantes dans la littérature, nous avons pu établir
le schéma général des voies de transformation redox des rouilles vertes carbonatée et sulfatée.
JE
Titre : Applications de la spectroscopie infrarouge a transformée de Fourier (IRTF) pour la caractérisaton de bactéries sulfurogènes présentes dans les biofilms marins
Année : 2006
Auteur(s) : Boudaud N. Pineau S. Amiel C. Mariey L. Travert J.
Abstract : Non disponible
Journées thématiques Biofilms 2006 BRGM Orléans, 14-15 Juin 2006
Titre : Electrochemical reduction of ferric corrosion products and evaluation of galvanic coupling with iron
Année : 2006
Auteur(s) : Lair V. Antony H. Legrand L. Chaussé A.
Corrosion Sciences, Volume 48, Issue 8, Août 2006, Pages 2050-2063
Titre : Coupled electrochemical and gravimetric study of iron corrosion products
Année : 2006
Auteur(s) : Antony H. Legrand L. Chaussé A.
Abstract : Understanding the transformation pathways that occur during the growth and
evolution of a corrosion layer on steel is a hard challenge since it is difficult to clearly identify
the contributions of each corrosion product and the influence of the iron substrate. Thin films
of iron products deposited on inert conducting substrate are very appropriate for performing
electrochemical measurements. Indeed, both oxidation and reduction behavior can be studied
by imposing anodic or cathodic perturbations to the iron corrosion product. Moreover, the
coupling of in-situ characterization methods is easily carried out.
Procedures were developed to synthesize commonly-occurring iron corrosion products
as thin films [1-3]. Once synthesized, the thin film was electrochemically studied through
voltametry or chronopotentiometry. Quartz crystal microbalance was used in order to get insitu
mass measurements during both the synthesis and the oxidation/reduction studies.
Gravimetric measurements give information on dissolved and non-dissolved reduced
quantities, providing details on transformation and allowing the establishment of reduction or
oxidation classification. Concerning green rusts (mixed Fe(II)-Fe(III) hydroxides occurring as
intermediates between iron and ferric oxyhydroxides), we could point out the possibility for
solid-state oxidation or solid-state reduction [1], giving to these compounds a redox flexibility
that may play a key role in the evolution of some corrosion layers. A reduction mechanism
was proposed for the ferric oxihydroxide model, Lepidocrocite g-FeOOH [4]. Several ferric
corrosion products (Ferrihydrite, Maghemite, …) were also studied. Complementary
information was obtained from usual techniques (FTIR, SEM, XRD, …).
EMCR
Titre : Electrochemical study of indoor atmospheric corrosion layers formed on ancient iron artefacts
Année : 2006
Auteur(s) : Antony H. Perrin S. Dillmann Ph. Legrand L. Chaussé A.
Abstract : The degradation of iron-based materials by atmospheric corrosion is a well-know
problem that may have incidence, especially for the storage of radioactive nuclear wastes. It is
of importance to evaluate the damages due to this kind of corrosion within long time-periods.
Atmospheric corrosion is thought to be a cycling process for which some parts of the
corrosion layer may play a key role of electron acceptor during the wet periods. Studying
atmospheric corrosion layers formed on ancient iron coupons provides helpful information on
this phenomenon.
Several indoor atmospheric corrosion layers (0-800 years old), were selected from
different localizations in France. Each sample was scrapped from its iron substrate. The
resulting powder was mixed with graphite in appropriate proportions and the mixture was
pressed onto a stainless steel grid to constitute a composite electrode. The electrochemical
responses of the different samples were recorded under galvanostatic regulation, in a nearneutral
pH-buffered NaCl solution at 25°C. The E-t reduction curves allowed the
determination of two characteristic parameters, Et / 2 , the potential value obtained at half the
transition time, and Qt , the coulombic charge obtained at the end of the reduction. The
diminution of Et / 2 and Qt with the age of the corrosion layer showed that the “reduction
reactivity” decreases with time, suggesting a progressive stabilisation of the corrosion layer.
In a second part of the work, we synthesised several common ferric or ferrous/ferric
products (goethite, lepidocrocite, magnetite, maghemite, ferrihydrite) and compared their
reduction responses (product alone or mixture of 2 or 3 products) to those of corrosion
samples.
EMCR
Titre : Approches méthodologiques pour la caractérisation des populations dominantes de biofilms marins naturels, sur acier au carbone
Année : 2005
Auteur(s) : Pineau S. Janvier M. Cabassut G. Dupont-Morral I.
Abstract : Non disponible
7ème forum de biodétérioration des matériaux, Ouistreham, 26-27 mai 2005
Titre : microbial diversity of marine biofilms from carbon steel in port environment: optimization of research approach in Accelerated Low Water Corrosion (ALWC) context
Année : 2005
Auteur(s) : Pineau S. Cabassut G. Dupont-Morral I. Janvier M.
Abstract : The degradation of carbon steel structures, especially in the case of Accelerated Low Water Corrosion (ALWC) in port environment, can be induced by the presence of microorganisms, or the products of their metabolic activities including enzymes, exopolymers substances, organic and inorganic acids. Bacteria most frequently studied in Microbiologically Induced Corrosion (MIC) are mainly the Sulphate-Reducing Bacteria (SRB). To study bacterial consortia in MIC, a research program is purposed for in situ experimentation in three French ports. Carbon steel samples have been placed in several different configuration sites. New molecular technologies have been developed and used to investigate the composition of microbial communities. However, successful application of molecular techniques relies on effective recovery of nucleic acids from environmental samples. The objective of this study is to develop a rapid method to remove biofilm from marine samples and further a robust, simple and effective total DNA extraction protocol. We applied the molecular approach of PCR-amplified 16S rDNA fragments separated by Denaturing Gel Electrophoresis (DGGE) to analyze the microbial community. The comparison of DGGE patterns from different samples gives us information about similarities and differences in their community structures. This approach can be used to compare bacterial diversity from different sampling sites. This molecular approach is combined to classic microbiological methods (cultivable strains).
13th International Biodeterioration and Biodegradation Symposium, Madrid (Spain), 4-9 septembre 2005
Titre : Study of lepidocrocite electrochemical reduction in neutral and slightly alkaline solutions at 25°C
Année : 2005
Auteur(s) : Antony H. Legrand L. Maréchal L. Perrin S. Dillmann Ph. Chaussé A.
Abstract : The electrochemical reduction of lepidocrocite ?-FeOOH was investigated at 25 °C in neutral or slightly alkaline solutions containing chloride, sulphate or bicarbonate anions by means of thin lepidocrocite film electrodeposited on inert gold substrate or graphite/lepidocrocite powder composite electrode. Electrochemical measurements were coupled to in situ electrochemical quartz crystal microbalance (EQCM) and ex situ SEM and FTIR analysis. The reduction of lepidocrocite occurs in all the electrolytes considered here. The initial reduction product is adsorbed ferrous ion, Feads2+. The desorption of Feads2+ is promoted as pH increases, leading to an increase of reduction depth. This promotion is related to the formation of secondary FeII-containing species, as revealed by SEM and FTIR. The comparison of ?-FeOOH reduction potentials and iron corrosion potentials let us state that the galvanic coupling is possible.
