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Monitoring of atmospheric pollutants is a key point for preventive conservation since these species are known to impact the integrity of many artifacts including metals, papers, pigment and textiles. The problem can be amplified in closed environments, like in exhibition rooms and showcases, where temperature and relative humidity gradients and levels can introduce additional micro-climatic problems. One objective of the EU-SensMat project concerns the development of low cost and low visual nuisance sensors sensitive to these pollutants, making them affordable for all museums including small ones. For this purpose, the Radio-Frequency Identification (RFID) technology was considered to produce air-quality sensors based on reactive metallic dosimeter. Besides the low cost, they can be easily integrated to other existing RFID applications such as identification tasks since the interrogation is made with a commercial UHF-RFID reader. The description and the main features of these sensors are discussed in this paper. Moreover, as it will be shown, the subsequent chemical analysis of the sensitive part of the sensors provide useful information to determine the origin of the pollutants.

International audience; In the present work, an industrial polyester coil-coated steel sample was characterized by electrochemical impedance spectroscopy. The diagrams were obtained for various immersion times in a 0.5 M NaCl solution for three different initial states of the same coil coating (as received, dried and dried after the impedance measurements). The aim of the study was to have a better knowledge of how the water uptake influences the coil coating physical properties and to extract relevant parameters of the ageing processes. From the high-frequency part of the impedance diagrams, the water uptake was calculated using a linear rule of mixtures. Two sorption regions were observed for the dried samples suggesting the presence of porosities already filled with ambient moisture for the as-received sample. It was shown that the water uptake was a slow process and, independently of the initial state of the sample, a saturation plateau was never reached, even after 456 h of immersion. A time constant, clearly visible on the phase angle of the impedance diagrams, was analysed through the dielectric permittivity formalism and attributed to the signature of the dielectric manifestation of the glass transition. This time constant was shifted to higher frequencies with increasing water fraction (increasing immersion time), consistent with a plasticization effect. This result was supported by differential scanning calorimetry measurements. Finally, the data obtained for the different initial states of the coating highlighted that, even if the water uptake was reversible, the sorption kinetics was different for the sample dried after the impedance measurements. This could be of importance in the degradation process of the coil coated steel.

Zinc substrates were electrochemically oxidized in NaCl solution to produce corrosion patinas. XRD, XPS and Raman analyses enabled the identification of simonkolleite and zinc oxide as the patina constituents. FIB-SEM imaging shows that the upper part of the patinas is a network of simonkolleite nanosheets with an open microstructure that is unlikely to act as a significant barrier for corrosion processes. STEM investigations and Raman mapping measurements reveal the presence of a ca. 20–400nm thin nanoporous ZnO-rich film below the simonkolleite and covering the zinc substrate. Under potentiostatic conditions, the reduced cathodic activity of the patina-covered zinc electrodes is assigned to this nanoporous ZnO layer. Keywords: Simonkolleite, Zinc oxide, Microstructure, Corrosion

Microorganisms increase the opencircuit potential of stainless Steel immersed in seawater in a phenomenon called ennoblement.This change of potential of several hundreds of millivolts raises the chance of localized corrosion.The ennoblement has been studied for more than 40 years, and despite the importance and impact of ennoblement, little is known about the microbial mechanisms responsible for the phenomenon. We have combined microbial ecology and electrochemistry to investigate the diversity of surface attached bacteria associated with stainless steel ennoblement. Seawater temperature and dissolved oxygen content are factors that influence the ennoblement and we used them to infer the bacterial fraction associated with the phenomenon. The ennoblement is inhibited by a critical seawater tempzrature (above 38°C/40°C) and low dissolved oxygen content.With DNA amplicon sequencing, we identified operational taxonomie units (OTUs) that were biomarkers of the ennoblement. There were some OTUs affiliated to hydrocarbon degrading bacteria, and one OTU affiliated to ‘Candidatus Tenderia electrophaga’, an electrotrophic bacteria able to reduce oxygen with electrons from an electrode.We investigated the role of electrotrophic bacteria with potentiostatic and open circuit conditions and with metagenomics we recovered a metagenome assembled genome (MAG) very close to 'Candidatus Tenderia electrophaga’ associated with the ennoblement.From these results, we proposed a new bacterial mechanism to explain the ennoblement : electrotrophic bacteria would be able to reduce oxygen with électron drawn from the stainless steel passivation film, hence influencing the open circuit potential and therefore the ennoblement.; Les microorganismes sont capables d'augmenter le potentiel libre des aciers inoxydables en eau de mer via un phénomène que l’on appelle anoblissement. Cette élévation de plusieurs centaines de millivolts du potentiel augmente le risque de corrosion localisé. L’anoblissement a été étudié pendant plus de 40 ans, et malgré son importance, les mécanismes microbiens responsables du phénomène n’ont pas été identifiés. Nous avons combiné l’écologie microbienne et l'électrochimie pour étudier la diversité des bactéries associées à l’anoblissement des aciers inoxydables. La température de l’eau de mer ainsi que la teneur en oxygène dissous sont des facteurs qui influencent l’anoblissement et nous les avons utilisés pour identifier la fraction bactérienne associée au changement de potentiel. L’anoblissement est inhibé par une température critique de l’eau de mer (au-dessus de 38°C/40°C) et par une teneur basse en oxygène dissous. A l’aide du séquençage d’amplicons ADN, nous avons identifié des unités taxonomiques opérationnels (OTUs) comme biomarqueurs de l’anoblissement. Certaines étaient affiliées à des bactéries capables de dégrader des hydrocarbures, et une OTU était affiliée à ‘Candidatus Tenderia electrophaga’, une bactérie électrotrophe capable de réduire l'oxygène avec des électrons provenant d’une électrode. Nous avons étudié le rôle de ces bactéries avec des conditions a potentiels fixés et libres avec une approche de métagénomique. Nous avons reconstitué un génome issu d’assemblage métagénomique (MAG) très proche de ‘Candidatus Tenderia electrophaga’ et associé à l'anoblissement. Avec ces résultats, nous avons proposé un nouveau mécanisme bactérien pour expliquer l’anoblissement : les bactéries électrotrophes seraient capables de réduire de l’oxygène avec des électrons provenant du film passif de l’acier inoxydable, et ainsi influencer le potentiel libre et donc l’anoblissement.

Microorganisms increase the opencircuit potential of stainless Steel immersed in seawater in a phenomenon called ennoblement.This change of potential of several hundreds of millivolts raises the chance of localized corrosion.The ennoblement has been studied for more than 40 years, and despite the importance and impact of ennoblement, little is known about the microbial mechanisms responsible for the phenomenon. We have combined microbial ecology and electrochemistry to investigate the diversity of surface attached bacteria associated with stainless steel ennoblement. Seawater temperature and dissolved oxygen content are factors that influence the ennoblement and we used them to infer the bacterial fraction associated with the phenomenon. The ennoblement is inhibited by a critical seawater tempzrature (above 38°C/40°C) and low dissolved oxygen content.With DNA amplicon sequencing, we identified operational taxonomie units (OTUs) that were biomarkers of the ennoblement. There were some OTUs affiliated to hydrocarbon degrading bacteria, and one OTU affiliated to ‘Candidatus Tenderia electrophaga’, an electrotrophic bacteria able to reduce oxygen with electrons from an electrode.We investigated the role of electrotrophic bacteria with potentiostatic and open circuit conditions and with metagenomics we recovered a metagenome assembled genome (MAG) very close to 'Candidatus Tenderia electrophaga’ associated with the ennoblement.From these results, we proposed a new bacterial mechanism to explain the ennoblement : electrotrophic bacteria would be able to reduce oxygen with électron drawn from the stainless steel passivation film, hence influencing the open circuit potential and therefore the ennoblement.; Les microorganismes sont capables d'augmenter le potentiel libre des aciers inoxydables en eau de mer via un phénomène que l’on appelle anoblissement. Cette élévation de plusieurs centaines de millivolts du potentiel augmente le risque de corrosion localisé. L’anoblissement a été étudié pendant plus de 40 ans, et malgré son importance, les mécanismes microbiens responsables du phénomène n’ont pas été identifiés. Nous avons combiné l’écologie microbienne et l'électrochimie pour étudier la diversité des bactéries associées à l’anoblissement des aciers inoxydables. La température de l’eau de mer ainsi que la teneur en oxygène dissous sont des facteurs qui influencent l’anoblissement et nous les avons utilisés pour identifier la fraction bactérienne associée au changement de potentiel. L’anoblissement est inhibé par une température critique de l’eau de mer (au-dessus de 38°C/40°C) et par une teneur basse en oxygène dissous. A l’aide du séquençage d’amplicons ADN, nous avons identifié des unités taxonomiques opérationnels (OTUs) comme biomarqueurs de l’anoblissement. Certaines étaient affiliées à des bactéries capables de dégrader des hydrocarbures, et une OTU était affiliée à ‘Candidatus Tenderia electrophaga’, une bactérie électrotrophe capable de réduire l'oxygène avec des électrons provenant d’une électrode. Nous avons étudié le rôle de ces bactéries avec des conditions a potentiels fixés et libres avec une approche de métagénomique. Nous avons reconstitué un génome issu d’assemblage métagénomique (MAG) très proche de ‘Candidatus Tenderia electrophaga’ et associé à l'anoblissement. Avec ces résultats, nous avons proposé un nouveau mécanisme bactérien pour expliquer l’anoblissement : les bactéries électrotrophes seraient capables de réduire de l’oxygène avec des électrons provenant du film passif de l’acier inoxydable, et ainsi influencer le potentiel libre et donc l’anoblissement.

A new method for atmospheric corrosion monitoring based on the variation of radiofrequency (RF) wave propagation in a resonator during its corrosion is presented. The ability of the proposed sensor to differentiate between uniform and localized corrosion mechanisms is demonstrated by considering two identical open stub microstrip resonators produced in zinc and aluminum materials, respectively. For that purpose, experimental characterization of electromagnetic wave propagation in the resonators and simulations are compared. The proposed sensitive resonator should therefore be considered as the key element of new corrosion mimetic sensors.

International audience; Zinc oxide (ZnO) is a chemical compound of great interest used, for example, as photocatalyst in the purification of wastewater or polluted air. However, neither dissolution, nor photo-dissolution of ZnO is negligible: indeed, both processes reduce significantly the efficiency of photocatalysis and then lead to a secondary pollution by free Zn2+ . In the present study, the stability of ZnMgO thin films in weak alkaline solution is investigated. We demonstrates that the replacement of Zn2+ ion with Mg2+ ion results in the production of a Zn0.84Mg0.16O solid solution, whose stability is higher than that of the ZnO sample. This alloy, thus, constitutes an alternative to the use of ZnO in photocatalysis applications. To gain more insights into the higher resistance of such alloys to the dissolution process, X-Ray photoelectron spectroscopy measurements were performed. They highlighted the role of OH group adsorption in the experimentally observed enhancement of ZnMgO stability.