O objetivo deste trabalho é analisar e comparar o comportamento quanto à resistência à corrosão, permeabilidade de hidrogênio e sua relação com a susceptibilidade ao trincamento induzido por hidrogênio de aços ARBL, em ambientes contendo H2S, enfatizando a influência da microestrutura. Foram realizados tratamentos térmicos de normalização e têmpera (em água) de dois tipos de tubos API 5L X65 para aplicação sour service, obtendo-se três condições com diferentes microestruturas para cada tubo. Assim, as duas amostras tais como recebidas apresentavam microestruturas de: ferrita/perlita e, o outro, ferrita/ferrita acicular; após tratamento de normalização os dois tipos de amostras apresentaram microestrutura de ferrita/perlita; e, por último, os aços que passaram por têmpera constituíram-se de martensita. O eletrólito empregado foi a solução A (ácido acético contendo cloreto de sódio) da norma NACE TM0284-2011, saturado com H2S. Os materiais foram submetidos a: ensaios de polarização linear para determinação da Resistência de Polarização (Rp), ensaios de permeabilidade de hidrogênio - baseado na ASTM G148-2003 - e ensaios de resistência ao trincamento induzido por hidrogênio (HIC) segundo a norma NACE TM0284-2011; exames em microscópio óptico e eletrônico de varredura para caracterização microestrutural, da morfologia da corrosão e do trincamento. Após os ensaios de polarização linear, foi observada uma diferença pequena dos valores de Rp entre as diferentes amostras estudadas, entre 120 ?.cm2 e 210 ?.cm2; dentro desta faixa, as microestruturas de martensita (aços temperados) apresentaram a menor resistência à corrosão. Foi realizado o tratamento dos dados obtidos por polarização linear com a metodologia desenvolvida por Mansfeld (1973) para cálculo da taxa de corrosão, observando mudanças nos declives de Tafel evidenciando a formação de produtos de corrosão. Apesar da formação destes produtos a taxa de corrosão não foi afetada, já que estes produtos são dissolvidos na solução A, oferecendo uma baixa proteção contra à corrosão. Nos ensaios de permeabilidade de hidrogênio foi utilizada uma célula modificada tipo Devanathan-Stachurski, com a solução A, com injeção de H2S no lado de geração de hidrogênio e 0,2M NaOH no lado de detecção. Foi realizado o tratamento dos dados com o método tlag, calculando a difusividade aparente, concentração de hidrogênio no metal e quantidade de sítios de ancoramento de hidrogênio. Também foi utilizado um método de ajuste da curva experimental com a equação obtida a partir da segunda lei de Fick para calcular a difusividade aparente. Foram comparados os valores obtidos com os dois métodos, obtendo-se resultados similares de difusividade aparente. As amostras temperadas foram as que apresentaram menor difusividade aparente, maior concentração de hidrogênio e maior número de sítios de ancoramento. Após o ensaio de resistência ao trincamento induzido por hidrogênio os exames em microscópio óptico mostraram que as amostras de tubos API 5L X65 como recebidas e normalizadas não apresentaram trincamento, já as amostras que passaram por tratamento de têmpera apresentaram trincas. A realização dos ensaios e tratamento dos dados permitiram observar a relação entre a quantidade de interface e a taxa de corrosão: assim a microestrutura martensítica apresenta a maior taxa de corrosão devido a maior quantidade de interfaces. A difusividade de hidrogênio também é afetada por esta mesma microestrutura, por ter maior quantidade de interface e maior número de discordâncias, apresentando menor difusividade aparente, maior concentração de hidrogênio e maior quantidade de sítios de ancoramento, tem-se que a microestrutura de martensita apresenta maior susceptibilidade ao trincamento induzido por hidrogênio. A nucleação e propagação das trincas nesta microestrutura depende de vários mecanismos que atuam simultaneamente: (i) nucleação das microtrincas, (ii) formação de H2 nas microcavidades com aumento da pressão local e (iii) migração de átomos de hidrogênio até a ponta da trinca diminuindo a força coesiva do reticulado facilitando a propagação. No entanto, esta relação entre microestrutura e HIC não pode ser generalizada, pois a susceptibilidade ao trincamento depende tanto da quantidade de sítios de ancoramento, como de sua energia de ligação, localização microestrutural e tamanho destes sítios. Outro fator importante é a presença de regiões de pouca ductilidade onde as trincas nucleadas tenham maior facilidade para sua propagação. Este trabalho contribuiu para o melhor entendimento dos mecanismos que levam à fragilização e danos provocados pelo hidrogênio, mostrando a relação entre microestrutura, corrosão, difusão e trincamento. Permitiu ampliar o conhecimento sobre os testes utilizados para avaliar o desempenho de aços microligados para aplicações em ambientes severos. / Pipelines produced from High Strength Low Alloy steels (HSLA) are a safe and cheap way to transport large quantities of petroleum and gas. HSLA steels offers mechanical and economic advantages. When HSLA steels are exposed to environments containing hydrogen sulphide (H2S), the steel can corrode and generate atomic hydrogen in the surface wich can diffuse and trapped, leading loss of mechanical properties and subsequent failures. The infrastructure to transport oil and gas represent a high cost investment, in adittion, they must be free from degradation processes that can causes severe health and environmental impacts. For this reason, the development of materials with high performance in aggressive environments is required. The aim of this study is to analyze and compare the corrosion behavior, hydrogen permeability and its relation with the susceptibility to Hydrogen Induced Cracking (HIC) of HSLA steels in environments containing H2S, with emphasis on the influence of microstructure. Normalizing and quenching heat treatments were applied in two different API 5L X65 pipelines for sour service. Three conditions were obtained (as received, normalized and quenched). The as received has a microstructure of ferrite / pearlite and ferrite / acicular ferrite, respectively; the microstructure of normalized specimens consist of ferrite / pearlite and finally quenched steels presented a microstructure of martensite. Solution A (acetic acid containing sodium chloride), according to NACE TM0284-2011 standard and saturated with H2S was used. The materials were tested by linear polarization technique, hydrogen permeability and Hydrogen Induced Cracking test (HIC). HIC tests were performed according to NACE TM0284-2011 standard. Optical microscope and scanning electron microscope were used for microstructural, corrosion and cracking characterization. Rp values show a slight difference between the different samples studied (120 ?.cm2 e 210 ?.cm2); the martensite microstructure (quenched) showed the lower corrosion resistance. Mansfeld (1973) method was used to calculate the corrosion rates from polarization curves. The Tafel slopes are differents between samples making evident the formation of corrosion products. Despite the growth of those corrosion products, the corrosion rate was not affected, since these products are dissolved in the solution A, providing a low corrosion protection. A modified Devanathan-Stachurski cell was used for the hydrogen permeability tests. It was used the solution A, with injection of H2S in the charging cell, and 0.1M NaOH solution on the oxidation cell. The hydrogen effective diffusivity, sub-surface concentration of atomic hydrogen at the charging side and number of hydrogen-trap sites were calculate by tlag method. Moreover, the experimental data were fitted using an equation derived from Fick\'s second law, in order to determinate the diffusion coefficient. The diffusion coefficient obtained from both methods were compare showing similar results. The quenching samples showed the lower diffusion coefficient, higher hydrogen concentration and number of trap sites. The steels in the as received and normalized conditins did not show cracks in Hydrogen Induced Cracking test; in the other hand, quenched samples presents cracks. The results shoed the relationship between the amount of interface and the corrosion rate. Being the martensitic microstructure the one with the higher corrosion rate. The diffusion coefficient in the martensitic microstructure, is a result of the high amount of interfaces and high dislocation density, leading to a lower diffusion coefficient, higher hydrogen concentration and number of trap sites. In the Hydrogen induced Cracking test the martensitic microstructure has shown the lower resistance to crack. The nucleation and propagation of the cracks in martensite depend of mechanisms that may act simultaneously: (i) nucleation of micro-cracks in preferential sites, (ii) formation of H2 in micro-cavities, with increase the local pressure, and (iii) hydrogen migration to the tip of the crack, decreasing the cohesive force in the lattice. However, the relationship between microstructure and Hydrogen Induced Cracking can not be generalized, since the susceptibility to cracking depends of several factors, like number of trap sites, binding trap energy, microstructural distribution and trap sizes. In addition, the presence of regions of low ductility can result in easy cracks nucleation and propagation. This thesis contributed to the understanding of the mechanisms that lead to hydrogen embrittlement and hydrogen damage, showing the relationship between microstructure, corrosion rate, diffusion and cracking, I ncreasing the scientific knowledge about the standard tests actually used to evaluate the performance of microalloyed steels in sour environments.

La détection et l'identification de bactéries pathogènes revêt une grande importance dans de nombreux domaines tels que la santé et l’industrie agroalimentaire. Dans ce contexte, les travaux de thèse s’intéressent à détection non invasive de Salmonella via la fraction volatile de son métabolome dont les métabolites volatils caractéristiques sont le sulfure d’hydrogène et la cadavérine. Ils illustrent également le concept de substrats osmogènes libérant des mCOV exogènes sous l’action d’enzyme spécifique d’Escherichia coli. Un premier capteur colorimétrique capable de distinguer le sulfure d’hydrogène du méthanethiol a été préparé. Il s’agit d’une matrice de silicate nanoporeuse dopée avec les réactifs N,N-diméthyl-p-phénylènediamine et ions Fe3+. Une bonne stabilité de l’intermédiaire réactionnel issu de ces réactifs, la quinonediimine (QD), est obtenue pour une forte concentration d’acide chlorhydrique. La réaction entre QD et 1000 ppm de sulfure d’hydrogène et de méthanethiol entraîne l’apparition respective d’une coloration verte et rouge-marron du capteur. Le capteur fluorimétrique de cadavérine, basé sur la formation d’un complexe fluorescent entre le Naphthol AS-BI déméthylé (ArOH) et la cadavérine, permet de détecter 250 ppb de cadavérine. La preuve de concept de substrats osmogènes a été illustrée avec la détection de p-nitrophénol (pNP) et de β-naphthylamine (β-NA) libérés en présence d’enzymes de E. coli, β-D-glucuronidase et L-alanine- β-naphthylamidase. Les capteurs nanoporeux produits, de taille de pores contrôlée, peuvent détecter 100 ppm de pNP, composé coloré (jaune) et 100 ppm de β-NA, composé fluorescent, ou encore 100 ppm de β-NA par dérivation chimique de ce dernier avec le diméthyl-p-aminocinnamaldéhyde (formation d’un produit rouge). En milieu biologique, l’eau est un interférent majeur. / Microbial contamination of food and biological samples is a big issue in the industry as much as in the medical field. In that context, the present thesis brings innovative solutions. A first explored way is the identification of Salmonella by detecting and measuring the specific metabolomics volatile organic compounds (mVOC) released, H2S and cadaverine. Another new concept is the use of osmogenic substrates able to release mVOC under the action of specific enzyme of Escherichia coli.A first colorimetric sensor able to discriminate H2S from CH3SH was produced, using a nanoporous silicate matrix doped with N,N-dimethyl-p-phenylenediamine and Fe3+ ions. A very acidic medium is needed to stabilize the “key” intermediate of the reaction, the quinonediimine species (QD), which gives with H2S and CH3SH a green and red-brown product, respectively. The fluorimetric sensor of cadaverine is based on the formation of a fluorescent complex between AS-BI demethylated Naphthol and cadaverine and can detect 250 ppb of cadaverine. A proof of concept of osmogenic substrates is given with the detection of p-nitrophenol (pNP) et de β-naphthylamine (β-NA) released under the action of Escherichia coli enzymes, β-D-glucuronidase et L-alanine- β-naphthylamidase. Various nanoporous sensors are produced with tailored pore size, which can detect 100 ppm of the yellow pNP, 100 ppm of the fluorescent β-NA and 100 ppm of the red product issued from the derivation of β-NA with dimethyl-p-aminocinnamaldehyde. In biological media, water remains the major interfering agent.

Inwardly rectifying potassium (Kir) channels establish and regulate the resting membrane potential of excitable cells in the heart, brain and other peripheral tissues. Phosphatidylinositol- 4,5-bisphosphate (PIP2) is a key direct activator of ion channels, including Kir channels. Gasotransmitters, such as carbon monoxide (CO), have been reported to regulate the activity of Kir channels by altering channel-PIP2 interactions. We tested, in a model system, the effects and mechanism of action of another important gasotransmitter, hydrogen sulfide (H2S) thought to play a key role in cellular responses under ischemic conditions. Direct administration of sodium hydrogen sulfide (NaHS), as an exogenous H2S source, and expression of cystathionine γ-lyase (CSE), a key enzyme that produces endogenous H2S in specific brain tissues, resulted in comparable current inhibition of several Kir2 and Kir3 channels. A “tag switch” assay provided biochemical evidence for sulfhydration of Kir3.2 channels. The extent of H2S regulation depended on the strength of channel-PIP2 interactions: H2S regulation was attenuated when strengthening channel-PIP2 interactions and was increased when channel-PIP2 interactions were weakened by depleting PIP2 levels via different manipulations. These H2S effects took place through specific cytoplasmic cysteine residues in Kir3.2 channels, where atomic resolution structures with PIP2 gives us insight as to how they may alter channel-PIP2 interactions. Mutation of these residues abolished H2S inhibition, and reintroduction of specific cysteine residues into the background of the mutant lacking cytoplasmic cysteine residues, rescued H2S inhibition. Molecular dynamics simulation experiments provided mechanistic insights as to how sulfhydration of specific cysteine residues could lead to changes in channel-PIP2 interactions and channel gating.

L'exploitation des champs de pétrole et de gaz sous haute pression (HP) et haute température (HT) a augmenté ces dernières années, nécessitant de réévaluer les risques de corrosion dans ces milieux de plus en plus sévères. Afin de contribuer à une meilleure évaluation des risques de rupture différée des aciers en présence d'H2S (SSC, Sulfide Stress Cracking) dans ces conditions, trois axes de recherche ont été suivis. Nous avons d'abord identifié un besoin d'amélioration de prédiction des conditions corrosives sous haute pression et haute température, et en particulier pour le calcul du pH in situ. Un modèle a été développé ; il prend en compte le comportement non-idéal des phases en équilibre, et permet un calcul plus précis du pH et de la fugacité des gaz acides à haute pression et haute température. Dans un deuxième temps, nous avons étudié l'effet de la pression partielle de CO2 (PCO2) sur les réactions de surface et sur les risques de SSC. Cette étude, réalisée à l'aide de mesures électrochimiques en l’absence d’un film de sulfure de fer, a permis de montrer que la présence de CO2 augmente sensiblement les cinétiques des réactions cathodiques à la surface de l'acier ainsi que le chargement en hydrogène, en particulier lorsque la pression partielle en H2S (PH2S) est faible. Enfin, des essais SSC ont été mis en œuvre dans des conditions fixes de pH et de PH2S, en faisant varier PCO2 entre zéro et 100 bar. L'objectif était de vérifier que la présence de CO2 sous forte pression augmentait bien les risques de fissuration, comme prévu par les résultats des essais électrochimiques. Les difficultés liées à la mise en œuvre d'essais en autoclave sous pression n'ont pas permis d'apporter une conclusion définitive. Néanmoins, ces travaux montrent qu'il peut exister un risque de sous-estimation de la sévérité des milieux dans les pratiques conventionnelles, lorsque PCO2 est significativement plus élevée que PH2S. Dans ces conditions spécifiques, les résultats de ce travail peuvent servir à améliorer les critères de choix de matériaux pour les milieux HP/HT. / The production of high pressure (HP) and high temperature (HT) wells has considerably increased in the last decade. It is therefore needed to reassess the risks of corrosion in always more severe environments. This work was three fold to better assess the risk of Sulfide Stress Cracking (SSC) in these environments. Firstly, there was a need to improve prediction methods for the evaluation of HP/HT environments severity, especially the in situ pH calculation. A model was which taking into account the non-ideal behaviour of gas and liquid phases in equilibrium. The determination of the in situ pH and the acid gas fugacity at high pressure and high temperature is more accurate. In a second part of the work, the impact of CO2 partial pressure (PCO2) on surface reactions and hence on the risk of SSC was examined. Electrochemical and hydrogen permeation measurements in the absence of an iron sulphide film showed that CO2 induces an increase of both cathodic reactions kinetics and hydrogen charging in the steel, especially at low H2S partial pressure (PH2S). In the last part of this work, SSC tests were performed at constant pH and constant PH2S, with various PCO2 from 0 to 100 bar. The objective was to experimentally confirm that increasing PCO2 increases the SSC risk, as inferred from the electrochemical study. Unfortunately, experimental artefacts linked with autoclave test conditions did not lead to clear conclusions on this point. However, this work shows that conventional tools might lead to underestimate SSC risks at high PCO2 and low PH2S. In these specific conditions, the new results presented in this report may contribute to improve materials selection criteria for high pressure and high temperature conditions.

Τρεις περιοχές της Δυτικής Ελλάδας, στις οποίες είχαν καταγραφεί διαφυγές ρευστών από τον πυθμένα της θάλασσας μελετήθηκαν στα πλαίσια της παρούσας διδακτορικής διατριβής, το υποθαλάσσιο πεδίο κρατήρων διαφυγής ρευστών στον Πατραϊκό κόλπο, το υποθαλάσσιο πεδίο κρατήρων διαφυγής στον Όρμο του Ελαιώνα στο Δυτικό Κορινθιακό κόλπο και οι διαφυγές ρευστών στον κόλπο του Κατακόλου. Η διατριβή βασίζεται στη μελέτη θαλάσσιων γεωφυσικών δεδομένων, στη μελέτη των φυσικοχημικών παραμέτρων της υδάτινης στήλης, στη χημική και ισοτοπική ανάλυση των ρευστών, στη μελέτη των δεδομένων που προέκυψαν από την πρώτη παγκόσμια καταγραφή μακράς περιόδου διαφυγών ρευστών από τον πυθμένα, στη μελέτη των διαφυγών στην παράκτια ζώνη πλησίον των υποθαλάσσιων θέσεων και τέλος στην οπτική παρατήρηση των θέσεων διαφυγών ρευστών. Το πεδίο κρατήρων διαφυγής ρευστών του Πατραϊκού κόλπου σχηματίζεται σε Ολοκαινικές ιλυούχες αποθέσεις που υπέρκεινται Πλειστοκαινικών ιζημάτων, και ελέγχεται από ρηξιγενείς δομές. Το πεδίο κρατήρων διαφυγής ρευστών του Πατραϊκού κόλπου παρουσιάζει μία σχεδόν συνεχή μικροδραστηριότητα η οποία διακόπτεται από παροξυσμικά γεγονότα μεγάλων διαφυγών ρευστών που σχετίζονται με μεγάλους σεισμούς. Το καθεστώς ενεργοποίησης ελέγχεται από το μέγεθος, το επίκεντρο και το είδος του σεισμού. Τα ρευστά που διαφεύγουν είναι αέριοι υδρογονάνθρακες (μεθάνιο μικροβιακής προέλευσης) με ή χωρίς νερό των πόρων των ιζημάτων. Στην παράκτια ζώνη της Πάτρας, πλησίον του πεδίου εντοπίζονται τρεις περιοχές με έντονες διαφυγές αερίων από το έδαφος. Συνολικά η παράκτια ζώνη της Πάτρας, τόσο το χερσαίο όσο και το θαλάσσιο περιβάλλον της, προσφέρει τουλάχιστον 4.7tn μεθανίου ετησίως στην ατμόσφαιρα, με τη μέγιστη προσφορά μεθανίου να μπορεί να φτάσει τους 19 τόννους ετησίως, ενώ μετά από ένα ισχυρό σεισμικό γεγονός εκτιμήθηκε ότι διαφεύγουν 500 κιλά περίπου μεθανίου από το θαλάσσιο πυθμένα σε διάστημα 16 ημερών. Στην περιοχή του Όρμου του Ελαιώνα οι κρατήρες διαφυγής ρευστών σχηματίζονται σε Ολοκαινικές ιλύες και ο πυθμένας των κρατήρων φτάνει στην διεπιφάνεια Ολοκαίνου/Πλειστοκαίνου, με κύριο μηχανισμό σχηματισμού την εκφόρτιση του γλυκού νερού. Οι βενθικές βιοκοινωνίες που εντοπίστηκαν στο εσωτερικό των κρατήρων διαφυγής ρευστών οδηγεί στο συμπέρασμα ότι το υπόγειο νερό, εμπλουτισμένο με θρεπτικά συστατικά και διαλυμένο οξυγόνο δημιουργεί ένα εξαιρετικό οικότοπο για την ανάπτυξη βενθικών οργανισμών. Στην περιοχή του Κατακόλου εντοπίστηκαν και καταγράφηκαν πολύ μεγάλες διαφυγές ρευστών σε τρεις περιοχές, στον Λιμένα Κατακόλου, στη θέση «Φάρος» Κατακόλου και νότια του Λιμένα. Οι έντονες διαφυγές ρευστών, κυρίως θερμογενούς μεθανίου με σημαντικές ποσότητες υδροθείου, φαίνεται να συνδέονται με τις ενεργές διαπυρικές δομές στην περιοχή, που επηρεάζουν τις υπερκείμενες ακολουθίες σχηματίζοντας κανονικά ρήγματα, τα οποία συγκροτούν μία ιδανική δίοδο μετανάστευσης των αερίων από τους Μεσοζωικούς ταμιευτήρες υδρογονανθράκων προς την επιφάνεια. Στην υποθαλάσσια περιοχή του Λιμένα Κατακόλου εκτιμήθηκε ότι η ποσότητα μεθανίου που διαφεύγει από το θαλάσσιο πυθμένα είναι της τάξεως των 1260-1500 τόννων το χρόνο. επικινδυνότητα τόσο για τον άνθρωπο, όσο και τις κατασκευές στην περιοχή του Λιμένα. H υψηλή συγκέντρωση μεθανίου στην ατμόσφαιρα μπορεί να προκαλέσει έκρηξη ή πυρκαγιά, ενώ οι υποθαλάσσιες διαφυγές και η παρουσία αερίων υδρογονανθράκων στα επιφανειακά ιζήματα μπορούν να προκαλέσουν εκρήξεις κατά τη διάρκεια γεωτρήσεων ή να καταστρέψουν θαλάσσιες κατασκευές. Το υδρόθειο είναι το πιο επικίνδυνο και τοξικό γεωρευστό και μπορεί να προκαλέσει σημαντικές ιατρικές βλάβες στον άνθρωπο στις συγκεντρώσεις που μετρήθηκε στην περιοχή του λιμένα. / Three areas in Western Greece studied, where seabed fluid flow have been reported. The dissertation is based on the study of marine geophysical data, on physicochemical parameters of seawater, on chemical and isotopic analysis of fluids, on the study of the data collected during the first long-term monitoring of seabed fluid flow ever done and on the study of the fluid flow on the surroundings inshore areas. The Patras Gulf pockmark field is formed on Holocene muds which overlies Pleistocene coarser sediments and is controlled by normal faults. The Patras Gulf pockmark field is characterized by ‘normal’ micro-activity which is interrupting by high activity periods after strong earthquakes. The fluids that flows from the pockmarks is mainly methane of microbial origin with/or without porewater. An estimation of the total methane that flows from the pockmark field and the surrounding inshore area of the field shows that the methane that leaks to the atmosphere is about 4.7-19 tn/year. After strong earthquakes, when the pockmark field is activated, the estimation of the methane that leaks from the seabed is about 500kgr for a period of 16 days. The Eleonas Bay pockmark field is formed on Holocene muds whereas the base of the pockmarks reaches the Holocene/Pleistocene boundary. The main mechanism for the formation of these pockmarks is the groundwater discharge. Benthic macrofauna that observed on the base of the pockmarks shows that the groundwater which is enriched in nutrients and dissolved oxygen is creating an excellent environment for the growth of benthic fauna. In the area of Katakolo have been observed three areas of enhanced fluid flow offshore and onshore. The studies of these areas have shown that the seeps are caused by thermogenic methane that had accumulated in Mesozoic limestone and had migrated upward through faults, or zones of weakness, induced by salt diapirism. An estimation of the methane that flows from the offshore part of the Katakolo Harbour area have shown that the methane that reaches the atmosphere is about 1260-1500 tn/year. Methane seeps in potentially explosive amounts at the area of the Harbour, and hydrogen sulfide is over the levels necessary to induce toxicological diseases and lethal effects.

La présence de microorganismes peut être révélée par des métabolites volatils caractéristiques. Cette approche est particulièrement intéressante pour la détection non-invasive de pathogènes dans des échantillons complexes comme les matrices alimentaires, les échantillons sanguins, ou encore les plaies chroniques. Des capteurs nanoporeux à grande surface spécifique ont été préparés par voie sol-gel (xérogels) ; leur rôle est à la fois de capturer, concentrer et permettre une détection optique des Composés Organiques Volatils (COV) microbiens. Des capteurs dopés avec une molécule sonde, l'acide 5,5′ dithiobis 2 nitrobenzoïque, ont été développés pour mettre en évidence le sulfure d'hydrogène (H2S) produit par Salmonella, un pathogène d'intérêt dans le domaine de l'agroalimentaire. La capture d'H2S provoque un changement de couleur du capteur dès 5 ppm. Une partie du travail de recherche porte également sur la détection de métabolites dits « exogènes », libérés suite à l'hydrolyse d'un substrat enzymatique. C'est alors l'activité enzymatique qui est spécifique du micro-organisme ciblé. Deux COV exogènes sont envisagés : la β naphthylamine (β NA) et le 2 nitrophénol (2 NP). La première est issue d'activités enzymatiques peptidases, le second est issu d'activités glycosidases ou estérases. Pour ce dernier, une détection directe est possible dès 14 ppb grâce à son absorbance intrinsèque dans le visible. Après un travail sur la composition chimique des xérogels, une mise en forme originale par moulage des gels en forme de coin de cube permet une lecture de l'absorbance des xérogels en réflexion. Enfin, les capteurs obtenus ont été testés vis-à-vis de COV générés par 3 pathogènes: Salmonella, Escherichia coli et Staphylococcus aureus dans des matrices complexes (sang et échantillons alimentaires). / The presence of micro-organisms can be revealed by specific volatile metabolites. This approach is interesting for the non-invasive detection of pathogenic species in complex samples, such as food, blood or exudate. Nanoporous materials developing a high surface area have been prepared by sol-gel process (xerogels). They trap, concentrate and reveal the presence of microbial Volatile Organic Compounds (VOC) by means of an optical detection. Sensors have been doped with a probe molecule (5,5′ dithiobis 2 nitrobenzoic acid) in order to detect hydrogen sulfide emitted by foodborne pathogen Salmonella. The colour of sensor changes in the presence of 5 ppm of H2S. Another detection method is the use of enzymatic substrates which release exogenous VOCs. In this approach, the enzymatic activity is specific to the targeted pathogenic bacteria. Sensors have been developed for two exogenous VOCs: β naphthylamine (β NA) and 2 nitrophenol (2-NP). β NA is issued from peptidase activity, whereas 2 NP is produced by glycosidase or esterase activity. The latter can be detected above 14 ppb through absorbance in the visible region. The work focused both on the chemical composition of the xerogels and on their shape. After molding the xerogels into a trihedral prism (“corner reflector”), the absorbance can be easily monitored using the reflected light. VOCs produced by 3 pathogenic bacteria, Salmonella, Escherichia coli and Staphylococcus aureus, in complex media (blood and food samples) have been monitored with the obtained sensors.

Made available in DSpace on 2016-06-02T20:34:19Z (GMT). No. of bitstreams: 1 3075.pdf: 8688023 bytes, checksum: 800e01878f1f0186b361618d6115dccd (MD5) Previous issue date: 2009-09-08 / Universidade Federal de Sao Carlos / This work presents a study of the 1020 and 1040 carbon steel corrosion in aqueous solution containing dissolved H2S in order to investigate the effect of H2Saq and HSaq species. Some different electrolytes were used: acetic acid buffer and phosphate buffer in presence or absence of 3.5 wt% NaCl solution containing 10, 25, 50, 100, 200, 500, 1000 and 2000 ppm of Na2S. The corrosion steel was described by means electrochemical impedance spectroscopy (EIS), potential polarization curves (PC), open circuit potential (Eoc) and in situ optical microscopy. Other experiments were carried out seeking to understand the steel corrosion process in sulfide solution. Thus, the influence of the 4 factors together (sulfide species, concentration, presence of chloride and steel type) was assessed by the interpretation of interactions and main effects in an experiments using factorial design. The characterization of the films was performed by electrochemical impedance spectroscopy in situ and ex situ techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The EIS measurements showed two distinct regions, high and low frequencies and the data analysis as a combination of diffusion and charge transference resistance, capacitances and constant phase elements (CPE). This parameters allow studying the corrosion of iron in presence of different sulfide species. The influence of total H2S concentration as well as the effect of immersion time on the corrosion was investigated too. In presence of the H2S the Rct values increase initially with immersion time but then decrease gradually. We concluded that there is formation of a protective film that reaches its maximum thickness after 3 h, and this layer is later dissolved to grow back again until reaching an equilibrium value at immersion time over 10 h. If the sulfide films has many porous, the capacitance presents high values to the corrosion process. In this case the number of defects of the sulfide films is proportional to increasing of corrosion. For the factorial design it was concluded that the species of sulfide is the most relevant factor for the corrosion process, followed by concentration and the presence of chloride in the solution. In the presence of H2S happens to active dissolution of iron and in the presence of HS- can occur the formation of a protective film. By images of in situ optical microscopy, carried out during the electrochemical measurements, one can observe the dissolution of ferrite in the pearlitic region and a formation of iron sulfide films with different colors. Morphological analysis and classification of surface corrosion damage, carried out by digital processing of images, show that happens grain-boundaries corrosion, pitting corrosion and formation of sulfide film initially over pearlitic grains. / Este trabalho apresenta o estudo da corrosão dos aços carbono 1020 e 1040 em solução aquosa contendo H2S dissolvido, em diferentes pHs de modo que se tivesse em solução as espécies H2Saq e HSaq. Os eletrólitos usados foram: tampão acetato e fosfato, na presença e ausência de 3,5% de NaCl em uma solução contendo 10, 25, 50, 100, 200, 500, 1000 e 2000 ppm de Na2S. A corrosão do aço foi estudada por meio de espectroscopia de impedância eletroquímica (EIE), curvas de polarização (CP), medidas de potencial de circuito aberto (Eca) e microscopia óptica in situ. Outros experimentos foram realizados buscando entender o processo de corrosão do aço em meio de sulfeto. Assim, a influência dos 4 fatores (espécie de sulfeto, concentração, presença de cloreto e tipo de aço) foi avaliada pela interpretação das interações e efeitos principais dentro de experimentos usando planejamento fatorial. A caracterização dos filmes foi realizada por espectroscopia de impedância eletroquímica in situ e por técnicas ex situ, como difração de raios X (DRX), microscopia eletrônica de varredura (MEV) e espectroscopia de energia dispersiva (EDS). As medidas EIE apresentaram duas regiões distintas, em alta e baixa frequências e a interpretação dos resultados envolveu uma combinação de parâmetros de circuitos equivalentes relacionados à difusão de espécies através do filme, resistências à transferência de carga, capacitâncias e elementos de fase constante (CPE). Esses elementos foram utilizados procurando descrever o mecanismo de corrosão do ferro na presença das diferentes espécies de sulfeto. A influência da concentração de H2S e o efeito do tempo de imersão da amostra de aço no meio corrosivo foi investigado. Na presença do H2S os valores Rct apresentam um aumento inicial e depois diminuem com tempo de imersão. Conclui-se que há a formação de uma película protetora que atinge uma espessura máxima em 3 h e esta camada então se dissolve e volta a crescer novamente, até atingir um valor de equilíbrio com o tempo de imersão de 10 h. Valores elevados de capacitância foram obtidos para filmes porosos e que apresentaram um grande número de defeitos levando a um aumento da corrosão. Pelo planejamento fatorial concluiu-se que a espécie de sulfeto é o fator mais relevante para o processo de corrosão, seguido da concentração e da presença de cloreto no meio. Na presença de H2S ocorre a dissolução ativa do ferro e na presença de HS- pode haver a formação de um filme protetor. Pelas imagens de microscopia óptica in situ, realizadas durante as medidas eletroquímicas, pode-se observar a dissolução da ferrita na região da perlita e a formação dos filmes de sulfeto de ferro com diferentes cores. A análise morfológica e classificação dos tipos de corrosão de superfície, realizadas por processamento digital das imagens, mostraram que ocorre a corrosão intergranular e por pites e que a formação do filme ocorre inicialmente sobre uma das fases do aço carbono, os grãos perlíticos.

O objetivo deste trabalho é analisar e comparar o comportamento quanto à resistência à corrosão, permeabilidade de hidrogênio e sua relação com a susceptibilidade ao trincamento induzido por hidrogênio de aços ARBL, em ambientes contendo H2S, enfatizando a influência da microestrutura. Foram realizados tratamentos térmicos de normalização e têmpera (em água) de dois tipos de tubos API 5L X65 para aplicação sour service, obtendo-se três condições com diferentes microestruturas para cada tubo. Assim, as duas amostras tais como recebidas apresentavam microestruturas de: ferrita/perlita e, o outro, ferrita/ferrita acicular; após tratamento de normalização os dois tipos de amostras apresentaram microestrutura de ferrita/perlita; e, por último, os aços que passaram por têmpera constituíram-se de martensita. O eletrólito empregado foi a solução A (ácido acético contendo cloreto de sódio) da norma NACE TM0284-2011, saturado com H2S. Os materiais foram submetidos a: ensaios de polarização linear para determinação da Resistência de Polarização (Rp), ensaios de permeabilidade de hidrogênio - baseado na ASTM G148-2003 - e ensaios de resistência ao trincamento induzido por hidrogênio (HIC) segundo a norma NACE TM0284-2011; exames em microscópio óptico e eletrônico de varredura para caracterização microestrutural, da morfologia da corrosão e do trincamento. Após os ensaios de polarização linear, foi observada uma diferença pequena dos valores de Rp entre as diferentes amostras estudadas, entre 120 ?.cm2 e 210 ?.cm2; dentro desta faixa, as microestruturas de martensita (aços temperados) apresentaram a menor resistência à corrosão. Foi realizado o tratamento dos dados obtidos por polarização linear com a metodologia desenvolvida por Mansfeld (1973) para cálculo da taxa de corrosão, observando mudanças nos declives de Tafel evidenciando a formação de produtos de corrosão. Apesar da formação destes produtos a taxa de corrosão não foi afetada, já que estes produtos são dissolvidos na solução A, oferecendo uma baixa proteção contra à corrosão. Nos ensaios de permeabilidade de hidrogênio foi utilizada uma célula modificada tipo Devanathan-Stachurski, com a solução A, com injeção de H2S no lado de geração de hidrogênio e 0,2M NaOH no lado de detecção. Foi realizado o tratamento dos dados com o método tlag, calculando a difusividade aparente, concentração de hidrogênio no metal e quantidade de sítios de ancoramento de hidrogênio. Também foi utilizado um método de ajuste da curva experimental com a equação obtida a partir da segunda lei de Fick para calcular a difusividade aparente. Foram comparados os valores obtidos com os dois métodos, obtendo-se resultados similares de difusividade aparente. As amostras temperadas foram as que apresentaram menor difusividade aparente, maior concentração de hidrogênio e maior número de sítios de ancoramento. Após o ensaio de resistência ao trincamento induzido por hidrogênio os exames em microscópio óptico mostraram que as amostras de tubos API 5L X65 como recebidas e normalizadas não apresentaram trincamento, já as amostras que passaram por tratamento de têmpera apresentaram trincas. A realização dos ensaios e tratamento dos dados permitiram observar a relação entre a quantidade de interface e a taxa de corrosão: assim a microestrutura martensítica apresenta a maior taxa de corrosão devido a maior quantidade de interfaces. A difusividade de hidrogênio também é afetada por esta mesma microestrutura, por ter maior quantidade de interface e maior número de discordâncias, apresentando menor difusividade aparente, maior concentração de hidrogênio e maior quantidade de sítios de ancoramento, tem-se que a microestrutura de martensita apresenta maior susceptibilidade ao trincamento induzido por hidrogênio. A nucleação e propagação das trincas nesta microestrutura depende de vários mecanismos que atuam simultaneamente: (i) nucleação das microtrincas, (ii) formação de H2 nas microcavidades com aumento da pressão local e (iii) migração de átomos de hidrogênio até a ponta da trinca diminuindo a força coesiva do reticulado facilitando a propagação. No entanto, esta relação entre microestrutura e HIC não pode ser generalizada, pois a susceptibilidade ao trincamento depende tanto da quantidade de sítios de ancoramento, como de sua energia de ligação, localização microestrutural e tamanho destes sítios. Outro fator importante é a presença de regiões de pouca ductilidade onde as trincas nucleadas tenham maior facilidade para sua propagação. Este trabalho contribuiu para o melhor entendimento dos mecanismos que levam à fragilização e danos provocados pelo hidrogênio, mostrando a relação entre microestrutura, corrosão, difusão e trincamento. Permitiu ampliar o conhecimento sobre os testes utilizados para avaliar o desempenho de aços microligados para aplicações em ambientes severos. / Pipelines produced from High Strength Low Alloy steels (HSLA) are a safe and cheap way to transport large quantities of petroleum and gas. HSLA steels offers mechanical and economic advantages. When HSLA steels are exposed to environments containing hydrogen sulphide (H2S), the steel can corrode and generate atomic hydrogen in the surface wich can diffuse and trapped, leading loss of mechanical properties and subsequent failures. The infrastructure to transport oil and gas represent a high cost investment, in adittion, they must be free from degradation processes that can causes severe health and environmental impacts. For this reason, the development of materials with high performance in aggressive environments is required. The aim of this study is to analyze and compare the corrosion behavior, hydrogen permeability and its relation with the susceptibility to Hydrogen Induced Cracking (HIC) of HSLA steels in environments containing H2S, with emphasis on the influence of microstructure. Normalizing and quenching heat treatments were applied in two different API 5L X65 pipelines for sour service. Three conditions were obtained (as received, normalized and quenched). The as received has a microstructure of ferrite / pearlite and ferrite / acicular ferrite, respectively; the microstructure of normalized specimens consist of ferrite / pearlite and finally quenched steels presented a microstructure of martensite. Solution A (acetic acid containing sodium chloride), according to NACE TM0284-2011 standard and saturated with H2S was used. The materials were tested by linear polarization technique, hydrogen permeability and Hydrogen Induced Cracking test (HIC). HIC tests were performed according to NACE TM0284-2011 standard. Optical microscope and scanning electron microscope were used for microstructural, corrosion and cracking characterization. Rp values show a slight difference between the different samples studied (120 ?.cm2 e 210 ?.cm2); the martensite microstructure (quenched) showed the lower corrosion resistance. Mansfeld (1973) method was used to calculate the corrosion rates from polarization curves. The Tafel slopes are differents between samples making evident the formation of corrosion products. Despite the growth of those corrosion products, the corrosion rate was not affected, since these products are dissolved in the solution A, providing a low corrosion protection. A modified Devanathan-Stachurski cell was used for the hydrogen permeability tests. It was used the solution A, with injection of H2S in the charging cell, and 0.1M NaOH solution on the oxidation cell. The hydrogen effective diffusivity, sub-surface concentration of atomic hydrogen at the charging side and number of hydrogen-trap sites were calculate by tlag method. Moreover, the experimental data were fitted using an equation derived from Fick\'s second law, in order to determinate the diffusion coefficient. The diffusion coefficient obtained from both methods were compare showing similar results. The quenching samples showed the lower diffusion coefficient, higher hydrogen concentration and number of trap sites. The steels in the as received and normalized conditins did not show cracks in Hydrogen Induced Cracking test; in the other hand, quenched samples presents cracks. The results shoed the relationship between the amount of interface and the corrosion rate. Being the martensitic microstructure the one with the higher corrosion rate. The diffusion coefficient in the martensitic microstructure, is a result of the high amount of interfaces and high dislocation density, leading to a lower diffusion coefficient, higher hydrogen concentration and number of trap sites. In the Hydrogen induced Cracking test the martensitic microstructure has shown the lower resistance to crack. The nucleation and propagation of the cracks in martensite depend of mechanisms that may act simultaneously: (i) nucleation of micro-cracks in preferential sites, (ii) formation of H2 in micro-cavities, with increase the local pressure, and (iii) hydrogen migration to the tip of the crack, decreasing the cohesive force in the lattice. However, the relationship between microstructure and Hydrogen Induced Cracking can not be generalized, since the susceptibility to cracking depends of several factors, like number of trap sites, binding trap energy, microstructural distribution and trap sizes. In addition, the presence of regions of low ductility can result in easy cracks nucleation and propagation. This thesis contributed to the understanding of the mechanisms that lead to hydrogen embrittlement and hydrogen damage, showing the relationship between microstructure, corrosion rate, diffusion and cracking, I ncreasing the scientific knowledge about the standard tests actually used to evaluate the performance of microalloyed steels in sour environments.

Le soufre est présent dans les systèmes pétroliers à la fois sous forme organique et minérale. Il est impliqué dans de nombreuses réactions d'oxydoréduction qui affectent la qualité des huiles (par des réactions de sulfuration ou de désulfuration) et du gaz naturel (par la génération de H2S en contexte de réduction thermochimique des sulfates), ainsi que la porosité des roches réservoirs (par la dissolution de l'anhydrite ou la précipitation de soufre élémentaire ou de pyrobitume). Ces réactions sont gouvernées par la température (et dans une moindre mesure la pression), les conditions d'oxydoréduction et la composition chimique globale du système. La thèse comporte trois parties : (1) une étude thermodynamique des réactions chimiques impliquant le soufre dans les bassins sédimentaires ; (2) une étude expérimentale des réactions de sulfuration et de désulfuration des composés organiques ainsi que de la réduction thermochimique des sulfates; (3) une étude pétrographique et d'inclusions fluides sur des échantillons d'un réservoir carbonaté du bassin Pré-Caspien / Sulfur occurs in petroleum systems as both organic compounds and minerals as well as under different oxidation states. It is involved in a number of redox reactions which may impact the quality of crude oils (through sulfurization or desulfurization reactions) and natural gas (through the generation of H2S during thermochemical sulfate reduction), as well as the petrophysical properties of reservoir rocks (through the dissolution of anhydrite and the precipitation of elemental sulfur and pyrobitumen). These reactions are controlled by temperature (and to a lesser extent pressure), the redox conditions, and the overall chemical composition of the system representing the petroleum reservoir. The thesis consists of three parts: (1) a thermodynamic study of chemical reactions involving sulfur which occur in sedimentary basins; (2) an experimental simulation of sulfurization and desulfurization reactions of organic compounds, as well as of thermochemical sulfate reduction; and (3) a petrographic and fluid inclusion study of carbonate rock samples from a sulfur-rich hydrocarbon reservoir of the northern Caspian Sea

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