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L’objectif de ce travail de thèse a été d’évaluer les propriétés inhibitrices de corrosion d’un traitement multifonctionnel utilisé dans l’industrie pétrolière. Dans la première partie de la thèse, l’influence des conditions hydrodynamiques, du temps d’immersion et de la température sur les processus de corrosion de l’acier API 5L-X65 en milieu CO2 en l’absence d’inhibiteur a été étudiée par des mesures électrochimiques (courbes de polarisation, courbes de Levich et spectroscopie d’impédance électrochimique) avec une électrode à disque tournant. A partir de ces essais, la vitesse de corrosion a été calculée pour les différentes conditions expérimentales. L’analyse couplée des résultats électrochimiques et des analyses de surface suggèrent la formation d’une couche de produits de corrosion, principalement de carbonate de fer qui recouvre la surface du métal et conduit à la diminution de la vitesse de corrosion quand le temps d’immersion, la vitesse de rotation et la température augmentent. La deuxième partie de la thèse a été consacrée à l’évaluation d’un traitement multifonctionnel contre la corrosion. Ce traitement est composé principalement de produits extraits de l’Aloe Vera (gel de l’Aloe Vera et « acibar »). Ces produits ont été choisis car ils empêchent la formation simultanée d’hydrates et de carbonate de calcium. Ces composés « verts », ainsi que la dodécylamine, qui est un inhibiteur de corrosion commercial, ont été testés à l’aide des mesures électrochimiques et par perte de masse afin de comparer leur efficacité et d’évaluer un possible effet de synergie lorsqu’ils sont utilisés en mélange. Les produits testés séparément ont un pouvoir protecteur comparable et il n’a pas été mis en évidence d’effet de synergie. En revanche, il a été montré que les composés sont compatibles entre eux. Ceci constitue un point très important pour l’utilisation de ces traitements qui permettent d’augmenter la fiabilité et la rentabilité pour la production du pétrole et du gaz. / The objective of this work was to evaluate the corrosion inhibitive properties of a multifunctional treatment used in the petroleum industry. In the first part of the thesis, the influence of hydrodynamic conditions, immersion time and temperature on the corrosion process of API 5L-X65 steel in CO2 medium in absence of inhibitor was studied by electrochemical measurements (polarization curves, Levich curves and electrochemical impedance spectroscopy) with a rotating disk electrode. From these tests, the corrosion rate was calculated for different experimental conditions. The analysis of the electrochemical results and surface analyses suggest the formation of a layer of corrosion products, mainly iron carbonate which covers the metal surface and leads to the decrease of the corrosion rate when the immersion time, the rotation speed and temperature increase. The second part of this work was devoted to the evaluation of a multifunctional treatment against corrosion. The treatment is mainly composed Aloe Vera extracts (Aloe Vera gel and "acibar”). These products were chosen because they prevent the simultaneous formation of hydrates and calcium carbonate. These "green" compounds and dodecylamine, which is a commercial corrosion inhibitor, were tested using electrochemical measurements and by mass loss in order to compare their efficiency and to evaluate a possible synergistic effect when they are used as a mixture. The products tested separately have a similar efficiency and did not reveal any synergistic effect. However, it was shown that the compounds are compatible. This is an important point for the use of these treatments which can increase the reliability and profitability for the production of oil and gas.

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[pt] Neste trabalho foi estudada a formação de camadas de produtos de corrosão em dois aços, o API 5L X80 usado para transporte de óleo e gás e o API 5CT utilizado em poço de petróleo case tubing. Foram utilizadas as técnicas de perda de massa e técnicas eletroquímicas tais como resistência a polarização linear RPL, curvas tafel e espectroscopia de impedância eletroquímica EIS foram empregadas para determinar as taxas de corrosão. Os ensaios foram realizados em condições estáticas numa solução de salmoura 3 porcento wt de NaCl sob 55 bar de pressão parcial de CO2 e total de 75bar, tempos de exposição de 7, 15, 21 e 30 dias e temperaturas de 25 Graus Celsius, 50 Graus Celsius e 75 Graus Celsius. Microscopia eletrônica de varredura MEV foi usada para a análise da morfologia. DRX e EDS foram utilizadas para determinar a composição química. As camadas formadas foram avaliadas em função da espessura, morfologia e composição química. Encontrou-se que a 25 Graus Celsius só houve formação de camada de carbonato de ferro após 30 dias de imersão para ambos os aços e que para 50 Graus Celsius e 75 Graus Celsius houve formação de duas camadas para todos os tempos de imersão cuja composição química mostrou o carbonato de ferro FeCO3 como principal produto de corrosão para os dois aços. A condição de teste que apresentou menor taxa de corrosão e maior proteção da camada de carbonato de ferro FeCO3 foi para 75 Graus Celsius e 30 dias de tempo de imersão. Os resultados de RPL e EIS são semelhantes aos obtidos por perda de massa mantendo a mesma tendência de redução com o tempo e a temperatura. / [en] This study evaluated the CO2 corrosion layer formation on the surface of two different steels, the API 5L X80 used for oil and gas transportation and the API 5CT used in oil production (case tubing). Techniques such as weight loss and electrochemical techniques as linear polarization resistance (LPR), Tafel curves, electrochemical impedance spectroscopy (EIS) were employed to determine the corrosion rate. Tests were conducted under static conditions in a brine 3 percent wt solution of of NaCl under CO2 partial pressure of 55 bar and total of 75 bar, immersion times of 7, 15, 21 and 30 days and temperatures of 25 Celcius, 50 Celcius and 75 Celcius. Analysis of the scale morphology was carried out by Scanning Electron Microscopy (SEM), and X-ray Diffraction. (XRD) and Energy Dispersive Spectroscopy (EDS) were used to determine the chemical composition. The layers formed were evaluated as a function of its thickness, morphology and chemical composition. It was found out that at 25 Celcius only after 30 days of immersion there was iron carbonate layer formation for both steels and at 50 Celcius and 75 Celcius there was the growth of two layers for all immersion times, being the chemical composition of these layers identifyed as iron carbonate FeCO3 as the main corrosion product for the two steels. The lowest corrosion rate and most protective layer of iron carbonate FeCO3 was for the condition at 75 Celcius and 30 days of immersion. The results obtained of LPR and EIS were similar to those obtained by mass loss showing the same tendency, reducing with time and temperature.