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Previous issue date: 2010-03-06 / Corrosion usually occurs in pipelines, so that it is necessary to develop new surface treatments to control it. Surfactants have played an outstanding role in this field due to its capacity of adsorbing on metal surfaces, resulting in interfaces with structures that protect the metal at low surfactant concentrations. The appearance of new surfactants is a contribution to the area, as they increase the possibility of corrosion control at specific conditions that a particular oil
field presents. The aim of this work is to synthesize the surfactants sodium 12 hydroxyocadecenoate (SAR), sodium 9,10-epoxy-12 hydroxyocadecanoate (SEAR), and sodium
9,10:12,13-diepoxy-octadecanoate (SEAL) and apply them as corrosion inhibitors, studying their action in environments with different salinities and at different temperatures. The conditions used in this work were chosen in order to reproduce oil field reality. The study of the micellization of these surfactants in the liquid-gas interface was carried out using surface tensiometry. It was observed that cmc increased as salt concentration was increased, and temperature and pH were decreased, while cmc decreased with the addition of two epoxy groups in the molecule. Using the values of cmc and the Gibbs equation, the values of Gibbs free energy of adsorption, area per adsorbed molecule, and surface excess were calculated. The surface excess increases as salt concentration and temperature decreases, increasing as pH is increased. The area per adsorbed
molecule and the free energy of adsorption decrease with salt concentration, temperature, and pH increase. SAXS results showed that the addition of epoxy group in surfactant structure results in a decrease in the repulsion between the micelles, favoring the formation of more oblong micellar structures, ensuring a better efficiency of metal coverage. The increase in salt and surfactant concentrations provides an increase in micellar diameter. It was shown that the increase in temperature does not influence micellar structure, indicating thermal stability that is advantageous for use as corrosion inhibitor. The results of inhibition efficiency for the surfactants SEAR and SEAL were considered the best ones. Above cmc, adsorption occurred by the migration of micelles from the bulk of the solution to the metal surface, while at concentrations below cmc film formation must be due to the adsorption of semi-micellar and monomeric structures, certainly due to the presence of the epoxy group, which allows side interactions of the molecule with the metal surface. The metal resistance to corrosion presented values of 90% of efficiency. The application of Langmuir and Frumkin isotherms showed that the later gives a better description of adsorption because the model takes into account side interactions from the adsorbing molecules. Wettability results showed that micelle formation on the solid surface
occurs at concentrations in the magnitude of 10-3 M, which isthe value found in the cmc study. This value also justifies the maximum efficiencies obtained for the measurements of corrosion
resistance at this concentration. The values of contact angle as a function of time suggest that adsorption increases with time, due to the formation of micellar structures on metal surface / O fen?meno da corros?o est? presente em oleodutos e por isso existe a necessidade de desenvolver novos materiais que controle tal fen?meno. Os tensoativos t?m se destacado para tal
fim devido ao seu poder de adsorver-se em interfaces e formar estruturas que protejam o metal em baixas concentra??es. O surgimento de novos tensoativos ? uma contribui??o para o setor, pois aumentam as possibilidades de controlar a corros?o nas condi??es espec?ficas de cada campo. Este trabalho objetiva, principalmente, sintetizar e aplicar os tensoativos 12
hidroxioctadecenoato de s?dio (SAR), 9,10-ep?xi-12 idroxioctadecanoato de s?dio (SEAR) e 9,10:12,13-diep?xi-octadecanoato de s?dio (SEAL) como inibidores de corros?o, estudando-os em ambientes que apresentam, simultaneamente, salinidade, acidez e temperatura variadas. As condi??es estudadas s?o para reproduzir o m?ximo poss?vel ? realidade do campo. O estudo da miceliza??o destes tensoativos na interface l?quido-g?s foi realizado a partir de medidas de tens?o superficial. Observou-se que a eleva??o da concentra??o salina, abaixamento da temperatura e diminui??o do pH proporcionam aumento nos valores da cmc, com tamb?m os valores da cmc
aumentam quando se adiciona um e dois grupos ep?xi na mol?cula, respectivamente. A partir da cmc, usando equa??o de Gibbs, foram encontrados valores para a energia livre de Gibbs de
adsor??o, ?rea por mol?cula adsorvida e excesso superficial. O aumento dos valores de excesso superficial ? provocado pela diminui??o da concentra??o salina e temperatura, e aumenta com a eleva??o do pH. A ?rea por mol?cula adsorvida e a energia livre de adsor??o diminuem com aumento da salinidade e temperatura, e com o aumento do pH. Os resultados de SAXS mostraram que a adi??o do grupo ep?xi e o seu aumento na estrutura do tensoativo proporcionam diminui??o na intera??o de repuls?o entre as micelas, assim como favorecem a forma??o de estruturas micelares mais alongadas, garantindo maior efici?ncia na cobertura do metal. O aumento da concentra??o salina e da concentra??o do tensoativo proporciona aumento do di?metro da micela. O aumento da temperatura mostrou que n?o influencia a estrutura micelar, o que indica estabilidade t?rmica, sendo vantajoso para sua atua??o como inibidor de corros?o. Os resultados de efici?ncia para os tensoativos SEAR e SEAL foram os melhores. A cima da cmc a adsor??o se deve a migra??o da micela do seio da solu??o para a superf?cie do metal, enquanto em concentra??es abaixo da cmc a forma??o do filme se deve a adsor??o de estruturas semimicelares e monom?ricas, nas quais s?o caracter?sticas dos tensoativos que apresentam o grupo
ep?xi, pois possibilita intera??o lateral da mol?cula com a superf?cie met?lica. A resist?ncia do metal ? corros?o apresentou valores de 90% de efici?ncia. A aplica??o das isotermas de
Langmuir e Frumkin mostrou que esta ?ltima melhor valida o fen?meno da adsor??o, devido haver em sua express?o matem?tica o par?metro de intera??o lateral. Os resultados de
molhabilidade mostraram que a forma??o da micela na superf?cie do s?lido se d? em concentra??es na ordem de 10-3 M, valor encontrado no estudo da cmc. Este valor justifica, tamb?m, os valores m?ximos de efici?ncia obtidos para as medidas de resist?ncia a corros?o a partir desta concentra??o. Os valores de ?ngulo de contato em fun??o do tempo sugerem que a adsor??o aumenta com o tempo, devido a forma??o de estruturas micelares na superf?cie do metal
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17721 |
| Date | 06 March 2010 |
| Creators | Wanderley Neto, Alcides de Oliveira |
| Contributors | CPF:07286937391, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4783139Z0&dataRevisao=null, Moura, Everlane Ferreira, CPF:28929136320, http://lattes.cnpq.br/5157139686256561, Huitle, Carlos Alberto Martinez, CPF:01139059980, http://lattes.cnpq.br/2485073932883264, Santanna, Vanessa Cristina, CPF:77938780430, http://lattes.cnpq.br/9445575768909084, Gurgel, Alexandre, CPF:59721421472, http://lattes.cnpq.br/5266735277153768, Dantas, Tereza Neuma de Castro |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Qu?mica, UFRN, BR, F?sico-Qu?mica; Qu?mica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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