Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-08-29T19:26:49Z No. of bitstreams: 1 2017 - Cristiane Frauches dos Santos.pdf: 7660831 bytes, checksum: d9f6418f111957d4be1789ee9411cc8f (MD5) / Made available in DSpace on 2018-08-29T19:26:49Z (GMT). No. of bitstreams: 1 2017 - Cristiane Frauches dos Santos.pdf: 7660831 bytes, checksum: d9f6418f111957d4be1789ee9411cc8f (MD5) Previous issue date: 2017-09-25 / CAPES / CNPq / FAPERJ / Petrobr?s / Corrosion is one of the serious problems faced in industrial processes, generating enormous financial losses. Several techniques are used to prevent or remedy corrosion in the different materials it affects. Among them, the use of organic or inorganic inhibitors has been widely used. Thus, in this thesis were synthesized 34 heterocyclic compounds, 18 chlorides of 1,3,4-thiadiazolium-2-phenylamines, (11 unpublished), and the other 16 compounds belonging to the class of mesoionic 1,3,4-triazolium -2-thiolate, (15 unpublished), with the objective of evaluating its efficiency as inhibitors of corrosion in acidic corrosion. Derivatives of the class 1,3,4-thiadiazolium-2-phenylamines were obtained with satisfactory purity and yields in the range of 42-96% and, in the class of 1,3,4-triazolium-2-thiolates in 20 -97%. All compounds were characterized by IR, 1H and 13C NMR spectroscopies. The theoretical study was conducted using the SPARTAN-PRO program in the semi-empirical method with the Hamiltonian AM1, to determine its structural and electronic properties of 1,3,4-thiadiazolium-2-phenylamines that could contribute to the efficiency of inhibition of corrosion. The compounds of 1,3,4-thiadiazolium-2-phenylamine class were tested against corrosion of AISI 1020 carbon steel in 0.5 mol L-1HCl and in 0.5 mol L-1 H2SO4. For this evaluation, the electrochemical techniques of Potenciodynamic Polarization (PP), Resistance to Linear Polarization (RPL) and Electrochemical Impedance Spectroscopy (EIS) were used. The results showed significant percentages of corrosion inhibition in both acidic solutions, reaching the rate of up to 95% efficiency for the compound 4-phenyl-5-(3'-methoxy-phenyl)-1,3,4-thiadiazolium-2-phenylamine chloride in the concentration of 3.5x10-4 mol L-1 for the HCl solution, and 99% efficiency for the 2'-chloro and 2'-fluorosubstituted compounds in the concentration of3.5x10-4 mol L-1 for the H2SO4 solution. In addition to the electrochemical techniques, the gravimetric technique was used, which presented 99% of anticorrosive efficiency for the 2'-trifluoromethyl-substituted 1,3,4-thiadiazolium-2-phenylamine derivative, showed the best inhibitory effect in HCl solution. However, the 2'-trifluoromethyl-substituted 1,3,4-triazolium-2-thiol derivative showed less corrosion efficiency than its corresponding isomer. The methodologies used to evaluate the corrosion activity (PP, RPL and EIE), including the theoretical evaluation by molecular modeling, indicated the mesoionic chloridrates as efficient mixed corrosion inhibitors. / S?ntese e avalia??o da atividade anticorrosiva de cloretos de 1,3,4-tiadiaz?lio-2-fenilaminas e 1,3,4-triaz?lio-2-tiolatos em meio ?cido. 2017. 251p Tese (Doutorado em Qu?mica, Ci?ncia exatas, s?ntese org?nica). Departamento de qu?mica, Universidade Federal Rural do Rio de Janeiro, Serop?dica, RJ, 2017. A corros?o ? um dos s?rios problemas enfrentados nos processos industriais, gerando enormes preju?zos financeiros. Diversas t?cnicas s?o utilizadas para evitar ou remediar a corros?o nos diferentes materiais que ela afeta. Dentre elas o uso de agentes inibidores org?nicos ou inorg?nicos tem sido muito utilizado. Assim, neste trabalho de tese foram sintetizados 34 compostos heteroc?clicos, sendo 18 cloretos de 1,3,4-tiadiaz?lio-2-fenilaminas (11 in?ditos) e os outros 16 compostos pertencentes ? classe dos mesoi?nicos 1,3,4-triaz?lio-2-tiolato (15 in?ditos), com o objetivo de avaliar sua efici?ncia como inibidores de corros?o em meio ?cido. Os derivados sintetizados da classe 1,3,4-tiadiaz?lio-2-fenilaminas foram obtidos com grau de pureza e rendimentos satisfat?rios na faixa de 42-96% e, da classe dos 1,3,4-triaz?lio-2-tiolatos em 20-97%. Todos os compostos foram caracterizados por espectroscopia de IV, RMN de 1H e13C. Foi realizado o estudo de modelagem molecular, utilizando o programa SPARTAN-PRO com o m?todo semi-emp?rico, hamiltoniano AM1, para determina??o das propriedades estruturais e eletr?nicas dos 1,3,4-tiadiaz?lio-2-fenilaminas que pudessem contribuir para a efici?ncia de inibi??o da corros?o. Os cloridratos mesoi?nicos da classe 1,3,4-tiadiaz?lio-2-fenilaminas foram testados frente ? corros?o de a?o carbono AISI 1020 em solu??o de HCl 0,5 mol L-1 e em H2SO4 0,5 mol L-1. Para tal avalia??o foram utilizadas as t?cnicas eletroqu?micas de Polariza??o potenciodin?mica (PP), Resist?ncia ? polariza??o linear (RPL) e Espectroscopia de imped?ncia eletroqu?mica (EIE). Os resultados mostraram percentuais significativos de inibi??o da corros?o em ambas solu??es ?cidas, alcan?ando o ?ndice de at? 95% de efici?ncia para o composto cloreto de 4-fenil-5-(3?-met?xi-fenil)-1,3,4-tiadiaz?lio-2-fenilamina na concentra??o de 3,5x10-4 mol L-1 para a solu??o de HCl e, 99% de efici?ncia para os compostos 2?-cloro e 2?-fluor-substitu?dos na concentra??o de 3,5x10-4 mol L-1 para a solu??o de H2SO4. Al?m das t?cnicas eletroqu?micas, foi utilizada a t?cnica gravim?trica que apresentou 99% de efici?ncia anticorrosiva para o derivado 2?-trifluormetil-substitu?do da classe 1,3,4-tiadiaz?lio-2-fenilamina que mostrou o melhor efeito inibidor em solu??o HCl. No entanto, o derivado 2?-trifluormetil-substitu?do da classe 1,3,4-triaz?lio-2-tiol apresentou menor efici?ncia anticorrosiva do que seu is?mero correspondente. As metodologias utilizadas para avalia??o da atividade anticorrosiva (PP, RPL e EIE), incluindo a avalia??o te?rica por modelagem molecular, indicaram os cloridratos mesoi?nicos como eficientes inibidores de corros?o mistos.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-11-09T17:58:22Z No. of bitstreams: 1 2017 - Mariana de Albuquerque Almeida.pdf: 2619920 bytes, checksum: 48c00262629bac9a7779fc4ea9ec94a6 (MD5) / Made available in DSpace on 2017-11-09T17:58:22Z (GMT). No. of bitstreams: 1 2017 - Mariana de Albuquerque Almeida.pdf: 2619920 bytes, checksum: 48c00262629bac9a7779fc4ea9ec94a6 (MD5) Previous issue date: 2017-05-10 / CAPES / This dissertation presents the evaluation of four thiosemicarbazones, from extracts of species of vegetables Talinum triangulare, Physalis angulata e Theobroma cacao L. besides formulation obtained from the combination extract of thiosemicarbazones vegetables as corrosion inhibitor in the presence of carbon steel AISI 1020. Thiosemicarbazones were obtained with good level of purity, satisfactory throughput and identified by NMR of 1H and 13C. The watery extract of Talinum triangulare was obtained using ultrasound device. The extracts of Physalis angulata species were obtained by maceration in water and the other one in ethyl acetate. The watery extracts of Theobroma cacao L. species were obtained using ultrasound device and decoction and hydroalcoholic extract was obtained by maceration in ethanol:water (80:20). The thiosemicarbazones, the vegetable extracts and their formulation were tested in the presence of corrosion of carbon steel AISI 1020 in solution 1 mol. L-1 of HCl. For this evaluation it was used the gravimetric techinique of weight loss and electrochemical techiniques of potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that the presence of thiosemicarbazones, as well as, the formulation increased significantly the resistence of carbon steel AISI 1020 in acidic medium. The results obtained in different used essays (weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy) show that these techniques are complementary in relation to the evaluation of corrosion inhibition. The best anti-corrosion efficiency was observed for thiosemicarbazone chloro and hydroxy-substituted and its formulations with the extract of T. triangulare achieving 88% and 87% of efficiency, by electrochemical impedance spectroscopy, respectively. / Nesta Tese ? apresentada a avalia??o de quatro tiossemicarbazonas, dos extratos das esp?cies vegetais Talinum triangulare, Physalis angulata e Theobroma cacao L., al?m de formula??es obtidas pela combina??o extrato vegetal:tiossemicarbazonas, como inibidores de corros?o frente ao a?o carbono AISI 1020 em meio de ?cido cloridr?co. As tiossemicarbazonas foram obtidas com bom grau de pureza, em rendimentos satisfat?rios e, caracterizadas por IV, RMN de ^1H e ^13C. O extrato aquoso de Talinum triangulare foi obtido em aparelho de ultrassom, os extratos da esp?cie Physalis angulata, foram obtidos sob macera??o em ?gua e o outro em acetato de etila; j? os extratos aquosos da esp?cie Theobroma cacao L. foram obtidos em aparelho de ultrassom e decoc??o e, finalmente, o extrato hidroalco?lico foi obtido por macera??o em etanol:?gua (80:20). As tiossemicarbazonas, os extratos vegetais e suas formula??es foram testadas frente ? corros?o de a?o carbono AISI 1020 em solu??o 1mol.L-1 de HCl. Para tal avalia??o foi utilizada a t?cnica gravim?trica de Perda de Massa e as t?cnicas eletroqu?micas de Polariza??o Potenciodin?mica e Espectroscopia de Imped?ncia Eletroqu?mica. Os resultados mostraram que a presen?a de tiossemicarbazonas, bem como, das formula??es aumentam significativamente a resist?ncia do a?o carbono AISI 1020 em ?cido. Os resultados obtidos nos diferentes ensaios utilizados (Perda de Massa, Polariza??o Potenciodin?mica e Espectroscopia de Imped?ncia Eletroqu?mica) mostraram que estas t?cnicas s?o complementares quanto a avalia??o da inibi??o da corros?o. A melhor efici?ncia anticorrosiva foi observada para as tiossemicarbazonas cloro e hidroxi-substitu?das e, para suas formula??es com o extrato da T. triangulare obtendo-se 88% e 87% de efici?ncia por espectroscopia de imped?ncia eletroqu?mica, respectivamente.