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Previous issue date: 2016-07-26 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O biodiesel e o diesel s?o subst?ncias org?nicas e corrosivas, que podem atacar tanques de
combust?veis met?licos, hastes de conex?o, sistemas de tubula??es, a?o de transporte e
armazenamento, dentre outros constituintes met?licos. Atualmente, metais e a?os, a exemplo
do a?o AISI 316, est?o sendo cada vez mais usados em tanques de transporte e
armazenamento de biocombust?veis. Com tais pressupostos, o objetivo do trabalho foi avaliar
e comparar a a??o corrosiva de diferentes biodieseis sobre o a?o AISI 316. A metodologia
consistiu na an?lise fisico-qu?mica dos ?leos de soja, girassol e mamona, posteriormente os
biodeiseis foram sintetizados atrav?s da rea??o de transesterifica??o pelas rotas met?lica e
et?lica, fazendo uso do KOH como catalisador. Os biocombust?veis foram caracterizados
seguindo as normas American Society of Testing Materials (ASTM) e por Espectroscopia de
Infravermelho por Transformada de Fourier (FTIR). Avaliou-se tamb?m o B7 dispon?vel
comercialmente. As estabilidades t?rmicas foram avaliadas via Termogravimetria (TG, DTG
e DTA) e Calorimetria Explorat?ria Diferencial Din?mica (DSC). O ensaio de corros?o
consistiu em teste de imers?o do a?o em estudo, em diferentes horas. Foram utilizadas as
medidas de Polariza??o Potenciodin?mica Linear (PPL) e Espectroscopia de Imped?ncia
Eletroqu?mica (EIE), para a avalia??o eletroqu?mica de corros?o. Posteriormente, o a?o foi
analisado atrav?s de Microscopia Eletr?nica de Varredura (MEV), acoplado ao Espectr?metro
de Energia Dispersiva de Raios X (EDS), e foi realizado an?lise qu?mica via Fluoresc?ncia de
Raio X (FRX). Os resultados comprovaram que os biodieseis est?o conforme as normas
espec?ficas da Ag?ncia Nacional do Petr?leo, G?s Natural e Biocombust?veis (ANP). Os
conjuntos das t?cnicas indicaram que houve perda de massa e a an?lise da superf?cie
evidenciou corros?o localizada por pitting. Com as curvas de polariza??o e imped?ncia
eletroqu?mica, observou-se que todos os biocombust?veis s?o agentes corrosivos, portanto,
redutores. O B7 ? o flu?do que mais corr?i os corpos de prova, fazendo uma nuclea??o de
?xido, formando a passiva??o met?lica ap?s serem atacados pelo biocombust?vel. Por meio do
FRX, observou-se que os biocombust?veis foram contaminados por metais de transi??o,
quando expostos ao a?o, catalisando rea??es de degrada??o dos biocombust?veis formando
hidroper?xidos, o que se confirmou pelas mudan?as nas vibra??es dos espectros do FTIR. O
tratamento estat?stico comprovou que o modelo ? aceit?vel e confi?vel, pois a an?lise de
ru?dos est? pr?xima ? linha padr?o. O Modelo de Superf?cie de Resposta (MSR) indicou que o
tempo de imers?o ? o fator que mais influencia na taxa de corros?o nos biodieseis sintetizados
pela rota met?lica, enquanto o ?ndice de acidez ? o que mais influencia nos ?steres et?licos. / Biodiesel and diesel are organic and corrosive substances that can attack metal fuel tanks,
connecting rods, piping systems, transportation and storage of steel, among other metallic
constituents. Currently, metal and steel, such as the AISI 316 steel, are being increasingly
used in tanks for transport and storage of biofuels. With such assumptions, the study aimed to
evaluate and compare the corrosive action of different biodiesels on steel AISI 316. The
methodology consisted of physic-chemical analysis of soybean oil, sunflower oil and castor
oil. The biodiesels were synthesized by the transesterification reaction by the methyl and ethyl
routes, making use of NaOH as catalyst. Biofuels were characterized following the guidelines
of the American Society of Testing Materials (ASTM), Fourier Transform Infrared
Spectrometry (FTIR). Also it evaluated B7 commercially available. The thermal stabilities
were evaluated by Termogravimetric Analysis (TG, DTG and DTA) and Differential
Scanning Calorimetry Dynamics (DSC). The corrosion test consisted of immersing the steel
under biofuel sat different times. It were used Linear Potentiodynamic Polarization (PPL)
measurements and Electrochemical Impedance Spectroscopy (EIS) for the electrochemical
evaluation of corrosion. Subsequently, the steel was analyzed by Scanning Electron
Microscopy (SEM) coupled with Energy Dispersive X-Ray Spectrometer (EDS), and was
carried out chemical analysis via X-Ray Fluorescence (XRF). Findings showed that biodiesels
were like stated by National Agency of Petroleum (NAP) standards. The sets of the
techniques indicated a weight loss, and surface analysis evidenced general pitting corrosion.
With the polarization curves and electrochemical impedance spectroscopy, it was observed
that all biofuels are corrosive agents, therefore, reducers. The B7 is the fluid that corrodes
more the samples, which by having a nucleation of oxide form the metal passivation after
being attacked by biofuels. By XRF, it was observed that biofuels have been contaminated
with transition metals when exposed to the steel, causing the formation of free radicals that
induce autoxidation, forming hydroperoxides, which was confirmed by changes in vibrations
of FTIR spectra. Statistical analysis indicated that the model is acceptable and reliable,
because the noise analysis is close to the standard range. The Response Surface Methodology
(RSM) indicated that the immersion time is the factor that most influences the corrosion rate
in biodiesels synthesized by methyl route, while the acid value is what most influences in
ethyl esters.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21872 |
| Date | 26 July 2016 |
| Creators | Dutra-Pereira, Franklin Kaic |
| Contributors | 02046752945, Barros, Joana Maria de Farias, 85239658404, Silva, Paulo S?rgio Gomes da, 31628419334, Bicudo, Tatiana de Campos, 25935096862, Alves, Salete Martins |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM ENGENHARIA MEC?NICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| 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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