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Previous issue date: 2017-04-19 / A efici?ncia de inibi??o ? corros?o de sistemas coloidais preparados a base de ?leos vegetais
provenientes das esp?cies Azadirachta indica A. Juss (SMEOAI) e Copaifera L. (SMECO) foi
avaliada via t?cnicas eletroqu?micas. Os formulados coloidais SMEOAI e SMECO foram
analisados em diferentes concentra??es (5 ppm - 150 ppm) na corros?o do a?o AISI 1018, em
meio salino (3,5% de solu??o NaCl). O extrato hidroalco?lico obtido das folhas de A. indica
(EAI) veiculado no sistema SMEOAI, forneceu o formulado SMEOAI-EAI que foi avaliado
como inibidor verde de corros?o. O sistema SMEOAI foi preparado com Tween? 80 (fase
tensoativo), ?leo isolado de A. indica (OAI, fase ?leo) e de ?gua bidestilada (fase aquosa
neutra). Este sistema veiculou, satisfatoriamente, o extrato EAI, resultando na microemuls?o
SMEOAI-EAI. Similarmente, o sistema coloidal SMECO foi preparado com Tween? 80, ?leo
de copaiba (CO) e ?gua bidestilada. Diagramas de fases tern?rios foram obtidos para SMEOAI
e SMECO, tendo sido comprovada a forma??o de microemuls?o com regi?o caracter?stica de
Winsor IV (WIV). As caracteriza??es destes sistemas foram realizadas pelas seguintes an?lises:
determina??o do ?ndice de refra??o, comportamento reol?gico, tens?o superficial e di?metro de
got?cula. O efeito de inibi??o dass microemuls?es obtidas a base de A. indica (SMEOAI e
(SMEOAI-EAI) foram analisadas pelas t?cnicas de resist?ncia a polariza??o linear (LPR) e
imped?ncia (EIS). A microemuls?o obtida a base de Copaifera (SMECO) foi avaliada via
m?todo LPR. Comparativamente, SMECO (100 ppm) apresentou a menor efici?ncia de inibi??o
? corros?o (77,15%), seguido de SMEOAI (25 ppm) com inibi??o mediana (79,28%). A
presen?a do extrato EAI no formulado SMEOAI, otimizou a efici?ncia de inibi??o, tendo sido
comprovado que o sistema SMEOAI-EAI (50 ppm) apresentou a efici?ncia m?xima (91,79%)
de inibi??o. Para estes inibidores, comprovou-se tamb?m, efeitos antioxidantes realizados em
experimentos in vitro. De forma abrangente, o efeito antioxidante mais eficaz foi observado
para a microemuls?o SMEOAI-EAI. Estes formulados coloidias foram avaliados pelas an?lises
de capacidade antioxidante total: 18,74% (SMEOAI) e 36,14% (SMEOAI-EAI); poder redutor:
56,34% (SMEOAI) e 290,49% (SMEOAI-EAI); quela??o de ?ons ferro: 58,97% (SMEOAI) e
51,29% (SMEOAI-EAI); bem como sequestro dos radicais hidroxila: 60,16% (SMEOAI) e
87,33% (SMEOAI-EAI). As diverg?ncias percentuais observadas encontram-se relacionadas
aos diferentes mecanismos antioxidativos de cada modelo, bem como pela presen?a do extrato
EAI no formulado SMEOAI. O sistema a base de ?leo de copa?ba (SNECO), apresentou
47,89% de efeito antioxidante na an?lise do poder redutor e valor mais elevado (72,92%), para
o sequestro de radicais hidroxila. Os inibidores verde de corros?o SMEOAI, SMEOAI-EAI e
SMECO s?o biodegrad?veis e em fun??o do amplo uso destes vegetais, poder?o despertar o
interesse do setor industrial com diferentes possibilidades de aplica??es, tais como: bioinseticida,
purificador de ?guas residuais, agente efluente, agente de recupera??o de petr?leo,
dentre outros. / The corrosion inhibition efficiency of colloidal systems based on vegetable oils such as
Azadirachta indica A. Juss (SMEOAI) and Copaifera L. (SMECO) were evaluated by
electrochemical techniques. The colloidal formulations SMEOAI and SMECO were analyzed
in different concentrations (5 ppm - 150 ppm) in the corrosion of AISI 1018 steel in corrosive
saline medium (3.5% NaCl solution). The hydroalcoholic extract obtained from the leaves of
A. indica (EAI) was loaded in the colloidal system SMEOAI and then applied as a green
corrosion inhibitor. The SMEOAI system was prepared by using Tween? 80 as surfactant, A.
indica oil (OAI) as the oil phase and bidistilled water (as a neutral aqueous phase). The
SMEOAI system satisfactorily loaded the EAI extract providing a derivative formulation so
called SMEOAI-EAI. Similarly, the SMECO system was prepared by using Tween? 80,
copaiba oil (CO), and bidistilled water. The formation of Winsor IV microemulsion region
(WIV) on both systems (SMEOAI and SMECO) was evidenced through the construction of the
ternary phase diagrams. The colloidal systems characterizations were performed by using the
following analyzes: determination of the refractive index, rheological behavior, surface tension
and droplet diameter. The coloidal formulations SMEOAI and SMEOAI-EAI were analyzed
by using electrochemical techniques of linear polarization resistance (LPR) and impedance
spectroscopy (EIS). Meanwhile, SMECO system was only analyzed by using the LPR method.
Comparatively, the SMECO system (100 ppm) showed the lowest corrosion inhibition
efficiency (77.15%), followed by SMEOAI (25 ppm) which showed median inhibition
(79.28%) and the maximum inhibition efficiency (91.79%) was found to the SMEOAI-EAI (50
ppm) system, justified by the presence of the EAI extract in the loading system SMEOAI. For
all of those green inhibitors systems the antioxidant effect was analyzed by using in vitro
experiments and the best result was found to SMEOAI-EAI system. For that analysis it was
applied: total antioxidant capacity, 18.74% (SMEOAI) and 36.14% (SMEOAI-EAI); reducing
power, 56.34% (SMEOAI) and 290.49% (SMEOAI-EAI); iron ion chelation, 58.97%
(SMEOAI) and 51.29% (SMEOAI-EAI); sequestration of hydroxyl radicals, 60.16%
(SMEOAI) and 87.33% (SMEOAI-EAI). The observed percentage divergences were related to
the different antioxidative mechanisms of each applied model, as well as the presence of the A.
indica extract (EAI) in the SMEOAI-EAI system. The colloidal system prepared with copaiba
oil (SNECO) showed the lower effect 47.89% in the analysis of reducing power. Meanwhile,
for this system a higher result (72.92%) was evidenced in the sequestration of hydroxyl radicals
analysis. The green corrosion inhibitors SMEOAI, SMEOAI-EAI and SMECO are
biodegradable and due to the wide use of these plants, may arouse the interest of the industrial
sector focusing some different possible applications such as: bio-insecticides, biological drug
carriers, waste water purifiers, effluents, oil recovery agents, among other applications.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/24498 |
| Date | 19 April 2017 |
| Creators | Emerenciano, Denise Porfirio |
| Contributors | 37320165449, Menezes, Fabricio Gava, 03114939988, Rocha, Hugo Alexandre de Oliveira, 76111830449, Dantas, Tereza Neuma de Castro, 07286937391, Xavier J?nior, Francisco Humberto, 06109671428, Tonholo, Josealdo, 16392398805, Moura, Maria de F?tima Vit?ria de, Maciel, Maria Aparecida Medeiros |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM QU?MICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| 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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