Obtenção e caracterização de novos sistemas coloidais a base de óleos das espécies vegetais de Azadirachta indica e Copaifera e suas avaliações como inibidores de corrosão em meio salino
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 pp...
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| Formato: | doctoralThesis |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/24498 |
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| Resumo: | 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. |
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