doctoralThesis
Caracterização dos revestimentos compósitos quitosana-tungstênio e quitosana-molibdênio obtidos por deposição eletroforética
Fecha
2021-01-21Registro en:
OLIVEIRA, José Anderson Machado. Caracterização dos revestimentos compósitos quitosana-tungstênio e
quitosana-molibdênio obtidos por deposição eletroforética. 2021. 101f. Tese (Doutorado em Química) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2021.
Autor
Oliveira, José Anderson Machado
Resumen
Chitosan is a naturally-occurring polysaccharide derived from chitin. It has
biocompatible, antibacterial, and biodegradable properties, low toxicity, and excellent
film formation capacity. Therefore, chitosan-based composite materials or coatings
can be applied in different technological and industrial sectors, such as in the food,
cosmetics, textile, biomedicine, and agriculture industries. Due to their mechanical
properties and corrosion resistance, tungsten, molybdenum and their compounds
can be used to produce materials with superior properties for applications in
environments with extreme operational requirements. Thus, based on the intrinsic
properties of chitosan, tungsten and molybdenum, two new composite coatings of
chitosan-tungsten (Chit-W) and chitosan-molybdenum (Chit-Mo), obtained by the
electrophoretic deposition process, were characterized in this work to evaluate its
possible application for protection of 1020 carbon steel against corrosion in a
medium containing chloride ions (NaCl). To define the best coatings, the evaluated
parameters were: electric field, pH of the electrolyte suspensions, and concentration
of reagents. The results of morphology (SEM), chemical composition (EDS),
crystallography (XRD), and spectroscopy in the infrared region (FT-IR) confirmed the
deposition of composite coatings in the form of films presenting different thicknesses
(on the micrometric scale), impregnated with nanoparticles of metal oxides (tungsten
or molybdenum) homogeneously distributed in the chitosan matrix and presenting
morphological and microstructural characteristics depending on the experimental
conditions used in the deposition process. The results of corrosion resistance
obtained by Potentiodynamic Polarization (PP) and Electrochemical Impedance
Spectroscopy (EIS) showed that the composite coatings improved the corrosion
resistance of 1020 steel exposed in corrosive NaCl medium (3.5 %). The Chit-W
composite coating obtained under the operating conditions of 10 V, pH 5.5, and 10
min of deposition showed a corrosion current density (icorr) of 4.0 ± 0.2 µA/cm². The
Chit-Mo composite coating obtained in the conditions of 5 V, pH 5.5 and 10 min of
deposition presented an icorr of 1.4 ± 0.3 µA/cm². Thus, 1020 steel coated with the
chitosan-molybdenum composite showed a better anticorrosive performance
compared to steel coated with the chitosan-tungsten composite. Therefore, the
results presented here prove the achievement of a new class of chitosan-based
composite materials with potential application for protection of metallic structures
against corrosion.