OLANDIR VERCINO CORREA

OLANDIR VERCINO CORREA

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Avaliação eletroquímica de alumina anódica nanoporosa aplicada a revestimentos biomédicos
2023 - PIERETTI, E.F.; CORREA, O.V.; NEVES, M.D.M.; OLIVEIRA, M.C.L.; ANTUNES, R.A.
Óxido de alumínio anódico tem atraído interesse devido ao arranjo regular denanoporos, grande área de superfície específica, boa estabilidade térmica,ausência de toxicidade e biocompatibilidade. As estruturas OAA têm sidoaplicadas em filtros, biossenssores, sensores de oxigênio, catálise efotocatálise. O arranjo geométrico dos nanoporos torna possível utilizar aalumina como molde para a síntese de várias nanoestruturas, como nanoporos,nanotubos, nanobastões e nanofios que apresentam muitas vantagens em áreas deaplicação avançadas devido a suas propriedades químicas, físicas, mecânicas eópticas únicas. Dentre os materiais de aplicação biomédica destacam-se algumasligas de alumínio, pois apresentam resistência mecânica satisfatória,resistência à corrosão e baixo custo.
Avaliação eletroquímica da liga Ti6Al4V produzida por manufatura aditiva
2023 - PIERETTI, E.F.; CORREA, O.V.; SILVA, L.C.E. da; PILLIS, M.F.; RIBEIRO, M.S.; ROSSI, W. de; NEVES, M.D.M.
O aprimoramento de propriedades de superfície é uma exigência para osbiomateriais. O objetivo deste trabalho foi investigar a resistência à corrosãode amostras da liga Ti6Al4V produzidas por manufatura aditiva, em solução deRinger, que simula os fluidos corpóreos. As amostras foram produzidas alterando-se alguns parâmetros do processo. A resistência à corrosão foi avaliadautilizando-se métodos eletroquímicos como: monitoramento de potencial decircuito aberto, medições de espectroscopia de impedância eletroquímica epolarização cíclica e análises de superfície por MEV. Algumas amostras forammais susceptíveis à corrosão, pois a alternância de parâmetros do processo defabricação produz superfícies distintas com acabamento superficialdiversificado, resultando em comportamentos diversos.
Structural, adhesion and electrochemical characterization of electroless plated Ni-P-carbon black composite films on API 5L X80 steel
2019 - OLIVEIRA, MARA C.L. de; CORREA, OLANDIR V.; SILVA, REJANE M.P. da; LIMA, NELSON B. de; OLIVEIRA, JEFFERSON T.D. de; OLIVEIRA, LEANDRO A. de; ANTUNES, RENATO A.
In this work, composite Ni-P-carbon black coatings were obtained by electroless deposition on API 5L X80 substrates. The effect of carbon black on structural, adhesion and electrochemical properties of the plated samples was evaluated. Scanning electron microscopy analyses were carried out to examine the top surface and cross section of the films. Scratch tests were employed to evaluate coating adhesion properties. Potentiodynamic polarization tests were carried out to investigate the global electrochemical behavior of the deposited layers. Scanning electrochemical microscopy (SECM) was employed to measure local electrochemical activity over the coated surfaces. The carbon black concentration markedly affects the morphology, adhesion and electrochemical properties of the Ni-P-carbon black layers. The results point to an optimum carbon black content to achieve the best performance against corrosion. The coatings obtained at a carbon black concentration of 0.25 g L21 provided the best protection ability. The results are discussed with respect to coating morphology, adhesion and electrochemical activity.
Electrochemical characterization of an optical fiber laser-treated biomaterial
2018 - PIERETTI, EURICO F.; CORREA, OLANDIR V.; PILLIS, MARINA F.; NEVES, MAURICIO D.M. das
The implant manufacturing process includes texturization to enhance its adhesion and marking the final products for their identification, long-term quality control and traceability. Marking is carried out after cleaning and prior to sterilization. These marks eventually can concentrate stress leading to premature failure. The marked areas are defective regions that affect the passive film formed on the metallic biomaterials used for implants favoring the onset of various corrosion types, such as pitting, crevice or fatigue. This study aims to evaluate the effect of a Yb optical fiber laser marking processes used for metallic implants on the localized corrosion resistance of the austenitic stainless steel ISO 5832-1. This is one of the most used materials for manufacturing implants. The electrochemical behavior of the marked areas obtained by this method was evaluated in a phosphate- buffered saline (PBS) solution with pH of 7.4 and the results were compared with unmarked samples. All tested surfaces were prepared according to the recommendations for the use in surgery. For localized corrosion resistance evaluation, electrochemical tests such as monitoring the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and cyclic potentiodynamic polarization measurements were performed. The results showed that the laser marks affect the protector characteristics of the biomaterial’s passive film. Lower pitting resistance was associated to the laser marked areas.
Synthesis and characterization of TiO2 films obtained by sol-gel method
2017 - SZURKALO, MARGARIDA; OLIVEIRA, EDUARDO C. de; CORREA, OLANDIR V.; BENTO, RODRIGO T.; PILLIS, MARINA F.
Borosilicate coated titanium dioxide thin films were produced by the sol-gel method. The films were calcinated at 450°C for 20 minutes for crystalization. X-ray diffration analyses show that before the heat treatment the film was amorphous and after that it crystallized in anatase phase presenting mean grain size of 34 nm and RMS roughness of 8 nm. The crystallized film was used as photocatalist in the degradation of methyl orange dye presenting an efficiency of 25% after 2h under UV light.
Effect of silicate-based films on the corrosion behavior of the API 5L X80 pipeline steel
2018 - OLIVEIRA, LEANDRO A. de; CORREA, OLANDIR V.; SANTOS, DEMETRIO J. dos; PAEZ, ALEJANDRO A.Z.; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.
The aim of this work was to investigate the effect of silicate-based films on the corrosion resistance of the API 5L X80 steel in carbonate-bicarbonate solution at room temperature. The films were electrochemically obtained by anodic and cathodic treatments and by immersion in 1.0 M sodium metasilicate solution. The corrosion behavior was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization. Film morphology was examined by scanning electron microscopy. Adhesion strength was measured by pull-off tests. The chemical composition was evaluated by X-ray photoelectron spectroscopy. The anodic film yielded the best corrosion resistance (protection efficiency 83%). The protection mechanism is discussed.
Preparation and characterization of hydrotalcite coatings to protect aluminium alloys
2016 - FERNANDES, S.M.C.; CORREA, O.V.; SOUZA, J.A.; ANTUNES, R.A.; LIMA, N.B. de; RAMANATHAN, L.V.
Pitting corrosion of the aluminium alloy cladding of spent research reactor fuels during wet storage is the main form of degradation. To prevent this, hydrotalcite (HTC) based coatings were proposed. This paper presents the effect of chemical bath parameters on the microstructure of HTC coatings and the corrosion behavior of HTC coated AA 6061 specimens. The HTC coating formed at 98 °C from nitrate baths and referred to as HT-HTC was homogeneous and consisted of intersecting blade-like crystallites. Electrochemical tests revealed that HT-HTC coated specimens that were treated in a cerium salt solution were the most resistant to corrosion. Field tests in which un-coated and HTC coated AA 6061 alloy coupons as well as full-size plates were exposed to the IEA-R1 reactor’s spent fuel basin for 23 months corroborated the high corrosion resistance imparted by the HT-HTC + Ce coating. The mechanism by which the HTC coating and cerium protect the Al alloy is discussed.
Efeito do revestimento a base de conversão a base de cerio sobre o comportamento de corrosão da liga de magnesio AZ91D
2016 - FERREIRA, RAFAEL L.E.; CORREA, OLANDIR V.; ANTUNES, RENATO A.
Este trabalho teve como objetivo avaliar o efeito de revestimentos de conversão à base de cério sobre o comportamento de corrosão da liga de magnésio AZ91D em solução de cloreto de sódio. A liga foi utilizada na condição bruta de fusão. Diferentes condições de formação dos revestimentos de conversão foram testadas, variando-se o tempo de tratamento. Foi utilizado o nitrato de cério como composto formador do revestimento. A morfologia dos filmes foi avaliada por microscopia eletrônica de varredura e sua composição por espectroscopia de energia dispersiva por raios-X (EDS). O comportamento de corrosão foi avaliado por espectroscopia de impedância eletroquímica e polarização pontenciodinâmica. Os resultados obtidos mostraram que houve uma dependência do comportamento eletroquímico com a morfologia da camada de conversão, a qual foi dependente do tempo de tratamento.
Susceptibility of M5sup(TM) (ZrNbO) alloy to pitting corrosion at different temperatures
2014 - CORREA, OLANDIR V.; OLIVEIRA, MARA C.L. de; PESSINE, ELISABETE J.; SOUZA, JOSE A.B. de; ANTUNES, RENATO A.
Corrosion of fuel cladding is a major concern in the nuclear industry. Zirconium alloys are the standard materials for nuclear fuel tubing due to its notable low neutron absorption crosssection. The M5sup(TM) alloy is currently employed for the production of nuclear fuel cladding in Brazil. Pitting corrosion has been associated with the intergranular stress corrosion cracking of these materials. In this regard, the study of pitting corrosion behavior of M5sup(TM) alloy is of great technological interest in order to allow the development of safer nuclear fuel claddings. The aim of this work was to evaluate the pitting corrosion behavior of M5sup(TM) alloy at different temperatures. Electrochemical measurements comprised potentiodynamic polarization and electrochemical impedance spectroscopy analyses. The tests were conducted in 5.0 wt.% NaCl solution at room temperature, 40 ºC and 60 ºC. The corrosion resistance was shown to be dependent on the testing temperature. The M5sup(TM) alloy showed good corrosion resistance with only a slight decay as the temperature increased.
Pitting susceptibility of AISI 304 stainless steel after cold rolling
2014 - CORREA, OLANDIR V.; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.
The austenitic grade AISI 304 stainless steel is traditionally employed for processing equipment in chemical plants due to its relatively good corrosion resistance and mechanical stability. However, it is susceptible to pitting corrosion due to chloride attack which can lead to catastrophic failures during operation. Cold rolling of the metallic sheets used to construct equipment such as tanks and pressure vessels can further aggravate the situation by increasing the material’s susceptibility to localized corrosion. In this work the pitting corrosion resistance of cold rolled AISI 304 stainless steel plates was assessed using chronoamperometric curves and potentiodynamic polarization curves. Cold rolling was performed in a two-roll mill at room temperature, achieving thickness reductions ranging from 10% to 70%. The presence of pits on the surface of the samples was assessed using optical microscopy. The onset of pitting corrosion was closely related to the strain level of the rolled plates. There was a steep decrease of resistance to localized attack as the thickness reduction increased.