RENATO ALTOBELLI ANTUNES

RENATO ALTOBELLI ANTUNES

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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.
Influence of aging time on the corrosion behavior of 6061 Al alloy in alkaline solution
2014 - CORREA, OLANDIR V.; SOUZA, JOSE A.B. de; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.
Al alloys of the 6XXX series (Al-Mg-Si) are employed as structural materials in a variety of industrial applications due to a combination of high mechanical strength and good corrosion resistance. The final mechanical properties are achieved after specific precipitation hardening heat treatments. The aging time during precipitation hardening is known to affect these properties and can also influence the corrosion resistance of the alloy. The susceptibility of Al alloys to corrosion in alkaline media is well-known. In this work the effect of aging time on the corrosion behavior of 6061 Al alloy was evaluated in NaOH and NaCl solutions. The material was aged at 200 ºC for times ranging from 1 to 36 h. The corrosion behavior of the aged alloy was studied using potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that the corrosion resistance was progressively lower for increasing aging times up to 8 h in NaCl and up to 24 h in NaOH. Longer aging times led to a decrease of the corrosion current density.
Efeito da temperatura de recozimento sobre a resistência à corrosão de revestimentos de Ni-W-P obtidos por deposição química
2015 - CORREA, OLANDIR V.; LIMA, NELSON B. de; ETT, BARDIA; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.
Efeito de filmes finos de oxido de niobio obtidos por magnetron sputtering sobre a resistencia à corrosão do aço inoxidável AISI 316
2014 - GERIBOLA, GUILHERME A.; SCHEIDT, GUILHERME; SILVA JUNIOR, OSWALDO P.V. da; ANTUNES, RENATO A.; OLIVEIRA, MARA C.L.; PILLIS, MARINA F.
Este trabalho teve por objetivo estudar o efeito de filmes finos de óxido de nióbio, nas espessuras de 36 e 70 nm, obtidos por magnetron sputtering, sobre a resistência à corrosão do aço inoxidável AISI 316. O comportamento de corrosão das amostras foi avaliado por ensaios de espectroscopia de impedância eletroquímica (EIE) e polarização potenciodinâmica em solução de NaCl 3,5%p à temperatura ambiente por um período de imersão de 19 dias. A estequiometria dos filmes foi obtida por Rutherford Backscattering Spectroscopy (RBS). Os resultados indicaram que a composição de ambos os filmes se aproxima do composto Nb2O5 e que a resistência à corrosão dos filmes é superior à do substrato.
Feasibility of niobium oxide-based films to prevent corrosion of AISI 304 stainless steel in nuclear fuel reprocessing plants
2014 - CORREA, OLANDIR V.; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.; SAIKI, MITIKO; SILVA JUNIOR, OSWALDO P.V. da; PILLIS, MARINA F.
Corrosion of TiOsub(2)-coated stainless steels studied by electrochemical tests and neutron activation analysis
2014 - CORREA, OLANDIR V.; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.; SAIKI, MITIKO; ARAUJO, EDVAL G. de; PILLIS, MARINA F.
Structural characterization and corrosion stability of a Si-doped DLC coating applied on cylinder liner
2014 - REJOWSKI, EDNEY D.; OLIVEIRA, MARA C.L.; ANTUNES, RENATO A.; PILLIS, MARINA F.
Efeito de filmes de TiOsub(2) obtidos pelo processo de deposição química de organometálicos em fase vapor (MOCVD) sobre a resistência à corrosão do aço inoxidável AISI 304
2012 - PILLIS, MARINA F.; OLIVEIRA, MARA C.L. de; CORREA, OLANDIR V.; ANTUNES, RENATO A.
O objetivo deste trabalho foi investigar o efeito de filmes de TiO2 produzidos pelo método MOCVD sobre a resistência à corrosão do aço inoxidável AISI 304. Os filmes foram obtidos em duas temperaturas diferentes do substrato: 300 ºC e 500 ºC. O comportamento de corrosão das amostras foi avaliado por ensaios de espectroscopia de impedância eletroquímica (EIE) e polarização potenciodinâmica em solução de NaCl 3,5%p à temperatura ambiente por um período de imersão de 14 dias. A morfologia dos filmes foi analisada por microscopia eletrônica de varredura (MEV). Os resultados indicaram que o filme obtido a 300 ºC produziu o material com maior resistência à corrosão, enquanto aquele obtido a 500 ºC mostrou um caráter protetor incipiente. Esse comportamento é discutido com base na morfologia e na espessura dos filmes, as quais dependem da temperatura de deposição.
Influence of the anodizing potential on the porosity of the anode oxide film and on the corrosion resistance of AZ91D magnesium alloy
2012 - OLIVEIRA, MARA C.L. de; PEREIRA, VIVIAM S.M.; CORREA, OLANDIR V.; ANTUNES, RENATO A.