OLANDIR VERCINO CORREA

OLANDIR VERCINO CORREA

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Hydrotalcite coatings to protect spent sluminum-clad nuclear fuels during long term wet storage
2015 - FERNANDES, S.M.C.; CORREA, O.V.; SOUZA, J.A. de; ANTUNES, R.A.; OLIVEIRA, M.C.L. de; RAMANATHAN, L.V.
Pitting corrosion of the aluminium cladding of spent research reactor (RR) fuels in wet storage has been reported and attributed to synergistic influence of certain water parameters. Hence, use of conversion coatings to protect spent Al-clad RR fuel during long term wet storage was proposed. The objective was to develop a coating using a conventional chemical process as opposed to an electrochemical process due to constraints related to the shape of the fuel and its high radioactivity. In this context hydrotalcite (HTC) and boehmite were considered. This paper presents: (a) preparation of boehmite and hydrotalcite (HTC) coatings from different baths followed by post-coating treatments; (b) corrosion behavior of coated AA 6061 alloy; (c) results of field studies in which uncoated and coated AA 6061 alloy coupons and plates, the latter assembled as a dummy fuel element, were exposed to the IEA-R1 reactor spent fuel basin for periods of up to 14 months. The laboratory tests revealed marked increase in corrosion resistance of HTC coated specimens. In field tests the HTC coated coupons and plates did not reveal any pits. The mechanism of corrosion protection is presented.
Coatings to protect spent aluminium-clad research reactor fuel during wet storage
2015 - FERNANDES, S.M.C.; CORREA, O.V.; SOUZA, J.A. de; RAMANATHAN, L.V.; ANTUNES, R.A.; OLIVIERA, M.C.L. de
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.
Corrosion behavior of hydrotalcite coated AA 6061 alloy
2014 - FERNANDES, STELA M.; CORREA, OLANDIR V.; SOUZA, JOSE A.; RAMANATHAN, LALGUDI V.; ANTUNES, RENATO A.; OLIVEIRA, MARA C. de
Pitting corrosion of the aluminium cladding of spent research reactor (RR) fuel during wet storage is the main form of degradation and this could eventually lead to release of fissile material and contamination of storage facilities. Hence, the use of conversion coatings to protect spent Al-clad RR fuel during long term storage was proposed. Preliminary laboratory and field investigations carried out at IPEN in São Paulo, Brazil, revealed that cerium hydroxide coatings increased the corrosion resistance of Al alloys. These investigations were extended to include boehmite, hydrotalcite (HTC), cerium modified boehmite and cerium modified HTC coatings on Al alloy surfaces. This paper presents: (a) the preparation of hydrotalcite coatings from different baths followed by post-coating treatments; (b) the results of x-ray diffraction analysis and scanning electron microscopic studies of the HTC coatings; (c) the effect of HTC coating process variables such as temperature, duration of treatment and the duration of cerium modification on HTC morphology and electrochemical polarization behavior of HTC coated AA 6061 alloy in NaCl; (d) results of field tests in which uncoated and HTC coated AA 6061 coupons were exposed to the IEA-R1 reactor spent fuel basin for up to 5 months. The laboratory test specimens as well as the field test coupons coated with HTC from a high temperature bath followed by cerium modification were the most resistant to pitting.
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.
Protective coatings for long term wet storage of spent aluminium-clad research reactor fuel
2014 - FERNANDES, S.M.; CORREA, O.V.; SOUZA, J.A.; RAMANATHAN, L.V.; ANTUNES, R.A.; OLIVEIRA, M.C.L de
Influence of testing temperature on the corrosion behavior of API 5L X70 pipeline steel
2014 - MACHADO, CARLOS A.V. de A.; ANTUNES, RENATO A.; PESSINE, ELISABETE J.; CORREA, OLANDIR V.
Effect of processing on microstructure and corrosion mitigating properties of hydrotalcite coatings on AA 6061 alloy
2015 - FERNANDES, STELA M. de C.; CORREA, OLANDIR V.; SOUZA, JOSE A.B. de; ANTUNES, RENATO A.; LIMA, NELSON B. de; RAMANATHAN, LALGUDI V.
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.