Navegação IPEN por Autores IPEN "VIVEIROS, BARBARA V.G. de"

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  • IPEN-DOC 29079

    KLUMPP, RAFAEL E. ; ARAUJO, JOAO V. de S. ; ANTUNES, RENATO A.; VIVEIROS, BARBARA V.G. de ; MAGNANI, MARINA; COSTA, ISOLDA . A cerium-based nanocoating for corrosion protection of the AA1230 as clad material for the AA2024-T3 alloy. Materials Research, v. 25, suppl. 1, p. 1-9, 2022. DOI: 10.1590/1980-5373-MR-2021-0616

    Abstract: Aluminum alloys are the state-of-art materials for structural components of aircrafts. As they are susceptible to localized corrosion, this kind of damage can become a major threat for its safe use in aircraft components. Therefore, surface protection of aluminum alloys against corrosion is a core issue in these applications. In this work, an alternative eco-friendly cerium-based surface pretreatment was developed and applied on the AA1230 clad of the AA2024-T3 alloy for corrosion protection. The corrosion resistance evaluation of this modified surface was evaluated by several techniques. The results were compared to chromium based conventional treatments and revealed that the coating layer, composed of spherical nodular nanostructures of cerium, obtained with the proposed eco-friendly treatment, improved the corrosion resistance of the alloy. Moreover, it was comparable to the corrosion behavior of chromate-treated alloy, showing that this treatment is a promising alternative to replace chromate based surface treatments.

    Palavras-Chave: aluminium alloys; atomic force microscopy; cerium; chromium; cladding; comparative evaluations; corrosion protection; corrosion resistance; nanofilms

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  • IPEN-DOC 28696

    VIVEIROS, BARBARA V.G. de ; DONATUS, UYIME ; ALENCAR, MAICON C. de ; BERBEL, LARISSA O. ; COSTA, ISOLDA . Comparing the corrosion behaviour of AA2050 and AA7050 aluminium alloys by scanning vibrating electrode and scanning ion-selective electrode techniques. Corrosion Engineering, Science and Technology, v. 57, n. 1, p. 85-96, 2022. DOI: 10.1080/1478422X.2021.1992132

    Abstract: The susceptibility to localised corrosion of the high strength alloys, AA2050-T84 and AA7050-T7451, used in the aerospace industry, was investigated in this study by localised electrochemical techniques, specifically, scanning vibrating electrode technique (SVET) and scanning ion-selective electrode technique (SIET), in 0.005 mol L−1 NaCl solution. The study was initially carried out using both alloys individually and then, coupling the two alloys and evaluating the effect of galvanic coupling between them. The results revealed that the AA2050-T84, being nobler than the AA7050-T7451, presented higher corrosion current density values when tested in isolation and the depth of corrosion penetration was significantly deeper in the AA2050-T84 alloy than in the AA7050-T7451. However, galvanic coupling of the two alloys resulted in cathodic protection of the AA2050-T84 alloy and a reduction in corrosion current densities on both alloys.

    Palavras-Chave: aluminium alloys; corrosion resistance; intergranular corrosion; pitting corrosion; coupling; electrochemical corrosion; electrodes; ion-selective electrodes

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  • IPEN-DOC 25749

    MILAGRE, MARIANA X. ; DONATUS, UYIME ; MACHADO, CARULINE S.C. ; ARAUJO, JOAO V.S. ; SILVA, REJANE M.P. da ; VIVEIROS, BARBARA V.G. de ; ASTARITA, ANTONELLO; COSTA, ISOLDA . Comparison of the corrosion resistance of an Al–Cu alloy and an Al–Cu–Li alloy. Corrosion Engineering, Science and Technology, v. 54, n. 5, p. 402-412, 2019. DOI: 10.1080/1478422X.2019.1605472

    Abstract: In this study, the corrosion mechanisms of the AA2024-T3 and the AA2098-T351 were investigated and compared using various electrochemical techniques in 0.005 mol L−1 NaCl solution. The severe type of corrosion in the AA2098-T351 was intragranular attack (IGA) although trenching and pitting related to the constituent particles were seen. On the other hand, the AA2024-T3 exhibited severe localised corrosion associated with micrometric constituent particles, and its propagation was via grain boundaries leading to intergranular corrosion (IGC). Electrochemical techniques showed that the corrosion reaction in both alloys was controlled by diffusion. The non-uniform current distribution in both alloys showed that EIS was not a proper technique for comparing the corrosion resistance of the alloys. However, local electrochemical techniques were useful for the evaluation of the corrosion resistance of the alloys.

    Palavras-Chave: corrosion resistance; corrosion resistant alloys; electrochemistry; electrochemical corrosion; aluminium base alloys; copper alloys; lithium base alloys

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  • IPEN-DOC 25087

    DONATUS, UYIME ; VIVEIROS, BARBARA V.G. de ; ALENCAR, MAICON C. de ; FERREIRA, RAPHAEL O.; MILAGRE, MARIANA X. ; COSTA, ISOLDA . Correlation between corrosion resistance, anodic hydrogen evolution and microhardness in friction stir weldment of AA2198 alloy. Materials Characterization, v. 144, p. 99-112, 2018. DOI: 10.1016/j.matchar.2018.07.004

    Abstract: Correlation between corrosion resistance, anodic hydrogen evolution and microhardness in the friction stir weldment of AA2198-T851 alloy has been investigated. Different microscopy techniques, scanning vibrating electrode technique (SVET) and potentiodynamic polarization tests were employed in the investigation. Unlike other 3rd generation Al-Cu-Li alloys where the regions that are most susceptible to corrosion are always within the weld region, the results reveal that the parent material is the most susceptible in this case. There is a direct correlation between corrosion resistance, anodic hydrogen evolution and microhardness in the weldment, and the T1 phase is associated with the direct correlation.

    Palavras-Chave: aluminium alloys; corrosion resistance; friction; microhardness; pitting corrosion; polarization; welded joints

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  • IPEN-DOC 25203

    DONATUS, UYIME ; FERREIRA, RAPHAEL O.; MOGILI, NAGA V.V.; VIVEIROS, BARBARA V.G. de ; MILAGRE, MARIANA X. ; COSTA, ISOLDA . Corrosion and anodizing behaviour of friction stir weldment of AA2198- T851 Al-Cu-Li alloy. Materials Chemistry and Physics, v. 219, p. 493-511, 2018. DOI: 10.1016/j.matchemphys.2018.08.053

    Abstract: Anodizing behaviour of AA2198-T851 friction stir weldment and the corrosion behaviour of unpolished and polished weldments of the alloy have been investigated. Electrochemical and microscopic techniques were employed in the study. The results revealed that the manufacturing-process induced near-surface deformed layer significantly affected the corrosion behaviour of the weldment. Thus, the corrosion behaviour of the weldment in the polished condition (which is the common practice) was different from that of the unpolished one due to the presence of near-surface deformed layer. Anodizing as a corrosion protection method for the weldment caused the formation of pronounced non-uniform oxide layer thicknesses across the weld zones. This was because the weldment oxidized at a higher rate compared with the parent material (PM) due to an increased proportion of Li in solid solution in the stir zone of the weldment.

    Palavras-Chave: chemical reactions; corrosion; anodization; aluminium alloys; friction welding; pitting corrosion; surface properties; lithium alloys; copper alloys; microstructure

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  • IPEN-DOC 29080

    BERBEL, LARISSA O. ; VIVEIROS, BARBARA V.G. de ; MICELLI, ANA L.P. ; NIGRO, FREDERICO ; ROSSI, JESUALDO L. ; COSTA, ISOLDA . Corrosion mechanism of Ti-6Al-4V morse taper dental implants connected to 316 L stainless steel prosthetic abutment. Materials Today Communications, v. 33, p. 1-13, 2022. DOI: 10.1016/j.mtcomm.2022.104583

    Abstract: The aim of this work was to investigate the effect of galvanic coupling between stainless steel AISI 316 L abutment type Morse taper and implant made of ASTM F1108–14 Ti-6Al-4V alloy. The assembly of the two alloys was carried out using mechanical imbrication by means of successive strikes at 0.05 J force onto the abutment inserted in the implant along the centerline. Corrosion attack at the interface of the alloys was evaluated according to the number of strikes used for joining the parts. Corrosion resistance was evaluated for the samples by open circuit potential measurements as function of time and scanning vibrating electrode technique (SVET) and scanning ion selective electrode technique (SIET) in phosphate buffer solution with pH adjusted to 3.0, and into which hydrogen peroxide was added to simulate tissue inflammatory conditions. Samples were evaluated at the cross and longitudinal sections. Results indicated that the number of strikes used in assembling affected corrosion susceptibility. The lowest amount of corrosion products was associated to the highest number of strikes used. The corrosion resistance was related to the characteristics of the crevice between the implant and the abutment.

    Palavras-Chave: dentistry; implants; titanium alloys; stainless steel-316l; morse potential; corrosion

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  • IPEN-DOC 28895

    BERBEL, LARISSA O. ; VIVEIROS, BARBARA V.G. de ; MICELLI, ANA L. ; NIGRO, FREDERICO ; ROSSI, JESUALDO L. ; COSTA, ISOLDA . Corrosion of dental implants made of Ti-6Al-4V connected to 316L SS in agressive environment. In: INTERNATIONAL CORROSION CONGRESS, 21st; INTERNATIONAL CORROSION MEETING, 8th, July 20-23, 2021, Online. Anais... Rio de Janeiro, RJ: Associação Brasileira de Corrosão - ABRACO, 2021.

    Abstract: Implants made of dissimilar alloys, such as Ti-6Al-4V, connected to abutment of stainless steel (SS), are being considered for application as dental implants leading to galvanic corrosion. Body fluids are corrosive electrolytes that contain aggressive ions, such as chlorides, leading to localized attack at weak points of the passive film on materials used for implants fabrication. Another reason of apprehension concerning corrosion is the method of joining the different materials. This might lead to small gaps between the two materials and promote crevice conditions that stimulate localized corrosion. In this study, the corrosion resistance of a Morse taper dental implants made of Ti-6Al-4V alloy in contact to a prosthetic abutment of 316L, with the two parts joined by mechanical forces consisting of strikes, using different numbers of strikes (3, 5 and 7), was studied. The study was carried out by SVET technique in phosphate buffer solution (PBS) with an addition of H2O2 and pH adjust to 3 to simulate inflammatory conditions. The results showed high electrochemical activity at the interface between the two alloys. SVET maps showed that the Ti alloy acted as anode whereas the 316L SS as cathode. At the interface of the dissimilar alloys, large amounts of corrosion products accumulated showing the effect of the galvanic corrosion. This was mainly observed for the samples with 3 strikes for joining both alloys. The electrochemical activity was the lowest for the dental implant mounted with 5 strikes. SVET maps and SEM images showed a strong effect of crevice corrosion for the implants joined by lowest number of strikes among the testes.

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  • IPEN-DOC 27712

    KLUMPP, RAFAEL E. ; DONATUS, UYIME ; SILVA, REJANE M.P. da ; ANTUNES, RENATO A.; MACHADO, CARULINE de S.C. ; MILAGRE, MARIANA X. ; ARAUJO, JOAO V. de S. ; VIVEIROS, BARBARA V.G. de ; COSTA, ISOLDA . Corrosion protection of the AA2198-T8 alloy by environmentally friendly organic-inorganic sol-gel coating based on bis-1,2-(triethoxysilyl) ethane. Surface and Interface Analysis, v. 53, n. 3, p. 314-329, 2021. DOI: 10.1002/sia.6919

    Abstract: In this work, a surface coating composed of organic‐inorganic hybrid sol‐gel based on bis‐1,2‐(triethoxysilyl) (BTSE) ethane was applied on AA2198‐T8 samples, and its effect on corrosion resistance was investigated and compared with that of a chromate layer formed in a solution with hexavalent chromium ions. The corrosion resistance of BTSE coated samples was evaluated by immersion tests in sodium chloride solution (0.005 mol/L NaCl) and monitored by global electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and local electrochemical techniques such as scanning vibrating electrode technique (SVET) and scanning electrochemical microscopy (SECM). The formed coating layers were characterized by X‐ray photoelectron spectroscopy (XPS). The results pointed out that the BTSE is an effective alternative coating for corrosion protection of new generation Al‐Cu‐Li alloys and could replace chromates obtained in toxic and carcinogenic CrVI containing solutions leading to improved corrosion protection.

    Palavras-Chave: corrosion; corrosion protection; surface coating; silanes; aluminium alloys; sol-gel process; hybrid systems; corrosion resistance

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  • IPEN-DOC 27567

    BERBEL, LARISSA O. ; VIVEIROS, BARBARA V.G. de ; MICELLI, ANA L. ; ROSSI, JESUALDO ; NIGRO, FREDERICO ; ARANHA, LUIS C. ; COSTA, ISOLDA . Effect of galvanic coupling between titanium alloy and stainless steel on behavior of corrosion of dental implants. International Journal of Advances In Medical Biotechnology, v. 3, n. 1, p. 23-27, 2020. DOI: 10.25061/ijamb.v3i1.68

    Abstract: Titanium and its alloys are widely used in dental implant manufacturing due its favorable properties, such as, biocompatibility, high mechanical strength and high corrosion resistance. This last one, is a result of the ability of titanium to form an oxide film (TiO2) in contact with oxygen. However, a several factors can accelerate the corrosion process of implants in contact with the oral environment, such as, acidification of the medium, differential aeration, inflammatory conditions, presence of protein and the junction of diferent metals. The goals of this research is to investigate the corrosion effect of galvanic coupling between titanium alloy (grade V) and stainless steel 316L. The investigative technique adopted was the scanning vibrating electrode technique (SVET) in phosphate buffer solution simulating inflammatory conditions. The results showed detrimental effects of acidity of the environment, induced by inflammatory conditions, accelerate the oxidation of Ti-6Al-4V. SVET maps and SEM images for the junction of the different metals showed that the region with the highest electrochemical activity it is at the interface between the metals, mostly concentrated on the Ti-6Al-4V alloy, depending on the conditions of the medium.

    Palavras-Chave: alloys; titanium; stainless steels; corrosion; implants; dentistry; biological materials

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  • IPEN-DOC 25763

    QUEIROZ, FERNANDA M.; DONATUS, UYIME ; RAMIREZ, OSCAR M.P.; ARAUJO, JOAO V. de S. ; VIVEIROS, BARBARA V.G. de ; LAMAKA, SVIATLANA; ZHELUDKEVICH, MIKHAIL; MASOUMI, MOHAMMAD; VIVIER, VINCENT; COSTA, ISOLDA ; MELO, HERCILIO G. de. Effect of unequal levels of deformation and fragmentation on the electrochemical response of friction stir welded AA2024-T3 alloy. Electrochimica Acta, v. 313, p. 271-281, 2019. DOI: 10.1016/j.electacta.2019.04.137

    Abstract: The effect of unequal levels of deformation and fragmentation on the electrochemical response of friction stir welded AA2024-T3 has been investigated using electron backscatter diffraction, scanning electron microscopy, global and localized electrochemical techniques. The friction stir welding process introduced unequal distribution and fragmentation of coarse intermetallic particles, such that more clusters of these particles were present in the thermomechanically affected zone of the weld. This resulted in a higher susceptibility to severe localized corrosion in this region when compared with the others. Results from electrochemical measurements using a microcell could not be clearly correlated with the corrosion behaviour because no significant differences were observed using these techniques. On the other hand, LEIS and SVET results were in agreement and correlated with the corrosion evolution at the surfaces of the tested samples.

    Palavras-Chave: aluminium alloys; electrochemistry; electrochemical cells; microstructure; corrosion; friction welding; cluster analysis; methylene blue; nanomaterials; optical properties; staphylococcus; inactivation; shells; bacteria

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  • IPEN-DOC 27178

    MILAGRE, MARIANA X. ; DONATUS, UYIME ; MOGILI, NAGA V.; SILVA, REJANE M.P. ; VIVEIROS, BARBARA V.G. de ; PEREIRA, VICTOR F.; ANTUNES, RENATO A.; MACHADO, CARULINE S.C. ; ARAUJO, JOAO V.S. ; COSTA, ISOLDA . Galvanic and asymmetry effects on the local electrochemical behavior of the 2098-T351 alloy welded by friction stir welding. Journal of Materials Science & Technology, v. 45, p. 162-175, 2020. DOI: 10.1016/j.jmst.2019.11.016

    Abstract: Scanning electrochemical microscopy (SECM) and scanning vibrating electrode technique (SVET) were used to investigate the electrochemical behaviour of the top surface of the 2098-T351 alloy welded by friction stir welding (FSW). The SVET technique was efficient in identifying the cathodic and anodic weld regions. The welding joint (WJ), which comprises the thermomechanically affected zone (TMAZ) and the stir zone (SZ), was cathodic relative to the heated affected zone (HAZ) and the base metal (BM). The reactivities of the welding joint at the advancing side (AS) and the retreating side (RS) were analyzed and compared using SECM technique in the competition mode by monitoring the dissolved oxygen as a redox mediator in 0.005 mol L−1 NaCl solution. The RS was more electrochemically active than the AS, and these results were correlated with the microstructural features of the welded alloy.

    Palavras-Chave: electrochemistry; scanning electron microscopy; friction; welding; welded joints; stirring; corrosion; corrosion resistance; electrochemical corrosion

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  • IPEN-DOC 27812

    MACHADO, CARULINE de S.C. ; DONATUS, UYIME ; MILAGRE, MARIANA X. ; ARAUJO, JOAO V. de S. ; VIVEIROS, BARBARA V.G. de ; KLUMPP, RAFAEL E. ; PEREIRA, VICTOR F.; COSTA, ISOLDA . How microstructure affects localized corrosion resistance of stir zone of the AA2198-T8 alloy after friction stir welding. Materials Characterization, v. 174, p. 1-14, 2021. DOI: 10.1016/j.matchar.2021.111025

    Abstract: In this study, the microstructure and corrosion resistance of the stir zone (SZ) of the AA2198-T8 Al-Cu-Li alloy welded by friction stir welding (FSW) were investigated by microscopy, immersion tests and electrochemical techniques such as measurements of open circuit potential variation with time, and scanning vibrating electrode technique (SVET) measurements. A low chloride-containing solution (0.005 mol L−1 NaCl) was employed in the corrosion studies and severe localized corrosion (SLC) was observed in the SZ related to intergranular attack. The results were compared to those of the non-affected areas by FSW, also known as base metal (BM). In the BM, SLC was found and the type of attack related to it was intragranular. In both zones, BM and SZ, SLC was due to precipitates of high electrochemical activity, specifically T1 (Al2CuLi) phase in the BM, whereas TB (Al7Cu4Li) / T2 (Al6CuLi3) in the SZ. Scanning vibrating electrode technique (SVET) analysis was very useful in the study of SLC in the AA2198-T8 alloy showing the development of high anodic current densities at the mouth of the SLC sites.

    Palavras-Chave: electrochemistry; friction welding; stir reactor; corrosion resistance; microstructure

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  • IPEN-DOC 28531

    MACHADO, CARULINE de S.C. ; SILVA, REJANE M.P. da ; ARAUJO, JOAO V. de S. ; MILAGRE, MARIANA X. ; DONATUS, UYIME ; VIVEIROS, BARBARA V.G. de ; KLUMPP, RAFAEL E. ; COSTA, ISOLDA . Influence of chloride ions concentration on the development of severe localised corrosion and its effects on the electrochemical response of the 2198-T8 alloy. Corrosion Engineering, Science and Technology, v. 56, n. 4, p. 341-350, 2021. DOI: 10.1080/1478422X.2020.1862390

    Abstract: The development of severe localised corrosion (SLC) on the 2198-T8 alloy was investigated in solutions of various NaCl concentrations (0.001, 0.005 and 0.01 mol L−1). Immersion tests, optical profilometry, conventional and local electrochemical analyses were performed to evaluate the corrosion behaviour of the alloy. Immersion tests showed that the alloy is susceptible to SLC in all conditions, although the pits sizes were dependent on the solution concentration. The largest anodic areas, corresponding to SLC sites, were observed for the sample immersed in 0.001 mol L−1 NaCl, whereas pits with similar sizes were observed for the samples immersed in solutions with 0.005 and 0.01 mol L−1 of NaCl. Moreover, the maximum depth of attack was observed for the sample immersed in 0.001 mol L−1 NaCl. These results were in agreement with the scanning ionselective electrode technique (SIET) maps which showed stronger acidification on the sample exposed to 0.001 mol L−1 NaCl solution.

    Palavras-Chave: aluminium alloys; lithium alloys; copper alloys; chlorides; ions; corrosion

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  • IPEN-DOC 27261

    VIVEIROS, BARBARA V.G. de . Resistência à corrosão das ligas de alumínio AA2050-T84 e AA7050-T7451 soldadas por fricção e mistura / Corrosion resistance in aluminum alloys AA2050-T84 and AA7050-T7451 welded by friction stir welding . 2020. Dissertação (Mestrado em Tecnologia Nuclear) - Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, São Paulo. 123 p. Orientador: Isolda Costa. DOI: 10.11606/D.85.2020.tde-14092020-114646

    Abstract: As ligas de alumínio mais comumente usadas na indústria aeronáutica são as das séries 2XXX e 7XXX, devido às suas boas propriedades mecânicas relacionadas à adição de elementos de liga que levam ao endurecimento. Algumas partes das aeronaves envolvem o uso de ligas de ambas as séries unidas por rebites, uma vez que as liga de alumínio apresentam baixa soldabilidade. O uso de rebites resulta em um aumento significativo no peso das aeronaves. Uma alternativa ao uso de rebites é soldar as ligas por soldagem por fricção e mistura, FSW. Pelo uso dessa técnica, os materiais não atingem seu ponto de fusão. No entanto, o FSW leva a alterações na microestrutura devido à deformação plástica em altas temperaturas às quais as ligas de alumínio são expostas a esse processo de soldagem. Isso causa alterações na resistência mecânica e na resistência à corrosão dessas ligas. Neste trabalho, a resistência à corrosão das ligas AA2050-T84 e AA7050-T7451 soldadas por FSW foi investigada usando soluções contendo cloreto. A solda produziu zonas com diferentes microestruturas nas duas ligas. Essas zonas são conhecidas como: zona termicamente afetada (ZTA), zona termomecanicamente afetada (ZTMA) e zona de mistura (ZM). Foram estudadas a resistência à corrosão e a microestrutura das ligas como recebidas. A microdureza foi obtida na seção transversal e na superfície superior da solda, e as medidas identificaram diferenças significativas entre as zonas. A caracterização da resistência à corrosão foi realizada por ensaios eletroquímicos, pela técnica de visualização em gel e ensaios de imersão. As técnicas eletroquímicas locais utilizadas neste estudo foram a técnica de varredura do eletrodo vibratório (SVET) e a técnica de varredura do eletrodo seletivo de íons (SIET). Os resultados mostraram que a zona mais ativa eletroquimicamente, na seção transversal das ligas soldadas, foi a ZTMA. Esta zona correspondeu à transição entre as duas ligas. Para a superfície superior das ligas soldadas, a zona mais ativa eletroquimicamente correspondeu à transição entre as zonas ZTMA e ZTA na liga AA7050. A alta atividade eletroquímica nessa última zona foi relacionada à formação de precipitados de endurecimento na ZTA do AA7050, enquanto na seção transversal, a alta atividade foi devida ao acoplamento galvânico entre as duas ligas. No acoplamento galvânico, a liga AA7050 atuou como ânodo e a AA2050, como cátodo. Quando as duas ligas, AA2050 e AA7050, foram expostas separadamente às soluções 0,005 mol.L-1 de NaCl ou 3,5% (massa) de NaCl e testadas por técnicas eletroquímicas localizadas e por ensaios de imersão, a liga AA2050 apresentou maior atividade eletroquímica em comparação com a liga AA7050, devido ao maior teor de precipitados micrométricos na liga AA2050. Esta última liga foi protegida catodicamente quando acoplada à liga AA7050.

    Palavras-Chave: mechanical properties; microhardness; thermal degradation; metallurgical flux; corrosion resistance; friction welding; stirring; aluminium alloys; probes; scanning tunneling microscopy; electrodes; signal conditioners; electrochemical coating; heat affected zone

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  • IPEN-DOC 29189

    BUGARIN, ALINE de F.S. ; VIVEIROS, BARBARA V.G. de ; TERADA, MAYSA; SILVA, LEANDRO S. da; GUILHERME, LUIS H.; NEVES, MAURICIO D.M. das ; COSTA, ISOLDA . Study of the corrosion resistance of duplex and lean duplex steels welded by the gas tungsten arc welding double fusion (GTAW-DF) applied in the construction of tanks. In: BRAZIL MRS MEETING, 20th, September 25-29, 2022, Foz do Iguaçu, PR. Abstract... São Carlos, SP: Aptor Software, 2022.

    Abstract: Duplex stainless steels has great technological importance due to the combination of high mechanical strength, high toughness and excellent corrosion resistance. New methods of joining these materials have been investigated and updated, with better cost-benefit. In this work, joints welded by the TIG process with root pass by the double-fusion method (GTAW-DF), typically applied in the construction of tanks for the citrus juice and biotechnology industry were investigated. The welding process of steels changes in its microstructures forming of deleterious precipitates which decrease the corrosion resistance. Thus, the aim of this work was to evaluate and compare the corrosion resistance after welding by the GTAW-DF process of similar joints of lean duplex 2101 steel and dissimilar joints of 2205 and 2304 steels, duplex and lean duplex respectively, both used in the citrus juice industry. Samples were made using optimized welding parameters under corrosion resistance criteria. Microstructural characterization was performed by metallographic etching and observation by optical microscopy (OM) and by scanning electron microscopy (SEM). Mechanical properties were evaluated by microhardness test. Corrosion resistance was evaluated by electrochemical tests by the double loop electrochemical potentiokinetic reactivation test (DL-EPR) and potentiodynamic polarization test. The results showed that the welding process caused microstructural changes in the materials, and that after welding the most susceptible regions to corrosion were in the fusion line and in the thermally affected zone. When analyzing the two welding conditions, it was observed that the welded samples with higher heat input showed lower tendencies to intergranular corrosion.

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  • IPEN-DOC 30166

    BUGARIN, ALINE de F.S. ; VIVEIROS, BARBARA V.G. de ; TERADA, MAYSA; GUILHERME, LUIS H.; NEVES, MAURICIO D.M. das ; COSTA, ISOLDA . Syringe cell method to study the corrosion resistance of the UNS S32101 lean duplex stainless steel welded by the gas tungsten arc welding double fusion (GTAW-DF). In: BRAZIL MRS MEETING, 21st, October 1-5, 2023, Maceió, AL. Abstract... São Carlos, SP: Aptor Software, 2023. p. 1178-1178.

    Abstract: This work aims to investigate the corrosion performance of the UNS S32101 lean duplex stainless steel (LDSS) welded by the gas tungsten arc welding double fusion (GTAW-DF). In the study, six welded samples were manufactured with different welding parameters. A Syringe cell was used to characterize the electrochemical behavior of the different welded zones by potentiodynamic polarization tests in NaCl 3,5 % (w.t.) and in a solution of citric acid with addiction of NaCl to simulate the food industry. The results showed that the welding parameters tested significantly affected the corrosion resistance of the LDSS UNS S32101. Besides, a correlation was stablished between microstructure and electrochemical behavior of fusion line (FL), heat affected zone (HAZ) and fusion zone (FZ).

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  • IPEN-DOC 28900

    VIVEIROS, BARBARA V.G. de ; BERBEL, LARISSA O. ; DONATUS, UYIME ; COSTA, ISOLDA . The corrosion behavior on AA2050-T84 and AA7050-T7451 welded and non-welded by FSW. In: INTERNATIONAL CORROSION CONGRESS, 21st; INTERNATIONAL CORROSION MEETING, 8th, July 20-23, 2021, Online. Anais... Rio de Janeiro, RJ: Associação Brasileira de Corrosão - ABRACO, 2021.

    Abstract: In this work, the corrosion resistance of the AA2050-T84 and AA7050-T7451 alloys welded by FSW and non-welded was investigated using chloride solutions. The corrosion resistance, microstructure and microhardness were studied. Microhardness measurements at the cross section and at the top surface of the weld identified significant differences between the various zones resulting from FSW. Characterization of the corrosion resistance was carried out by electrochemical and immersion tests. Localized electrochemical techniques were used in this work, specifically scanning vibrating electrode technique (SVET) and scanning ion-selective electrode technique (SIET). The results showed that the most electrochemically active zone at of the welded alloys was the thermomechanically affected zone (TMAZ). This zone corresponds to the transition between the two alloys. In the top surface of the welded alloys, besides the TMAZ, the heat affected zone (HAZ) was also highly active corresponding to the transition between zones of the AA7050. This was due to the formation of hardening precipitates in the HAZ of the AA7050. In the cross-section, the high activity related to the TMAZ was due to the galvanic coupling between the two alloys where the AA7050 alloy acted as anodic zones, and the AA2050, as the cathodic ones. When the two alloys, AA2050 and AA7050, were exposed separately to 0.005 mol.L-1 NaCl or 3.5 (wt%) NaCl solutions, the AA2050 alloy showed higher electrochemical activity compared to the AA7050 alloy which was due to the higher content of active micrometric precipitates in the AA2050 alloy relatively to the AA7050. However, when the alloys were coupled, the AA2050 was cathodically protected by the AA7050 alloy.

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  • IPEN-DOC 26841

    VIVEIROS, BARBARA V.G. de ; BERBEL, LARISSA O. ; BUGARIN, ALINE F.S. ; DONATUS, UYIME ; COSTA, ISOLDA . The corrosion resistance between AA2050-T84 and AA7050-T7451 welded by friction stir weld. In: BRAZIL MRS MEETING, 18th, September 22-26, 2019, Balneário Camburiú, SC. Abstract... São Carlos, SP: Aptor Software, 2019. p. 2089-2089.

    Abstract: Aluminum alloys of the 2XXX and 7XXX series are among the most used materials in the aerospace industry. These alloys have good mechanical, specific strength and corrosion resistance, and for the 2XXX series, further reduction in density can be achieved by lithium addition. So, in this case, it can reduce the weight of the aeroplane and fuel usage leading to the minimization of CO 2 emissions and cost savings. Aluminum alloys have poor weldability, and to use these alloys for aeroplane structures, joining is unavoidable. To make this, the industry uses rivets to join these alloys. But rivets increase the mass of aeroplanes, and to minimise this, a non-fusion (unconventional) welding technique capable of welding aluminium alloys easily was developed. This new technique is friction stir welding, which exposes the aluminum alloys to thermomechanical effects, changing the microstructure of the alloys, and resulting in different regions with different metallurgical and mechanical properties. An example of the regions is the thermomechanically affected region which experiences both plastic deformation and high temperature but without recrystallization. There is also the stir zone which is the region of recrystallized grains, the heat affected zone and the base metal (that is not affected by the welding process). The goals of this work are to analyze the corrosion resistance of the friction stir weldment of dissimilar AA2050-T84 and AA7050-T7451 alloys using electrochemical tests, characterizing the different regions of the weldment, and establishing the most susceptible region to corrosion using a sodium chloride solution.

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  • IPEN-DOC 27114

    COUTO, CAMILA P. ; COSTA, ISOLDA ; VIVEIROS, BARBARA V.G. de ; ALENCAR, MAICON C. de ; COLOSIO, MARCO A.; PANOSSIAN, ZEHBOUR; ROSSI, JESUALDO L. . The use of scanning vibrating electrode technique to evaluate the effect of hot stamping on the corrosion resistance of 22MnB5 press-hardened steel electroplated with Zn-Ni. Materials Research, v. 22, suppl. 1, p. 1-6, 2019. DOI: 10.1590/1980-5373-MR-2019-0163

    Abstract: Carmakers must achieve the worldwide targets for lightweight materials, safety and reducing the fuel consumption. The use of press-hardened steel (PHS), in vehicle structures has been contributing with these requirements. This type of steel is widely used for the hot-stamping which consists in heating the steel blank to total austenitization temperature and then transferring it from the furnace into the die tool where the steel is formed and quenched at the same time. PHS is usually protect with metallic coatings in order to avoid both steel oxidation and decarburization. Hot-dip Al-Si coating is currently the main used in this application. However, alternative coatings, like zinc-based, are under investigation. This work aims at evaluating the corrosion resistance of the 22MnB5 grade PHS, electroplated with Zn-Ni, before and after hot stamping, using the scanning vibrating electrode technique (SVET). Results from SVET showed that samples prior to hot stamping, the corrosion mechanism was uniform over the exposed surface, and was mainly related to selective dissolution of zinc from the coating. On the other hand, hot stamped samples showed localized corrosion mechanism with decrease in current with time of immersion due to the formation of corrosion products on the exposed surface.

    Palavras-Chave: coatings; metals; hardening; steels; automotive industry; electrolytes; zinc; nickel; electroplating; corrosion resistance; scanning electron microscopy; backscattering; electrons; corrosion protection

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  • IPEN-DOC 29721

    VIVEIROS, BARBARA V.G. de ; SILVA, REJANE MARIA P. da ; DONATUS, UYIME ; COSTA, ISOLDA . Welding and galvanic coupling effects on the electrochemical activity of dissimilar AA2050 and AA7050 aluminum alloys welded by Friction Stir Welding (FSW). Electrochimica Acta, v. 449, p. 1-15, 2023. DOI: 10.1016/j.electacta.2023.142196

    Abstract: In this work, the effects of friction stir welding (FSW) on the microstructure and electrochemical activities of dissimilar AA2050 and AA7050 aluminum alloys have been investigated. Local electrochemical tests supported by surface analytical characterization were used to study the local electrochemical activities developed along the weld zones of the dissimilar alloys. The investigation was carried out on the cross-section of the welded Al alloys. The results showed that the friction stir welding (FSW) of the dissimilar alloys affected the microstructure and the electrochemical behavior of the different regions (HAZ, TMAZ, SZ) formed by the welding process. Scanning vibrating electrode technique (SVET) and micropotentiometry by using an ion-selective microelectrode showed that TMAZ was the zone with the highest electrochemical activity. This zone corresponded to the transition region between the two welded alloys. The high electrochemical activity observed in this region was associated with the effect of welding on the microstructure and, also, with the galvanic coupling between the two alloys, where the alloy AA7050 acted as an anode and the AA2050 as a cathode. Preferential corrosion attack on the AA7050 alloy was also evident.

    Palavras-Chave: aluminium alloys; friction; welding; coupling; electrochemical corrosion; potentiometry

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A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

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A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

O gerenciamento do Repositório está a cargo da Biblioteca do IPEN. Constam neste RI, até o presente momento 20.950 itens que tanto podem ser artigos de periódicos ou de eventos nacionais e internacionais, dissertações e teses, livros, capítulo de livros e relatórios técnicos. Para participar do RI-IPEN é necessário que pelo menos um dos autores tenha vínculo acadêmico ou funcional com o Instituto. Nesta primeira etapa de funcionamento do RI, a coleta das publicações é realizada periodicamente pela equipe da Biblioteca do IPEN, extraindo os dados das bases internacionais tais como a Web of Science, Scopus, INIS, SciElo além de verificar o Currículo Lattes. O RI-IPEN apresenta também um aspecto inovador no seu funcionamento. Por meio de metadados específicos ele está vinculado ao sistema de gerenciamento das atividades do Plano Diretor anual do IPEN (SIGEPI). Com o objetivo de fornecer dados numéricos para a elaboração dos indicadores da Produção Cientifica Institucional, disponibiliza uma tabela estatística registrando em tempo real a inserção de novos itens. Foi criado um metadado que contém um número único para cada integrante da comunidade científica do IPEN. Esse metadado se transformou em um filtro que ao ser acionado apresenta todos os trabalhos de um determinado autor independente das variáveis na forma de citação do seu nome.