LARISSA OLIVEIRA BERBEL

LARISSA OLIVEIRA BERBEL

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Corrosion mechanism of Ti-6Al-4V morse taper dental implants connected to 316 L stainless steel prosthetic abutment
2022 - BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G. de; MICELLI, ANA L.P.; NIGRO, FREDERICO; ROSSI, JESUALDO L.; COSTA, ISOLDA
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.
The corrosion behavior on AA2050-T84 and AA7050-T7451 welded and non-welded by FSW
2021 - VIVEIROS, BARBARA V.G. de; BERBEL, LARISSA O.; DONATUS, UYIME; COSTA, ISOLDA
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.
Corrosion of dental implants made of Ti-6Al-4V connected to 316L SS in agressive environment
2021 - BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G. de; MICELLI, ANA L.; NIGRO, FREDERICO; ROSSI, JESUALDO L.; COSTA, ISOLDA
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.
Comparing the corrosion behaviour of AA2050 and AA7050 aluminium alloys by scanning vibrating electrode and scanning ion-selective electrode techniques
2022 - VIVEIROS, BARBARA V.G. de; DONATUS, UYIME; ALENCAR, MAICON C. de; BERBEL, LARISSA O.; COSTA, ISOLDA
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.
A study on corrosion resistance of ISO 5832-1 austenitic stainless steel used as orthopedic implant
2020 - BRAGUIN, L.N.M.; SILVA, C.A.J. da; BERBEL, L.O.; VIVEIROS, B.V.G. de; ROSSI, J.L.; COSTA, I.; SAIKI, M.
The ISO 5832-1 austenitic stainless steel used as biomaterial is largely applied in the area of orthopedics, especially in the manufacture of implants, such as temporary or permanent replacement of bone structures. The objective of this study was to evaluate the localized corrosion resistance of the ISO 5832-1 stainless steel used in orthopedic implants by electrochemical tests in two different solutions. The results of this study are of great interest to evaluate the corrosion of metallic implants that can result in the release of corrosion products into bodily fluids causing possible adverse biological reactions. The determination of the chemical elements in the composition of the ISO 5832-1 stainless steel was performed by neutron activation analysis (NAA). The samples for electrochemical tests were grinded with silicon carbide paper up to #4000 finishing, followed by mechanical polishing with diamond paste. The open circuit potential measurements and anodic polarization curves were obtained in solution of 0.90 wt. % of NaCl and of simulated body fluid (SBF). The results indicated that the ISO 5832-1 stainless steel presented a high resistance to crevice corrosion in simulated body fluid solution but high susceptibility to this form of corrosion in the chloride solution.
Study of ph effect on AZ31 magnesium alloy corrosion for using in temporary implants
2020 - SILVA, CAIO A.J. da; BRAGUIN, LILIAN N.M.; BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G.; ROSSI, J.L.; SAIKI, M.; COSTA, I.
Currently, magnesium alloys are gaining great interest for medical applications due to their degrading properties in the human body ensuring a great biocompatibility. These alloys also provide profitable mechanical properties due similarities with human bone. However, a difficulty in applying these materials in the biomaterials industries is the corrosion prior to cell healing. The effect of the chemical composition of Mg alloys on their corrosion behavior is well known. In this study, samples of AZ31 magnesium alloy were cut into chips for elemental chemical analysis by neutron activation analysis (NAA). Concentrations of the elements As, La, Mg, Mn, Na, Sb and Zn were determined in the AZ31 alloy. Visualization tests of agar corrosion development in various media, of 0.90% sodium chloride solution (mass), phosphate buffer saline (PBS) and simulated body fluid (SBF) were performed. Visualizations of the effect of agar gel corrosion revealed pH variation during the corrosion process due to the released into the cathode. The highest released of hydroxyl ions occurred in NaCl solution compared to PBS and SBF solutions indicating that NaCl solution was much more aggressive to the alloy compared to the others.
Effect of galvanic coupling between titanium alloy and stainless steel on behavior of corrosion of dental implants
2020 - BERBEL, LARISSA O.; VIVEIROS, BARBARA V.G. de; MICELLI, ANA L.; ROSSI, JESUALDO; NIGRO, FREDERICO; ARANHA, LUIS C.; COSTA, ISOLDA
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.
Estudo do comportamento frente à corrosão da liga de magnésio AZ31 de uso em implantes temporários utilizando soluções simuladoras de fluidos corpóreos
2019 - SILVA, C.A.J.; BRAGUIN, L.N.M.; VIVEIROS, B.G.; BERBEL, L.O.; ROSSI, J.L.; COSTA, I.; SAIKI, M.
Atualmente, ligas de magnésio estão ganhando grande interesse para aplicações médicas devido a sua propriedade de degradação no corpo humano, principalmente para aplicações de interesse como stents cardiovasculares e próteses ortopédicas. Estes implantes temporários fornecem uma estabilidade mecânica necessária para o reparo e corroem completamente após o tempo de vida útil e fim do tratamento. Contudo, uma dificuldade na aplicação destes materiais na indústria de biomateriais é a corrosão antecipada e precoce à cura celular. Amostras da liga de magnésio AZ31 foram cortadas em lascas e a técnica escolhida para análise química elementar foi a Análise por Ativação com Nêutrons (NAA). Irradiações de curta e longa duração foram realizadas nas amostras juntamente com padrões sintéticos no reator IEA-R1 em um fluxo de nêutrons térmicos abaixo de 4,0x1012 n cm-2s-1. Concentrações dos elementos As, La, Mg, Mn, Na, Sb e Zn foram determinadas na liga AZ31, calculadas pelo método comparativo. Para os ensaios de corrosão, as amostras foram limpas com álcool etílico, acetona e água purificada MilliQ por agitação ultrassônica, e, em seguida foram lixadas com lixas de SiC com granulometria de #500, #800, #1200, #2000 e #4000. Testes de visualização em ágar-ágar e imersão foram realizados em solução de cloreto de sódio 0,90 % (massa), solução tampão de fosfato (PBS) e solução simuladora de fluidos corpóreos (SBF) utilizando fenolftaleína como indicador ácido-base. A observação das superfícies das amostras, antes e após exposição às soluções, foi realizada por microscopia óptica (MO) e microscopia eletrônica de varredura (MEV). A superfície também foi observada após remoção dos produtos de corrosão por desmutting e irradiação para análise quantitativa pela técnica NAA. Visualizações em gel ágarágar revelaram aumento do pH local proveniente da liberação de íons hidroxila da reação catódica e menor liberação de íons ocorreu em SBF em comparação às soluções de NaCl e PBS. As micrografias da superfície evidenciaram a formação instantânea de uma camada de produtos de corrosão após uma hora de ensaio e o desmutting revelou microcavidades caracterizadas por pites.
The corrosion resistance between AA2050-T84 and AA7050-T7451 welded by friction stir weld
2019 - VIVEIROS, BARBARA V.G. de; BERBEL, LARISSA O.; BUGARIN, ALINE F.S.; DONATUS, UYIME; COSTA, ISOLDA
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.
Estudo da resistência à corrosão das ligas AA2050-T84 e AA7050-T7451 soldadas por FSW
2018 - VIVEIROS, B.V.G. de; ALENCAR, M.C.; BERBEL, L.O.; DONATUS, U.; COSTA, I.
As ligas de alumínio da série 2XXX e 7XXX são muito utilizadas comercialmente em indústrias aeronáuticas pela presença de boas características como resistência à corrosão, resistência mecânica e baixa densidade. Porém, quando soldadas, suas microestruturas sofrem mudanças, o que altera suas propriedades. Neste estudo, as ligas 2XXX e 7XXX foram soldadas pelo método de fricção e mistura, também conhecido como “friction stir welding” (FSW), que aquece e quebra os grãos pela tensão aplicada resultando na soldagem no estado sólido das duas ligas. Neste estudo a resistência à corrosão das ligas AA2050-T84 e AA7050-T7451 soldadas por FSW foi investigada pela técnica “Scanning Vibrating Electrode Technique” (SVET), e por “Scanning Ion - Electrode Technique” (SIET), em que foi realizada a medição de pH localizado. O eletrólito usado neste estudo foi composto por 5 mM de NaCl sendo que a região analisada da solda foi a secção transversal. As zonas afetadas pelo processo FSW são apresentadas e caracterizadas a partir do tamanho de grãos existentes, como metal base (MB), zona termicamente afetada (ZTA), zona termomecanicamente afetada (ZTMA), zona de transição da zona termomecanicamente afetada das ligas (ZTMA trans) e a zona de mistura (ZM), que é a área de recristalização dos grãos. Foram também realizados ensaios de potencial de circuito aberto (OCP) e impedância eletroquímica (EIS) nas mesmas regiões observadas e ensaiadas dos ensaios anteriores, também com solução de 5 mM de NaCl. Os resultados mostraram que nas primeiras horas de ensaio, a área mais suscetível ao ataque foi a zona de transição das ligas (ZTMA trans), mas após 24 h de ensaio, a zona mais suscetível foi a ZTMA da liga 7050-T7451. Esses resultados foram correlacionados com a microestrutura das diferentes zonas.