Papers by Assis Vicente Benedetti
Corrosion Engineering, Science and Technology, 2019
Portugaliae Electrochimica Acta, 2003
Journal of Thermal Analysis and Calorimetry
Thermogravimetry, cyclic voltammetry and other analytical techniques were used to study the react... more Thermogravimetry, cyclic voltammetry and other analytical techniques were used to study the reactions of mercury with pure iridium. The results allowed to suggest when subjected to heat or anodic stripping voltammetry an electrodeposited mercury film reacts with Ir substrate and at least three mass loss steps and three peaks appear in the mercury desorption process. The first two were attributed to Hg(0)species removal like a mercury bulk and a mercury monolayer. The last can be ascribed to the mercury removal from a solid solution with iridium.
Journal of Thermal Analysis and Calorimetry
Thermogravimetry (TG) and other analysis techniques (EDX, SEM, Mapping surface, X-ray diffraction... more Thermogravimetry (TG) and other analysis techniques (EDX, SEM, Mapping surface, X-ray diffraction, inductively coupled argon plasma emission spectroscopy and atomic spectrometry with cold vapor generation) were used to study the reaction of Hg with Rh. The results permitted the suggestion that, when subjected to heat, an electrodeposited Hg film reacts with Rh to form intermetallic products with different stabilities, as indicated by at least three mass loss steps. In the first step, between room temperature and 160°C, only the bulk Hg is removed. From this temperature up to about 175°C, the mass loss can be attributed to the desorption of a film of metallic Hg. The last step, from 175 to 240°C, can be ascribed to the removal of Hg from a thin dark film of RhHg2 .
Portugaliae Electrochimica Acta, 2003
Key Engineering Materials, 2001
CUHK Sir. ...
The Electrochemical Society, 2014
Advanced Materials Research, 2007
The electrochemical response of chalcopyrite was studied using electrochemical noise analysis (EN... more The electrochemical response of chalcopyrite was studied using electrochemical noise analysis (ENA). The assay was carried out under constant aeration using 30 mL in two electrochemical cells containing iron-free mineral salts solution. These cells were initially monitored for 56 hours. After 72 hours, 7.25×1010 cells mL-1 of A. ferrooxidans strain LR were added in both cells and monitored until 128 h. Subsequent to this period, 0.927 mmol L-1 of silver ions and 400 mmol L-1 of chloride ions were added each one separately. Both conditions were monitored until 168 hours. According to results obtained, it was observed that Cl- ions addition induced an accelerated corrosion process. However, there is a tendency of the system to reach the stationary state due to repassivation of the electrodic surface. In the other side, the Ag+ addition contributed for the maintenance of the oxidant atmosphere, in spite of controversial effect caused by considerable variations in the Rn values, resulting in a instability in the chalcopyrite reactivity.
Journal of Materials Science, 1997
The influence of silver additions on the structure and phase transformation of the Cu-13 wt% Al a... more The influence of silver additions on the structure and phase transformation of the Cu-13 wt% Al alloy was studied by differential thermal analysis, X-ray diffraction, scanning electron microscopy and energy dispersive analysis of X-rays. The results indicate that the presence of silver modifies the phase-stability field, the transition temperature and the structure of the alloy. These effects are more pronounced
Thin Solid Films, 1999
Mercury thin films prepared by electrochemical deposition on Pt–Ir alloy and after partial removi... more Mercury thin films prepared by electrochemical deposition on Pt–Ir alloy and after partial removing of mercury at different temperatures were studied by means of an interferometric surface mapping microscope and by X-ray photoelectronic spectroscopy. Mercury film samples having mercury partially removed by anodic stripping at a potential more positive than the corresponding peak in the voltammogram were also studied using
Surface and Coatings Technology, 2006
Stainless steel coatings obtained by High Velocity Oxygen Fuel (HVOF) were characterized using op... more Stainless steel coatings obtained by High Velocity Oxygen Fuel (HVOF) were characterized using optical (OM) and scanning electron microscopy (SEM), electron probe micro-analysis, X-ray diffraction (XRD), open-circuit potential (EOC) measurements, electrochemical impedance spectroscopy (EIS) and polarisation tests. Differences among coated steels were mainly related with the gun-substrate distance parameter (310 mm for samples A and B and 260 mm for
Journal of Thermal Analysis and Calorimetry, 2007
Thermogravimetry, Differential Scanning Calorimetry and other analytical techniques (Energy Dispe... more Thermogravimetry, Differential Scanning Calorimetry and other analytical techniques (Energy Dispersive X-ray Analysis; Scanning Electron Microscopy; Mapping Surface; X-ray Diffraction; Inductively Coupled Plasma Atomic Emission Spectroscopy and Cold Vapor Generation Atomic Absorption Spectroscopy) have been used to study the reaction of mercury with platinum foils. The results suggest that, when heated, the electrodeposited Hg film reacts with Pt to form intermetallic compounds each having a different stability, indicated by at least three mass loss steps. Intermetallic compounds such as PtHg 4 , PtHg and PtHg 2 were characterized by XRD. These intermetallic compounds were the main products formed on the surface of the samples after partial removal of bulk mercury via thermal desorption. The Pt(Hg) solid solution formation caused great surface instability, attributed to the atomic size factor between Hg and Pt, facilitating the acid solution's attack to the surface.
Journal of Thermal Analysis and Calorimetry, 2006
... to the formation of IrO-[19] and PtO-containing spe-cies [20] respectively, and the hydrogen ... more ... to the formation of IrO-[19] and PtO-containing spe-cies [20] respectively, and the hydrogen evolution was observed at around –0.25 V. Figure 4 shows cyclic voltammograms recorded for a laminar electrode of Pt–30% Ir alloy in the sup-porting electrolyte without and with Hg(I ...
Journal of the Brazilian Chemical Society, 2003
Eletrodos de bornita foram caracterizados na presença e na ausência de Acidithiobacillus ferrooxi... more Eletrodos de bornita foram caracterizados na presença e na ausência de Acidithiobacillus ferrooxidans, um importante microorganismo envolvido nos processos de lixiviação de metais. A presença da bactéria modificou significativamente a interface mineral/eletrólito, aumentando a taxa de corrosão, como revelado pelas análises interferométricas, AEM, ICP e EIS. A atividade bacteriana sobre o eletrodo de bornita o tornou poroso e conseqüentemente aumentaram sua área e heterogeneidade. Este comportamento foi correlacionado com a evolução dos diagramas de impedância obtidos durante o tempo do experimento. A principal diferença nestes diagramas foi a presença de uma característica indutiva (até 44 h), a qual está relacionada com a ação bacteriana sobre a dissolução do mineral e não com sua adesão. A impedância real total medida na presença da bactéria foi cerca de 10 vezes menor do que na sua ausência, devido a aceleração na dissolução do mineral, uma vez que é mantido o meio oxidante. Bornite electrodes were characterized in the absence or in the presence of Acidithiobacillus ferrooxidans, which is an important microorganism involved in metal bioleaching processes. The presence of the bacterium modified the mineral/electrolyte interface, increasing the corrosion rate, as revealed by interferometric, AEM, ICP and EIS analyses. As a consequence of bacterial activity the electrode became porous, increasing its surface heterogeneity. This behavior was correlated with the evolution of impedance diagrams obtained during the time course of experiments. The main difference in these diagrams was the presence of an inductive feature (up to 44 h), which was related to bacterial action on the mineral dissolution, better than to its adhesion on the bornite. The total real impedance measured in presence of the bacterium was about 10 times lower than in its absence, due to the acceleration of the mineral dissolution, because an oxidant environment was maintained.
Journal of The Electrochemical Society, 2011
The corrosion resistance of 316L stainless steel in 65 wt % ethanol, 35 wt % water, 1 wt % H 2 SO... more The corrosion resistance of 316L stainless steel in 65 wt % ethanol, 35 wt % water, 1 wt % H 2 SO 4 solution containing different NaCl concentrations and at different temperatures was investigated using open circuit potential measurements, polarization curves, and electrochemical impedance spectroscopy. At 25 C, the minimum NaCl concentration required for occurrence of pitting was 0.58 wt %. In 0.35 wt % NaCl solution, localized corrosion was observed at temperatures higher than 40 C and, depending on the potential, metastable or stable pits were observed. No pits were observed below 40 C in 0.35 wt % NaCl solution.
Journal of The Electrochemical Society, 1993
In open-circuit potential measurements of certain Cu-based alloys in NaOH solutions oscillations ... more In open-circuit potential measurements of certain Cu-based alloys in NaOH solutions oscillations were observed in Cu-A1 and Cu-Ag-A1. Studies with various electrolyte concentrations and rotation speeds of the electrode led to a possible explanation of the phenomenon in terms of A1 dissolution altering the main Cu dissolution/passivation process. The accumulation of aluminate ions on the interphase and its transportation to the bulk solution are the main causes of the oscillations.
Journal of Applied Electrochemistry, 1992
The localized corrosion of A1-(5.03 %)Zn-(l. 67%)Mg-(0.23 %)Cu alloys and high purity A1 has been... more The localized corrosion of A1-(5.03 %)Zn-(l. 67%)Mg-(0.23 %)Cu alloys and high purity A1 has been studied using electrochemical techniques, optical microscopy, SEM and EDX. The samples were previously submitted to different heat treatments in which coherent and incoherent MgZn2 precipitates with different distribution and aggregation degree were produced. The influence of NaC1 and Na2 SO4, dissolved oxygen, immersion time and convection were studied. In NaC1 solutions, pitting potentials for the alloys were more negative than for aluminium, indicating an increase in their susceptibility to localized corrosion. Moreover, annealed and cold-rolled alloys presented more negative pitting and repassivation potentials than those submitted to age hardening with direct or interrupted quenching. In annealed and cold-rolled samples, pit nucleation and propagation takes place in the zones where MgZn 2 is accumulated. In the case of the age-hardened alloys, a double pitting behaviour is observed, the first one in the magnesium and zinc enriched regions and the second in the matrix. While the cold water quenched alloy is susceptible to stress corrosion cracking, the alloy submitted to the interrupted quenching process is less susceptible to intergranular attack. The sulphate ion shifts the pitting potential of aluminium and the alloys by chloride towards more positive values because it impedes local accumulations of the latter.
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Papers by Assis Vicente Benedetti