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Electrochemical studies of the interface Fe/0.5 mol L(-1) H(2)SO(4) in the presence of benzotriazole and tolytriazole

CUNHA, M. T. da; RODRIGUES, P. R. P.; CORDEIRO, G. G. O.; D`ELIA, E.; AGOSTINHO, S. M. L.
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.79%
The effect of benzotriazole (BTAH) and tolytriazole (TTAH) on the electrochemical behaviour of the Fe/0.5 mol L(-1) H(2)SO(4) interface at 25 degrees C was studied using cronopotentiometry, anodic and cathodic polarization curves and electrochemical impedance spectroscopy. BTAH and TTAH are inhibitors of anodic iron dissolution and the subsequent hydrogen evolution in 0.5 mol L(-1) H(2)SO(4) medium. Mass transport is an important step in the anodic process of inhibitive film formation. Electrochemical impedance spectroscopy was used to investigate the iron dissolution mechanism in the presence of the inhibitors and showed that BTAH and TTAH are adsorbed on the iron surface, thereby changing its dissolution mechanism in sulfate media. Starting from an iron dissolution model, it was possible to suggest two different mechanisms for iron dissolution in 0.5 mol L(-1) H(2)SO(4) containing BTAH or TTAH that involve a complex Fe(II)-inhibitor. (C) 2009 Elsevier B.V. All rights reserved

The processes involved in the Se electrodeposition and dissolution on Au electrode: the H2Se formation

SOLALIENDRES, M. O.; MANZOLI, A.; SALAZAR-BANDA, G. R.; EGUILUZ, K. I. B.; TANIMOTO, S. T.; MACHADO, S. A. S.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.37%
The processes involved in the Se electrodeposition, mainly the one related to the formation of H2Se species on Au electrode in perchloric acid solutions, have been investigated through cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), rotating ring-disc electrode (RRDE), and atomic force microscopy (AFM) techniques. In the experiments performed with the EQCM, with the potential sweep in the negative direction, the responses for the mass variation were divided in three well-defined potential regions: A (from 1.55 to 0.35 V), B (from 0.35 to -0.37 V), and C (from -0.37 to -0.49 V). It was verified that the following processes can occur, respectively: the species (AuO)(2)H2SeO3 was desorbed during the AuO reduction, the reduction of Se(IV) to Se(0), and the formation of H2Se. When the potential was swept in the positive direction, the responses for the mass variation were divided in four well-defined potential regions: D (from -0.49 to 0.66 V), E (from 0.66 to 0.99 V), F (from 0.99 to 1.26 V), and G (from 1.26 to 1.55 V), and the described processes in these regions were, respectively: the Se deposition and adsorption of water molecules and/or perchlorate ions, the Se dissolution, the Se incorporating mass in the form of HO-Se...

Probing the Enamel Topography After Acid Erosion by Scanning Electrochemical Microscopy

Castro, Pollyana Souza; Dantas, Luiza Maria Ferreira; Nishida, Alexander Cassandri; Francci, Carlos Eduardo; Bertotti, Mauro
Fonte: ELECTROCHEMICAL SCIENCE GROUP; BELGRADE Publicador: ELECTROCHEMICAL SCIENCE GROUP; BELGRADE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.33%
In this work, we present an investigation on the thickness of the eroded enamel layer in tooth samples after exposure to citric and hydrochloric acid by using Scanning Electrochemical Microscopy (SECM). Approaching curves with typical negative feedback behavior were obtained in enamel samples for evaluation of topographic changes. In a control experiment, SECM images showed no significant difference in the current monitored during the scan, implying that enamel demineralization did not occur in mineral water medium. Topographic SECM images obtained after contact with citric and hydrochloric acid for different periods of time showed a significant increase in the current relative to a previously protected surface, indicating the structural loss of enamel. The thickness of the enamel layer eroded after contact with hydrochloric acid was significantly higher when compared to the one obtained with citric acid. Hence, our results showed that the enamel acid erosion is a relatively fast process, which is strongly dependent on parameters such as pH, time, acid strength and acid concentration.; FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)

Estudo da estabilidade de catalisadores catódicos em célula eletroquímica; Study of the stability of cathode catalysts in electrochemical cell

Zignani, Sabrina Campagna
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 03/03/2009 PT
Relevância na Pesquisa
36.62%
O objetivo do presente trabalho foi avaliar a estabilidade de eletrocatalisadores de Pt/C e ligas binárias de Pt-Co/C e Pt-Ni/C contendo 20% em massa de metal sobre carbono frente à reação de redução de oxigênio em células eletroquímicas. O trabalho experimental desenvolvido compreende várias etapas como preparação de catalisadores, tratamento térmico e preparação de eletrodos. O catalisador foi preparado pela redução de precursores com borohidreto de sódio, e suportado em carbono de alta área superficial (Vulcan XC-72, Cabot, 240m2g-1). O eletrodo da célula é um eletrodo de difusão de gás (EDG) de alta área superficial. Os catalisadores foram tratados termicamente em atmosfera de H2 a 550°C por uma hora. Os testes de estabilidade foram 30h de cronoamperometria ou ciclagem de potencial totalizando 1000 ciclos. Absorção Atômica, DRX (difração de raios-x) e EDX (energia dispersiva de raios-x) foram feitos antes e após os experimentos. Em geral observou-se que os catalisadores de Pt-Co/C e Pt-Ni/C apresentaram maior atividade para a RRO comparados a Pt/C, mas em contrapartida estes materiais sofrem corrosão e após algumas horas de operação há dissolução de metal e a atividade decresce muito. Os testes de cronoamperometria revelaram maior estabilidade de corrente para os materiais bimetálicos...

Estudo eletroquímico de ligas à base de cobalto-cromo e níquel-cromo; Electrochemical study of Co-Cr and Ni-Cr based alloys

Souza, Klester dos Santos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/08/2011 PT
Relevância na Pesquisa
36.46%
Ligas metálicas não nobres são amplamente utilizadas em odontologia desde a segunda metade do século XX. Várias ligas metálicas para utilização em próteses sobre o implante dentário têm sido propostas nos últimos anos, visando uma melhor interação metal-cerâmica e maior resistência eletroquímica ao ambiente bucal. O objetivo deste trabalho é avaliar e comparar o comportamento eletroquímico in vitro de ligas à base de cobalto-cromo e níquel-cromo, utilizadas em supra estruturas de implantes dentários. Estas ligas foram estudadas em meios de solução aquosa de NaCl 0,15 mol L-1, saliva artificial e NaCl 0,15 mol L-1 com adição de caseína, fluoreto de sódio ou ácido acético, a partir de técnicas eletroquímicas e não eletroquímicas. Como técnicas eletroquímicas foram empregadas: medidas de potencial de circuito aberto, curvas de polarização anódica, cronoamperometria, voltametria cíclica e espectroscopia de impedância eletroquímica. As técnicas não eletroquímicas utilizadas foram: espectroscopia de absorção atômica com atomização eletrotérmica (EAA-FG), espectroscopia de fotoelétrons excitados por raios-X (XPS), microscopia eletrônica de varredura (MEV) e espectroscopia de energia dispersiva (EDS). Foram realizados testes de citotoxicidade utilizando a metodologia de incorporação do vermelho neutro. Uma boa correlação foi estabelecida entre os resultados obtidos pelas diferentes técnicas. Em solução de NaCl e saliva artificial as ligas apresentaram a seguinte ordem de resistência à oxidação: CoCrW < NiCrMo < CoCrMo. O filme formado em meio de saliva artificial se mostrou mais protetor do que o formado em meio de NaCl para todas as ligas...

Electrochemical and structural characterization of heat-treated Cr3C2-NiCr coatings

Suegama, P. H.; Espallargas, N.; Guilemany, J. M.; Fernandez, J.; Benedetti, A. V.
Fonte: Electrochemical Soc Inc Publicador: Electrochemical Soc Inc
Tipo: Artigo de Revista Científica Formato: B434-B445
ENG
Relevância na Pesquisa
36.63%
The influence of heat-treatments on the electrochemical behavior of thermal spray Cr3C2-NiCr coatings prepared by high velocity oxygen fuel (HVOF) was studied in NaCl solution, at 25 degrees C, using open-circuit potential (E-OC) and electrochemical impedance spectroscopy (EIS) measurements. Coating characterization were performed before and after the heat-treatments and electrochemical tests by scanning electron microscopy, X-ray diffraction, and Auger electron spectroscopy. In addition to the changes in the original powder composition occurring during HVOF process, heat-treatment performed at 450 degrees C caused no significant changes in electrochemical response compared with untreated sample, and at 760 degrees C the main difference was the formation of a thin and defective layer of Cr2O3 at the coating surface, which increased the total impedance at the first day of immersion. Higher influence on the electrochemical was noted for samples treated at 880 degrees C, which also showed higher E-OC and total impedance, and lower corrosion current. This behavior was interpreted considering the formation of a chromium oxide layer on the coating surface, dissolution and decomposition of smaller carbide particles and their surface enrichment with Cr due to C diffusion and dissolution into the matrix...

Electrochemical behavior of metallic chromium in chloride media

Silva, G. C.; Vilchenski, M. C.; Sumodjo, PTA; Benedetti, A. V.; Shifler, D. A.; Natishan, P. M.; Tsuru, T.; Ito, S.
Fonte: Electrochemical Society Inc Publicador: Electrochemical Society Inc
Tipo: Conferência ou Objeto de Conferência Formato: 183-+
ENG
Relevância na Pesquisa
36.33%
The electrochemical behavior of metallic chromium in aqueous solutions containing chloride ions at different pH was studied by means of open-circuit potential vs. time measurements, cyclic voltammetry and electrochemical impedance spectroscopy. The composition of the surface oxides was analyzed by XPS. For solutions with pH<3 the formation of a passive layer occurs via a dissolution/precipitation process while for pH>3 the mechanism changes. XPS analysis revealed that Cr2O3 basically constitutes the passive layer.

ELECTROCHEMICAL-BEHAVIOR OF COPPER ELECTRODE IN CONCENTRATED SULFURIC-ACID-SOLUTIONS

Moreira, A. H.; Benedetti, A. V.; Cabot, P. L.; Sumodjo, PTA
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 981-987
ENG
Relevância na Pesquisa
36.53%
The electrochemical behaviour of copper in 6.0 mol l-1 sulfuric acid at 30-degrees-C, was studied by means of the potentiodynamic method.At low potential sweep rates, v < 200 mV s-1, the data reveal that the anodic process is basically constituted of copper dissolution and a film formation which inhibits further metal oxidation and which may undergo further dissolution. For higher potential sweep rates, a modification in the passivation region of the voltammogram is observed. It can be ascribed to a change in the passivation mechanism which possibly involves different surface species. The kinetic relationships derived from the potentiodynamic I/E curves obtained at low v suggest a film formation via a dissolution/precipitation mechanism.

Oxidative dissolution of chalcopyrite by Acidithiobacillus ferrooxidans analyzed by electrochemical impedance spectroscopy and atomic force microscopy

Bevilaqua, D.; Diez-Perez, I; Fugivara, C. S.; Sanz, F.; Benedetti, A. V.; Garcia, O.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 79-84
ENG
Relevância na Pesquisa
36.52%
The microbiological leaching of chalcopyrite (CuFeS2) is of great interest because of its potential application to many CuFeS2-rich ore materials. However, the efficiency of the microbiological process is very limited because this mineral is one of the most refractory to bacterial attack. Knowledge of bacterial role during chalcopyrite oxidation is very important in order to improve the efficiency of bioleaching operation. The oxidative dissolution of a massive chalcopyrite electrode by Acidithiobacillus ferrooxidans was evaluated by electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). A massive chalcopyrite electrode was utilized in a Tait-type electrochemical cell in acid medium for different immersion times in the presence or absence of bacterium. The differences observed in the impedance diagrams were correlated with the adhesion process of bacteria on the mineral surface. (C) 2004 Elsevier B.V. All rights reserved.

ELECTROCHEMICAL STUDIES WITH COPPER-BASED ALLOYS - OPEN-CIRCUIT POTENTIAL OSCILLATIONS IN ALKALINE MEDIA

Hurtado, MRF; Sumodjo, PTA; Benedetti, A. V.
Fonte: Electrochemical Soc Inc Publicador: Electrochemical Soc Inc
Tipo: Artigo de Revista Científica Formato: 1567-1571
ENG
Relevância na Pesquisa
36.37%
In open-circuit potential measurements of certain Cu-based alloys in NaOH solutions oscillations were observed in Cu-Al and Cu-Ag-Al. Studies with various electrolyte concentrations and rotation speeds of the electrode led to a possible explanation of the phenomenon in terms of Al 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.

Electrochemical noise analysis of bioleaching of bornite (Cu5FeS4) by Acidithiobacillus ferrooxidans

Bevilaqua, D.; Acciari, H. A.; Benedetti, A. V.; Fugivara, C. S.; Tremiliosi Filho, G.; Garcia, O.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 50-54
ENG
Relevância na Pesquisa
36.37%
Electrochemical noise (EN) is a generic term describing the phenomenon of spontaneous fluctuations of potential or current noise of electrochemical systems. Since this technique provides a non-destructive condition for investigating corrosion processes, it can be useful to study the electrochemical oxidation of mineral sulfides by microorganisms, a process known as bacterial leaching of metals. This technique was utilized to investigate the dissolution of a bornite electrode in the absence (first 79 h) and after the addition of Acidithiobacillus ferrooxidans (next 113 h) in salts mineral medium at pH 1.8, without addition of the energy source (Fe2+ ions) for this chemolithotrophic bacterium. Potential and current noise data have been determined simultaneously with two identical working bornite electrodes which were linked by a zero resistance ammeter (ZRA). The mean potential, E-coup, coupling current, I-coup, standard deviations of potential and current noise fluctuations and noise resistance, R-n, have been obtained for coupled bornite electrodes. Noise measurements were recorded twice a day in an unstirred solution at 30 degrees C. Significant changes in these parameters were observed when the A. ferrooxidans suspension was added...

Electrochemical behaviour of copper electrode in concentrated sulfuric acid solutions

Moreira, A. H.; Benedetti, A. V.; Cabot, P. L.; Sumodjo, P. T A
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 981-987
ENG
Relevância na Pesquisa
36.53%
The electrochemical behaviour of copper in 6.0 mol 1-1 sulfuric acid at 30°C, was studied by means of the potentiodynamic method. At low potential sweep rates, v < 200 m V s-1, the data reveal that the anodic process is basically constituted of copper dissolution and a film formation which inhibits further metal oxidation and which may undergo further dissolution. For higher potential sweep rates, a modification in the passivation region of the voltammogram is observed. It can be ascribed to a change in the passivation mechanism which possibly involves different surface species. The kineticrelationships derived from the potentiodynamic I/E curves obtained at low v suggest a film formation via a dissolution/precipitation mechanism. © 1993.

Electrochemical studies of copper, copper-aluminium and copper-aluminium-silver alloys: Impedance results in 0.5M NaCl

Benedeti, A. V.; Sumodjo, P. T A; Nobe, K.; Cabot, P. L.; Proud, W. G.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 2657-2668
ENG
Relevância na Pesquisa
36.37%
The electrochemical behaviour of Cu, Cu-Al and Cu-Al-Ag alloys in aqueous solutions of NaCl (0.5 M, pH = 3.00) was studied by means of voltammetric methods and electrochemical impedance spectroscopy. The surfaces were examined by SEM and EDX analysis. Cu-Al-Ag alloy shows a potentiodynamic behaviour similar to that of the pure copper electrode while the Cu-Al alloy presents some minor differences. In the active dissolution region the electrodes suffer pitting corrosion and in the other potential regions there are the formation of a passivant film with composition depending on the potential. The impedance responses of the electrodes are discussed. An electrodissolution mechanism is proposed and the effect of the alloying elements upon the impedance response and polarisation curves is explained. The main effects are due to the production of copper and silver chlorides and aluminium oxides/ hydroxides at the corroding interface. The addition of Al or (Al + Ag) increases the corrosion resistance of pure copper. © 1995.

The effect of chloride ions and A. ferrooxidans on the oxidative dissolution of the chalcopyrite evaluated by electrochemical noise analysis (ENA)

Horta, D. G.; Acciari, H. A.; Bevilaqua, D.; Benedetti, A. V.; Garcia, O.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 397-400
ENG
Relevância na Pesquisa
36.79%
It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Clions only produced some effect after some time due to the barrier effect caused by bacteria adhesion. © (2009) Trans Tech Publications.

Instabilities in electrochemical systems with a rotating disc electrode

Pontes,J.; Mangiavacchi,N.; Conceição,A. R.; Mattos,O. R.; Barcia,O. E.; Tribollet,B.
Fonte: The Brazilian Society of Mechanical Sciences Publicador: The Brazilian Society of Mechanical Sciences
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2002 EN
Relevância na Pesquisa
36.37%
Polarization curves experimentally obtained in the electro-dissolution of iron in a 1 M H2SO4 solution using a rotating disc as the working electrode present a current instability region within the range of applied voltage in which the current is controlled by mass transport in the electrolyte. According to the literature (Barcia et. al., 1992) the electro-dissolution process leads to the existence of a viscosity gradient in the interface metal-solution, which leads to a velocity field quantitatively different form the one developed in uniform viscosity conditions and may affect the stability of the hydrodynamic field. The purpose of this work is to investigate whether a steady viscosity profile, depending on the distance to the electrode surface, affects the stability properties of the classic velocity field near a rotating disc. Two classes of perturbations are considered: perturbations monotonically varying along the radial direction, and perturbations periodically modulated along the radial direction. The results show that the hydrodynamic field is always stable with respect to the first class of perturbations and that the neutral stability curves are modified by the presence of a viscosity gradient in the second case, in the sense of reducing the critical Reynolds number beyond which perturbations are amplified. This result supports the hypothesis that the current oscillations observed in the polarization curve may originate from a hydrodynamic instability.

Electrochemical impedance and current fluctuations analysis during slow strain rate test of a UNS S30400 stainless steel in low pH media

Bastos,Ivan N.; Nogueira,Ricardo P.; Ponciano,José A. C.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
36.42%
This paper is aimed at investigating the electrochemical behavior of austenitic stainless steel UNS S30400 under stress corrosion cracking conditions in acidic solutions at room temperature. Electrochemical impedance spectroscopy and electrochemical current noise measurements were performed at different stress levels during slow strain rate tests at pH 0.00 and 1.00 in order to evaluate the influence of mechanical deformation on the evolution of the electrochemical responses of the interface. Results have shown that, differently to what happens at pH 1.00, the corrosive attack at pH 0.00 is characterized by intensive cracking concomitantly to the progressive spreading out of uniform corrosion on the metallic surface. The coupling of both electrochemical impedance and current noise techniques provided complementary information about the interplay between dissolution and cracking of the stainless steel exposed to electrolytes of different aggressiveness.

Scanning electrochemical microscopy: study of the deposition and stripping mechanism of lead in the presence of copper

Sousa,M. Fátima B.; Sanchez,E. M. S.; Bertazzoli,Rodnei
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
Relevância na Pesquisa
36.33%
This paper describes the application of scanning electrochemical microscopy (SECM) in the substrate-generation/tip-collection (SG/TC) mode to elucidate mechanistic aspects of the deposition and stripping of Pb2+ ions in the presence of Cu2+ into a glassy carbon substrate electrode. A stripping peak was observed between the main peaks corresponding to the pure metals. Its position, height and shape were investigated, and the peak intensity was found to depend on the Pb2+/Cu2+ concentration ratio. The results suggested that this peak was due to the dissolution of lead deposited in copper, as a result of an underpotential deposition. The scanning electrochemical microscope provided additional information towards the understanding of the stripping mechanisms in analytical studies. In particular, the SECM-tip response yielded direct evidence about the speciation of some of the compounds evolved during stripping. This information was not available from the voltammetric response of the substrate electrode alone.

Texturização superficial eletroquímica sem mascaramento com finalidades tribológicas; Maskless electrochemical texturing surfaces for tribological purposes

Parreira, Jakeline Guimarães
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
56.75%
A texturização superficial pode ser utilizada para melhorar o desempenho tribológico de contatos mecânicos, em particular em regimes lubrificados. O presente trabalho tem o objetivo de aprimorar uma metodologia alternativa para a texturização de superfícies baseada em princípios de usinagem eletroquímica. A dissolução eletroquímica alia rapidez, reprodutibilidade e elevado custo-benefício, que são extremamente importantes quando se visa a aplicação da microtexturização em escala industrial. O não mascaramento da área a ser texturizada otimiza a técnica, dispensando um tratamento prévio e posterior de cada superfície. Uma técnica também não convencional de usinagem, a eletroerosão, foi utilizada para a microfuração da tampa da ferramenta a ser usada na microtexturização. O padrão de microfuração da ferramenta é copiado à peça pela ação da dissolução eletroquímica. O aprimoramento da técnica de texturização eletroquímica foi acompanhado pelo projeto de um circuito eletrônico com sistema de aquisição de dados, de uma célula eletroquímica e pelo dimensionamento de um sistema para bombeamento e fluxo de eletrólito, que permitiram uma melhora no acabamento superficial das peças microtexturizadas...

Electrochemical studies of copper, copper-aluminium and copper-aluminium-silver alloys: Impedance results in 0.5M NaCl

Benedetti, Assis Vicente; Sumodjo, P. T. A.; Nobe, K.; Cabot, P. L.; Proud, W. G.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 2657-2668
ENG
Relevância na Pesquisa
36.37%
The electrochemical behaviour of Cu, Cu-Al and Cu-Al-Ag alloys in aqueous solutions of NaCl (0.5 M, pH = 3.00) was studied by means of voltammetric methods and electrochemical impedance spectroscopy. The surfaces were examined by SEM and EDX analysis. Cu-Al-Ag alloy shows a potentiodynamic behaviour similar to that of the pure copper electrode while the Cu-Al alloy presents some minor differences. In the active dissolution region the electrodes suffer pitting corrosion and in the other potential regions there are the formation of a passivant film with composition depending on the potential. The impedance responses of the electrodes are discussed. An electrodissolution mechanism is proposed and the effect of the alloying elements upon the impedance response and polarisation curves is explained. The main effects are due to the production of copper and silver chlorides and aluminium oxides/ hydroxides at the corroding interface. The addition of Al or (Al + Ag) increases the corrosion resistance of pure copper. © 1995.

Electrochemical behaviour of copper electrode in concentrated sulfuric acid solutions

Moreira, A. H.; Benedetti, Assis Vicente; Cabot, P. L.; Sumodjo, P. T A
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 981-987
ENG
Relevância na Pesquisa
36.53%
The electrochemical behaviour of copper in 6.0 mol 1-1 sulfuric acid at 30°C, was studied by means of the potentiodynamic method. At low potential sweep rates, v < 200 m V s-1, the data reveal that the anodic process is basically constituted of copper dissolution and a film formation which inhibits further metal oxidation and which may undergo further dissolution. For higher potential sweep rates, a modification in the passivation region of the voltammogram is observed. It can be ascribed to a change in the passivation mechanism which possibly involves different surface species. The kineticrelationships derived from the potentiodynamic I/E curves obtained at low v suggest a film formation via a dissolution/precipitation mechanism. © 1993.