Micro- and nano-electrodes have distinct advantages over large electrodes, including their decreased iR drop and enhanced mass transport due to radial diffusion characteristics which leads to the ready establishment of a steady state (or near steady-state) signal without convection. This enhanced mass transport also leads to increased current densities and signal to noise ratios. However, there is a need for fabrication techniques which reproducibly give micro- and nano-electrodes of controlled size and shape. The optimisation of systematic arrays on the nano-scale, open up possibilities for developing highly sensitive electrode devices, for use in physical chemistry and the determination of fast electrode kinetics and rates of reaction, as well as to provide highly sensitive electroanalytical devices, able to detect very low concentrations of substrates. This thesis first presents work involving the fabrication and characterisation on silicon substrates of square platinum microelectrodes. There is already an established theory for the behaviour of microdisc electrodes however, it is easier to make microsquares reproducibly using pixellated photomasks. The voltammetric and ac impedance characteristics of these electrodes in background electrolyte and in the presence of ferri/ferrocyanide redox couple are presented and the response is theoretically analysed. A combination of computer simulation, theory and experimentation show that these electrodes have increased current densities (14% greater) compared with a microdisc of equivalent radius and an alternative theoretical expression is presented to calculate the limiting current of microsquares at all dimensions. This thesis then discusses the development and optimisation of novel nano-band cavity array electrodes (CaviArE), using standard photo-microlithographic techniques. The resulting architecture encloses a Platinum nanoband of 50 nm width within each array element that is positioned half way up the vertical edges of shallow square cavities (depressions), with a total depth of 1050 nm. The width of the square cavity and the separation of the array elements can be controlled and systematically altered, with great accuracy. The CaviArE devices are shown to give quantitative pseudo-steady-state responses characteristic of multiple nanobands, whilst passing overall currents consistent with a macroelectrode. The array has a much enhanced signal-tonoise ratio compared with an equivalent microsquare array, as it has 0.167% of the area and is therefore markedly less affected by non-Faradaic currents, while it passes comparable Faradaic currents. At high sweep rates the response is also virtually unaffected by solution stirring. The impedammetric characteristics presented show different diffusional regimes at high, medium and low frequencies, associated with diffusion within individual square cavities, outside of the cavity and finally across the whole array as the diffusional fields of the neighbouring array elements overlap. Justification and fitting of equivalent circuits to these frequency regions provide details about the charge transfer, capacitance and diffusional processes occurring. The results show that these systems are highly sensitive to surface transfer effects and a rate constant for ferricyanide of 1.99 cm s-1 was observed, suggesting fast kinetic processes can be detected. Together, these characteristics make nanoband electrode arrays, with this architecture, of real interest for sensitive electroanalytical applications, and development of devices for industrial application is currently being undertaken.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / Electrochemical behaviour of Ce, Fe, Cr,V and Mn in the presence of DTPA, EDTA, EDDS, NTA ligands were investigated by using cyclic voltammetry, a rotating disc electrode and electrochemical impedance spectroscopy for use in redox flow battery (RFB) systems. RFB is currently used for energy storage, the vanadium, which is used in most of the RFB’s, however suffers from species crossover and sluggish reactions, which limit the lifetime of the battery. These various ligands and metal complexes mentioned above where all examined to identify the suitable and favoured electrolyte that can be used for a RFB system. Kinetic parameters such as potential, limiting current, transfer coefficient, diffusion coefficients, and rate constants were studied. RDE experiments confirmed that the parameters measured by CV are similar under hydrodynamic conditions and can be used to determine the kinetic parameters of the redox couples. The use of DTPA as a ligand for complexation of Ce(IV) gave more favourable results compared to other ligand with various metal complexes used in this study [1-3]. The results of kinetic studies of Ce(IV)–DTPA complex shows promise as an electrolyte for a redox flow battery. The separation of V(IV)/(V), Fe (III)/(IV),Cr(III)/(IV),Mn (III)/(IV) and Ce(III)/(IV) with various ligands (EDTA, EDDS, NTA and DTPA) were also investigated using capillary electrophoresis. To understand the speciation of these metal complexes as used in this study and particularly the vanadium, for the reason that it has a complicated (V) oxidation state. The charge/discharge performance of all electrolytes used in this work was determined and a high voltage achieved when Ce-DTPA was used, and it is compared to that of the vanadium electrolyte currently in use. This was evaluated with systems studied previously. Therefore, Ce-DTPA will be a suitable electrolyte for redox flow battery systems.

The molecular identity of the green emission of polyfluorene is investigated in the view point of the molecular interactions between modeled segments. The semi-empirical quantum methods, ZINDO/S and AM1 (AM1-CIS), are used in combination to provide reasonable explanations for experimental spectroscopic properties of monodisperse fluorene oligomers and fluorene oligomers with a central keto defect in dilute solutions. Applying the same method, the molecular interactions between model segments are found to exist and are significant. However, the spectroscopic property change from the molecular interactions is negligible. In addition, the effects of mechanical stress and multi-defects on fluorene oligomers are investigated. On the other hand, the redox mechanisms proposed for the oxidation of an amphiphilic cyanine (C8S3) J-aggregates immobilized at ITO electrode and the subsequent dehydrogenated dimmer formation during cyclic voltammetry based on analysis of absorption spectra during the process are verified with the combined semi-empirical quantum methods similar to the previous methods. The absorption spectra assigned by experiment for electrochemical species involved in the proposed mechanism show reasonable match to the theoretically estimated absorption energies of the corresponding simplified model systems. In addition, the standard reduction potentials of the fairly large molecules, C8S3 monomer and its dehydrogenated dimer, are pursued with quantum mechanical calculations. The free energy difference between the oxidized and reduced states of the target systems is decomposed to electronic energy, solvation energy and temperature-dependent free energies terms. Based on AM1 ground state geometries and with the corresponding temperature dependent free energies, the electronic energies and the solvation energies are each evaluated by two different methods. The electronic energies are calculated with AM1 method and DFT calculation and, also, the solvation energies are obtained based on the atomic partial charges from AM1 and DFT wavefunctions with continuum dielectric solvent approximation. The four calculation schemes from the combinations of the electronic and solvation energy estimation methods are tested with the redox compounds with various molecular weights and the estimations are compared with the corresponding experimental redox potentials. The relative redox potentials between two different redox systems are found to be reasonably estimated with the four calculation schemes. / text

This thesis is concerned with the deposition of nanoparticle films onto boron-doped diamond and tin-doped indium oxide (lTO) surfaces and the characterisation of the films using electron microscopy, powder diffraction methods and quartz crystal microbalance (QCM) data. The redox behaviour of the porous films was examined using cyclic voltammetry in various media to investigate potential electroanalytical applications. TiOz (anatase) mono-layer films were immobilised onto an inert boron-doped diamond substrate. Cyclic voltammetry experiments allowed two distinct steps in the reduction - protonation processes to be identified that are consistent with the formation of Ti(III) surface sites accompanied by the adsorption of protons. Preliminary data for electron transfer processes at the reduced TiOz surface such as the dihydrogen evolution process and the 2 electron - 2 proton reduction of maleic acid to succinic acid are discussed. Novel multi-layer TiOz films were deposited with a variety of organic binder molecules onto ITO substrates. The redox reactivity of Cuz+ with 1,4,7,10- tetraazacyclododecane- 1,4,7, IO-tetrayl- tetrakis (methyl-phosphonic acid) in solution and immobilised on an electrode surface are investigated. The influences of film thickness, scan rate, and pH on the electrochemistry of immobilised pyrroloquinoline quinone was investigated with two possible electron transport processes observed. The thickness of TiOz phytate films was found to change the shape of the resulting cyclic voltammograms dramatically. Computer simulation and impedance spectroscopy allowed insights into the diffusion of electrons to be obtained. 1, 1 ~Ferrocenedimethanol was employed as an adsorbing redox system to study the voltammetric characteristics of carboxymethyl-y-cyclodextrin films and evidence for two distinct binding sites is considered. The apparent transport coefficients for dopamine and Ru(NHJ)6J+ are estimated for TiOz Nafion® films. The electrochemical processes in biphasic electrode systems for the oxidation of water-insoluble N,N-didodecyl-N;N~diethyl-benzene-diamine (DDPD) pure and dissolved in di-(2-ethyl-hexyl)phosphate (HDOP) immersed in aqueous electrolyte media are described. Transfer of the anion from the aqueous electrolyte phase into the organic phase accompanies the oxidation of pure DDPD. In the presence of HOOP, oxidation is accompanied by proton exchange. The electrochemically driven proton exchange process occurs over a wide pH range. Organic microdroplet deposits of OOPD in HDOP at basal plane pyrolytic graphite electrodes are studied using voltammetric techniques and compared to the behaviour of organic microphase deposits in mesoporous Ti02 thin films. Two types of Ti02 thin film electrodes were investigated, (i) a 300-400 nm film on ITa and (ii) a 300-400 nm film on ITa sputter-coated with a 20 nm porous gold layer. The latter biphasic design is superior. Titanium carbide (TiC) nanoparticies were deposited onto ITa electrodes. Partial anodic oxidation and formation of novel core-shell TiC-Ti02 nanoparticies was observed at applied potentials positive of 0.3 V vs. SCE. Significant thermal oxidation of TiC nanoparticies by heating in air occurs at 250 °c leading to coreshell TiC-Ti02 nanoparticies, then Ti02 (anatase) at ca. 350 °c, and Ti02 (rutile) at temperatures higher than 750 °c. The electrocatalytic properties of the core-shell TiC-Ti02 nanoparticulate films were surveyed for the oxidation of hydroquinone, ascorbic acid, dopamine and nitric oxide (NO) in aqueous buffer media. Mono- and multi-layer Ce02 deposits on ITa are shown to be electrochemically active. A reduction assigned to a Ce(IV/III) process has been observed and followup chemistry in the presence of phosphate discovered. The interfacial formation of CeP04 has been proven and effects of the deposit type, pH and phosphate concentration on the process analysed. The electrochemistry of multi-layer Ce02 nanoparticulate films in organic solvent is shown to be more stable.

FABRICATION OF NANOPOROUS GOLD AND BIOLOGICAL APPLICATIONS By Badharinadh Uppalapati A Dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University. Virginia Commonwealth University, 2014 Major Director: Maryanne M. Collinson, Professor, Department of Chemistry Fabrication of nanoporous gold electrodes by dealloying Au:Ag alloys has attracted much attention in sensing applications. In the first part of this work, the electrochemical response of the redox active molecule, potassium ferricyanide, in a solution of bovine serum albumin in buffer, serum or blood was studied using nanoporous gold and comparisons made to planar gold. Nanoporous gold electrodes with different surface areas and porosity were prepared by dealloying Au:Ag alloy in nitric acid for different dealloying times, specifically, 7.5, 10, 12.5, 20 minutes. Characterization was done using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Using cyclic voltammetry, planar gold electrodes exposed to bovine serum albumin in buffer showed a decrease in Faradaic peak current and an increase in peak splitting for potassium ferricyanide. The time required for the peak Faradaic current to drop to one-half of its original value was 3 minutes. At nanoporous gold electrodes, however, no significant reduction in Faradaic peak current or increase in peak splitting was observed. Nanoporous gold electrodes having the smallest pore size and largest surface area showed ideal results to biofouling. These electrodes are believed to impede the mass transport of large biomolecules while allowing small redox molecules to exchange electrons effectively with the electrode. In the second part of this work, the open circuit potential (OCP) of biologic solutions (e.g., blood) was measured using nanoporous gold electrodes. Historically, the measurement of blood redox potential has been hindered due to significant fouling and surface passivation of the metal electrodes. As nanoporous gold electrodes retained electrochemical activity of redox probes like potassium ferricyanide in human serum and rabbit blood, they were used to measure the OCP of blood and plasma from various animals like pig, rabbit, rat, monkey and humans. Comparisons were made to planar gold electrodes. The OCP values at both the planar gold and nanoporous gold electrodes were different from each other and there was variability due to different constituents present in blood and plasma. The OCP of rabbit blood and crashed rabbit blood was measured and the values were found to be different from each other indicating that ORP helps in measuring the animal condition. Ascorbic acid was added to rabbit and sheep blood and OCP measured at the nanoporous electrodes. Addition of reducing agent to blood at different intervals and different concentrations showed a change in potential with concentration.

>Magister Scientiae - MSc / The motivation to determine H2O2 lies in the fact that this chemical species plays a crucial role in diverse fields of practise such as cosmetic, food, diagnostic, pharmaceutical, clinical and environmental protection industries. Several methods such as chromatography, colorimetry, titrimetry and spectrophotometry have been developed for its detection. However, these methods are known to manifest underlying disadvantages such as high cost, time consuming, instability and complicated immobilization procedures. In this present study an enzyme-less electrochemical sensor based on Ag-Fe2O3/POM/RGO nanocomposite (POM stands for polyoxometalate and RGO stands for reduced graphene oxide) was successfully synthesised via a hydrothermal method and a photochemical reduction method for the detection of hydrogen peroxide (H2O2).

Nesse estudo foi sintetizado e caracterizado o óxido de grafeno (OG) a partir do método de Hummers modificado. O OG foi utilizado como suporte para nanopartículas de paládio para uso como eletrocatalisador em células a combustíveis abastecidas diretamente a etanol. O uso de carbono grafite como suporte de nanopartículas metálicas é deteriorado com mais rapidez, levando a diminuição do tempo de vida útil da célula a combustível. O objetivo principal foi a incorporação do paládio no óxido de grafeno via feixe de elétrons, e a comparação com o catalisador incorporado por via química, utilizando o borohidrato de sódio. Foram utilizadas técnicas de caracterização tais como: termogravimetria (TG), difração de raios-X (DRX), as espectroscopias de Raman e infravermelho com transformada de Fourier (FT-IR), microscopia de transmissão eletrônica (MET), Espectroscopia de fotoelétrons por raios- X (XPS) e estudos voltamétricos como a voltametria cíclica e cronoamperometria. Os resultados indicaram que para a dose de 288 kGy, houve a incorporação, porém, não foi suficiente para que houvesse a redução dos grupos oxigenados, estudos com o oxido de grafeno previamente reduzido via térmica e incorporado via feixe de elétrons foram comparados na mesma dose. / In this study, graphene oxide (GO) was synthesized by the modified Hummers method and characterized. GO was used as support for palladium nanoparticles as an electrocatalyst on direct ethanol fuel cell (DEFC). One of the drawbacks using carbon graphite as a support for metal nanoparticles was because it deteriorates more quickly, leading to shortened fuel cell life. The main objective was the incorporation of Pd on the graphene oxide by the electron beam and was compared with the chemical incorporation, using sodium borohydride. Characterization techniques such as thermogravimetry (TG), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FT-IR), electron transmission microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and voltammetric studies such as cyclic voltammetry and chronoamperometry. The results indicated that at a dose of 288 kGy, there was an incorporation, however, it was not enough for there to be a decrease in the groups of oxygenates, studies with the graphene oxide downloaded through the thermal and through electron beams were compared in the same dose.

Pertencendo à família dos eletrodos de carbono, o carbono polimérico vítreo (CPV) apresenta condutividade elétrica, estabilidade térmica, resistência mecânica e grande intervalo de potencial. Dessa forma, se torna possível sua aplicação como eletrodo sólido para o monitoramento de processos de transferência de carga, suporte para polímeros eletroativos e modificadores de superfície. O processo de obtenção do CPV se baseia na carbonização em ambiente inerte de materiais precursores, dentre os quais, podem-se destacar as resinas fenólicas, como por exemplo, resol (C7H8O2). Neste contexto, este trabalho investiga a obtenção do CPV a partir da resina fenólica resol, bem como o efeito da incorporação de íons metálicos (crômio, ferro e cério) na estrutura cristalina e nas propriedades eletroquímicas. Os materiais foram caracterizados por análise térmica, microscopia eletrônica de varredura, difratometria de raio-X, espectrofotometria no infra-vermelho e por voltametria cíclica. O difratograma de raio-X confirmou a obtenção de um material com estrutura similar a do carbono vítreo e, através da microscopia eletrônica de varredura, ficou comprovada a baixa porosidade do CPV. Por espectrofotometria no infra-vermelho, ficou demonstrada a presença de grupos funcionais, como carbonilas e hidroxilas, na estrutura do material. Os resultados mostram que tanto o CPV quanto o CPV modificado por íons metálicos possuem boa estabilidade térmica, pois não houve nenhuma decomposição desses materiais abaixo de 400ºC. E, tanto o CPV quanto o CPV modificado por íons metálicos apresentam comportamento eletroquímico similar no sistema ferricianeto/ferrocianeto. Concluindo, o método desenvolvido para obtenção do CPV modificado por íons metálicos é satisfatório, reprodutivo além de proporcionar uma dispersão homogênea dos íons na fase do CPV. Desta forma, possibilita uma nova frente de estudos destes materiais eletródicos em eletrocatálise e eletroanalítica. / Belonging to the family of the carbon electrodes, the glassy polymeric carbon (GPC) presents electric conductivity, thermal stability, mechanical resistance mechanics and great potential interval. In this way, it is possible its application as solid electrode in order to follow electron transfer process, act as support of electroactive molecules and surface modifier. The glassy polymeric carbon production is based on carbonization of organic precursors in inert atmosphere such as phenolic resins (for example, resol - C7H8O2) In this context, this work investigates the production of GPC from phenolic resin, as well as the effect of incorporation of metallic ions (chromium, iron, and cerium) on crystalline structure and electrochemical properties. The materials were characterized by thermal analysis, scanning electron microscopy, X-ray diffraction, infrared spectrophotometry, and cyclic voltammetry. X-ray diffraction patterns had confirmed the presence of a material with similar structure of that found in conventional glassy carbon, and through SEM images it has shown a low porosity carbon material. From infrared spectrum, it can be observed carbonyl and hydroxide groups. The found results showed that both GPC and metallic ion modified GPC exhibit thermal stability, since no decomposition has occurred up to 450 oC. And, both carbon materials present similar electrochemical behavior in hexacyanoferrate system. In conclusion, the method developed for attainment of the GPC modified for ions metallic is satisfactory, and reproductive. Besides, it provides a homogeneous dispersion of ions in the bulk phase of the GPC. As a consequence, it makes possible a new front of studies of these materials in electrocatalysis and electroanalysis.

Parmi tous les matériaux oxydes de type pérovskite (ABO3), les ferro-cobaltites de terre rares (LSCF) ont suscité beaucoup d’intérêt en raison de leur conductivité mixte ionique et électronique (MIEC) et de leur forte activité catalytique. L’objectif de cette étude fondamentale est de comprendre l’influence de la microstructure, de la composition de LSCF et de la pression partielle d’oxygène sur l’allure des voltammogrammes et sur la variation de la résistance en série, Rs, en fonction de la polarisation. Ainsi, les propriétés redox de LSCF déposé sur CGO ont été étudiées par voltammétrie cyclique et par des mesures d’impédance sous courant continu dans la gamme de température de 300 à 700 °C et sous une pression partielle d’oxygène égale à 0,21 et 1,8.10-4 atm. Nous avons tout d’abord démontré les effets importants de la microstructure sur l’allure des voltammogrammes de l’électrode LSCF/CGO. Dans le cas d’une couche dense, les voltammogrammes expérimentaux présentent des pics cathodiques et anodiques symétriques caractéristiques d’un composé d’intercalation et Rs augmente avec la polarisation cathodique. Pour une couche poreuse sous air, les voltammogrammes sont identiques à la courbe de polarisation et Rs ne varie pas. Puis, nous avons montré que la pression partielle d’oxygène influe également fortement sur la réponse voltammétrique du matériau poreux avec apparition des pics cathodiques et anodiques. La nature des pics et leur attribution au changement de concentration en lacunes dans LSCF ont été confirmées par un travail de simulation des voltammogrammes en fonction de paramètres microstructuraux et de la pression partielle d’oxygène. Enfin, l’étude de cinq compositions de LSCF de microstructure poreuse a montré sous faible p(O2) que les voltammogrammes cycliques sont plus complexes pour les composés LSCF riches en cobalt que pour les riches en fer. / Among perovskite-type oxide materials (ABO3), rare earth doped cobalt ferrites (LSCFs) aroused a lot of interest because of their mixed ionic and electronic conductivity (MIEC) and their high catalytic activity. The objective of this fundamental study was to understand the influence of the microstructure, the LSCF composition and the oxygen partial pressure on the voltammogram shape and on the variation of the series resistance, Rs, as a function of continuous polarization. Thus, the redox properties of LSCF deposited on CGO were studied by cyclic voltammetry and by DC impedance measurements in the temperature range of 300-700 °C and under oxygen partial pressure equal to 0.21 and 1.8 × 10-4 atm. First, we demonstrated the significant effects of the microstructure on the voltammogram shape of the LSCF / CGO electrode. In the case of a dense layer, the voltammograms exhibit symmetrical cathodic and anodic peaks characteristic of an intercalation compound and Rs increases with cathodic polarization. For a porous layer in air, the voltammograms are identical to the polarization curve and Rs do not vary. Then, we have shown that the oxygen partial pressure strongly influences the voltammetric response of the porous material with appearance of cathodic and anodic peaks. The nature of the peaks and their attribution to the change of concentration in vacancies in LSCF were confirmed by a study of simulation of the voltammograms according to microstructural parameters and the oxygen partial pressure. Finally, the study of five LSCF compositions with porous microstructure showed under low p(O2) that cyclic voltammograms are more complex for cobalt-rich LSCF compounds than for iron-rich ones.

Este trabalho consiste no estudo da eletrodeposição de ligas de Zn/Co para diferentes relações de concentração [Zn2+]/[Co2+] (1:1, 3:1, 6:1, 9:1 e 12:1) sobre aço-carbono ABNT 1020 e sua resistência à corrosão, usando como banho um eletrólito à base de cloretos. Foram realizados estudos preliminares sobre o mecanismo de deposição da liga Zn/Co usando a técnica de voltametria cíclica e estabeleceram-se assim os parâmetros de deposição da liga. Os ensaios de deposição para as relações de concentração [Zn2+]/[Co2+] : 9/1 e [Zn2+]/[Co2+] : 12/1 no banho foram realizados usando a técnica potenciostática (cronoamperometria) e a técnica galvanostática (cronopotenciometria). As relações 1:1, 3:1 e 6:1 não foram escolhidas já que os teores de cobalto de seus eletrodepósitos não estavam na faixa de 1 % a 2 %. Foram feitas análises por microscopia eletrônica de varredura (MEV) para conhecer a diversidade morfologia dos eletrodepósitos como conseqüência do aumento do conteúdo de íons de zinco no banho. A identificação das fases dos eletrodepósitos foi feita por difração de raios X (XRD) e a composição elementar mediante espectroscopia de energia dispersiva de raios X (EDS) e fluorescência de raios X (XRF). Os ensaios de avaliação da resistência à corrosão foram realizados em solução naturalmente areada de NaCl 0,1 M por técnicas eletroquímicas como espectroscopia de impedância eletroquímica e curvas de polarização potenciodinâmicas. A partir dos resultados obtidos na voltametria cíclica foi possível selecionar a faixa de potencial adequada para a realização dos ensaios potenciostáticos e galvanostáticos das relações [Zn2+]/[Co2+] 9:1 e 12:1. As análises dos dados obtidos dos transientes de corrente (ensaios potenciostáticos) para cada relação (9:1 e 12:1) permitiram concluir que para ambas as relações seus processos de nucleação ocorrem seguindo uma transição, iniciando-se como progressiva para t/tmax < 1 e passando a instantânea para t/tmax > 1. As técnicas eletroquímicas usadas para avaliar a resistência à corrosão mostraram que os eletrodepósitos obtidos com a técnica potenciostática foram mais resistentes à corrosão que os eletrodepósitos obtidos com a técnica galvanostática, sendo o potencial de - 1450 mV vs Ag/AgCl e a densidade de corrente catódica de 30 mA/cm2 as melhores condições para a obtenção de eletrodepósitos de Zn/Co com boa resistência à corrosão. / This work reports the study of the electrodeposition of Zn/Co alloys with different concentration ratios [Zn2+]/[Co2+] (1:1, 3:1, 6:1, 9:1 e 12:1) on carbon steel ABNT 1020 and its corrosion resistance, using a chloride - based electrolyte. Initial studies were performed to find the best parameters of deposition by cyclic voltammetry. The alloy deposition for concentration ratios of [Zn2+]/[Co2+] : 9/1 and [Zn2+]/[Co2+] : 12/1 were carried out using potentiostatic (chronoamperometry) and galvanostatic (chronopotenciometry) techniques. The ratios 1:1, 3:1 e 6:1 were not chosen because them composition in cobalt were not within the range of 1% to 2%. Scan electron microscopy (SEM) was performed in order to verify the morphological diversity of the electrodeposits as a consequence of the increasing zinc concentration in the bath. X-ray diffraction was used to identify the phases present in the electrodeposits; their elemental composition was determined by X-ray dispersive energy spectroscopy and X-ray fluorescence. Corrosion resistance experiments were performed in aerated 0,1 M NaCl solution by electrochemical techniques such as electrochemical impedance spectroscopy and potenciodynamic polarization curves. From the voltametric results it was possible to select the adequate potential range in order to perform the potenciostatic and galvanostatic experiments for concentration ratios of [Zn2+]/[Co2+] 9:1 and 12:1. Analysis of the data obtained from the current transients for each ratio (9:1 and 12:1) allow us to conclude that, for both ratios, the processes of nucleation occur following a transition which starts as progressive for t/tmax < 1 and become instantaneous for t/tmax > 1. The electrodeposits obtained by potentiostatic and galvanostatic techniques were evaluated for their corrosion resistant and the best results were found for potentiostatic deposition at -1450 mV vs Ag/AgCl and galvanostatic deposition at 30 mA/cm2. In general, the deposits obtained potentiostatically showed better corrosion resistant.