ResumoElectrochemical techniques are among the most commonly techniques used for the evaluation and study of corrosion in reinforced concrete, including electrochemical impedance spectroscopy (EIS). Electrochemical impedance spectroscopy (EIS) is a powerful technique for characterizing a wide variety of electrochemical systems and for determining the contribution of electrode or electrolytic processes in these systems. The analysis of EIS results on samples of concrete is highly complex due to overlapping arcs from simultaneous phenomena and noise measurement, of course, associated with the heterogeneity of the samples and that complicate the analysis considerably. Thus, this paper proposes a new form of analysis based on the characteristic relaxation angular frequency, w, of each phenomenon and associating the typical capacitances and frequencies.Keywords: corrosion, spectroscopy, concrete, durability, electrochemical techniques.Entre as técnicas mais utilizadas para a avaliação e estudo da corrosão em concreto armado estão as técnicas eletroquímicas, entre elas a espectroscopia de impedância eletroquímica (EIE). A EIE é uma técnica poderosa para a caracterização de uma grande variedade de sistemas eletroquímicos e para a determinação da contribuição de processos individuais de eletrodo ou eletrólito nestes sistemas. A análise dos resultados de EIE em amostras de concreto armado é de alta complexidade, devido à sobreposição de arcos provenientes de fenômenos simultâneos e a ruídos da medida, associados, evidentemente, à heterogeneidade das amostras e que dificultam de forma considerável esta análise. Assim, o presente trabalho propõe uma nova forma de análise, baseada na frequência angular de relaxação característica, w, de cada fenômeno e associando às capacitâncias e frequências típicas.Palavras-chave: corrosão, espectroscopia, concreto, durabilidade, monitoramento.
A novel cyanide-free zinc deposition bath was developed in which sorbitol was added at various concentrations. Voltammetric studies indicated that the reduction process is influenced thermodynamically and kinetically by the sorbitol concentration. Also, two cathodic processes were observed, one (wave) associated with the hydrogen evolution reaction (HER) on 1010 steel, the other (peak) with zinc bulk reduction, simultaneous to the HER. Furthermore, the plating-process kinetics was controlled by mass transport. The presence of sorbitol in the bath led to formation of light-grey zinc films, even during the HER, without cracks and dendrites. Plating current efficiency decreased from $62% to 43% on increasing the sorbitol concentration in the plating bath. In the presence of 0.1 M ½Zn(OH) 4 2À and/or sorbitol concentrations higher than 0.2 M, Zn electrode dissolution was inhibited. However, a small dissolution of zinc electrode was observed with 0.05 M sorbitol in alkaline solution without zincate. SEM micrographs showed that the 1010 steel substrate was fully covered by Zn film and that the sorbitol affected the morphology of zinc films, acting as a grain refiner.
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