Estudo da influência do complexo bórico-sorbitol no processo de eletrodeposição, morfologia e composição da liga Zn-Mn

Abstract

Zn-Mn electrodeposition on to platinum using an acid electrolyte based on boric acid (BA) or boric-sorbitol complex (BSC) has been studied. The influence of these additives concentrations on the electrodeposition process was investigated by potentiodinâmic techniques, such as voltammetry, and the electrodeposits by SEM, EDS and XRD analyses. Voltammetric studies indicated that the feature characteristics Zn-Mn deposition voltammograms, without any additives or with BA or BSC both in different concentrations were similar, and that an increase in the BSC concentration led to decrease in the current density as for zinc deposition. The current efficiency of deposition process was lower 100 Porcentagem in the absence or presence of additives due to hydrogen evolution reaction and presence of compounds containing oxygen in the deposits. SEM analysis showed that Zn-Mn electrodeposits obtained at -1.60 V in the absence of additives or in the presence of 0.08 mol L-1 BA or 0.24 mol L-1 BSC were not dendritic. EDS analysis indicated that the Zn and Mn codeposition occurred beyond -1.50 V and also showed that for electrodeposits obtained at -1.60 V the increase of the BA or BSC concentration in the deposition bath induced to a decrease of the Mn content in the electrodeposit and that for BSC this decrease was more significant. X-Ray Diffraction analysis of the electrodeposits obtained in the absence or presence additives indicated that they were formed, in general, of a mixture of Zn, ZnMn2O4, ZnMnO3 and MnH0.8.