SciELO - Scientific Electronic Library Online

 
vol.21 issue1Cathodic Behaviour of Pyrite With Molten Salts ElectrolyteElectrodeposition of Co and Co-Fe Films on Platinum and on Copper Substrates author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand

Journal

Article

Indicators

Related links

  • Have no similar articlesSimilars in SciELO

Share


Portugaliae Electrochimica Acta

Print version ISSN 0872-1904

Abstract

D'ALKAINE, C.V.; BERTON, M.A.C.  and  TULIO, P.C.. Galvanostatic Growth of Passivating Films Under Transient Conditions. I. Model and Quantitative Analysis for the Zn/ZnO System. Port. Electrochim. Acta [online]. 2003, vol.21, n.1, pp.15-32. ISSN 0872-1904.

On the basis of an ohmic model and a Tafel equation describing relations between current density and overpotentials in the film and at the metal/film interface, respectively, it is shown that a quantitative analysis of galvanostatic transients for the growth of passivating ultra-thin films on the so-called non-noble metals can be obtained. As an example, the growth of ZnO on Zn in a boric/borate buffer solution is considered. In this case, the values of the transfer coefficient and the exchange current density of the reaction at the metal/film interface were found to be 1.2 and 0.11 mA cm-2, respectively. It was shown that a single, first film occurred at low current densities and two films at high ones. The ionic resistivity inside the single, first film, during the transients, has an initial constant value region followed by a final increase indicating the aging process. For this variation the evolution of the point defect concentrations is taken into account. For the variation of the ionic resistivity with the galvanostatic current density two types of behaviors were found, depending on the current density. An interpretation of these results is advanced in terms of the concentrations, mobilities and recombination rate of point defects inside the film.

Keywords : passivation kinetics; ultra-thin films; galvanostatic experiments; quantitative analysis; zinc.

        · text in English     · English ( pdf )

 

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License