variavel0=<b>José da Rocha Miranda Pontes</b> - jopontes@ufrj.br Universidade Federal do Rio de Janeiro
<b>Norberto Mangiavacchi</b> - norberto@lcad.icmc.sc.usp.br USP-S.Carlos
<b>Anderson Rodrigues Conceição</b> - anderson@metalmat.ufrj.br DMT/EE/UFRJ
<b>Oscar Rosa Mattos</b> - omattos@metalmat.ufrj.br PEMM/COPPE/UFRJ
<b>Oswaldo Esteves Barcia</b> - barcia@metalmat.ufrj.br Instituto de Química - UFRJ
<b>Bernard Tribollet</b> - bt@ccr.jussieu.fr UPR15 - CNRS Physique de Liquides et Eletrochimie
<b>Daniel Walgraef</b> - dwaelgr@ulb.ac.be Université Libre de Bruxelles
<b>Abstract.</b> Polarization curves experimentally obtained in the electro-dissolution of iron in a 1 M H2SO4 solution using a rotation disk as the working electrode present a current instability region within the rage of applied voltage in wich the current is controlled by mass transport in the electrolyte. According to the literature (Barcia et. all., 1992) the electrodissolution process leads to the existence of a viscosity gradient in the interface metal-solution. The viscosity gradient changes the velocity field and may affect the stability properties of the steady flow developed close to the rotating disk electrode. On a previous paper, Pontes et. al. (2002) showed that this is indeed the case when the steady flow is perturbed by disturbances with periodic variation along the radial direction. In this paper we extend those results by considering the linear stability of the flow with respect to perturbations with periodic variation along the radial and azimutal directions. It is shown that the neural stability curves are modified by the presence of a viscosity gradient, in the sense of reducing the critical Reynolds number beyond which perturbations are amplified. Comparison with the result obtained by Malik (1986) for constant viscosity fluids show good agreement. The results presented suport the hypothesis that the current oscillations observed in the polarization curve may originate from a hydrodynamic instability.
<b>Keywords.</b> Rotating Disk Flow, Eletrochemical Instabilities, Hydrodynamic Stability, Turbulence.