The effects of dislocation patterns on the dissolution process of polycrystalline nickel

The contribution of dislocations to the electrochemical reactions arising on the surface of face-centred cubic metals is discussed in terms of long-range internal stresses in relation to dislocation patterns. To support the modelling approach, tensile straining effects on the dissolution of polycrystalline nickel have been investigated in 1 M H2SO4 at 291 K. It is demonstrated that a good correlation exists between dislocation distributions and current density. A thermodynamic analysis of the modification of the solid-liquid balance in the presence of dislocations is proposed in order to take into account dislocation patterns. A limitation of this approach is discussed in terms of adsorption processes. In a way similar to the hydrogen adsorption process, plastic strain seems to promote adsorption for dislocation densities lower than 6 x 10(13) m(-2). This feature is partially suppressed for higher dislocation densities in relation to the idea that geometric and/or energetic disorder developed by the concentration of dislocations in walls lead to the spacing of adsorption sites and so to a decrease in the number of active adsorption sites. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.