General Theory of Disperse Metal Electrodeposits Formation

Abstract

In this chapter, the fundamental aspects of disperse metals electrodeposition are discussed. The shapes of polarization curves in relation to the deposition process parameters are analyzed. Disperse metal deposits are formed with a nonuniform current density distribution over the surface of the macroelectrode. Adherent granular disperse deposits are produced in an electrodeposition process characterized by a large exchange current density, due to the formation of nucleation exclusion zones around growing grains on the inert substrate. Nonadherent dendritic or spongy deposits are formed in the dominant diffusion control on the level of the macroelectrode and an activation control on the tips of microelectrodes placed inside the diffusion layer of the macroelectrode. Nonadherent honeycomblike deposit is formed in the presence of strong hydrogen codeposition. All the above cases are discussed in detail and explained using appropriate mathematical models. It is also shown that the formation of dendritic deposits at low level of coarseness strongly increases the apparent exchange current density for the deposition process, producing electrocatalytic effect.