FORMULATION OF A GENERAL-MODEL FOR NUCLEATION AND GROWTH OF ELECTRODEPOSITS

A general model for the initial nucleation and growth of electrodeposits, based upon hemispheroidal growth forms (hemi-ellipsoids of revolution), is proposed and analysed in detail. The transient current is shown to pass through a single maximum prior to the approach of the steady-state value, with the ratio of the maximum current to the steady-state value being 1.285 and 1.332 for so-called "instantaneous" and "progressive" nucleation, respectively. The shape of the current-time transients are shown to be independent of the eccentricity of the ellipsoids, though the current is scaled according to the eccentricity values. The transients thus follow the same pattern of behaviour as those predicted for hemispherical growth forms. The effect of concurrent hydrogen evolution on the form of the current-time transient has been analysed. It is shown that the maximum current in the transient is suppressed when hydrogen is evolved on hemispheroidal growth forms characterized by eccentricity values less than one, whereas it is accentuated for eccentricity values greater than one.