Abstract
The conditions to be met to achieve cathodic deposition of compounds or alloys of well‐defined stoichiometric composition are discussed. If the deposition rate constants of the components are of the same order, two classes of codeposition have to be distinguished, differing in whether the difference in electrode potential of the individual components is larger (class I) or smaller (class II) than the shift in electrode potential of either component as a result of compound or alloy formation. In the former case the potential of the deposit is determined by the less noble component over the entire composition range, the deposition potential shifting monotonically with composition. In the latter case the role of potential‐determining species may shift from one component to the other at an intermediate composition, the deposition potential at this composition being more positive than that of either of the components when deposited individually. For class I , quasi rest potentials uniquely characterize the deposits. For class II different deposits may have the same quasi rest potential. Compounds are stable in electrolytes with large concentrations of the normal ions of one of the components in the absence of nonmetal complexes necessary to make cathodic deposition of the compounds possible. If the potential is not determined by adsorbed noncomponent species, the potentials are determined by the normal ions, the concentrations of which are linked by solubility products.