It is well-known that uniform layers of Ni(OH)(2) can be formed by cathodic electrochemical deposition. The product phase Ni(OH)(2) is predominately an ionic conductor, not an electronic conductor. This means that the electrochemical reaction must occur underneath the ionic conductor at the substrate/Ni(OH)(2) interface, whereas the formation of the hydroxide layer takes place at the Ni(OH)(2)/electrolyte interface. A model of a growth mechanism requiring the transport of several species through the growing product layer to the Ni(OH)(2)/electrolyte interface is discussed.