Intermediate layers in electrodeposited CMA coatings

The existence of an intermediate layer in electrodeposited CMA coatings composed of a Ni+Cd alloy layer and a pure Cd layer has been investigated by the anodic linear sweep voltammetry technique. It was shown that the voltammogram of a single layer of the pure Ni+Cd alloy differs from that representing the dissolution of a two-layer deposit composed of a Ni+Cd alloy layer and a pure Cd layer on top of it. This difference is ascribed to the formation of an intermediate layer. It was found that the contribution of beta and gamma phases in the intermediate layer depends on the alloy layer composition as well as on the composition of the plating bath. From the charges corresponding to the contribution of these two phases, assuming a homogeneous distribution of phases. the thickness of the intermediate layer has been estimated. The maximum thickness of the intermediate layer was found to be about 40 nm. (C) 1998 Elsevier Science S.A.