Characterization of electrodeposited Cd–Co alloy coatings by anodic linear sweep voltammetry

The electrodeposited Cd–Co alloys were characterized by the anodic linear sweep voltammetry (ALSV) technique in the solution of 1 M NaCl (pH 2). It is shown that Cd–Co alloys could be deposited with high current efficiency (>90%) from the solution containing 0.2 M boric acid, low concentration of cadmium sulfate (0.01 M and 0.02 M) and high concentration of cobalt sulfate (0.2 M and 0.4 M) under the conditions of convective diffusion (RPM = 1000). The ALSVs were characterized by the presence of three peaks: one corresponding to the dissolution of pure Cd, one corresponding to the dissolution of pure Co and one corresponding to the dissolution of unknown phase formed in the system Cd–Co (since the phase diagram of the Cd–Co system does not exist in the literature). Depending on the charge and on the alloy composition (amount of Cd and Co) the peak of the unknown phase can either be hardly seen, or can prevail on the ALSV. This phase is formed mainly on the account of Co, but certain limiting amount of Cd must be deposited for the unknown phase to be formed and seen on the ALSV.