The Mechanical Properties and Rate of Electrodeposition of Co−W Alloys from a Boron−Gluconate Bath: Impact of Anodic Processes

The effects the anode material has on the rate of electrodeposition (current efficiency) and microhardness of Co–W alloys deposited from a boron–gluconate bath are studied in a broad range of bath ages Q (A h/L). We use nonconsumable (platinum and graphite) and consumable (tungsten, cobalt–tungsten) anodes. With the cobalt–tungsten double anode, the total concentration of W and Co species in the bath is maintained constant during electrodeposition. We find that, as Q increases, the anodic processes have a significant impact on both the rate of deposition and microhardness of the prepared coatings. Departing from the mechanism of induced codeposition in which the first stage is the formation of an intermediate species of the metal component that induces codeposition (Co), here we propose a model that takes into account the effects associated with the anodic processes. In this model, along with reduction at the cathode to give an alloy, this metal component can undergo oxidation at the anode.