Macroscopic Size Effect on the Microhardness of Electroplated Iron Group Metal—Tungsten Alloy Coatings: Impact of Electrode Potential and Oxygen-Containing Impurities

Abstract

The cause of the microscopic size effect in the microhardness of electroplated binary alloys between iron group metals and tungsten is identified by studying electrodeposition of Co-W alloys. The effect is caused by the presence of oxygen-containing impurities in electroplated alloys, the impurity content growing with increasing the volume current density, which leads to a reduction in the coating microhardness. We find that the nature of anodes used affects the properties of deposited coatings, in particular, microhardness, because a deposition-inducing metal complex, which is a complex of an iron group metal, is consumed during electrolysis not only at the cathode, but it may also undergo oxidation at the anode, which identifies the way the anode affects the coating properties.