Electrodeposition of Fe-W Nanocrystalline Coatings from Citrate Bath

Abstract

Using cyclic voltammetry, electrode processes of electrodeposition of nanocrystalline Fe-W coatings from citrate bath are analyzed. The electrolyte contained ferrous iron and tungstate (pH 6.9; 80°C, graphite anode). It is shown that electrodeposition takes place with a current efficiency of up to 30% in a range of current densities of 20–50 mA/cm². This interval is confined by the limiting current density of the reduction of the oxidized form of citrate complex Fe (II) formed at the preparation of the bath due to oxidation of Fe(II) in the citrate solution. This interval is bounded from below by the evolution of hydrogen and/or reduction of the organic components of the bath. The opportunities of using a soluble iron anode are shown (current efficiency of anodic dissolution of iron in this electrolyte is 93 ± 2%). Coatings contain up to 25% (at.) W and their micro-hardness (up to 900 kG/mm²) depends on the volume current density. The possibilities of the studied system for the local maskless electrodeposition are shown.