Electrodeposition of Tungsten Coatings from Scheelite by Molten Salt Electrolysis

A molten-salt electrodeposition method based on the CaCl 2 –scheelite system was developed to prepare dense and phase-pure tungsten coatings on nickel substrates. Cyclic voltammetry (CV) and square-wave voltammetry (SWV) revealed the reducibility sequence of metal ions in molten CaCl 2 as Fe(III) → Mo(VI) → W(VI) → Ti(IV) → Al(III). The optimal cell-voltage range of −0.86 to −1.17 V enabled selective removal of Fe while preventing co-reduction of tungsten. After impurity removal at −1.00 V for 1.25 h, WO 4 2− in the CaCl 2 –scheelite melt underwent a two-step, six-electron reduction under diffusion control, promoting compact nucleation. Electrolysis at 1123 K and 10 mA cm −2 for 5 h produced a uniform, defect-free tungsten coating with strong adhesion to the Ni substrate. The coating thickness followed a diffusion-controlled growth model. This study demonstrates a simple, green, and low-cost electrochemical approach for producing high-quality tungsten coatings from natural scheelite resources. This study demonstrates a simple, green, and low-cost electrochemical approach for producing high-quality tungsten coatings from natural scheelite resources, offering significantly enhanced hardness and corrosion resistance for Ni-based components.