Electrodeposition of Tungsten from Molten KF–KCl–WO3 and CsF–CsCl–WO3

Abstract

Electrodeposition of W coatings in KF–KCl eutectic melts was investigated after adding 0.5–2.0 mol% of WO3 at 923 K. Cyclic voltammetry at a Ag electrode suggested that the electrodeposition of W from W(VI) ions proceeds from 1.65 V vs K+/K. Electrodeposition of the α-W phase was confirmed by X-ray diffractometry (XRD). The effects of current density and amount of WO3 on the morphology of W coatings were investigated by surface and cross-sectional scanning electron microscopy (SEM). The smoothest W coating with a thickness of ∼15 μm was formed at 12.5 mA cm−2 and 2.0 mol% WO3 in KF–KCl eutectic melts. By increasing the charge density, a coating thickness of ∼30 μm was attained; however, it significantly increased the surface roughness of the coating. The electrodeposition of W was also performed in CsF–CsCl eutectic melts at a lower temperature of 873 K to suppress the growth of crystal grains. XRD confirmed the existence of both α-W and β-W phases in the W coatings deposited in the CsF–CsCl eutectic melts. SEM analyses revealed the successful formation of dense and smooth W coatings with ∼30 μm thickness in the CsF–CsCl eutectic melts.