Preparation of Mg-Yb alloy film by electrolysis in the molten LiCl-KCl-YbCl3 system at low temperature

The electrochemical behavior of Yb3+ and electrodeposition of Mg-Yb alloy film at solid magnesium cathode in the molten LiCl-KCl-YbCl3 (2 wt.%) system at 773 K was investigated. Transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry were used in order to explore the deposition mechanism of Yb. The reduction process of Yb3+ is stepwise reactions which are single-electron and double-electron reversible charge transfer reactions. The speed control step was a diffusion-controlled step which is caused by concentration polarization. The microstructures of Mg-Yb alloy film were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and EPMA area analysis. A very thin Mg2Yb alloy film (∼200 nm) was formed by potentiostatic electrolysis at −1.85 V (vs. Ag/AgCl) for 12 h. A much thicker Mg2Yb alloy film (∼450 μm) was obtained at −2.50 V (vs. Ag/AgCl) for 2.5 h. The corrosion resistance of magnesium can be enhanced by electrochemical formation of Mg-Yb alloy film on its surface.