Preparation of Mg-Yb alloy film by electrolysis in the molten LiCl-KCl-YbCl_3 system at low temperature

摘要

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.