Electrochemical reduction of Tm on Mg electrodes and co-reduction of Mg, Li and Tm on W electrodes

The reduction process of Tm(III) ions was investigated in LiCl-KCl-MgCl2 melt on a W electrode and in LiCl-KCl melt on a Mg electrode at 753 K, respectively. On the W electrode, in LiCl-KCl-MgCl2 melt the reduction of Tm(III) ions was a two-step process: Tm(III) + e−1 → Tm(II) and yTm(II) + 2ye−1 + xMg → MgxTmy. The reduction process of Tm(III)/Tm(II) was not observed on the Mg electrode, and only two signals, related to Mg-Tm intermetallic compounds were observed, in the cyclic voltammogram and chronopotentiogram. Galvanostatic electrolysis was employed to prepare Mg-Li-Tm alloys on both W and Mg electrodes. The deposits were characterized by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Mg24Tm5 and Mg2Tm phases were detected in the deposits. The effect of Tm addition on Mg-Li alloy was investigated via potentiodynamic polarization and OM at room temperature. The grain size of Mg-Li alloy becomes much smaller after addition of Tm element. The corrosion potentials of Mg-Li-Tm alloys shift toward a more positive direction than that of Mg-Li alloy.