Facility for testing the high-porous ceramic membranes for metal refining is created. Air-permeability of magnesium oxide-based ceramic specimens is studied. Resistivity and polarization of the specimens, impregnated with KCl+NaCl+10 wt.% PbCl2 fused salt mixture, are measured at 700°C. The use of thin porous dielectrics in separation of liquid electrodes (lead) permits practically fully to eliminate a convection contribution of electrolyte into mass transfer.