Thin-layer electrorefining of lead in the homogeneous mixture of fused NaCl-KCl chlorides with the small current densities is carried out. The porous dielectric diaphragms, which are permeable for fused salt and deterrent for mechanical permeation of liquid metal, are used in separation of the electrolyte and pure metal. The diaphragm thickness is equal to interpole distance that is can be decreased considerably to loser a voltage drop in electrolyte. A procedure is suggested to determine the mass transfer coefficients from value of summary polarization of electrodes.