The electrolyzer was constructed for the electrodeposition of niobium coatings on long conductors from copper alloys. Method devised for deposition of protective niobium coatings on long conductors showed that by addition of K2ZrF6 into the electrolyte it is possible to suppress electroreduction of niobium oxofluoride complexes, which has an adverse effect on the quality of the coatings, and to prolong the life of the electrolyte. Electrodeposition of niobium coatings was carried out on a copper brand M1 and internally oxidized dispersion-reinforced copper alloys MAGT-0.05 and MAGT-0.2 containing aluminum, hafnium, and titanium oxides. Electrolysis conducted at temperature 1023 K in the NaCl-KCl-K2NbF7(10 wt%)-K2ZrF6(3 wt%) melt. The following conditions for electrodeposition coatings were chosen experimentally rate of wire drawing 2.0 and 6 m/h at current density 0.03 and 0.1 A/cm(2), respectively. Smooth dendrite-free coatings 12-14 mu m were obtained under these electrolysis conditions. The porosity of niobium coatings was measured by the Erhardt's method modified for long conductors. Measurements showed that niobium coatings with a thickness of 12-14 mu m were without pores. Coefficients of the interdiffusion of compositions MAGT-0.05-niobium and MAGT-0.2-niobium were determined. The time of life of compositions was calculated from the interdiffusion coefficients. (C) 2019 The Electrochemical Society.