Electrodeposition of metal molybdenum from electrolytes containing hydrofluoric acid

The effect of hydrofluoric acid on the cathodic reduction of molybdate ions is studied. It is shown that the mechanism of this process is determined by the acid concentration: in a concentration range below 25 g/l the intermediate products of molybdate-ion reduction, namely, black or colored deposits containing molybdenum with the average valence of 3.6–4 are formed on the cathode. For the concentration above 50 g/l, molybdate ions are completely reduced and form at the cathode dense light metallic coatings with a thickness of 3–5 μm and good adhesion to the substrate. The addition of hydrofluoric acid prevents polymerization of molybdate ions. Original Russian Text ? N.D. Ivanova, S.V. Ivanov, E.I. Boldyrev, O.A. Stadnik, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 4, pp. 388–392.