INFLUENCE OF STRUCTURE AND CHEMICAL-COMPOSITION ON THE ANODIC-DISSOLUTION KINETICS AND PASSIVATION OF MOLYBDENUM IN ALKALINE-SOLUTIONS

The influence of structure and alloying on the anodic dissolution kinetics and passivation of molybdenum was studied in argon-deaerated 1 M KOH solutions over the potential range of -1.00 < E < 1.00 V. It was found that rhenium when added (4 atom %) to alloy TsM-10 raises the overpotential of anodic molybdenum dissolution and the passivating tendency. It was shown that anodic dissolution at potentials more positive than -0.20 V and passivation at more negative potentials are made more difficult by a larger grain size; this is attributed to a decrease in the concentration of active sites on the surfaces of recrystallized alloys. It was shown by Auger electron and X-ray photoelectron spectroscopy that the passive state of alloys in the potential range of -0.90 < E < - 0.20 V is due to the formation of a passivating oxide layer containing the dioxide MoO2.