At a corrosion potential, layers of oxidic reaction products containing molybdenum, lead, potassium and small amounts of sodium occur on the surface of molybdenum electrodes in lead glass melts. The molybdenum valency of 3 corresponds best to the oxygen content in the products. The corrosion very probably proceeds in particular in areas which are not covered by the layer. When the potential is raised by 400 mV or more, the layers contain only molybdenum and oxygen whose ratio is close to the composition of MO3. The corrosion rate of molybdenum expressed as the rate of precipitation of lead is proportional to the sum of molar concentration of both alkalies reduced by a constant value of approximately 10.5 mol%, independently of the ratio of the two alkalies.
