A Note on Oxidation Resistant Coatings on Molybdenum and Their Use in Glass Seals for Mercury Lamps

JSGT 1955 V39 T211-T214

It is a fact well known to makers of glass-metal seals that the low oxidation resistance of molybdenum and tungsten largely determines the techniques which must be used in making glass seals to these metals, and also limits the conditions under which the seals can be used. The layers of tungsten trioxide and molybdenum trioxide, which form on heating these metals in air, have very little protective action. The oxide layer produced on tungsten is porous and easily breaks away from the underlying metal, whilst molybdenum trioxide is volatile at temperatures above 700°, and so has no protective action whatever.

H. Rawson