Editing Refractory metals (section)

===Chemical===
The refractory metals show a wide variety of chemical properties because they are members of three distinct groups in the [[periodic table]]. They are easily oxidized, but this reaction is slowed down in the bulk metal by the formation of stable oxide layers on the surface ([[Passivation (chemistry)|passivation]]). Especially the oxide of rhenium is more volatile than the metal, and therefore at high temperature the stabilization against the attack of oxygen is lost, because the oxide layer evaporates. They all are relatively stable against acids.<ref name="Lipi"/>