Kinetics and mechanisms of tantalum corrosion in glass melts

The kinetics and mechanisms of corrosion of pure tantalum in three molten glasses are investigated in the 1200-1400°C temperature range by thickness loss measurements. The corrosion layers formed at the metal/glass interface, the elemental concentration profiles in the glass, and the corrosion rates are determined. Corrosion rates are repotted on an Arrhenius representation for each glass. They yield to the determination of the activation energies of corrosion processes that depend on the glass composition. The limiting process is probably the diffusion of oxygen through one of the corrosion layers. The corrosion mechanisms are described in the form of successive redox reactions between the glass and the substrate. The Ta^v/Ta⁰ standard potential is estimated to be below -1.200 V. The formation of an intermetallic compound containing boron (TaB) as a corrosion layer is evidenced for the first time.