The corrosion of tantalum in oxidizing sub- and supercritical aqueous solutions of HCl, H2SO4 and H3PO4.

The corrosion of tantalum was investigated in sub- and supercritical oxidizing solutions of hydrochloric, sulfuric and phosphoric acid at temperatures between 360 and 500 °C. The corrosion rates in HCl and H₂SO₄ increased strongly above the critical temperature of water, which was attributed to a phase transformation from vitreous to crystalline Ta₂O₅. Corrosion rates in H₃PO₄ were low at all temperatures due to the formation of a top phosphate layer. [ABSTRACT FROM AUTHOR]