T 6716 (OTTO) Tantalum foil, 0.25 mm thick, 99.95% Cas 7440-25-7 - used to produce a variety of alloys that have high melting points, strength, and ductility. T 6716 (OTTO) Tantalum foil, 0.25 mm thick, 99.95% Cas 7440-25-7 - used in making carbide tools for metalworking equipment and in the production of superalloys for jet engine components, chemical process equipment, nuclear reactors, and missile parts.