Ta, metallic elements, mainly in tantalite, coexist with niobium. Tantalum moderate hardness , rich ductility, can be drawn into thin-wire thin foil system. Its coefficient of thermal expansion is small. Tantalum has very good chemical properties, with high corrosion resistance. Neither hydrochloric acid nor concentrated nitric acid nor aqua regia reacted under cold and hot conditions. Can be used to make evaporating vessels, etc., can also do the tube electrode, rectifier, electrolytic capacitor. Medical used to make thin slices or thin lines, sewing damaged tissue. Although tantalum is highly resistant to corrosion, its corrosion resistance is due to the formation of a stable tantalum pentoxide (Ta2O5) coating on the surface.