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Tantalum Corrosion Resistance
Jun 22, 2017

Tantalum, metal elements, mainly in tantalite, with niobium symbiosis. Tantalum hardness is moderate [1], rich ductility, can be drawn into thin filament thin film. Its thermal expansion coefficient is very small. Tantalum has a very good chemical properties, with high corrosion resistance. Whether in cold and hot conditions, hydrochloric acid, concentrated nitric acid and "aqua regia" do not respond. Can be used to make evaporative containers, etc., can also do the tube electrode, rectifier, electrolysis, capacitance. Tantalum Medical used to make thin slices or thin lines, sew the damaged organization. Although the corrosion resistance of tantalum is very strong, but its corrosion resistance is due to the surface of the stable tantalum pentoxide (Ta2O5) protective film.

Chemical symbol Ta, steel gray metal, Tantalum in the periodic table is a VB family, atomic number 73, atomic weight 180.9479, body-centered cubic crystal, the common parity is +5.

Tantalum was discovered by the Swedish chemist Ekeberg in 1802, named after the Greek mythology Tantalus (Tantalus) named tantalum. 1903 German chemist Bolton (W.von Bolton) for the first time the preparation of plastic metal tantalum used as filament material. 1940 large-capacity tantalum capacitors appear, and widely used in military communications. During the Second World War, Tantalum the demand for tantalum increased dramatically. Since the 1950s, the application of tantalum in capacitors, superalloys, chemical and atomic energy industry has been expanding, the demand has increased year by year, and the research and production of tantalum extraction technology have been promoted. China in the early 1960s established a tantalum metallurgical industry.

Tantalum hardness is low, and with the oxygen content, ordinary pure tantalum, annealed Vickers hardness of only 140HV [1]. Its melting point of up to 2995 ℃ [1], Tantalum in the elemental [1], second only to carbon, tungsten, rhenium and osmium, ranked fifth. Tantalum is ductile and can be drawn into thin filaments. Its thermal expansion coefficient is very small. Each increased by one degree Celsius only expansion of 6.6 points per million. In addition, its toughness is stronger than copper.

Tantalum also has a very good chemical properties, with a high degree of corrosion resistance, whether in cold and hot conditions, hydrochloric acid, Tantalum concentrated nitric acid and "aqua regia" do not respond. But the tantalum in the hot concentrated sulfuric acid can be corroded at 150 ℃ below, tantalum will not be concentrated sulfuric acid corrosion, only at this temperature will react, in the 175 degrees of concentrated sulfuric acid in 1 year, the corrosion thickness 0.0004 mm, the tantalum into 200 ℃ sulfuric acid soak for one year, the surface damage only 0.006 mm. At 250 degrees, the corrosion rate increased, the corrosion per year for the thickness of 0.116 mm, at 300 degrees, the corrosion rate is faster, soaking for 1 year, the surface was corrosion 1.368 mm. In the fuming sulfuric acid (containing 15% SO3) corrosion rate is more serious than concentrated sulfuric acid, 130 degrees in the solution soak for 1 year, the surface corrosion thickness of 15.6 mm. Tantalum at high temperatures will be corrosion of phosphoric acid, but the reaction is generally more than 150 degrees occurred in the 250 degrees of 85% phosphoric acid, Tantalum soaking for 1 year, the surface was corrosion 20 mm, in addition, tantalum in hydrofluoric acid and nitric acid Of the mixed acid can quickly dissolve in hydrofluoric acid can also be dissolved. However, tantalum is more afraid of strong alkali, in the 110 degrees 40% concentration of caustic soda solution, tantalum will be quickly dissolved in the same concentration of potassium hydroxide solution, as long as 100 degrees will be quickly dissolved. Tantalum In addition to the above mentioned circumstances, the general inorganic salt in the 150 degrees below the general can not corrosion tantalum. Experiments show that tantalum at room temperature, the alkaline solution, chlorine, bromine, dilute sulfuric acid and many other agents do not work, only in the hydrofluoric acid and heat concentrated sulfuric acid under the reaction. This situation is relatively rare in the metal.

But at high temperatures, Tantalum the oxide film on the surface of tantalum is destroyed, so it can react with a variety of substances, tantalum can react with fluorine at room temperature. At 150 ° C, tantalum is inert to chlorobromide at 250 ° C. Tantalum is still resistant to dry chlorine and is heated to 400 ° C in water containing steam. It remains bright at 500 ° C It began to be corroded, Tantalum more than 300 degrees tantalum and bromine reaction, the iodine vapor when the temperature reached before the red hot were inert. Hydrogen chloride at 410 degrees and tantalum reaction, the production of pentachloride, hydrogen bromide at 375 degrees with tantalum reaction. When heated to a temperature of 200 degrees or less, S can interact with Ta, carbon and hydrocarbons at 800-1100 degrees with tantalum.





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