Chemical Properties Of Tantalum

Tantalum also has excellent chemical properties, with very high corrosion resistance, both in cold and hot conditions, and does not react to hydrochloric acid, concentrated nitric acid and aqua regia. However, tantalum can be corroded in hot concentrated sulfuric acid, below 150 ℃, tantalum will not be corroded by concentrated sulfuric acid, only at temperatures higher than this temperature will have a reaction, at 175 ℃ in concentrated sulfuric acid for 1 year, the thickness of the corrosion of 0.0004 mm, tantalum will be put into 200 ℃ of sulfuric acid immersion for one year, the surface layer of the damage is only 0.006 mm. At 250 ℃, the corrosion rate increased, for each year was corroded thickness of 0.116 mm, at 300 ℃, was corroded more quickly, immersed in 1 year, the surface was corroded 1.368 mm. In fuming sulfuric acid (containing 15% of SO3) corrosion rate than in concentrated sulfuric acid is more serious, at 130 ℃ in this solution immersed in 1 year, the surface was corroded thickness of 15.6 mm. Tantalum will also be corroded by phosphoric acid at high temperature, but the reaction generally occurs above 150 ℃, at 250 ℃ in 85% phosphoric acid, immersed in 1 year, the surface was corroded 20 mm, in addition, tantalum in the mixed acid of hydrofluoric acid and nitric acid can be dissolved quickly. But tantalum is more afraid of strong alkali, in 110℃ 40% concentration of caustic soda solution, tantalum will be quickly dissolved, in the same concentration of potassium hydroxide solution, as long as 100℃ will be quickly dissolved. In addition to the situation described above, general inorganic salts can not generally corrode tantalum below 150℃. Experiments have proved that tantalum at room temperature, alkali solution, chlorine, bromine, dilute sulfuric acid and many other agents are not effective, only in hydrofluoric acid and hot concentrated sulfuric acid reaction. Such a situation is relatively rare in metals.

However, at high temperatures, the oxide film on the surface of tantalum is destroyed, so it can react with a variety of substances, and at room temperature tantalum can react with fluorine. At 150 ℃, tantalum is inert to chlorine bromine iodine, at 250 ℃, tantalum is still corrosion resistant to dry chlorine, in the chlorine containing water vapor heated to 400 ℃, can still maintain the bright, at 500 ℃ is beginning to be corroded, at 300 ℃ above tantalum and bromine reaction, iodine vapor when the temperature reaches the red heat before are inert. Hydrogen chloride reacts with tantalum at 410°C to produce pentachloride, and hydrogen bromide reacts with tantalum at 375°C. Sulfur reacts with Ta when heated to 200°C or lower, and carbon and hydrocarbons react with Ta at 800-1100°C.