The most corrosion-resistant metal material in legend
Thread Content
The most corrosion-resistant metal material in legend – niobium-tantalum alloys – oxidizes slowly only in hydrofluoric acid among inorganic acids. Tantalum also possesses excellent chemical properties, featuring extremely high corrosion resistance. It shows no reaction to hydrochloric acid, concentrated nitric acid, and aqua regia, whether under cold or hot conditions. However, tantalum can be corroded in hot concentrated sulfuric acid; below 150 degrees, it is not corroded by concentrated sulfuric acid, and a reaction occurs only at temperatures higher than this. In concentrated sulfuric acid at 175 degrees, the thickness of corrosion after one year is 0.0004 millimeters. When tantalum is immersed in sulfuric acid at 200°C for one year, the surface layer is damaged by only 0.006 millimeters. At 250 degrees, the corrosion rate increases, with an annual corrosion thickness of 0.116 millimeters; at 300 degrees, the corrosion rate is even higher, resulting in a surface corrosion depth of 1.368 millimeters after one year of exposure. The corrosion rate in fuming sulfuric acid (containing 15% SO3) is more severe than that in concentrated sulfuric acid; after being immersed in this solution at 130 degrees for 1 year, the thickness of corrosion on the surface reached 15.6 millimeters. Tantalum is also corroded by phosphoric acid at high temperatures, but this reaction generally occurs only above 150 degrees. When immersed in 85% phosphoric acid at 250 degrees for one year, the surface corrodes by 20 millimeters. Additionally, tantalum dissolves rapidly in a mixture of hydrofluoric acid and nitric acid, and it can also be dissolved in hydrofluoric acid. However, tantalum is even more sensitive to strong alkalis; in an alkaline solution at 110 degrees with a concentration of 40%, tantalum dissolves rapidly. In a potassium hydroxide solution of the same concentration, it dissolves quickly at just 100 degrees. Apart from the situations mentioned above, ordinary inorganic salts generally cannot corrode tantalum at temperatures below 150 degrees. Experiments have shown that at room temperature, tantalum is inert to alkaline solutions, chlorine gas, bromine water, dilute sulfuric acid, and many other chemicals; it reacts only in the presence of hydrofluoric acid and hot concentrated sulfuric acid. Such a situation is relatively rare in metals. Niobium is a grayish-white metal with a melting point of 2468°C, a boiling point of 4742°C, and a density of 8.57 grams per cubic centimeter. At room temperature, niobium is stable in air; it does not get completely oxidized even when heated red-hot in oxygen. At high temperatures, it reacts directly with sulfur, nitrogen, and carbon, and it can form alloys with titanium, zirconium, hafnium, and tungsten. It does not react with inorganic acids or bases, nor is it soluble in aqua regia, but it is soluble in hydrofluoric acid. The oxidation states of niobium are –1, +2, +3, +4, and +5, among which the +5 compounds are the most stable.
This post was last edited by lanye55 on 2009-9-21 08:17. I’m sorry, moderator – this post was already posted on September 7th; your content and title are exactly the same as those of that post. For more details, see http://bbs.hcbbs.com/viewthread. ... 0%CA%F4%B2%C4%C1%CF
Please see the introduction to niobium. Chinese name of the element: Niobium; Atomic number: 41; Element symbol: Nb; English name of the element: Niobium; Relative atomic mass: 92.91; Number of protons in the nucleus: 41; Number of electrons outside the nucleus: 41; Nuclear mass number: 41; Proton mass: 6.8593E-26; Relative proton mass: 41.287; Period it belongs to: 5; Group it belongs to: VB; Molar mass: 93; Hydride: NbH5; Oxides: Nb2O5; Chemical formula of the highest oxidation state oxide: Nb2O5; Density: 8.57; Melting point: 2468.0°C; Boiling point: 4927.0°C; Outer electron configuration: 4d4 5s1; Inner electron configuration: 2,8,18,12,1; Color and state: Platinum-gray metal; Atomic radius: 2.08; Common oxidation states: +2, +3, +5; Discoverers: Hatchett and H. Ross; Time and place of discovery: 1801, England; Source of the element: Found in columbite and various other rare minerals; it is always present alongside tantalum (due to their very similar chemical properties), and tantalum can be separated from it as a by-product. Uses of the element: Niobium can absorb gases and is used as a degassing agent; it is also an excellent superconductor. Niobium is primarily used in alloys (such as in stainless steel, where a small amount of niobium helps prevent intergranular corrosion). Additional information: It is a ductile metallic element with a very bright platinum-gray luster, and it exists mainly in the +5 valence state
Introduction to Tantalum: The Chinese name for this element is Tantalum; its atomic number is 73, and its element symbol is Ta. The English name for this element is Tantalum. Its relative atomic mass is 180.9. It has 73 protons in its nucleus and 73 electrons outside the nucleus as well. The mass of a proton is 1.22129E-25, while the relative mass of a proton is 73.511. Tantalum belongs to period 6 and group VB. Its molar mass is 181, and its density is 16.654. The melting point of tantalum is 2996.0 degrees Celsius, while its boiling point is 5425.0 degrees Celsius. The electron configuration of tantalum is 5d3 6s2. The full electron configuration is 2,8,18,32,11,2. Tantalum appears as a platinum-gray metal. Its atomic radius is 2.09. The common oxidation states of tantalum are +3 and +5. It was discovered by Abel Berg in 1802 in Sweden. Tantalum is found in niobium ores and various other rare minerals. It is used in the manufacture of evaporating vessels, as well as in electrodes for electronic tubes, rectifiers, electrolytic devices, and capacitors. In medicine, it is used to create sheets or fine threads for repairing damaged tissue. Extended introduction: A lustrous platinum-gray, hard, ductile metallic element with an extremely high melting point; it exists mainly in the pentavalent state, is resistant to the corrosion of most chemicals, with hydrofluoric acid being an exception