When great corrosion resistance is required, tantalum makes sense. In terms of chemical resistance, tantalum is similar to noble metals despite not being one of them. Additionally, despite having a body-centered cubic crystal structure, tantalum is particularly easy to work with at temperatures much below ambient temperature. Because of this, it's a useful metal for a variety of industrial uses. Our incredibly resilient material is used to create a wide range of items, such as semifinished goods, medical technology implants, furnace building components, and ion implantation parts.
Facts about tantalum
| Atomic number | 73 |
| CAS number | 7440-25-7 |
| Atomic mass | 180.95 [g/mol] |
| Melting point | 2996 °C |
| Boiling point | 5458 °C |
| Density at 20 °C | 16.65 [g/cm3] |
| Crystal structure | Body-centered cubic |
| Coefficient of linear thermal expansion at 20 °C | 6.4 × 10-6 [m/(mK)] |
| Thermal conductivity at 20 °C | 57.5 [W/(mK)] |
| Specific heat at 20 °C | 0.14 [J/(gK)] |
| Electrical conductivity at 20 °C | 8.0 × 106 [S/m] |
| Specific electrical resistance at 20 °C | 0.125 [(Ωmm2)/m] |
What are the physical properties of tantalum?
Refractory metals are generally characterized by a high density and a low coefficient of thermal expansion. For tantalum, the same is true. Tantalum does, however, have a lower heat conductivity than molybdenum and tungsten. Tantalum's thermophysical characteristics vary with temperature. The curves for the key variables are depicted in the diagrams below:
What are the mechanical properties of tantalum?
Tantalum's mechanical characteristics can be altered by intervening elements, including carbon, hydrogen, nitrogen, and oxygen, even in minute amounts. Its mechanical properties are further influenced by the type of heat treatment applied, the degree of deformation, and the production process.
The crystal structure of tantalum is body-centered cubic, just like that of tungsten and molybdenum. The brittle-to-ductile transition temperature is -200 °C, which is significantly below ambient temperature. Consequently, working with the metal is quite simple. Increased forming results in a decrease in the material's breaking elongation while simultaneously increasing its tensile strength and hardness. But the substance doesn't break easily.
The material's stability at high temperatures is comparable to that of pure molybdenum, but it is lower than that of tungsten. We add refractory metals like tungsten to our tantalum alloy to improve its stability at high temperatures.
Tantalum has an elastic modulus that is similar to pure iron and is lower than that of tungsten and molybdenum. The temperature increases with a decrease in the modulus of elasticity.
Tantalum is a good material for chipless forming techniques such bending, stamping, pressing, and deep drawing because of its high degree of ductility. Tantalum presents a significant challenge when using machining methods. The chips don't shatter perfectly. For this reason, we advise using chip breakers. Tantalum is far more weldable than molybdenum and tungsten.
Do you have any inquiries regarding the refractory metals' mechanical processing? We would be happy to use our many years of knowledge to assist you.
What is the chemical behavior of tantalum?
Tantalum is frequently compared to noble metals due to its resistance to all kinds of chemicals. Nonetheless, tantalum is a base metal in thermodynamic terms and may combine with a wide range of elements to generate stable compounds. Tantalum creates an extremely thick oxide layer (Ta2O5) in the presence of air, shielding the base material from chemical damage. Tantalum is consequently resistant to corrosion because of this oxide layer.
The only inorganic substances that tantalum is not resistant to at normal temperature are hydrofluoric acid, hydrogen fluoride, fluorine, and acid solutions that contain fluoride ions. Tantalum is also attacked by molten sodium hydroxide, potassium hydroxide, and alkaline solutions. Conversely, the substance exhibits resistance towards aqueous ammonia solutions. Tantalum becomes brittle when hydrogen penetrates its metal lattice due to chemical aggressiveness. As temperature rises, tantalum's resistance to corrosion gradually decreases.
Tantalum reacts inertly with a wide range of liquids. Even while tantalum is resistant to each of the constituent elements when handled separately, its ability to withstand corrosion may be compromised if it is subjected to combined solutions. Do you have any inquiries on difficult corrosion-related subjects? Our in-house corrosion laboratory and years of experience would be happy to assist you.
| MEDIUM | RESISTANT (+), NON-RESISTANT (-) | NOTE |
| Water | ||
| Hot water < 150 °C | + | |
| Acids | ||
| Hydrofluoric acid, HF | - | |
| Hydrochloric acid, HCI | + | < 30%, < 190 °C |
| Phosphoric acid, H3PO4 | + | < 85%, < 150 °C |
| Sulfuric acid, H2SO4 | + | < 98%, < 190 °C |
| Nitric acid, HNO3 | + | < 65%, < 190 °C |
| Organic acids | + | |
| Lyes | ||
| Ammonia solution, NH4OH | + | < 17%, < 50 °C |
| Potassium hydroxide, KOH | + | < 5%, < 100 °C |
| Sodium carbonate, Na₂CO₃ | + | < 20%, < 100 °C |
| Sodium hydroxide, NaOH | + | < 5%, < 100 °C |
| Halogens | ||
| Fluorine, F2 | - | |
| Chlorine, Cl2 | + | < 150 °C |
| Bromine, Br2 | + | < 150 °C |
| Iodine, I2 | + | < 150 °C |
| Non-metals | ||
| Borine, B | + | < 1000 °C |
| Phosphorous, P | + | < 150 °C |
| Sulfur, S | + | < 150 °C |
| Gases | ||
| Noble gases do not react with tantalum. High purity noble gases can therefore be employed as protective gases. Tantalum, on the other hand, interacts very strongly with oxygen or air at higher temperatures and can absorb significant amounts of nitrogen and hydrogen. The material becomes brittle as a result. These contaminants are eliminated by annealing tantalum under intense vacuum. At 800 °C, hydrogen is gone, and at 1700 °C, nitrogen. | ||
| Ammonia, NH3 | + | < 700 °C |
| Carbon monoxide, CO | + | < 1100 °C |
| Carbon dioxide, CO2 | + | < 500 °C |
| Hydrocarbons | + | < 800 °C |
| Air and oxygen, O2 | + | < 300 °C |
| Noble gases (He, Ar, N2) | + | |
| Hydrogen, H2 | + | < 340 °C |
| Water vapor | + | < 200 °C |
| Melts | ||
| When noble materials like platinum and base materials like tantalum come into contact, chemical reactions start very quickly. Because of this, you should pay close attention to how tantalum behaves when it comes into contact with the other components of the system, particularly when operating temperatures are high. | ||
| Aluminum, Al | - | |
| Beryllium, Be | - | |
| Lead, Pb | + | < 1000 °C |
| Cesium, Cs | + | < 980 °C |
| Copper, Cu | + | < 1300 °C |
| Gallium, Ga | + | < 450 °C |
| Iron, Fe | - | |
| Lithium, Li | + | < 1000 °C |
| Magnesium, Mg | + | < 1150 °C |
| Mercury, Hg | + | < 600 °C |
| Nickel, Ni | - | |
| Potassium, K | + | < 1000 °C |
| Silver, Ag | + | < 1200 °C |
| Sodium, Na | + | < 1000 °C |
| Tin, Sn | + | < 260 °C |
| Zinc, Zn | + | < 500 °C |
| Furnace construction materials | ||
| Tantalum may react with building materials composed of graphite or refractory oxides in high-temperature furnaces. When tantalum comes into touch with particularly stable oxides, such aluminum, magnesium, or zirconium oxide, it can decrease them at very high temperatures. Tantalum carbide may occur when it comes into contact with graphite, which could cause the tantalum to become embrittled. Tantalum may react with hexagonal boron nitride and silicon nitride, however it may generally be mixed with other refractory metals like molybdenum or tungsten without any issues. In a vacuum, the following limit temperatures are applicable. These temperatures are about 100 to 200 °C lower when a protective gas is utilized. | ||
| Alumina, Al2O3 | + | < 1900 °C |
| Beryllium oxide, BeO | + | < 1600 °C |
| Hex. boron nitride, BN | + | < 700 °C |
| Graphite, C | + | < 1000 °C |
| Magnesium oxide, MgO | + | < 1800 °C |
| Molybdenum, Mo | + | |
| Silicon nitride, Si3N4 | + | < 700 °C |
| Thorium oxide, ThO2 | + | < 1900 °C |
| Tungsten, W | + | |
| Zirconium oxide, ZrO2 | + | < 1600 °C |
Corrosion behavior of tantalum against selected substances
Emrittlement of hydrogen
| Sulfuric acid 98% at 250 °C | Atomic hydrogen > 25 °C |
| Hydrochloric acid 30% at 190 °C | Hydrogen at 350 °C |
| Hydrofluoric acid | Cathodic polarization with less noble, dissolving materials |
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