Tantalum and Tantalum Alloys
Tantalum melts at 3,017 °C, weighs 16.6 g/cm³ and is protected by a tenacious oxide film that makes it inert to hydrochloric, sulfuric and nitric acid at almost any concentration and to body fluid. Annealed pure tantalum yields only about 140–200 MPa with 30–40 % elongation — it forms like copper — and welds cleanly under argon. Ta-2.5W raises the yield to roughly 220–300 MPa with the same corrosion resistance; Ta-10W reaches 450 MPa or more and holds strength in vacuum furnaces to 2,000 °C. Only hydrofluoric acid, fuming sulfuric acid, hot strong alkalis and hydrogen pickup attack it.
Popular tantalum grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Pure Ta | 170 | 250 | 16.6 | Poor | Very good | Acid heat exchangers, liners, implant markers |
| Ta-2.5W | 310 | 415 | 16.7 | Poor | Very good | Stronger acid-service sheet and tube |
| Ta-10W | 550 | 690 | 16.8 | Poor | Very good | Vacuum-furnace crucibles and shields to 2,000 °C |
| R05400 | 170 | 250 | 16.6 | Poor | Very good | Powder-metallurgy sheet and sputter targets |
| T-111 | 415 | 550 | 16.8 | Poor | Very good | Creep-resistant space-reactor alloy |
| Ta-40Nb | 220 | 330 | 12.1 | Poor | Excellent | Lighter, cheaper grade for less severe acids |
| 5N Tantalum (99.999%) | 120 | 200 | 16.65 | Poor | Good | Semiconductor sputter-target purity |
Choose tantalum for
Hot concentrated hydrochloric, sulfuric and nitric acid — heat exchangers, condensers, bayonet heaters, thermowells, reactor liners and repair patches — where even Hastelloy C276 and Zr 702 corrode; capacitor anodes; radiopaque implant markers, porous bone-ingrowth implants and coatings; and vacuum-furnace crucibles and shields above the range of molybdenum (Ta-10W).
Look elsewhere when
The acid is dilute or moderately hot, where Zr 702, titanium Grade 2 or Hastelloy C276 hold at a fraction of the cost; the medium is hydrofluoric acid, fuming sulfuric acid or hot caustic (tantalum fails in all three); the part sees air above 400 °C (a nickel or platinum alloy); the job is a bulk high-temperature structure where Pure Mo or Pure W is far cheaper and lighter; or the part is a large vessel — tantalum-clad steel or a thin loose liner delivers the surface without the mass.
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Tantalum by application
- Hot acid equipment
- Pure Ta and R05400 for heat-exchanger tubes, bayonet heaters, thermowells and liners in hot hydrochloric, sulfuric and nitric acid; Ta-2.5W when pressure calls for more strength in the same thickness.
- Vacuum-furnace hardware
- Ta-10W crucibles, heat shields and hearths at 1,600–2,000 °C where molybdenum has run out of strength; Pure Ta for getter parts and the lowest outgassing.
- Implants and electronics
- Pure Ta for radiopaque markers, porous bone-ingrowth structures and coatings on titanium implants; capacitor anode powder and wire; 5N Tantalum (99.999%) for barrier-layer sputter targets in copper interconnects.
- Aerospace and nuclear
- T-111 and T-222 for long-life creep at 1,300–1,600 °C in space power systems; Ta-10W nozzle inserts and thrust-chamber parts.
Working with tantalum
- Machining
- Soft, gummy and prone to galling: sharp positive carbide or high-speed-steel tools, high speed, light feeds and a chlorinated or heavy sulfurized oil to stop the chip welding to the tool. Ta-10W cuts more like a stainless steel. Chips are valuable and are collected for refining.
- Forming
- Deep-drawn, spun, bent to a zero inside radius and roll-formed like annealed copper; Ta-2.5W follows with a little more spring-back. Anneal at 1,100–1,300 °C in high vacuum; any trace of oxygen, nitrogen or hydrogen in the furnace embrittles the metal.
- Welding
- TIG and electron-beam welds are as ductile and as corrosion-resistant as the base metal — provided the joint sees no air at all. Weld in a glove box or under a trailing shield with argon on both sides; even 50 ppm oxygen turns the weld brittle. Never let tantalum touch steel while hot.
- Finishing
- Pickle in nitric-hydrofluoric mixtures with care (hydrogen pickup embrittles), electropolish for vacuum and implant use, and anodize for colored, insulating oxide films on markers and capacitors. No coating is needed against corrosion at room temperature.
Other refractory metal series
Tantalum and Tantalum Alloys — frequently asked
What is tantalum?
Tantalum melts at 3,017 °C, weighs 16.6 g/cm³ and is protected by a tenacious oxide film that makes it inert to hydrochloric, sulfuric and nitric acid at almost any concentration and to body fluid. Annealed pure tantalum yields only about 140–200 MPa with 30–40 % elongation — it forms like copper — and welds cleanly under argon. Ta-2.5W raises the yield to roughly 220–300 MPa with the same corrosion resistance; Ta-10W reaches 450 MPa or more and holds strength in vacuum furnaces to 2,000 °C. Only hydrofluoric acid, fuming sulfuric acid, hot strong alkalis and hydrogen pickup attack it.
Which grade of tantalum should I use?
Pure Ta (R05200, electron-beam melted) for acid heat exchangers, bayonet heaters, thermowells, liners, capacitor anodes and implant markers — the most formable and weldable grade. R05400 is the powder-metallurgy version: finer grain and a little more strength, the usual choice for sheet and for sputter targets. Ta-2.5W for the same acid-service parts when pressure or wall thickness pushes the design: 1.5 times the strength, still deep-drawable and weldable. Ta-10W for crucibles, hot-zone shields and rocket-nozzle parts in vacuum at 1,600–2,000 °C. T-111 and T-222 are the hafnium-strengthened alloys for space-reactor and long-life creep service; Ta-40Nb is the lighter, cheaper grade for acids that are severe but not the worst; 5N Tantalum (99.999%) is the semiconductor sputter-target purity.
Which grade of tantalum is the strongest?
Ta-10W has the highest yield strength in the series at 550 MPa; T-222 follows at 470 MPa. Values are for each grade's default condition.
Which grade of tantalum is easiest to machine?
5N Tantalum (99.999%) (machinability poor, 25/100), then T-111 (25/100).
Pure Ta or Ta-2.5W?
Same corrosion resistance, so the choice is mechanical. Pure Ta forms and welds most easily and is the default for liners, patches and low-pressure heat exchangers. Ta-2.5W yields about 1.5 times as much, which lets a pressure part be thinner — and thickness is metal, and metal is most of the cost — so it is specified for tube, bayonet heaters and anything designed to a pressure code. Ta-10W is for strength at furnace temperature, not for acid.
Tantalum or zirconium for a hot acid?
Zr 702 first, if it survives: it is a third of the density and far cheaper, and it handles hydrochloric acid at all concentrations, sulfuric acid to about 70 % and boiling nitric acid. Tantalum takes over in concentrated sulfuric acid above 70 %, in acids contaminated with ferric or cupric chlorides (which pit zirconium), in mixed and unknown acid streams, and where a leak would be catastrophic. Neither survives hydrofluoric acid.