Tantalum Fasteners
Manufacturer
India · Mumbai
Why Tantalum — Chemistry, Properties & When It Is Specified
Tantalum (atomic number 73, symbol Ta) is a refractory transition metal with a melting point of 2,996°C (5,425°F) — the fourth highest of any element. In corrosion engineering, tantalum is specified not for its mechanical properties or its temperature rating, but for one unique characteristic: near-universal acid corrosion resistance.
Tantalum forms an extremely stable, adherent tantalum pentoxide (Ta₂O₅) passive film that is chemically inert in virtually all acid environments encountered in the chemical process industry. HCl at all concentrations and temperatures up to boiling, H₂SO₄ at all concentrations up to 98%, HNO₃ at all concentrations, phosphoric acid, aqua regia (mixed HNO₃/HCl), and most organic acids — in all of these, tantalum is essentially unaffected. This places tantalum above platinum, gold, and all commercially practical engineering alloys including Hastelloy B3, Hastelloy C276, and titanium in acid resistance breadth.
The engineering limitation of tantalum: its high density (16.6 g/cm³ — nearly twice the density of stainless steel), high cost (approximately 50–100× the cost of stainless steel per kg), and moderate room-temperature mechanical strength (≥207 MPa UTS pure Ta). Tantalum is specified only when the corrosion environment is so aggressive that no other engineering material is adequate — high-temperature concentrated HCl, mixed acid combinations, or processes where even minute concentrations of corrosion product contamination are unacceptable.
| Property | Value |
|---|---|
| Density | 16.6 g/cm³ |
| Melting Point | 2,996°C (5,425°F) |
| Min UTS (Annealed) | ≥ 207 MPa |
| Min Yield Strength | ≥ 138 MPa |
| Elongation | ≥ 20% |
| Hardness | ≈ 80 HV (annealed) |
| Thermal Conductivity | 57.5 W/(m·K) |
| Biocompatibility | Excellent (implant-grade) |
| Magnetic | Non-magnetic |
• Strong alkali — NaOH above 40% attacks tantalum. For caustic: specify Nickel 200/201.
• Hydrogen embrittlement — cathodic protection or galvanic couple with less noble metal will cause hydrogen absorption and embrittlement at >150°C.
• Cost — approximately 50–100× stainless steel per kg. Specify only where no other alloy is adequate.
Pure Tantalum · Ta-2.5W · Ta-10W — Grade Profiles
Three tantalum grades available as fasteners. Pure Ta for maximum corrosion resistance and formability. Ta-2.5W for strength without sacrificing corrosion resistance. Ta-10W for the highest strength in demanding mechanical service. All to ASTM B365.
Pure Tantalum
Ta-2.5W
Ta-10W
Tantalum Acid Resistance Matrix vs Other Alloys
Tantalum compared with the best-performing alloys in the same environment. “Excellent” = corrosion rate below 0.1 mm/year. Tantalum is the correct specification only when all less-costly alternatives fail.
| Corrosion Environment | Tantalum R05200 This Page | Hastelloy B3 (N10675) | Hastelloy C276 (N10276) | SS 316L |
|---|---|---|---|---|
| MINERAL ACIDS — STRONGEST ENVIRONMENTS | ||||
| HCl all conc. + temp to 100°C | ✔ Excellent | ✔ Excellent | ✗ Fails >5% | ✗ Fails dilute |
| H₂SO₄ all conc. to 98%, 25°C | ✔ Excellent | ✗ Fails conc. | Good (≤30%) | ✗ Fails >30% |
| H₂SO₄ hot concentrated (>60%, >80°C) | ✔ Excellent | ✗ Fails | ✗ Fails | ✗ Fails |
| HNO₃ all conc., boiling | ✔ Excellent | ✗ Fails | Good (mod.) | ✗ Fails conc. |
| Aqua Regia (HNO₃ + HCl) | ✔ Excellent | ✗ Attacks | ✗ Attacks | ✗ Attacks |
| H₃PO₄ all concentrations | ✔ Excellent | Moderate | Good | Moderate |
| HCl >30% at elevated temp (>100°C) | ✔ Excellent | ✔ Excellent (B3) | ✗ Fails | ✗ Fails |
| MIXED & SPECIAL MEDIA | ||||
| Bromine and Bromic acid | ✔ Excellent | Moderate | Good | Moderate |
| Formic acid, acetic acid | ✔ Excellent | ✔ Excellent | ✔ Excellent | Good |
| Wet chlorine gas (Cl₂) | ✔ Excellent | Moderate | Good | Fails |
| WHERE TANTALUM IS NOT APPROPRIATE | ||||
| HF acid (pure, reducing) | ✗ Attacks Ta | Moderate | Moderate | Fails |
| Strong NaOH (caustic >40%) | ✗ Attacks Ta | Fails | Fails | Fails |
HCl service: Hastelloy B3 (far lower cost) · Caustic: Nickel 200/201 · HF: Monel 400
Why Tantalum — Where No Other Metal Works
Near-Universal Acid Immunity
The only metallic engineering material resistant to HCl at all concentrations, H₂SO₄ at all concentrations, HNO₃, aqua regia, and H₃PO₄ simultaneously. When the process acid is highly concentrated, at elevated temperature, or a mixture where no individual alloy handles all components — tantalum is the only option.
Highest Melting Point of Any Metal Alloy
2,996°C (5,425°F) — the fourth highest melting point of any element and the highest among practical engineering metals. For fastener applications in high-temperature acid service (concentrated H₂SO₄ or HCl at elevated temperature), tantalum maintains its protective oxide film and corrosion immunity at temperatures where all other engineering alloys fail.
Biocompatible — Pharmaceutical & Medical
Tantalum is biocompatible (ISO 10993) and is used for medical implants. In pharmaceutical and biotechnology applications where contamination from metal corrosion is unacceptable and the process acids are aggressive — tantalum fasteners eliminate corrosion product contamination risk and comply with biocompatibility requirements that no steel alloy can meet.
Aqua Regia Resistance
One of only a handful of metallic materials resistant to aqua regia (the mixture of concentrated HNO₃ and HCl that dissolves gold and platinum). In mixed acid processing — nitration reactors, acid recovery systems, and chemical synthesis operations — where the exact acid composition varies or where high-concentration mixed mineral acids are used, tantalum is the only commercially practical metallic fastener material.
Tantalum Fastener Types & Standards
Pure Tantalum R05200 is the primary stocking grade. Ta-2.5W and Ta-10W available on order from ASTM B365 certified rod/bar. All forms machined in a dedicated refractory metal machining environment. Chemical analysis certificate dispatched with every order. M4–M36 (larger sizes on enquiry).
Stud Bolts
Fully threaded tantalum stud bolts for pressure flanges in concentrated acid service. Pure R05200 for maximum acid resistance; Ta-2.5W (R05252) for higher-load applications requiring better mechanical strength. M6–M36, lengths to 500mm. Chemical plant acid reactor flanges, HCl synthesis unit connections, H₂SO₄ absorber flanges, and mixed acid reactor bodies.
Hex Bolts
Full thread and partial thread hex bolts in pure tantalum and Ta-2.5W. M4–M36. Acid plant equipment cover bolts, reactor body connections, heat exchanger bonnet bolts in concentrated HCl and H₂SO₄ service, and pharmaceutical processing equipment fasteners where biocompatibility and near-zero corrosion product tolerance are the specifications.
Hex Nuts
Standard hex nuts in pure tantalum (R05200) and Ta-2.5W (R05252). M4–M36. Matched from same ASTM B365 certified rod as stud bolts — single chemical analysis certificate for the complete stud bolt assembly. For concentrated acid service where tantalum nuts must match tantalum studs to eliminate galvanic corrosion at the thread engagement crevice.
Washers
Plain flat washers in pure tantalum (R05200). M4–M36. Matched-grade washer supply with tantalum stud bolt and nut sets for complete tantalum assembly documentation. For pharmaceutical and food-grade acid applications where every metal surface in contact with the process fluid must be tantalum. Same ASTM B365 certified rod stock as nuts and bolts.
Socket Cap Screws
Hex socket cylindrical head cap screws in pure tantalum (R05200). M4–M24. For confined-access acid plant connections — heat exchanger internal baffle screws, acid pump body internals, instrument flange connections in HCl and H₂SO₄ service, and pharmaceutical reactor internal fixtures where PTFE-coated or Hastelloy socket screws are insufficient.
Custom Tantalum
Non-standard dimensions, specialised head forms, inch UNC/UNF thread, and drawing-specific configurations. Tantalum is machined to tight tolerances — all custom tantalum fasteners machined in-house with dedicated tooling and chemical analysis certificate per piece available for critical pharmaceutical and nuclear applications. Contact sales@akbarfasteners.in.
Industry Applications
Concentrated acid, aqua regia, mixed mineral acid, and pharmaceutical/biomedical applications where no other engineering alloy can provide adequate corrosion resistance or contamination control.
HCl Synthesis Plant
acid absorber flange stud sets
H₂SO₄ Contact Plant
absorber tower stud bolts
Mixed Acid / Aqua Regia
aqua regia dissolving vessels
Pharmaceutical
API synthesis reactor fasteners
Hydrometallurgy
gold cyanide / acid dissolution
Nuclear Industry
acid dissolution vessel bolts
Semiconductor / Electronics
ultra-pure HF/HNO₃ bolts
Bromine Chemistry
hydrobromic acid connections
Tantalum Fastener Standards Coverage
Same ISO 9001:2015 quality system as our Hastelloy and Monel ranges. Chemical analysis certificate per ASTM B365 on every tantalum order as standard.
Complete Documentation Package
ASTM B365 Traceable
XRF + ICP-OES
Conformance
Tensile · Hardness
TÜV · BV · Lloyds
Less Costly Alternatives for Specific Acid Service
Tantalum should be specified only when no other alloy is adequate. In many acid applications, a far less expensive alloy provides sufficient resistance — check these first.
Hastelloy B3 — HCl Service
For HCl at all concentrations and temperatures — Hastelloy B3 (28% Mo, no Cr) provides near-zero corrosion in HCl at a fraction of tantalum’s cost. B3 is the correct first specification for HCl service. Tantalum is the fallback for B3-unsuitable mixed acid or HCl/HNO₃ combinations.
View B3 Page →Hastelloy C276 — Mixed Acids
For mixed or undefined acid media where B3 fails — C276’s Ni-Cr-Mo-W alloy provides the broadest coverage of mixed acid environments at significantly lower cost than tantalum. Use C276 when the acid environment is variable or undefined.
View C276 Page →Nickel 200/201 — Caustic
Where tantalum is contraindicated (concentrated NaOH above 40%) — pure Nickel 200/201 provides the caustic soda resistance that tantalum cannot, at far lower cost. For mixed caustic/acid service, consult Akbar Fasteners engineering.
View Nickel Page →Monel 400 — HF Acid
For HF acid service where tantalum is unsuitable — Monel 400 is the standard HF acid alloy for low-to-moderate temperature service. For high-temperature HF where Monel 400 is also borderline, consult Akbar Fasteners for process-specific guidance.
View M400 Page →Need Tantalum
Fasteners Now?
Grade (R05200/R05252/R05255) · product form · size · quantity · application description · documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Export: +91 8696 32 4646 · Support: +91 800 9315 333 · export@akbarfasteners.in