Titanium fasteners are bought for one of two reasons, and the five grades here divide cleanly between them. Grades 1, 2, 7 and 12 are commercially pure or lean alloys chosen for corrosion resistance — outstanding in seawater, brine, oxidising acids and wet chlorine, with the palladium-bearing Grade 7 and the molybdenum-nickel Grade 12 added to beat the crevice corrosion that limits plain CP titanium in hot chlorides. Grade 5, Ti-6Al-4V, is chosen for strength-to-weight: a specified minimum 895 MPa tensile at a density of 4.42 g/cm³, around 57% that of steel. Exotic Alloy manufactures all five to ASTM B348 and to ASTM F467 and F468 for nonferrous nuts and bolts, with full EN 10204 3.1 certification.
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This is the single most important practical fact about titanium fasteners. Titanium’s protective oxide is thin and the metal beneath it is adhesive, so a titanium thread run against another titanium thread will cold-weld and seize, often badly enough that the fastener has to be cut off. Specify one of three mitigations on every order: an anti-seize compound or dry-film lubricant such as molybdenum disulphide; a plated or coated thread, commonly silver or solid-film lubricant; or a nut in a dissimilar material rather than titanium. Tell us the mating material and we will advise.
Titanium is also galvanically noble. It will not corrode itself, but a titanium fastener in an aluminium, carbon steel, zinc or magnesium assembly will drive accelerated corrosion of the structure around it — and the small-anode, large-cathode geometry of a bolted joint is the worst case. Insulating washers and sleeves or a barrier coating should be specified in those assemblies.
Three absolute exclusions apply to every grade: titanium must not be used in dry chlorine, with which it reacts violently; not with red fuming nitric acid; and it is rapidly attacked by hydrofluoric acid at any concentration. The palladium and molybdenum-nickel additions improve crevice and reducing-acid performance — they do not change these limits.
Titanium’s low thermal conductivity is the governing machining problem — the heat generated at the cut stays at the cutting edge instead of being carried away into the work or the chip. Grade 5 is the worst case at around 6.7 W/m·K, roughly 40% that of the CP grades. Exotic Alloy machines titanium on rigid setups with sharp tooling, low surface speeds, heavy positive feeds and high-volume flood coolant directed into the cutting zone, never allowing the tool to dwell. Threads are rolled rather than cut wherever the section permits, both for fatigue life and because cutting titanium threads invites the same galling that plagues them in service. Fine chips and grinding dust are a fire hazard and are handled wet.
All mechanical values are ASTM B348 specified minimums, not typical figures.
| Grade | UNS | W.Nr. | Key Addition | UTS min | YS min | Elong. min | Chosen For |
|---|---|---|---|---|---|---|---|
| Grade 1 | R50250 | 3.7025 | None — CP, lowest interstitials | 240 MPa | 138 MPa | 24% | Maximum formability |
| Grade 2 | R50400 | 3.7035 | None — CP | 345 MPa | 275 MPa | 20% | General purpose corrosion |
| Grade 5 | R56400 | 3.7165 | 6% Al, 4% V | 895 MPa | 828 MPa | 10% | Strength-to-weight |
| Grade 7 | R52400 | 3.7235 | 0.12–0.25% Pd | 345 MPa | 275 MPa | 20% | Best crevice resistance |
| Grade 12 | R53400 | – | 0.3% Mo, 0.8% Ni | 483 MPa | 345 MPa | 18% | Crevice resistance plus strength |
Grades 2H and 7H are identical material to Grades 2 and 7 but certified to a higher 400 MPa (58 ksi) minimum tensile strength — useful where a slightly higher guaranteed minimum is needed without changing alloy. ASTM B348 tensile requirements apply to sections up to 76 mm thick and 64.5 cm² in area; properties for larger sections are negotiated between manufacturer and purchaser, so large-diameter bolting acceptance values must be agreed on the order.
We are committed to delivering zero-defect titanium fasteners. All products undergo rigorous testing including PMI (Positive Material Identification), interstitial analysis against the ASTM B348 limits, dimensional inspection, anti-gall treatment to specification, and material traceability with EN 10204 3.1 certification.
Exotic Alloy exports titanium fasteners to chemical processing, desalination, offshore, aerospace and motorsport clients worldwide. Our dedicated logistics team ensures secure export packaging and timely deliveries by sea and air freight with full customs documentation support.