Monel K-500 Fasteners
Monel K-500 nickel-copper fasteners for flowing-seawater service — exceptional seawater corrosion resistance in high-velocity conditions and biofouling resistance per the collected offshore reference, aged rod tensile 140–190 ksi in the manufacturer bulletin, cryogenic-suitable with no ductile-to-brittle transformation, and a documented high-pressure hydrogen caution.
Last updated: 2026-11
Specifications
Monel K-500 is the precipitation-hardened nickel-copper alloy the collected offshore-platforms reference singles out for "exceptional resistance to seawater corrosion, particularly in high-velocity conditions", making it ideal for shafts, valves and fasteners exposed to flowing seawater, with the added behaviour that it resists biofouling and so reduces marine growth. The manufacturer technical bulletin fills in the numbers the corrosion references leave out: aged rod and bar reaches 140–190 ksi tensile (965–1310 MPa nominal range), fastener-specific test samples run 165–169 ksi smooth tensile, tensile and yield strengths increase as temperature drops — the bulletin reports NASA low-temperature data down to -423 °F, states no ductile-to-brittle transformation occurs even at liquid-hydrogen temperature, and tabulates hot hardness of aged rod still at Brinell 293 at 900 °F. One documented caution from the hydrogen-embrittlement reference: K-Monel (Monel K-500) has been known to be embrittled by hydrogen at high pressure — while solid-solution Monel 400 (UNS N04400) is generally resistant — so hydrogen-exposed joints should be reviewed, not assumed.
| Designation | Monel K-500 (K-Monel), precipitation-hardened nickel-copper alloy (collected sources use the Monel K-500 / K-Monel designations; the manufacturer bulletin carries UNS N05500; the collected spec-library line names N04400 for the Monel 400 family) |
|---|---|
| Seawater service | Exceptional resistance to seawater corrosion, particularly in high-velocity conditions; ideal for shafts, valves and fasteners exposed to flowing seawater (collected offshore reference, verbatim basis) |
| Biofouling | Resists biofouling, reducing marine growth (collected offshore reference) |
| Marine standing | Monel cited among the best fastener materials for marine applications, for exceptional resistance in high-velocity seawater (collected offshore reference) |
| Ultimate tensile strength, room temperature | Rod and bar, hot-finished and aged: 140–190 ksi (965–1310 MPa nominal range; manufacturer bulletin Table 6). Fastener-relevant Table 7 samples (cold-drawn and aged): threaded stud 165.0 ksi tensile (232.0 ksi notched), threaded cap screw 169.0 ksi (205.0 ksi notched) |
| Temperature behaviour | No tabulated design window: the bulletin's short-time hot tensile curves run to 1200–1400 °F and hot hardness of aged rod is tabulated at 900 °F (Brinell 293), 1000 °F (255) and 1100 °F (179). Cryogenic: tensile and yield strengths increase as temperature decreases; no ductile-to-brittle transformation even at liquid-hydrogen temperature, with NASA-reported base-metal and welded-sheet data to -423 °F — bulletin states the alloy is suitable for many cryogenic applications |
| Hydrogen caution | K-Monel (Monel K-500) has been known to be embrittled by hydrogen at high pressure; solid-solution Monel 400 is generally resistant (collected hydrogen-embrittlement reference) |
| Positioning vs Monel 400 | K-500 is the precipitation-hardened (higher-strength) variant; Monel 400 is solid-solution and generally hydrogen-resistant — the collected sources distinguish exactly this pair |
| MOQ / lead time | Not owner-confirmed for this family — confirmed at quotation |
| Sample | Temper | Yield strength, 0.2% offset (ksi) | Notched tensile strength (ksi) | Tensile strength (ksi) | NT/TS | Elongation (%) | Reduction of area (%) | Hardness (Rc) |
|---|---|---|---|---|---|---|---|---|
| Rod, 2 5/8-in. dia. | Cold-drawn, annealed and aged | 97.5 | 185.5 | 152.5 | 1.22 | 25 | 43.0 | 28 |
| Rod, 3 5/8-in. dia. | Hot-rolled and aged | 119.0 | 212.0 | 165.0 | 1.28 | 22 | 45.2 | 32 |
| Rod, 3-in. dia. | Cold-drawn and aged | 122.0 | 215.0 | 161.0 | 1.34 | 22 | 43.2 | 29 |
| Threaded cap screw | Cold-drawn and aged | 125.5 | 205.0 | 169.0 | 1.21 | 18 | 28.5 | 31 |
| Threaded stud | Cold-drawn and aged | 128.0 | 232.0 | 165.0 | 1.41 | 20 | 42.0 | 33 |
Materials
- Monel K-500 nickel-copper alloy
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (Monel K-500 Fasteners) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantities and lead times for this family are confirmed at quotation — send your sizes, grades and quantities on the RFQ and the quote will carry a firm schedule. Sample availability is confirmed with the quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Monel K-500 or Monel 400 for a marine joint?
The collected references split them by condition: K-500 is the precipitation-hardened alloy renowned for exceptional resistance in high-velocity flowing seawater and resists biofouling; Monel 400 (solid-solution, UNS N04400) is generally resistant to hydrogen embrittlement where K-Monel has been embrittled at high hydrogen pressure. Flowing-seawater strength points to K-500; high-pressure hydrogen exposure points to Monel 400.
Is Monel K-500 a high-temperature fastener alloy?
Only modestly, and the manufacturer bulletin says so by data rather than a design window: hot hardness of aged rod falls from Brinell 331 at 70 °F to 293 at 900 °F and 179 at 1100 °F, and short-time tensile curves are published to 1200–1400 °F without a tabulated design-strength window — so long-term load-bearing service above roughly 900 °F is not something the collected evidence supports quoting. Where it is exceptional is the cold end: strength rises as temperature drops and the bulletin reports no ductile-to-brittle transformation down to liquid-hydrogen temperature (NASA data to -423 °F). State the real service temperature on the RFQ either way.
What should an RFQ for Monel K-500 fasteners state?
State the designation (Monel K-500), fastener type and thread sizes, the seawater velocity/immersion case, and any hydrogen exposure in service — the collected references tie K-500's caution specifically to high-pressure hydrogen. Commercial terms are confirmed at quotation.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support