Metal · Material guide
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Monel is a family of nickel-copper alloys (roughly 67% Ni, 30% Cu) that resists seawater, salt spray, reducing acids, and alkaline service better than most stainless. The marine, naval, and chemical-process standard where 316 stainless corrodes. Upload your drawing and we route it to shops set up for Ni-Cu work.
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Grades
Monel grades shops run most
Two grades dominate practical specification: solid-solution Monel 400 and precipitation-hardening K-500.
Monel 400 (UNS N04400)
The baseline nickel-copper alloy (~67% Ni, 30% Cu, balance Fe/Mn). Excellent seawater and salt-air corrosion resistance, immune to chloride-induced stress-corrosion cracking, strong in reducing acids. Not heat-treatable; strength set by cold work.
Best for Marine hardware, seawater pump wet-ends, propeller shafts, valve bodies, fittings, chemical-process piping
Monel K-500 (UNS N05500)
Monel 400 with aluminum and titanium additions for age-hardening. Roughly 2× the yield strength of Monel 400 with the same corrosion profile, used where seawater service meets a strength requirement.
Best for Pump and valve shafts, fasteners for marine and oilfield, downhole hardware, propeller shafts
Monel 404 (UNS N04404)
A low-magnetic variant with controlled low aluminum, for electronic and vacuum tube applications where magnetic properties matter.
Best for Vacuum electronics, specialty magnetic applications
Monel R-405 (UNS N04405)
A free-machining Monel 400 with added sulfur for better machinability at the cost of some corrosion resistance. For high-volume turned parts where the base alloy is too gummy.
Best for High-volume machined fasteners, fittings, screw-machine parts
Specs
Material properties
Representative values for Monel 400 (annealed) and K-500 (aged).
| Property | Typical value |
|---|---|
| Density | 8.80 g/cm³ (0.318 lb/in³) |
| Melting range | 1300–1350 °C |
| Tensile strength (400 annealed) | ~70 ksi min |
| Yield strength (400 annealed) | ~28 ksi min |
| Tensile strength (K-500 aged) | ~130–160 ksi |
| Yield strength (K-500 aged) | ~85–120 ksi |
| Hardness (400 annealed) | ~75 HRB |
| Hardness (K-500 aged) | ~27–35 HRC |
| Machinability | 400: gummy, work-hardens; R-405 is better. K-500: machine solution-annealed, then age. |
| Welding | Readily welded with matching NiCu filler (ERNiCu-7). |
Monel work-hardens; keep the cut heavy enough to stay under the hardened layer, avoid dwelling, and use positive-geometry carbide. For K-500, machine in the solution-annealed condition and age-harden after rough machining, then finish-machine.
Processes
Manufacturing methods for monel
The right process depends on part geometry, tolerances, and production volume.
Finishing
Finishes for monel
Monel is usually left bare or passivated; the alloy itself provides the corrosion resistance.
As-machined
Standard for most marine and industrial parts.
Pickled & passivated
Removes heat tint and surface iron from machining and welding; restores full corrosion profile.
Electropolished
For pharma and semi applications where surface particulate matters.
Bead or glass-bead blasted
Uniform matte finish, common on visible marine and architectural parts.
For sour service and oil & gas, specify NACE MR0175 compliance and the heat-treat condition on the drawing (annealed vs aged).
Applications
Where monel parts are used
Monel wins when the service is seawater, salt spray, or reducing acids where stainless pits or stress-corrosion cracks.
Compare
Monel vs other materials
How Monel compares to the alloys buyers consider alongside it.
Monel vs 316L stainless steel
316L stainless steel →- Monel resists seawater pitting and chloride stress-corrosion cracking; 316L is vulnerable to both
- 316L is far cheaper per pound and more widely available
- For general industrial corrosion where chlorides are moderate, 316L is usually adequate
Choose Monel for seawater and chloride-rich service. Choose 316L for general industrial and food-grade service.
Monel vs Hastelloy C-276
Hastelloy C-276 →- Hastelloy handles mixed oxidizing + reducing media better than Monel
- Monel is better in hot HF (hydrofluoric acid), where Hastelloy and stainless both fail
- Monel is less expensive than Hastelloy and more widely available
Choose Monel for seawater, salt, and HF. Choose Hastelloy for mixed-acid chemical process and higher-temperature service.
Monel vs Inconel 625
Inconel 625 →- Inconel 625 covers a wider temperature range and more aggressive mixed media
- Monel is better suited to seawater and reducing-acid wet service
- Monel is more machinable and typically less expensive
Choose Inconel for high-temperature or mixed-oxidizer service. Choose Monel for marine and reducing wet service.
Questions
Frequently asked questions
Both have the same corrosion profile (seawater, salt spray, reducing acids, HF). Monel 400 is a solid-solution alloy with strength set by cold work. K-500 adds aluminum and titanium so it can be age-hardened to roughly double the yield strength (85–120 ksi vs 28 ksi for annealed 400). Use K-500 where you need both the corrosion resistance and the strength — pump shafts, downhole fasteners, propeller shafts.
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Need Monel 400 or K-500 parts?
Upload a drawing and we route it to shops set up for nickel-copper work, with marine, oilfield, or chemical-service experience as the project requires.
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