Monel Alloys
UNS N04400 / N05500 · For seawater and hydrofluoric acid
Monel is a nickel-copper alloy, roughly 67% nickel and 30% copper, with outstanding resistance to seawater, brine and hydrofluoric acid. It retains strength and toughness from cryogenic temperatures up to about 500°C. Monel 400 is the standard grade; K-500 is precipitation hardened for roughly three times the yield strength.
When to specify Monel
Choose Monel 400 for seawater handling, brine, hydrofluoric acid and alkalis, where it outperforms stainless steel by a wide margin. Choose K-500 where the same corrosion resistance is needed together with high strength and galling resistance — pump shafts, valve stems, fasteners and propeller shafts.
Chemical Composition (%)
Composition and mechanical values are the limits set by the governing ASTM specification and are given for reference. The mill test certificate supplied with your consignment carries the actual heat analysis.
| Element | Monel 400 | Monel K-500 |
|---|---|---|
| Nickel | 63.0 min | 63.0 min |
| Copper | 28.0 – 34.0 | 27.0 – 33.0 |
| Iron | 2.50 max | 2.00 max |
| Manganese | 2.00 max | 1.50 max |
| Aluminium | — | 2.30 – 3.15 |
| Titanium | — | 0.35 – 0.85 |
| Carbon | 0.30 max | 0.25 max |
| Sulphur | 0.024 max | 0.010 max |
Mechanical & Physical Properties
| Property | Monel 400 | Monel K-500 (aged) |
|---|---|---|
| Tensile strength | 480 MPa min | 965 MPa min |
| Yield strength (0.2%) | 170 MPa min | 690 MPa min |
| Elongation | 35% min | 20% min |
| Density | 8.80 g/cm³ | 8.44 g/cm³ |
| Max continuous service | ≈ 540 °C | ≈ 480 °C |
Governing Standards
| Standard | Covers |
|---|---|
| ASTM B165 | Alloy 400 seamless pipe and tube |
| ASTM B127 | Alloy 400 plate, sheet and strip |
| ASTM B164 | Alloy 400 and K-500 bar and rod |
| ASTM B366 | Buttweld fittings |
| ASTM B564 | Forged fittings and flanges |
| ASTM F467 / F468 | Nuts and bolts |
Equivalent Designations
| Standard | Designation |
|---|---|
| UNS | N04400 / N05500 |
| EN | 2.4360 / 2.4375 |
| Werkstoff | NiCu30Fe / NiCu30Al |
Typical Applications
- Seawater piping, valves and pump components
- Hydrofluoric acid plant and alkylation units
- Marine propeller and pump shafts (K-500)
- Heat exchangers in brackish and salt water
- Crude oil distillation and sour service hardware
Industries Served
- Marine
- Oil & Gas
- Chemical
- Petrochemical
Monel Products We Supply
Available in the forms below, minimum order quantity 5 kg, with a mill test certificate to EN 10204 3.1 traceable to the heat number.
Need Monel in a form not listed above? We source to requirement — and we will confirm availability and lead time.
Monel by product form
Governing standards, dimensions and stock availability for each form.
Monel — Frequently Asked Questions
- What is the difference between Monel 400 and K-500?
- K-500 adds aluminium and titanium and is precipitation hardened, which raises minimum yield strength from about 170 MPa to about 690 MPa while keeping essentially the same corrosion resistance. K-500 also resists galling better, which is why it is used for shafts, stems and fasteners. Monel 400 is more ductile and easier to form and weld.
- Why is Monel used for hydrofluoric acid?
- The nickel-copper composition is exceptionally resistant to HF across a wide range of concentrations and temperatures, where stainless steels corrode rapidly. This makes Monel a standard material for HF alkylation units in refineries. Always confirm against the specific concentration, temperature and aeration of your service.
- Can Monel be used in place of stainless steel for seawater?
- For flowing seawater Monel 400 performs very well and resists the pitting that affects 316. In stagnant or low-flow seawater it can suffer crevice attack, and it is attacked by strongly oxidising media such as nitric acid or ferric chloride. Selection should always be made against the actual service conditions.
Send your Monel requirement
Tell us the form, size, quantity and standard and our technical team will confirm stock and send a firm price. Minimum order quantity 5 kg, mill test certificates supplied as standard.