Monel 400: properties, composition, uses and standards
Monel 400 is a nickel–copper alloy, chosen for seawater, hydrofluoric acid and marine service. UNS N04400, W.Nr 2.4360, density 8.8 g/cm³.
What is Monel 400?
Monel 400 is a nickel–copper alloy. Engineers choose it for seawater, hydrofluoric acid and marine service. It is also known as Alloy 400, UNS N04400, W.Nr 2.4360, Nicorros.
- UNS
- N04400
- W.Nr
- 2.4360
- EN
- NiCu30Fe
- BS
- NA 13
- JIS
- NW 4400
- Trade names
- Monel 400 · Nicorros
- Density
- 8.8 g/cm³
- Melting range
- 1300 – 1350 °C
- Magnetic
- Slightly magnetic at room temperature
Chemical composition and what each element does
| Element | Weight % |
|---|---|
| Nickel (+Co) | 63.0 min |
| Copper | 28.0 – 34.0 |
| Iron | 2.5 max |
| Manganese | 2.0 max |
| Carbon | 0.3 max |
| Silicon | 0.5 max |
| Sulphur | 0.024 max |
Per ASTM B127 for UNS N04400.
Very low corrosion rates in flowing seawater and brackish water.
One of the few alloys that handles hydrofluoric acid in all concentrations (air-free).
Resists caustic alkalis and chloride stress-corrosion cracking.
Avoid nitric acid, aerated ammonia and oxidising salts.
Monel 400 at a glance
See the Monel 400 product page for every form we supply and its standard.
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength | 480 MPa · 70 ksi |
| Yield strength 0.2% | 195 MPa · 28 ksi |
| Elongation | 35% |
Annealed plate, minimum values. Values for pipe, bar and forgings differ slightly — see the product standard.
Where Monel 400 is used
- Marine. Pump shafts, valves and seawater piping. Industry →
- HF alkylation. Refinery HF-acid units. Industry →
- Chemical. Caustic and brine handling. Industry →
- Boiler feedwater. Heaters and exchangers. Industry →
Welding 400
The matching filler is ERNiCu-7 (AWS A5.14). ENiCu-7 electrode.
Keep heat input moderate and interpass temperature low, clean joints thoroughly, and pickle or passivate after welding where the service is corrosive.
Monel 400 compared with similar grades
| Grade | PREN | Choose it for |
|---|---|---|
| Monel 400 | — | Seawater, hydrofluoric acid and marine service |
| Inconel 625 | ≈ 51 | Seawater, high strength and high temperature in one alloy |
| Super Duplex 2507 | ≈ 42 | Seawater and high-chloride service where strength also matters |
| SS 316 / 316L | ≈ 24 | Chloride-bearing process fluids, marine air and pharmaceutical service |
Monel 400 standards by product
Buying Monel 400: what to specify
- The product standard and the UNS or designation — for example ASTM B127 UNS N04400.
- Size, thickness or schedule, and quantity in pieces and kg or metres.
- Heat-treatment condition where the standard offers a choice.
- Certificate: EN 10204 3.1 as standard, 3.2 if a third party must witness.
- NACE MR0175 / ISO 15156 compliance if the service contains H₂S.