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
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Nickel (+Co) | As specified |
| Copper | As specified |
| Iron | As specified |
| Manganese | As specified |
| Carbon | As specified |
| Silicon | As specified |
| Sulphur | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: 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
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM B127 for UNS N04400 — Annealed plate.
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
| Product | Standard |
|---|---|
| Monel 400 sheet | ASTM B127 |
| Monel 400 plate | ASTM B127 |
| Monel 400 coil | ASTM B127 |
| Monel 400 pipe & tube | ASTM B165 · ASTM B725 |
| Monel 400 fittings | ASTM B366 WPNC · ASTM B564 |
| Monel 400 flanges | ASTM B564 |
| Monel 400 fasteners | ASTM F468 (N04400) where specified for applicable bolts, hex cap screws, socket-head cap screws and studs (0.250–1.500 in.), and ASTM F467 for applicable nuts (0.250–1.500 in.); for other types, material may be supplied to ASTM B164 bar where applicable, subject to the purchase specification |
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 or 3.2 available on request / as specified in the PO; ask for 3.2 if a third party must witness.
- NACE MR0175 / ISO 15156 compliance if the service contains H₂S.