Monel 400
Fasteners
UNS N04400
Monel 400 — Permanent Seawater & HF Acid Immunity
Monel 400 (UNS N04400) is a nickel-copper binary alloy — at least 63% Ni with 28–34% Cu — developed specifically for environments where stainless steels fail: permanently immersed seawater, brine, and HF acid service. The critical difference from stainless steel is that Monel 400 requires no passive oxide layer to resist corrosion; it is thermodynamically stable in seawater, neutral salt solutions, and alkaline conditions without any surface treatment or cathodic protection.
For fastener applications: Monel 400 stud bolts and hex bolts resist seawater corrosion at all flow velocities, including cavitation conditions at pump impellers and high-velocity seawater injection lines where stainless steels and even duplex steels suffer erosion-corrosion failure within months. In HF acid service — alkylation unit piping, fluorosilicate processing, and HF acid regeneration systems — Monel 400 is the industry standard alloy where stainless steels are not used due to SCC risk in fluoride environments.
Where higher bolt loads are required — ASME B16.5 Class 1500/2500 flanges, FPSO riser clamps, and subsea wellhead bolting — our Monel K500 fasteners (UNS N05500, ≥1000 MPa age-hardened) provide identical corrosion immunity at three times the strength. For HCl and reducing acid service beyond HF, our Hastelloy B3 stud bolts are the specification.
| Element | Min % | Max % | Typical |
|---|---|---|---|
| Nickel + Cobalt | 63.0 | — | ~67% |
| Copper (Cu) | 28.0 | 34.0 | ~31% |
| Iron (Fe) | — | 2.5 | ~1.5% |
| Manganese (Mn) | — | 2.0 | ~1.0% |
| Carbon (C) | — | 0.30 | — |
| Silicon (Si) | — | 0.50 | — |
| Sulfur (S) | — | 0.024 | — |
Monel 400 Fasteners — All Product Forms
All product forms manufactured from ASTM B164 certified UNS N04400 bar stock, annealed, PMI-verified. Complete matched assemblies from the same certified heat available.
Monel 400 Stud Bolts
Fully threaded and equal-end double stud. Class 150–2500. M12–M100, lengths to 3,000mm. Primary Monel 400 fastener for ASME B16.5 pressure flanges in seawater piping, HF acid units, and saltwater systems.
View Stud Bolts →Monel 400 Hex Bolts
Full thread DIN 933, partial thread DIN 931, heavy hex ASME B18.2.3.6M. M6–M100. Marine structural connections, pump housing covers, and seawater equipment closures where broad corrosion immunity is required.
View Hex Bolts →Monel 400 Hex Nuts
Standard hex DIN 934, heavy hex ASME B18.2.2, and coupling nuts DIN 6334. M6–M100. Supplied from same ASTM B164 certified heat as stud bolts — matched material eliminates galvanic corrosion at bearing face in seawater.
View Hex Nuts →Monel 400 Washers
Plain flat DIN 125 A/B and spring helical DIN 127 in Monel 400. M5–M100. Same-heat as stud bolts — zero galvanic potential at washer-nut bearing interface in seawater, HF acid, and brine immersion service.
View Washers →Monel 400 Threaded Rods
Full thread DIN 975 and end-thread DIN 976. M6–M100, lengths to 3,000mm. Marine pipe hanger systems, seawater equipment support tie-rods, and desalination plant structural rods in high-chloride environments.
View Threaded Rods →Socket Cap Screws
Hex socket cylindrical head in Monel 400 for confined marine equipment access — seawater pump internals, saltwater valve bodies, and offshore instrument enclosures where hex head clearance is unavailable. M4–M36.
View All Forms →Matched Assembly Sets
Stud bolts + heavy hex nuts + washers from same certified UNS N04400 heat — one MTC, one PMI XRF report, one COC for the complete assembly. Simplifies vendor documentation for marine and offshore projects.
Request Matched Set →Custom Configurations
Left-hand thread, inch UNC/UNF, non-standard diameters, drawing-specific head forms and configurations. Monel 400 naval vessel fittings, marine engineering custom hardware, and bespoke desalination equipment fasteners.
Send Drawing →Monel 400 vs Monel K500 — Which Grade to Specify
Both Monel 400 and K500 share identical Ni-Cu composition and seawater corrosion immunity. The selection depends on bolt load requirements and whether the application is NACE sour service. Both grades are supplied by Akbar Fasteners Pvt. Ltd. from the same ISO 9001:2015 certified Mumbai facility.
Monel 400 (UNS N04400)
Monel K500 (UNS N05500)
See our full Monel K500 Fasteners range for the complete age-hardened product range.
Standards We Manufacture & Test To
Same quality system as our Hastelloy B3 stud bolts and complete exotic alloy range. Full heat traceability from mill certificate to dispatch.
Industry Applications
Permanently corrosive marine, saltwater, and HF acid environments where stainless steel fails by pitting, crevice corrosion, or stress corrosion cracking — and where K500’s high strength is not required.
Seawater Piping
seawater injection systems
HF Alkylation Units
reactor closure bolts
Desalination Plants
brine circuit flanges
Offshore Platforms
caisson and riser connections
Oil & Gas
subsea seawater service
Naval & Marine
propeller shaft fittings
Marine Pumps
impeller housing bolts
Power Generation
cooling water covers
Complete Documentation Package
Heat & Lot Traceable
Conformance
100% Lots Verified
Tensile · Hardness
TÜV · BV · Lloyds
Compare Monel Grades & Alloy Alternatives
Monel 400 for standard-load seawater service. K500 for high-load offshore. Hastelloy for acid service.
ASTM B164 Monel 400 Overview
Full Monel 400 product range under ASTM B164 — composition, all product forms, standard stud bolt lengths, and documentation package.
View Page →Monel K500 Fasteners
Age-hardened K500 at ≥1000 MPa for Class 1500/2500 flanges, FPSO riser clamps, and subsea wellhead — same seawater immunity, three times the strength.
View Page →Hastelloy B3 Stud Bolts
For reducing HCl and H₂SO₄ service beyond Monel 400’s range. Near-zero corrosion in HCl at all concentrations — where Monel alloys are not the specification.
View Page →Hastelloy Fasteners India
Complete Hastelloy range — six grades for mixed acid, chlorinated, and reducing acid service where Monel alloys are not specified. All product forms, Mumbai manufacture.
View Range →Need Monel 400
Fasteners Now?
Product form · size · quantity · matched set · documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours with full pricing, lead time, and MTC documentation list.