Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Hiduron Seawater Corrosion Resistance
The Hiduron family carries the Cu-Ni-Al passive film that gives 70/30 cupronickel its known seawater performance, lifted by the iron addition that tunes the film and the gamma-prime strength response that lets the alloy carry structural load in the same body that carries the corrosion duty. The flowing seawater general-corrosion rate sits at below 0.025 mm/year on both Hiduron 130 and Hiduron 191 at sea-flow velocities of 1 to 3 m/s and water temperatures of 5 to 30 deg C. The film stabilises inside the first 24 hours of immersion and remains protective in low-flow, biofouling-prone, chloride-rich water where 316L stainless suffers crevice attack inside the same exposure window. The data table below summarises the flowing-seawater behaviour against the standard reference rates that the offshore bolting community uses for comparison.
Hiduron Flowing Seawater Corrosion Rates
| Condition | Hiduron 130 rate | Hiduron 191 rate | Carbon steel reference |
|---|---|---|---|
| Flowing seawater 1 m/s, 20 deg C | <0.025 mm/year | <0.025 mm/year | 0.10 to 0.15 mm/year |
| Flowing seawater 3 m/s, 20 deg C | <0.025 mm/year | <0.025 mm/year | 0.15 to 0.20 mm/year |
| Static seawater, low-flow crevice | <0.05 mm/year | <0.05 mm/year | 0.05 to 0.20 mm/year |
| Splash-zone wet-dry tidal band | <0.05 mm/year | <0.05 mm/year | 0.20 to 0.40 mm/year |
| Polluted harbour (sulphide-spiked) | <0.10 mm/year | <0.10 mm/year | 0.30 to 0.60 mm/year |
Passive Film Behaviour and Why It Stays Protective
The seawater oxide film on Hiduron is a cupric oxide layer modified by nickel and iron from the alloy matrix. The nickel raises the film electronic resistance and slows the reduction of dissolved oxygen at the surface, which is the cathodic step that drives copper dissolution. The iron substitutes into the cuprous-oxide sublayer and reduces the lattice defect density, which slows the outward diffusion of copper ions through the film. The combined effect is that the steady-state general corrosion rate sits at less than 0.025 mm/year in flowing seawater after the first 30 days of exposure. The film also resists biofouling because the cuprous-ion release rate at the surface is high enough to deter macro-fouling settlement but low enough that the underlying metal is not consumed at a structural rate.
Crevice Corrosion and Pitting Behaviour
In low-flow and crevice geometries (under washers, between flange faces, inside threaded engagement) the dissolved-oxygen supply is reduced and the film equilibrium shifts. On 316L stainless this depletes the chromium-oxide film and chloride pitting initiates inside weeks. On Hiduron the film remains protective because the cathodic step is the reduction of cuprous ions, not the reduction of dissolved oxygen, which means the film can sustain itself in the depleted-oxygen crevice environment. The result is that Hiduron bolting in flange and joint assemblies does not suffer the under-washer pitting that drives the routine bolt replacement schedule on stainless bolting in the same service. The crevice-corrosion onset temperature on Hiduron in 6 percent ferric chloride exceeds 50 deg C, against 25 deg C on 316L.
Biofouling Resistance
The copper-nickel matrix releases cuprous ions at the surface at a rate that suppresses macro-fouling settlement (barnacles, mussels, tube worms) on submerged Hiduron components. Riser bolting and subsea connector bodies in Hiduron stay clear of macro-fouling for the design service life without antifouling coatings, which is the operational reason that North Sea and Gulf of Mexico operators specify the alloy on splash-zone and subsea applications where ROV-recovered inspection windows are limited.
Hiduron 130 + 191 Designation Chain
| Designation system | Hiduron 130 | Hiduron 191 |
|---|---|---|
| UNS (Unified Numbering System) | C72400 | C72420 |
| Werkstoff (German register) | 2.1504 | not formally assigned |
| Chemical-symbol designation | CuNi14Al3Fe1 | CuNi14Mn4AlFe |
| UK Air Ministry | DTD 900/4805 | not applicable |
| UK Naval Engineering Standard | not applicable | NES 835 |
| UK Ministry of Defence | not applicable | DEF STAN 02-835 |
| US Department of Defense | not applicable | DOD-C-24676 |
| Originator and brand | Langley Alloys (UK) | Langley Alloys (UK) |
Related Hiduron Property Pages
- Chemical Composition: Element ranges for both grades with role notes for each addition.
- Mechanical Properties: Yield, tensile, elongation and hardness at room and elevated temperature.
- Heat Treatment: Solution-anneal plus age cycle for gamma-prime Ni3Al precipitation.
- Seawater Corrosion: Cu-Ni-Al passive film behaviour in flowing seawater.
- SCC Resistance: Stress-corrosion cracking and hydrogen embrittlement immunity.
- Magnetic Permeability: Non-magnetic naval and aerospace qualification.
- Machinability: Cu-Ni-Al cutting parameters and tooling notes.
- Density and Physical Properties: Density, modulus, thermal expansion, conductivity.
Hiduron Forms TorqBolt Supplies
| Form factor | Standard sizes | Page |
|---|---|---|
| Round bar (raw stock) | OD 16 to 250 mm | Round Bar |
| Stud bolts | M12 to M100, 50 to 600 mm | Stud Bolts |
| Hex bolts (DIN 931 / ISO 4014) | M12 to M64 | Hex Bolts |
| Heavy hex bolts (ASME B18.2.1) | 1/2 to 3 inch | Heavy Hex Bolts |
| Nuts and heavy hex nuts | M12 to M100 | Nuts |
| Washers (flat, spring, locking) | M12 to M48 | Washers |
| Forgings (subsea connector blank) | up to 600 kg piece | Forgings |
| Machined components (custom) | to project drawing | Machined Components |
Where Hiduron Is Specified
- Subsea Connectors: Hiduron 130 flying-lead, stab-plate and umbilical termination bodies.
- Riser Bolting: Hiduron 191 splash-zone bolting on North Sea and Gulf of Mexico platforms.
- Splash Zone Bolting: Hiduron 191 fasteners for the wet-dry tidal band.
- Naval Fasteners: NES 835 and DEF STAN 02-835 procurement on Royal Navy and allied bolting.
- Pump Shafts and Valve Spindles: Marine pump shafts and subsea valve spindles.
- Mechanical Seals: Seal-face bodies against tungsten-carbide running faces.
- Propeller Shafts: Naval and commercial marine propeller shafts.
- Sour Service (NACE): NACE MR0175 qualified bolting for sour oil and gas service.
Hiduron Controlling Standards
| Standard | Scope | Relevance |
|---|---|---|
| NES 835 | UK Naval Engineering Standard for Cu-Ni-Al bolting | Hiduron 191 controlling spec |
| DEF STAN 02-835 | UK Ministry of Defence adoption of NES 835 | Hiduron 191 MoD procurement |
| DOD-C-24676 | US Department of Defense Cu-Ni-Al spec | Hiduron 191 US Navy procurement |
| DTD 900/4805 | UK Air Ministry specification | Hiduron 130 original spec |
| NACE MR0175 | Sour service materials qualification | Hiduron 191 qualified to 286 HBW limit |
EN 10204 Certification and Inspection
Every Hiduron 130 and Hiduron 191 stock and finished fastener ships with EN 10204 type 3.1 mill test certificate as standard. Type 3.2 third-party witness by Lloyd's Register, DNV, BV, SGS or TUV is supplied on call-out and is standard practice on naval and subsea procurement orders. The certificate carries the melt heat number, full chemical analysis to the controlling specification, solution-anneal plus age cycle parameters, tensile and yield results, hardness, Charpy V impact result where called out, and the dimensional report. For Hiduron 191 sour-service orders, an additional NACE MR0175 hardness certificate confirms that every test piece reads below the 286 HBW (28 HRC) limit.
Request a Quote on Hiduron Bolting
TorqBolt supplies Hiduron 130 (UNS C72400, DTD 900/4805) and Hiduron 191 (UNS C72420, NES 835, DEF STAN 02-835, DOD-C-24676) in round bar, stud bolts, hex bolts, heavy hex bolts, nuts, washers, forgings and machined components. Standard fastener lead time is 4 to 8 weeks from order, subsea machined components quote project-specific lead time. Send an enquiry through TorqBolt Contact with the controlling specification, the form factor, the size envelope and the certification level (3.1 default, 3.2 on call-out, NACE on call-out).
Request a Quote on Hiduron 130 and Hiduron 191 Bolting Stock and Fasteners
Reference and Downloads
- Hiduron 130 Datasheet: Consolidated chemistry, mechanicals and heat treatment.
- Hiduron 191 Datasheet: NACE-qualified naval and subsea grade datasheet.
- Bolt Dimensions: Imperial and metric thread, head and stress-area tables.
- Torque Chart: Cu-Ni-Al fastener torque values, dry and lubricated.
- FAQ: Consolidated questions on Hiduron specification, certification and supply.
Hiduron Seawater Corrosion FAQ
Q. What is the Hiduron seawater corrosion rate?
The flowing-seawater general corrosion rate sits at below 0.025 mm/year at velocities of 1 to 3 m/s and water temperatures of 5 to 30 deg C. The rate stays protective on both Hiduron 130 and Hiduron 191 with the same cupric oxide film mechanism.
Q. Does Hiduron need a coating in seawater service?
No. The native Cu-Ni-Al oxide film is the corrosion barrier and is self-healing inside the design service envelope. Coatings are not required on subsea, splash-zone or naval bolting applications and are typically not applied.
Q. Does Hiduron suffer biofouling?
No. The copper-ion release rate at the surface suppresses macro-fouling settlement on submerged components. Riser bolting and subsea connector bodies stay clear of barnacles, mussels and tube worms for the design service life without antifouling coatings.
Q. Does Hiduron suffer crevice corrosion under washers and inside threaded engagement?
No. The cuprous-ion cathodic mechanism sustains the film in the depleted-oxygen crevice environment, which is the geometry that drives under-washer pitting on stainless bolting. The crevice-corrosion onset temperature in 6 percent ferric chloride exceeds 50 deg C against 25 deg C on 316L.
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