Alloys stocked: Silicon bronze · Monel 400 · Aluminum 2024 / 6061
Scope
ASTM F467 / F467M covers nonferrous nuts in inch and metric sizes intended for general-purpose use. It defines chemistry and mechanical requirements for a broad range of copper alloys, nickel alloys, and aluminum alloys commonly used as fasteners.
F467 is the nut side; F468 is the companion bolt spec for the same alloy groups.
Alloy groups
| UNS / alloy | Common name | Characteristics | Typical use |
|---|---|---|---|
| C46400 / Naval Brass | Copper-zinc-tin | Moderate strength, good marine corrosion | Marine, architectural |
| C51000 / Phosphor Bronze | Copper-tin | Spring-temper capability, good fatigue | Electrical, spring applications |
| C65100 / C65500 | Silicon Bronze | Copper-silicon; strong, weldable, marine-resistant | Marine, architectural, decorative |
| C67000 / C67500 | Manganese Bronze | High strength, moderate corrosion | Marine propellers, heavy hardware |
| C70600 | Copper-Nickel 90/10 | Excellent seawater resistance | Offshore, shipbuilding |
| N04400 | Monel 400 | Ni-Cu alloy; outstanding seawater and acid resistance | Severe marine, chemical |
| N05500 | Monel K500 | Age-hardenable Monel; higher strength | Severe marine, strength-critical |
| 2024 (AA) | Aluminum alloy | High strength, lower corrosion resistance | Aerospace, weight-critical |
| 6061-T6 (AA) | Aluminum alloy | Good strength + weldability | General aluminum assembly |
| 7075-T73 (AA) | High-strength aluminum | Highest aluminum strength | Aerospace structural |
Silicon bronze — the marine and architectural workhorse
Silicon bronze (C65100 / C65500) is the alloy that comes up most often in F467:
- Corrosion resistance: Excellent in saltwater, freshwater, and most atmospheric service. Develops a protective oxide layer that prevents further corrosion.
- Strength: Moderate — not a high-strength material, but adequate for most architectural and marine service.
- Weldability: Good. Can be brazed, welded, and soldered with standard techniques.
- Appearance: Warm gold-to-bronze color; stable patina over time. Specified extensively in decorative architectural hardware.
- Machinability: Good. Machines cleanly and holds threads well.
Silicon bronze is often specified in two finishes: plain (natural bronze color, develops patina) or tinned (coated with pure tin for maximum corrosion protection and electrical conductivity — used in underwater hardware and electrical bonding applications).
Monel 400 — severe environments
Monel 400 (N04400) is a nickel-copper alloy with a specific performance profile:
- Corrosion resistance: Outstanding in seawater, hydrofluoric acid, brine, many organic acids. Resistant to stress corrosion cracking in chloride environments — one of its defining features.
- Strength: Moderate. Higher than silicon bronze but less than carbon steel.
- Cost: High — Monel is a premium material.
- Typical applications: Subsea hardware, chemical processing equipment, hydrofluoric acid plants, naval shipbuilding. Specified where lesser materials have failed in service.
Monel K500 is the age-hardenable version, delivering significantly higher strength while retaining the corrosion profile. Used where strength-critical marine applications need both properties.
Aluminum nuts
Aluminum nuts serve two distinct niches:
- Weight-critical assembly — aerospace, defense, drones, some electronics. Aluminum weighs about 1/3 of steel.
- Electrical / thermal conductivity — aluminum conducts electricity well and is non-magnetic.
Aluminum is not a general-purpose nut material. It has lower strength than steel, gall-prone threads (especially on aluminum-to-aluminum), and is vulnerable to galvanic corrosion when paired with steel in wet service. When aluminum is used, pair with an aluminum bolt (F468 in matching alloy) or a stainless bolt with care given to galvanic isolation.
Mechanical properties — silicon bronze (C65100 / C65500)
| Size range | Proof Load Stress | Hardness |
|---|---|---|
| 1/4" through 1-1/2" | 60 ksi | 55 HRB min (typical) |
Mechanical properties vary widely by alloy group — reference F467 tables for specific grades.
Matching bolts and nuts
For nonferrous assemblies, always pair within alloy group to prevent galvanic corrosion:
| Nut (F467) | Bolt (F468) | Washer |
|---|---|---|
| Silicon bronze | Silicon bronze | Silicon bronze or 316 stainless |
| Monel 400 | Monel 400 | Monel 400 or compatible stainless |
| Aluminum 6061 | Aluminum 6061 | Aluminum 6061 |
Galvanic mismatch in wet service. A steel nut on a bronze bolt in seawater will rust the nut and streak the bronze. A stainless nut on a Monel bolt in seawater is usually OK (nearly galvanically compatible), but matching always safer.
Applications
Silicon bronze
- Marine hardware (boats, docks, piers)
- Architectural fasteners (exposed decorative applications)
- Outdoor lighting and signage
- Water-treatment equipment
- Electrical bonding (tinned)
Monel 400
- Offshore platforms
- Chemical processing (acids)
- Seawater pumps and valves
- Naval hardware
- Oil-and-gas downhole (specific services)
Aluminum
- Aerospace structures
- Drone and UAV hardware
- Electronics enclosures
- Racing and performance applications
Related specifications
- F468 — Nonferrous bolts (the companion spec)
- F593 / F594 — Stainless fastener alternatives (often cross-specified with silicon bronze for marine work)
- F3125 — Carbon-steel structural bolts (when corrosion is not a concern)
- AMS specifications — Aerospace aluminum and nickel alloy references
Documentation
California Fastener F467 orders ship with mill certificates showing alloy (UNS number), heat number, chemistry, mechanical properties, and finish. Silicon bronze stocking includes both plain and tinned finishes. Monel orders include heat-to-heat traceability and, on request, DFARS specialty-metals compliance.