Executive Summary

Brass fasteners are critical components in industries requiring specific material properties that steel or stainless steel cannot offer. Primarily an alloy of copper and zinc, brass is selected for its superior corrosion resistance, non-magnetic nature, electrical conductivity, and aesthetic appeal. This technical report details the functional applications of brass in fastening technology, catalogs the specific fastener types produced, and provides a comparative analysis of the most prevalent brass grades (C26000, C27000, C36000, and C46400) used in manufacturing.

1. Applications of Brass in Fasteners

The application of brass in fasteners is dictated by its unique physical and chemical properties. Unlike steel, which is chosen primarily for high tensile strength, brass is chosen for environmental stability and conductivity.

1.1 Marine and Naval Environments
Brass is extensively used in marine hardware due to its resistance to saltwater corrosion.

• Dezincification Resistance: Specific grades (like Naval Brass) prevent the leaching of zinc from the alloy, a common failure mode in saltwater.
• Biofouling: Copper alloys naturally deter the growth of algae and barnacles (antimicrobial/antifouling properties), making them ideal for underwater fastenings.

1.2 Electrical and Electronic Components
Brass is a standard material for electrical hardware because of its conductivity and non-magnetic properties.

• Conductivity: Brass is significantly more conductive than steel, making it the material of choice for terminal screws, grounding bolts, and bus bar fasteners.
• Non-Magnetic: In sensitive electronic instrumentation (e.g., MRI machines, navigational equipment), brass fasteners prevent magnetic interference that could disrupt sensor readings.

1.3 Plumbing and Fluid Transfer

• Corrosion Resistance: Brass resists corrosion from water and mild acids better than carbon steel. It is standard for pipe unions, valve stems, and flange bolts in water systems.
• Thermal Conductivity: It handles hot water systems well without the rapid degradation seen in some ferrous metals.

1.4 Aesthetic and Decorative Use

• Appearance: The gold-like luster of brass is prized in architectural hardware, furniture making, and restoration of antique machinery.
• Finishing: Brass accepts plating (nickel, chrome) exceptionally well, but is often left raw to develop a desirable patina over time.

2. Types of Fasteners Manufactured from Brass

While almost any fastener can be machined from brass, certain types benefit most from the material’s properties.

• Machine Screws: The most common brass fastener, used in electrical terminals and electronic assemblies.
• Wood Screws: Used in marine woodworking and high-end furniture where rust would stain the wood.
• Hex Bolts and Nuts: Used in corrosion-prone environments where high tensile strength (Grade 5/8 steel levels) is not the primary requirement.
• Washers (Flat and Lock): Essential for preventing galvanic corrosion. Using a steel washer with a brass bolt can lead to rapid corrosion; brass washers ensure material compatibility.
• Threaded Rods: Used in plumbing suspension and electrical conduit hanging.
• Rivets: Brass rivets are widely used in leatherwork and apparel due to their malleability and cold-heading properties.

3. Common Brass Grades for Fasteners

The manufacturing method (machining vs. cold heading) determines the grade of brass used.

3.1 C26000 (Cartridge Brass)

• Composition: ~70% Copper, 30% Zinc.
• Characteristics: Known for having the highest ductility of the yellow brasses. It has excellent cold-working properties.
• Fastener Use: ideal for fasteners made via cold heading (the process of forming a head on a wire blank without removing material), such as screws, rivets, and bolts.

3.2 C27000 (Yellow Brass)

• Composition: ~65% Copper, 35% Zinc.
• Characteristics: Similar to C26000 but with slightly higher zinc content, which increases strength slightly at the cost of some ductility.
• Fastener Use: General-purpose cold-headed fasteners; screws and bolts requiring a balance of strength and formability.

3.3 C36000 (Free-Cutting Brass)

• Composition: ~61.5% Copper, 35.5% Zinc, 3% Lead.
• Characteristics: The industry standard for machinability. The lead content acts as a microscopic chip breaker and lubricant.
• Fastener Use: Used for machined fasteners (turned on a lathe) rather than cold-headed ones. This includes complex nuts, standoffs, and custom bolts. Note: Due to lead content, regulatory compliance (RoHS/REACH) must be verified for certain markets.

3.4 C46400 (Naval Brass)

• Composition: ~60% Copper, 39.25% Zinc, 0.75% Tin.
• Characteristics: The addition of tin gives this alloy exceptional resistance to seawater corrosion and dezincification.
• Fastener Use: Heavy-duty marine fasteners, propeller shafts, and bolts used in naval architecture. It offers higher strength than C260/C360.

4. Comparative Analysis of Brass Grades

The following table and analysis compare these grades to assist in material selection.

Technical Comparison Matrix

Feature	C26000 (Cartridge)	C27000 (Yellow)	C36000 (Free-Cutting)	C46400 (Naval)
Primary Alloy	Cu-Zn (70/30)	Cu-Zn (65/35)	Cu-Zn-Pb	Cu-Zn-Sn
Machinability	Fair (30%)	Fair (30%)	Excellent (100%)	Fair (30%)
Cold Working	Excellent	Good	Poor	Fair
Corrosion Resistance	Good	Good	Good	Excellent (Saltwater)
Strength (Tensile)	Moderate	Moderate	Moderate	High
Manufacturing Method	Cold Heading / Forming	Cold Heading	Machining / Turning	Hot Forming / Machining

 

Analysis

• Machinability vs. Formability:
  • C36000 is the superior choice for machined fasteners (nuts, complex inserts). If you try to cold-head C36000, it will likely crack due to the lead content.
  • C26000 is the superior choice for cold-formed fasteners (standard wood screws, machine screws). It flows well under pressure without fracturing.
• Environmental Suitability:
  • For general atmospheric exposure, C26000 and C36000 are sufficient.
  • For saltwater immersion, C46400 (Naval Brass) is the mandatory choice. The tin content inhibits dezincification, a process where saltwater selectively corrodes the zinc, leaving a porous, weak copper sponge structure.
• Strength Requirements:
  • Brass fasteners are generally weaker than steel fasteners. However, C46400 offers the highest strength among common brass fastener grades, making it suitable for structural marine applications where load-bearing is required alongside corrosion resistance.

5. Conclusion

Selecting the correct brass grade for fasteners is a trade-off between manufacturing method and environmental application. C36000 is the standard for custom, machined parts; C26000 is the standard for mass-produced, cold-headed screws; and C46400 is the critical specification for marine environments requiring high durability and corrosion resistance.