Muntz metal, also known as C28000 brass, is a 60% copper–40% zinc alloy that is strong, resistant to corrosion, and cheap. It has an alpha-beta microstructure that makes it easy to shape and long-lasting, which makes it perfect for marine, heat exchanger, and architectural uses. This article talks about C28000’s composition, properties, processing, and engineering uses. It helps engineers get the best performance and reliability in tough situations.
What is C28000 brass？
C28000 brass, also known as Muntz metal or alpha–beta brass, is a copper–zinc alloy containing roughly 60% copper and 40% zinc. It offers a strong combination of high strength, good corrosion resistance, and moderate ductility, making it ideal for marine hardware, architectural components, and heat exchanger applications.
Key facts:
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Material type: Alpha–beta (duplex) brass
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Chemical composition (approx.): Cu 59–62%, Zn balance, Pb ≤0.07%
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Tensile strength: 400–600 MPa (depending on temper)
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Density: ~8.45 g/cm³
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Formability: Good for hot working; moderate for cold working
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Corrosion resistance: Excellent in seawater and atmospheric conditions
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Equivalent names: Muntz Metal, 60/40 Brass
Typical applications:
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Marine fittings, propeller components, and condenser tubes
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Architectural trim and decorative panels
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Fasteners, valve bodies, and heat exchangers
In summary, C28000 brass is a durable, cost-effective copper alloy that combines mechanical strength with good corrosion resistance, particularly suited for marine and industrial environments where both performance and economy are essential.
Chemical Composition and Alloy Classification
UNS and ASTM Standards
C28000 brass, also known as Muntz Metal, is classified as a copper–zinc alloy under the UNS C28000 designation. It is standardized by ASTM B36/B36M (Copper Alloy Sheets, Strips, and Plates), and its equivalents include EN CW509L, JIS C2801, and ISO CuZn40. The alloy derives its common name “Muntz Metal” from George F. Muntz, who developed it in the 1830s as a cost-effective substitute for pure copper in marine sheathing applications. This innovation combined the corrosion resistance of copper with the enhanced strength and lower cost of zinc-containing alloys, marking a significant step in the evolution of industrial brass materials.
C28000 remains a popular choice in marine, architectural, and heat exchanger applications due to its balanced mechanical performance, corrosion resistance, and excellent hot workability.
C28000 Chemical Composition
| Element | Content (%) | Engineering Function |
| Cu (Copper) | 59.0–63.0 | Provides electrical conductivity, ductility, and corrosion resistance. |
| Zn (Zinc) | Balance | Increases strength and stiffness while reducing cost. |
| Pb (Lead) | ≤ 0.09 | Improves machinability and lubrication during cutting. |
| Fe (Iron) | ≤ 0.07 | Enhances strength and wear resistance. |
| Others (Sb, Bi) | Trace | Improve resistance to dezincification and enhance corrosion performance. |
This composition positions C28000 between α-phase brasses (such as C26000, 70/30 brass) and β-phase brasses (like C34000), combining good ductility with superior strength. The precise Cu–Zn balance allows C28000 to maintain both formability and structural rigidity, making it ideal for medium-load engineering components.
Phase Structure (α + β Brass System)
C28000 belongs to the α + β dual-phase brass category. When zinc content exceeds approximately 37%, part of the structure transforms from the softer α-phase (face-centered cubic solid solution) to the harder β-phase (body-centered cubic). This two-phase combination provides a unique synergy:
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α-phase: High ductility, excellent formability, and good cold working characteristics.
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β-phase: High strength, hardness, and better wear performance but lower ductility.
In metallographic observations, α grains appear lighter and more equiaxed, while β grains exhibit a darker, elongated morphology. The presence of both phases allows C28000 to exhibit superior hot formability and high mechanical strength, explaining its extensive use in marine hardware, industrial fittings, and heat exchanger tubing where both durability and workability are required.
Microstructure, Corrosion Mechanisms, and Dezincification Behavior
Typical Microstructure
C28000 brass exhibits a dual-phase (α + β) microstructure, where the α-phase (a face-centered cubic solid solution of zinc in copper) provides ductility and corrosion resistance, while the β-phase (a body-centered cubic phase richer in zinc) contributes strength and hardness.
Under microscopic examination, β-phase regions appear darker and are typically distributed along α-grain boundaries, forming a network-like structure. This configuration enhances strength and wear resistance but also increases the alloy’s susceptibility to stress and corrosion at grain boundaries if improperly processed.
Key microstructural implications:
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Higher β-phase content → Increased hardness and tensile strength but reduced cold formability.
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Refined α-grains (via controlled annealing) → Better ductility and improved resistance to cracking.
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Uniform phase distribution → More stable mechanical behavior during hot forming and machining.
The dual-phase nature of C28000 enables superior hot workability compared with α-brasses (like C26000), making it ideal for forging, extrusion, and rolling applications.
Dezincification and Corrosion Behavior
Dezincification is a selective corrosion process in which zinc dissolves preferentially, leaving behind a spongy copper-rich layer that weakens the material. This typically occurs in warm, moist, or chloride-containing environments, especially in stagnant water systems.
In C28000 brass, the presence of the β-phase increases susceptibility to dezincification compared with α-brasses (like C26000). However, it still performs better than free-cutting brass (C36000) due to its lower lead content and more uniform microstructure.
Comparative dezincification resistance:
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C26000 (α-brass) — Excellent resistance (nearly immune).
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C28000 (α + β brass) — Moderate resistance; requires protection in aggressive environments.
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C36000 (leaded brass) — Lower resistance; dezincification occurs readily in warm or acidic water.
Common protection strategies include:
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Electroplating: Nickel or chrome layers prevent direct electrolyte contact.
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Passivation or coating: Improves barrier protection and reduces galvanic reactions.
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Alloy substitution: Use arsenic- or tin-modified brasses (e.g., C35300, C44300) or dezincification-resistant bronzes (Cu–Sn–Zn systems).
When properly coated or used in non-aggressive environments, C28000 offers long service life with minimal corrosion degradation.
Environmental Suitability
C28000 brass demonstrates good general corrosion resistance in many industrial and architectural environments but has limitations depending on exposure conditions.
Suitable environments:
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Atmospheric exposure (indoor/outdoor, non-industrial)
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Freshwater and mildly acidic solutions
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Non-oxidizing acid environments at moderate temperatures
Unsuitable environments:
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Ammonia-containing atmospheres → May induce stress-corrosion cracking (SCC)
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Chloride-rich or marine immersion → Promotes dezincification and pitting
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Strong acids or alkalis → Rapid zinc leaching and phase degradation under high pH extremes
In engineering design, protective coatings and controlled operating environments are essential to ensure long-term performance. For marine or chloride exposure, nickel-aluminum bronze (C95500) or tin brass (C44300) may offer superior corrosion stability compared with C28000.
Mechanical and Physical Properties
Mechanical Properties (Annealed vs Cold-Worked)
C28000 brass (Muntz Metal) offers a balanced combination of strength, ductility, and wear resistance, derived from its α + β dual-phase microstructure. Its mechanical response varies significantly between annealed and cold-worked conditions:
| Condition | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness (HRB) |
| Annealed | 340–440 | 110–180 | 35–50 | 60–80 |
| Cold-Worked (H04) | 470–550 | 250–320 | 10–20 | 85–100 |
In the annealed state, C28000 maintains excellent formability and elongation, suitable for hot rolling, forging, and deep drawing. When cold-worked, its strength and hardness increase due to strain hardening, while ductility decreases. The β-phase provides reinforcement, enhancing load-bearing capability, fatigue resistance, and impact toughness—making it a preferred choice for structural and mechanical components in marine and industrial systems.
Physical Properties
C28000 brass combines good mechanical strength with favorable thermal and electrical performance, characteristic of copper alloys.
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Density: 8.44 g/cm³
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Melting Range: 900–950°C
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Thermal Conductivity: 120 W/m·K
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Electrical Conductivity: 28% IACS
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Coefficient of Thermal Expansion: 20.5 µm/m·K
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Elastic Modulus: ~110 GPa
These properties make C28000 particularly suitable for heat exchanger components, condenser tubing, and pump housings, where both mechanical reliability and heat transfer efficiency are required. Its moderate coefficient of expansion ensures dimensional stability under thermal cycling, a critical factor in pressure fittings and marine valve assemblies.
Comparison with Other Brasses
| Property | C26000 (70/30 Brass) | C28000 (Muntz Metal) | C36000 (Free-Cutting Brass) |
| Tensile Strength (MPa) | 340–520 | 440–550 | 360–480 |
| Ductility (Elongation %) | 40–50 | 10–35 | 20–30 |
| Machinability Rating | 40–50% | 60–70% | 100% |
| Dezincification Resistance | Excellent | Moderate | Low |
| Best Forming Type | Cold forming | Hot forming | Machining |
Key insights:
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C28000 provides higher strength than C26000 due to its β-phase reinforcement but sacrifices some cold formability.
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Compared with C36000, it has better corrosion resistance and structural integrity, though its machinability is lower.
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Its combination of strength, corrosion performance, and cost efficiency makes it particularly advantageous for marine fittings, architectural panels, and valve bodies where both appearance and durability are important.
Fabrication, Machinability, and Processing Guidelines
Hot Working and Cold Forming
C28000 brass demonstrates excellent hot workability but only limited cold formability due to the presence of both α and β phases. The recommended hot working temperature range is 650–750°C, where the alloy exhibits optimal ductility and reduced cracking tendency.
During cold forming operations—such as deep drawing, bending, or stamping—careful process control is essential to prevent stress concentration and brittle fracture along β-phase regions. Intermediate annealing between cold-working stages (typically at 450–550°C) helps restore ductility by relieving internal strain and refining grain structure.
Forming guidelines:
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For simple bending and rolling, cold forming is acceptable with intermediate annealing steps.
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For complex shapes or deep-drawn components, preheating to ~400°C significantly improves plasticity.
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Grain orientation control (rolling direction alignment) enhances fatigue strength and prevents cracking in structural parts.
C28000’s balanced hot and warm forming behavior makes it well-suited for forged fittings, marine hardware, and architectural panels.
Machining and Work Hardening
C28000 has a machinability rating of approximately 30–40% relative to C36000 (Free-Cutting Brass, 100%). The presence of the harder β-phase increases cutting resistance and tool wear, demanding optimized machining strategies and tooling selection.
Recommended machining parameters:
| Operation | Cutting Speed (m/min) | Feed Rate (mm/rev) | Tool Material | Lubrication |
| Turning | 60–120 | 0.05–0.25 | PVD-coated carbide | Emulsion / oil mist |
| Milling | 80–150 | 0.05–0.20 | TiAlN-coated carbide | Oil-based coolant |
| Drilling | 50–100 | 0.05–0.15 | HSS or carbide drill | Cutting oil |
| Threading / Tapping | 10–25 | — | TiN-coated tap | Oil or semi-synthetic |
Due to work hardening, C28000 tends to increase in hardness near the cutting zone. To counter this:
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Use sharpened tools and moderate cutting speeds to avoid excessive heat buildup.
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Apply continuous lubrication to minimize friction and maintain surface integrity.
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For precision components, perform stress-relief annealing after rough machining (425–500°C for 1–2 hours) to ensure dimensional stability during finishing operations.
Joining and Surface Treatment
C28000 brass has moderate weldability. Its zinc-rich composition makes it susceptible to zinc evaporation and oxidation under high-temperature fusion welding, potentially leading to porosity or weak joints. Therefore, brazing, silver soldering, and gas welding are preferred over arc welding methods.
Recommended joining methods:
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Silver brazing: Produces clean, strong joints for fittings and valves.
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Gas brazing: Suitable for larger assemblies; flux control is important to prevent oxidation.
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Soldering: Feasible for small electrical or plumbing connections.
For enhanced performance and corrosion protection, C28000 can undergo various surface treatments:
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Electroplating (Ni, Cr): Improves wear resistance and decorative appeal.
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Anti-dezincification coatings: Protect against chloride-induced corrosion.
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Paints or polymer coatings: Applied for marine and outdoor structures.
Stress-relief or annealing temperature range: 425–600°C, adjusted according to section thickness and prior cold work level.
Applications and Industry Case Studies
Industrial Applications
C28000 brass (Muntz Metal) is widely used across architectural, marine, and industrial sectors due to its ideal combination of strength, corrosion resistance, and aesthetic appearance. Its hot workability and structural integrity make it a preferred choice in applications where mechanical robustness and visual appeal must coexist.
Key application sectors:
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Architectural Facades and Decorative Panels: Used for curtain walls, exterior claddings, and artistic installations where long-term color stability and oxidation patterns are desired. The alloy’s warm golden hue and natural patina development provide both aesthetic and functional protection.
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Heat Exchangers and Condenser Plates: Its high thermal conductivity (≈120 W/m·K) and resistance to mild corrosion environments make it suitable for heat exchangers, condensers, and radiator fins operating in non-aggressive water or air systems.
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Marine and Shipbuilding Components: Commonly used for propeller sleeves, seawater pumps, and valve housings. C28000’s α+β microstructure offers superior mechanical strength compared to pure copper, though protective coatings are required for continuous saltwater exposure.
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Plumbing and Pump Components: Ideal for valve bodies, pipe fittings, and flange assemblies requiring both machinability and corrosion resistance.
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Electrical and Decorative Hardware: Employed in connectors, terminals, handles, and trim accessories due to its conductivity and excellent polishability.
Case Studies and Performance Insights
Case Study 1 — Heat Exchanger Plate Service Life Evaluation In an industrial cooling system, C28000 brass plates were used for condenser tubes operating under moderate chloride conditions. After approximately seven years of service, minor dezincification pits were observed at flow stagnation zones. Metallographic analysis confirmed selective zinc leaching within β-phase regions. Solution:
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Transition to arsenic-inhibited brass (C35300) for enhanced dezincification resistance.
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Application of nickel-phosphorus coatings to minimize localized corrosion. Result: Service life extended by 40%, with consistent heat transfer efficiency.
Case Study 2 — Architectural Facade Oxidation and Maintenance C28000 panels installed on a commercial building facade exhibited natural patina formation within 12 months, transitioning from bright gold to a matte bronze tone. While structurally unaffected, surface oxidation was uneven due to environmental exposure variations. Maintenance Strategy:
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Implemented periodic cleaning with mild acid-based solutions to maintain uniform appearance.
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Applied a clear polyurethane coating for UV and humidity protection. Outcome: Achieved a stable, aesthetically consistent surface with extended weathering durability.
Selection and Design Considerations
When selecting C28000 brass for engineering and architectural projects, it’s essential to balance mechanical strength, corrosion behavior, and environmental conditions:
Recommended for:
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Medium-load structural components requiring high strength and aesthetic finish.
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Environments with freshwater, neutral atmospheres, or controlled humidity.
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Applications where thermal conductivity and visual appeal are both critical.
Not recommended for:
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High-chloride or ammonia-containing environments (risk of dezincification or stress cracking).
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Potable water systems, due to trace lead content and dezincification risks.
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High-temperature chemical environments, where zinc leaching accelerates.
Comparison with Alternative Materials:
| Material | Key Advantage | Typical Use Case |
| C28000 (Muntz Metal) | Strength + Appearance | Architecture, marine fittings |
| C69300 (Lead-free Brass) | RoHS compliance, dezincification resistance | Drinking water systems |
| C44300 (Admiralty Brass) | Excellent corrosion resistance | Condenser and heat exchangers |
| Bronze (Cu-Sn) | Superior wear resistance | Bearings, bushings |
| Stainless Steel (304/316) | High corrosion and strength | Marine, chemical environments |
Design and Material Selection Guidelines
Material Comparison and Substitutes
When selecting a brass alloy for industrial or architectural components, it’s essential to evaluate mechanical strength, formability, machinability, and corrosion resistance based on application requirements. The following comparison highlights how C28000 (Muntz Metal) positions itself among commonly used brasses:
| Material | Key Characteristics | Recommended Applications |
| C26000 (Cartridge Brass) | High ductility, excellent cold workability, good corrosion resistance | Deep-drawn parts, thin sheet components, tubing |
| C28000 (Muntz Metal) | Higher strength, moderate corrosion resistance, excellent hot formability | Heat exchanger plates, marine fittings, architectural structures |
| C36000 (Free-Cutting Brass) | Outstanding machinability (100%), low ductility, fair corrosion resistance | Precision machined parts, threaded fittings, connectors |
C28000 strikes a balance between strength and formability, making it ideal for medium-load structural and marine applications. Compared with C26000, it offers higher strength but lower ductility; compared with C36000, it offers superior corrosion and mechanical integrity at a moderate cost.
Engineering Trade-Offs
Material selection often involves balancing multiple performance and production factors. Engineers should consider the following trade-offs when evaluating C28000 and related brasses:
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Mechanical Strength vs. Formability: C28000 provides greater tensile strength and hardness than α-phase brasses, but its β-phase reduces cold formability. Hot forming or intermediate annealing is recommended for complex shapes.
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Cost vs. Corrosion Life: C28000 is more cost-effective than bronze or stainless steel but requires protective coatings (e.g., nickel, tin, or anti-dezincification layers) for long-term marine or chemical exposure.
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Machining Difficulty vs. Production Efficiency: While not as free-cutting as C36000, optimized CNC parameters and tool coatings can maintain productivity. In high-volume production, hot-forged or pre-machined blanks minimize material waste and machining time.
By aligning design priorities—such as strength, aesthetics, or lifecycle cost—engineers can effectively select the optimal brass alloy for each application.
RPS Manufacturing Capabilities
At RPS, we specialize in CNC machining, sheet metal forming, surface finishing, and assembly of C28000 brass components, serving demanding industries from marine engineering to architectural design.
Our core capabilities include:
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CNC Precision Machining: High-accuracy turning, milling, and drilling of C28000 plates, rods, and fittings with tolerances down to ±0.005 mm.
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Sheet Metal Fabrication: Hot and cold forming of C28000 sheets for decorative panels, enclosures, and structural elements.
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Surface Treatment: Nickel/chrome plating, passivation, polishing, and anti-dezincification coatings to enhance corrosion resistance and appearance.
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Assembly & Inspection: Integrated part fitting, brazing, and dimensional quality control per ISO 9001 and IATF 16949 standards.
Custom manufacturing capabilities: RPS provides prototype-to-production solutions for plates, tubing, decorative parts, precision fittings, and load-bearing components made from C28000 and other copper alloys. With over 80 advanced machines and a comprehensive supplier network, RPS ensures consistent material quality, machining accuracy, and surface excellence—helping clients achieve both engineering performance and aesthetic precision in every component.
Summary
C28000 brass (Muntz metal) is a copper–zinc alloy with two phases (α and β). It has about 60% copper and 40% zinc, which makes it strong, easy to shape, and cheap. It has the ductility of the α-phase and the hardness of the β-phase, which makes it stronger than C26000 and easier to work with when hot for rolling, forging, and extrusion. It has a bright golden color and is easy to machine. It works well in structural, marine, and architectural applications, especially when it is protected from chloride or ammonia corrosion by surface coatings.
C28000 provides long-lasting mechanical performance and visual stability by combining the right material selection, surface finishing, and environmental control. It works well for marine fittings, heat exchangers, and decorative parts because it strikes a good balance between performance and cost. C28000 is a strong and flexible engineering alloy that can be used for both industrial and aesthetic purposes on a large scale. However, it should not be used in systems that come into contact with a lot of seawater or drinking water.
FAQ
Q1: What is C28000 brass made of?
A: C28000, also known as Muntz Metal or 60/40 brass, is composed of approximately 60% copper and 40% zinc, forming a dual-phase α + β brass microstructure that provides both strength and moderate ductility.
Q2: Is C28000 corrosion-resistant?
A: Yes, it performs well in air, freshwater, and mild industrial atmospheres, but it is susceptible to dezincification in chloride-rich or ammonia-containing environments. Applying nickel or chrome plating can significantly enhance its corrosion resistance.
Q3: Can C28000 be machined easily?
A: C28000 has moderate machinability (around 30–40% compared to C36000). It is more suitable for hot forming, forging, and rolling than for high-speed precision machining. Using PVD-coated carbide tools and proper lubrication improves machining quality.
Q4: What are common applications of C28000?
A: This alloy is widely used in heat exchangers, condenser plates, marine components, architectural panels, and decorative fittings, where a balance of strength, cost efficiency, and corrosion performance is required.
Q5: What’s the difference between C26000 and C28000?
A: C26000 (Cartridge Brass) has higher ductility and superior cold workability, ideal for deep-drawn parts. C28000 (Muntz Metal) offers greater strength and hardness, making it better suited for structural or thermal applications—though with slightly lower corrosion resistance and formability.
About the Author: Gavin Xia
This article was written by engineers from the RAPID PROTOS team. Gavin Xia is a professional engineer and technical expert with 20 years of experience in rapid prototyping, metal parts, and plastic parts manufacturing.
