C21000 vs. C22000
C21000 and C22000 are two commercially significant copper alloys that occupy the "red brass" category, positioned between pure copper and traditional brasses. While they may appear similar at first glance, their subtle compositional differences yield distinct performance characteristics that make each suitable for specific applications. This technical analysis provides a comprehensive comparison to guide material selection.
Fundamental Composition & Classification
The core distinction between these alloys lies in their zinc content, which fundamentally alters their properties.
| Composition Aspect | C21000 (Commercial Gilding Metal, 95% Cu) | C22000 (Commercial Bronze, 90% Cu) |
|---|---|---|
| Copper (Cu) Content | 94.0 - 96.0% | 89.0 - 91.0% |
| Zinc (Zn) Content | 4.0 - 6.0% | 9.0 - 11.0% |
| Other Elements | May contain ≤ 0.05% Pb, ≤ 0.10% Fe | May contain ≤ 0.05% Pb, ≤ 0.05% Fe |
| UNS Number | C21000 | C22000 |
| Common Names | Gilding Metal, 95/5 Brass | Commercial Bronze, 90/10 Brass |
| Alloy Family | High-Copper Alloy / Red Brass | Red Brass |
Mechanical & Physical Properties
The increased zinc content in C22000 provides a noticeable shift in mechanical behavior.
| Property | C21000 | C22000 | Technical Implication |
|---|---|---|---|
| Tensile Strength (Annealed) | ~ 35 ksi (240 MPa) | ~ 40 ksi (275 MPa) | C22000 offers approximately 15% higher base strength. |
| Yield Strength (Annealed) | ~ 12 ksi (80 MPa) | ~ 14 ksi (95 MPa) | C22000 has slightly higher resistance to permanent deformation. |
| Elongation (Annealed) | ~ 40% | ~ 45% | C22000 is generally more ductile in the soft temper. |
| Hardness (Rockwell F, Annealed) | ~ 40 HRF | ~ 50 HRF | C22000 is measurably harder in the same temper condition. |
| Modulus of Elasticity | ~ 18 x 10⁶ psi (124 GPa) | ~ 17 x 10⁶ psi (117 GPa) | Both have similar stiffness; C21000 is marginally stiffer. |
| Density | ~ 0.323 lb/in³ (8.94 g/cm³) | ~ 0.318 lb/in³ (8.80 g/cm³) | C22000 is slightly less dense due to higher zinc content. |
| Melting Range | ~ 1880-1970°F (1027-1077°C) | ~ 1825-1880°F (996-1027°C) | C22000 has a lower melting point, affecting welding/brazing. |
| Color | Rich, reddish-copper (very close to pure copper) | Warm, salmon-red or reddish-gold | C21000 is redder; C22000 has a more distinct gold hue. |
Performance Characteristics
These properties determine how each alloy behaves in service environments and manufacturing processes.
| Performance Factor | C21000 | C22000 | Comparative Analysis |
|---|---|---|---|
| Corrosion Resistance | Excellent, very close to pure copper. Superior resistance to dezincification, atmospheric, and water corrosion. | Very Good, but slightly more susceptible to dezincification than C21000 in aggressive waters. Still excellent for most environments. | C21000 is superior in highly corrosive environments, especially where dezincification is a risk. |
| Electrical Conductivity | ~56% IACS (Excellent) | ~44% IACS (Very Good) | C21000 is significantly better (≈27% higher conductivity). Critical for electrical applications. |
| Thermal Conductivity | ~234 W/m·K (High) | ~159 W/m·K (Moderate-High) | C21000 is superior for heat transfer applications. |
| Formability (Cold Work) | Good. Ductile and suitable for bending and forming. | Excellent. One of its standout features. Superior deep-drawing and bending capability. | C22000 is significantly more formable, especially for severe draws and complex shapes. |
| Machinability | Poor (20% of free-cutting brass C36000). Gummy, tends to adhere to tools. | Fair (30% of C36000). Better than C21000 but still not ideal for high-volume machining. | C22000 is better, but neither is considered a free-machining alloy. Both require sharp tools and proper lubricants. |
| Joinability | Excellent for soldering, brazing, and welding. | Excellent for soldering, brazing, and welding. | Comparable. Both are easy to join using standard techniques for copper alloys. |
| Stress Corrosion Cracking (SCC) Resistance | Highly resistant. | Good resistance, but slightly more susceptible than C21000 due to higher Zn. | C21000 has an edge in environments conducive to SCC (e.g., ammonia). |
Typical Applications
Primary Applications for C21000:
Electrical & Thermal Components: Spring contacts, terminals, connectors, heat exchanger tubes, and waveguides where conductivity is paramount.
Corrosion-Sensitive Architecture: Roofing, flashing, gutters, and decorative elements where long-term exposure and a pure copper aesthetic are required.
Coinage & Medallions: The "red" portion of bi-metallic coins and high-quality commemorative items.
Bullet Jackets: For certain specialized ammunition.
Primary Applications for C22000:
Drawn & Formed Parts: Radiator cores, heat exchanger shells, flexible hose, bellows, and intricate architectural shapes.
Grills & Mesh: Screens, filters, and decorative grilles that require extensive forming.
Hardware & Fasteners: Screw machine products, bolts, nuts, and plumbing fittings that benefit from its strength and formability.
Cost-Effective "Bronze" Look: Applications like jewelry findings, nameplates, and emblems where the salmon-red/gold color is desirable and superior formability is needed.
How to Choose
| Your Primary Requirement is... | Recommended Alloy | Rationale |
|---|---|---|
| Maximum Electrical or Thermal Conductivity | C21000 | Its conductivity is significantly closer to that of pure copper. |
| Optimum Corrosion/Dezincification Resistance | C21000 | Lower zinc content minimizes selective leaching in harsh waters. |
| A Color Closest to Pure Copper | C21000 | It retains the classic, rich red copper color. |
| Superior Formability for Deep Drawing or Severe Bending | C22000 | Its excellent ductility makes it the preferred choice for complex forming. |
| Higher Mechanical Strength (in same temper) | C22000 | The higher zinc content provides greater strength and hardness. |
| A Warmer, Gold-Red Color at a Lower Cost than C21000 | C22000 | It offers a desirable aesthetic at a slightly lower material cost (less copper). |
| A Balance of Good Conductivity and Good Formability | Evaluate Both | C21000 if conductivity is >50% critical. C22000 if formability is >50% critical. |
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Our supply scope covers a comprehensive range of high-performance copper and copper alloy products tailored to diverse industrial applications. We provide precision-engineered copper tubes for HVAC and refrigeration systems, sheets and plates for architectural cladding and electrical components, rods and bars for machining and fabrication, wires for conductive and mechanical purposes, as well as strips and foils for electronic and automotive industries. All products are available in various alloys - including pure copper, brass, bronze, phosphor bronze, copper-nickel, and specialty alloys - and can be supplied in standard sizes or customized dimensions, tempers, and finishes to meet your exact specifications.
