C21000 vs. C11000
In the spectrum of copper materials, C11000 (Electrolytic Tough Pitch Copper) and C21000 (Commercial Gilding Metal) represent fundamentally different categories-one is essentially pure copper while the other is a carefully engineered alloy. Understanding their distinctions is crucial for applications ranging from electrical systems to architectural elements.
Fundamental Composition & Classification
| Composition Aspect | C11000 (Electrolytic Tough Pitch Copper) | C21000 (Commercial Gilding Metal, 95/5 Brass) |
|---|---|---|
| Copper (Cu) Content | ≥ 99.90% (typically 99.95%+) | 94.0 - 96.0% |
| Primary Alloying Element | Oxygen (0.02-0.05%) for deoxidation | Zinc (4.0-6.0%) |
| Other Elements | ≤ 0.04% total impurities | May contain ≤ 0.05% Pb, ≤ 0.10% Fe |
| UNS Number | C11000 | C21000 |
| Common Names | ETP Copper, Pure Copper | Gilding Metal, 95/5 Brass |
| Material Category | Wrought Copper (Unalloyed) | High-Copper Alloy / Red Brass |
Mechanical & Physical Properties
| Property | C11000 | C21000 | Technical Implication |
|---|---|---|---|
| Tensile Strength (Annealed) | ~ 32 ksi (220 MPa) | ~ 35 ksi (240 MPa) | C21000 offers ~10% higher base strength due to solid solution strengthening from zinc. |
| Yield Strength (Annealed) | ~ 10 ksi (70 MPa) | ~ 12 ksi (80 MPa) | C21000 provides better resistance to permanent deformation. |
| Elongation (Annealed) | ~ 45% | ~ 40% | C11000 is more ductile in the soft condition. |
| Hardness (Rockwell F, Annealed) | ~ 35 HRF | ~ 40 HRF | C21000 is noticeably harder due to alloying. |
| Modulus of Elasticity | ~ 17 x 10⁶ psi (117 GPa) | ~ 18 x 10⁶ psi (124 GPa) | Comparable stiffness; both are quite flexible. |
| Density | 0.323 lb/in³ (8.94 g/cm³) | 0.323 lb/in³ (8.94 g/cm³) | Essentially identical density. |
| Melting Point | ~ 1981°F (1083°C) | ~ 1880-1970°F (1027-1077°C) | C11000 has a higher, sharper melting point. |
| Color | Classic reddish-pink copper | Rich reddish-copper, slightly duller than C11000 | C11000 has the quintessential "pure copper" color that develops a green patina. |
Performance Characteristics
| Performance Factor | C11000 | C21000 | Comparative Analysis |
|---|---|---|---|
| Electrical Conductivity | 101% IACS (Industry Standard) | ~56% IACS | C11000 is vastly superior (nearly twice as conductive). The benchmark for electrical applications. |
| Thermal Conductivity | ~391 W/m·K | ~234 W/m·K | C11000 is far better for heat transfer applications (≈67% higher). |
| Corrosion Resistance | Excellent, but susceptible to hydrogen embrittlement if heated in reducing atmospheres. Forms protective patina. | Excellent, with better resistance to certain corrosive environments than pure copper due to zinc content. | Context-dependent. C11000 excels in atmospheric corrosion; C21000 may resist specific chemicals better. |
| Formability (Cold Work) | Excellent. Extremely ductile and malleable. | Good, but less ductile than pure copper. | C11000 is superior for severe deformation and intricate forming. |
| Machinability | Very Poor (20% of free-cutting brass). Gummy, requires sharp tools. | Poor (20% of free-cutting brass). Similar challenges. | Both are difficult to machine; neither is recommended for high-volume machining operations. |
| Joinability | Excellent soldering/brazing. Cannot be welded in reducing atmospheres (hydrogen embrittlement risk). | Excellent soldering, brazing, and welding. No hydrogen embrittlement concerns. | C21000 wins for weldability. C11000 requires careful atmosphere control for welding. |
| Work Hardening Rate | High. Rapidly strengthens with cold work but requires frequent annealing. | Moderate. More forgiving during forming operations. | C21000 is easier to work with in multi-stage forming processes. |
| Cost Factor | Higher raw material cost (purification premium). | Lower raw material cost (zinc is cheaper than copper). | C21000 is more cost-effective for non-conductive applications. |
Typical Applications
C11000 (ETP Copper) - Where Maximum Conductivity is Paramount:
Electrical Conductors: Busbars, windings, transformers, switchgear, cable sheathing, and electrical connectors.
Thermal Management: Heat sinks, heat exchanger tubes (where corrosion isn't extreme), and cookware.
Roofing & Architecture: Where the traditional copper appearance and patina are desired for long-lasting roofs and decorative elements.
Magnet Wire: For motors and generators requiring optimal electrical efficiency.
Printed Circuit Boards: As conductive traces and layers.
C21000 (Gilding Metal) - The Balanced Performance Choice:
Electrical Springs & Contacts: Where good (not maximum) conductivity combines with better spring properties and wear resistance.
Architectural Metalwork: Gutters, flashings, and decorative trim where a copper appearance is needed with better formability and lower cost than pure copper.
Ammunition Components: Jackets for bullets.
Heat Exchanger Tubes: In moderately corrosive environments where C11000 might be vulnerable.
Coins & Medallions: The "red" portion of bi-metallic coins.
Waveguides & RF Components: Where good conductivity and better strength are needed.
How to Choose
| Your Primary Requirement is... | Recommended Alloy | Rationale |
|---|---|---|
| Maximum Electrical Conductivity | C11000 | The undisputed standard; no practical alloy surpasses it. |
| Maximum Thermal Conductivity | C11000 | Best heat transfer capability available in common metals. |
| The Classic Copper Aesthetic & Patina | C11000 | Provides the authentic, recognizable copper look. |
| Superior Formability / Ductility | C11000 | More malleable and easier to form into complex shapes. |
| Higher Strength & Hardness | C21000 | Zinc addition provides solid solution strengthening. |
| Better Weldability | C21000 | No risk of hydrogen embrittlement; more forgiving to weld. |
| Cost Reduction (Non-Electrical Apps) | C21000 | Significant savings while maintaining a copper-like appearance. |
| Corrosion Resistance in Specific Chemicals | Context-specific | C21000 may outperform in some environments; testing is recommended. |
| Spring Properties in Electrical Components | C21000 | Better elastic modulus and strength for spring applications. |
Product Range of GNEE
| Product Category | Product Forms | Comprehensive Materials & Standards (UNS / Common Names) |
|---|---|---|
| Copper & Copper Alloy Tubes | Round, Square, Rectangular, Capillary, Coiled, Bundles, Straight Lengths | Pure Copper: C10200 (OFE), C11000 (ETP) Brass: C21000 (Gilding 95%), C23000 (Red Brass 85%), C26000 (Cartridge Brass 70/30), C28000 (Muntz Metal 60/40), C44300, C68700 (Arsenical Aluminum Brass) Bronze: C22000 (Commercial Bronze 90%), C38500 (Architectural Bronze) Copper-Nickel: C70600 (90/10), C71500 (70/30) Others: C12000 (DLP), C12200 (DHP) |
| Copper & Copper Alloy Sheets/Plates | Sheets, Plates, Rolls, Circles/Blanks, Embossed, Perforated | Pure Copper: C11000, C10200 Brass: C26000, C26800, C27200 (Yellow Brass 65/35),C21000 Phosphor Bronze: C51000 (A), C52100, C52400 Nickel Silver (German Silver): C75200 (65-18), C77000 (55-18) Beryllium Copper: C17200, C17500 High Copper Alloys: C19400 |
| Copper & Copper Alloy Rods/Bars | Round, Hex, Square, Flat, Rectangular, Forging Billets, Hollow Bars | Free-Cutting Brass: C36000 (CDA 360) Leaded Brass: C38500, C35600 Naval Brass: C46400, C48200, C48500 Bronze: C22000, C51000, C54400 (Free-Cutting Phosphor Bronze) Copper-Nickel: C71000, C71500 Pure Copper: C11000, C10100 |
| Copper & Copper Alloy Wires | Round, Flat, Square, Stranded, Bare, Tin-Plated, Annealed, Hard Drawn | Pure Copper Wire: C11000 (ETP), C10200 (OF) for magnet wire Brass Wire: C26000, C27200, C21000 Beryllium Copper Wire: C17200, C17500 Phosphor Bronze Wire: C51000, C52100 Resistance Welding Wire: C11000, C18200 (Chromium Copper) Spring Wire: Various tempers of C51000, C52100, C17200 |
| Copper & Copper Alloy Strips/Foils | Thin Strip, Foil (down to 0.05mm), Precision Slit Coils, Shim Stock, Finned Strip | Brass Strip: C26000, C26800, C22000,C21000 Phosphor Bronze Strip: C51000, C51900, C52100, C52400 Pure Copper Strip: C11000, C10200, C12000 Nickel Silver Strip: C75200, C77000 Electronic Alloys: C19400 (Lead Frame), C70250, C70350 Special Alloys: C72500 (Cu-Ni-Sn) |
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