What C11000 Electrolytic Tough Pitch Copper Is
C11000, also called electrolytic tough pitch copper or ETP copper, is the workhorse grade of the copper industry. Purity is 99.90 % copper minimum. The residual oxygen left by electrolytic refining is deliberately retained at a low level, because it combines with harmful impurities and protects the conductivity that the grade is bought for.
ETP copper is the reference material against which electrical conductivity is measured: annealed C11000 is defined as 100 % IACS, equal to 58 MS/m at 20 C. That is why bus bar, cable, switchgear and transformer windings are normally specified in this grade.
Chemical Composition and Conductivity
| Item | Value | Note |
|---|---|---|
| Cu | 99.90 % min | Electrolytically refined base |
| Total other elements | 0.10 % max | Balance, including residual oxygen and impurities |
| Electrical conductivity, annealed | 100 % IACS | 58 MS/m at 20 C; the international reference value |
Because the grade is defined by conductivity, the certificate matters as much as the chemistry: a heat can satisfy the copper minimum and still miss the conductivity requirement unless residual elements are controlled to a low total.
Mechanical and Physical Properties
| Property | Value |
|---|---|
| Tensile strength | 235 - 315 MPa |
| Elongation, in 50 mm gauge length | 10 % min |
| Vickers hardness | 75 - 120 HV |
| Density | 8.94 g/cm3 |
| Melting point | about 1083 C |
| Thermal conductivity | about 390 W/(m*K) at 20 C |
Strength and hardness rise as the temper is hardened by cold rolling or drawing, while elongation falls. The range quoted above covers the annealed to lightly worked conditions used for most electrical, thermal and architectural products.
Product Forms, Standards and Typical Applications
| Product form | Typical specification | Common size range |
|---|---|---|
| Seamless tube and pipe | ASTM B75, ASTM B280 | Wall 0.3 - 3.2 mm, OD 3.2 - 152 mm, straight lengths 3 - 6 m or coils |
| Sheet, plate and strip | ASTM B152 | Sheet 0.15 - 4.8 mm thick; plate over 4.8 mm; width 305 - 1220 mm |
| Architectural sheet and coil | ASTM B370 | Roofing, cladding and rainwater goods, flat sheet or coil |
| Bus bar, rod and bar | ASTM B187 | Round 3 - 150 mm diameter, flat bar 6 - 305 mm wide |
| Wire | ASTM B1, ASTM B2, ASTM B3 | 0.25 - 12.7 mm diameter, supplied in coils |
| Foil | ASTM B152 | 12 - 250 micrometre thick, 457 - 1220 mm wide |
Hydrogen Embrittlement and Service Temperature
Because ETP copper contains residual oxygen, heating above roughly 370 C in a reducing atmosphere can cause hydrogen embrittlement, often called hydrogen disease. Hydrogen diffuses into the metal, reacts with copper oxide at the grain boundaries and forms steam that opens internal voids, destroying ductility without any obvious external change.
For high-temperature reducing service such as hydrogen brazing or bright annealing in a protective atmosphere, oxygen-free grades are selected instead, for example C10200 oxygen-free copper or C12000 deoxidised low-phosphorus copper. In ordinary electrical, thermal, plumbing and architectural service the residual oxygen has little effect on electrical or thermal conductivity, nor on forming and joining behaviour.
Typical applications follow directly from these properties:
Electrical: bus bar, switchgear, transformer windings, cable and stranded conductors, commutators.
Thermal: automobile radiators, heat-exchanger tube, gaskets, heating elements and heat sinks.
Building: roofing, cladding and architectural sheet where the natural patina is part of the design.
Equipment: radio and electronic parts, electrode holders and current-carrying contacts.
Process: seamless tube bent into coils for refrigeration and air-conditioning circuits.
Frequently Asked Questions
Q: What does electrolytic tough pitch mean?
The copper is refined electrolytically and then melted and cast in air, so a controlled amount of oxygen remains in the metal as copper oxide. That oxygen scavenges impurities and keeps conductivity high, which is why the grade dominates electrical applications.
Q: What is the electrical conductivity of C11000?
Annealed ETP copper is the material that defines 100 % IACS, equivalent to 58 MS/m at 20 C. Hard-drawn tempers are slightly lower because cold work adds crystal defects that scatter electrons.
Q: How strong is C11000 copper?
Tensile strength is 235 to 315 MPa with elongation of at least 10 % and a Vickers hardness of 75 to 120 HV. Cold working raises strength and hardness at the cost of ductility, so the temper should always be stated on the order.
Q: Why is C11000 limited to about 370 C in reducing atmospheres?
Residual oxygen in the metal forms copper oxide inclusions. Hydrogen from a reducing atmosphere reacts with them to create steam at the grain boundaries, and the resulting internal pressure causes hydrogen embrittlement and loss of ductility.
Q: What is the difference between C11000 and oxygen-free copper?
Oxygen-free grades such as C10200 and C12000 are used for high-temperature reducing service, vacuum devices and applications that need maximum ductility after brazing. C11000 is the economical choice where conductivity, formability and cost matter more than those special conditions.
Q: Which standards apply to C11000 products?
Seamless tube is covered by ASTM B75 and ASTM B280, plate, sheet and strip by ASTM B152, architectural sheet by ASTM B370, bus bar and rod by ASTM B187, and wire by the ASTM B1, B2 and B3 series according to temper.
