What C11000 and C10100 Copper Are
C11000 and C10100 are unalloyed wrought copper grades identified by UNS numbers and covered by ASTM and ASME specifications such as ASTM B152 for plate, sheet and strip, ASTM B75 for seamless pipe, ASTM B187 for rod, bar and busbar, and ASTM B111 for condenser and heat exchanger tube. Neither grade contains an intentional alloying addition; the difference lies in how the copper is refined and how much oxygen is left in the metal.
C11000, also called electrolytic tough pitch (ETP) copper, is the standard high-conductivity electrical copper. A small, deliberate oxygen content remains in the melt, normally 0.02 % to 0.04 % and limited to a maximum of 0.06 %. The oxygen exists as fine cuprous oxide particles dispersed in the copper matrix and is harmless in normal service. Annealed C11000 is the practical realisation of the International Annealed Copper Standard, so it is rated at 100 % IACS.
C10100, also called oxygen-free electronic (OFE) copper, is a more highly refined product. Copper plus silver is specified at 99.99 % minimum and oxygen at 0.0005 % (5 ppm) maximum, which lifts annealed conductivity to 101 % IACS and removes any possibility of hydrogen embrittlement. C10100 is therefore the grade of choice for vacuum electronics and for parts that must be brazed or annealed in strongly reducing atmospheres.
Chemical Composition Comparison
| Element | C11000 (ETP) | C10100 (OFE) |
|---|---|---|
| Cu + Ag, % min | 99.90 | 99.99 |
| Oxygen, % max | 0.06 | 0.0005 |
| Tin, % max | 0.002 | Restricted to ppm level |
| Zinc, % max | 0.005 | Restricted to ppm level |
| Lead, % max | 0.005 | Restricted to ppm level |
| Iron, % max | 0.005 | Restricted to ppm level |
| Other residual elements | 0.10 total | Individual limits plus a cap on the sum |
Because C10100 restricts every residual element to the low parts-per-million range, the standard sets both individual maxima and a maximum for the total of the specified impurities. C11000 is less restrictive, which is exactly what makes it economical for general electrical duty.
Physical, Electrical and Mechanical Properties
| Property | C11000 (ETP) | C10100 (OFE) |
|---|---|---|
| Density | 8.89 to 8.94 g/cm³ | 8.94 g/cm³ |
| Melting point | 1083 °C | 1083 °C |
| Electrical conductivity, annealed | 100 % IACS min | 101 % IACS min |
| Volume resistivity at 20 °C | about 1.7241 µΩ·cm | about 1.7071 µΩ·cm |
| Thermal conductivity | about 390 W/m·K | about 390 W/m·K |
| Modulus of elasticity | 110 to 130 GPa | 110 to 130 GPa |
| Annealed tensile strength | about 220 MPa | about 220 MPa |
| Annealed elongation | about 45 % | about 45 % |
In the fully annealed condition the two grades behave almost identically in tension, bending and deep drawing. Once cold worked, both harden rapidly, so temper designation matters more to the mechanical result than the choice between them. The meaningful engineering gap is the one-percent conductivity difference together with the hydrogen behaviour described below.
Selection Guidance by Application
C11000 is specified for busbar and busbar connections, cable and magnet wire, transformer and motor windings, switchgear contacts, contact strips, seamless tube and architectural sheet. It offers the best balance of conductivity and cost whenever oxygen is not a service concern.
C10100 is selected when the residual oxygen itself is a hazard: electronic tubes and vacuum devices, microwave cavities, accelerator and superconducting magnet stabilisers, high-end microwave and RF connectors, and any component that will be brazed, welded or annealed in a hydrogen-bearing furnace atmosphere. In those duties C11000 cannot be substituted at any price, because the cuprous oxide reacts with hydrogen.
Where the requirement sits between the two, a phosphorus-deoxidised high-conductivity grade such as C12200 delivers freedom from hydrogen embrittlement at a conductivity of roughly 85 % IACS and a lower material cost than OFE copper.
Processing and Joining Notes
Reducing atmospheres: C11000 must not be heated above roughly 370 °C in hydrogen or a strongly reducing atmosphere. Cuprous oxide plus hydrogen forms steam inside the metal, producing internal voids and intercrystalline cracking known as hydrogen embrittlement. C10100 is immune to this mechanism.
Annealing: both grades recrystallise between about 400 °C and 650 °C; use a neutral or slightly oxidising atmosphere for C11000 and a dry, oxygen-free atmosphere for C10100.
Joining: soldering and brazing are straightforward on both grades. Resistance welding works well; fusion welding of C11000 requires a deoxidised filler and a shielding gas free of hydrogen.
Machining: use sharp, high-rake tooling, generous cutting speed and good lubrication because copper is gummy and conducts heat away from the cutting edge.
Verification: conductivity is normally confirmed by resistivity measurement on a sampled specimen, and temper by tensile test, hardness or grain size depending on the product form.
FAQ
Q: Is C11000 the same as C10100 copper?
No. Both are unalloyed copper, but C11000 contains up to 0.06 % oxygen while C10100 is limited to 0.0005 % oxygen and 99.99 % minimum copper plus silver.
Q: Which grade has higher electrical conductivity?
Annealed C10100 is rated at 101 % IACS minimum, against 100 % IACS minimum for annealed C11000. The difference is small but decisive in precision electronics.
Q: Is C11000 prone to hydrogen embrittlement?
Yes. Because of its cuprous oxide content it can crack when heated above roughly 370 °C in a hydrogen-rich atmosphere, so vacuum or hydrogen furnace operations should use C10100 or a phosphorus-deoxidised grade.
Q: Can C11000 be welded?
It can be brazed, soldered and resistance welded without difficulty. Fusion welding is possible with a deoxidised copper filler and a hydrogen-free shielding gas, but joint efficiency is lower than in the annealed base metal.
Q: Is C10100 worth the extra cost?
Only where the specification demands it - vacuum devices, microwave hardware, hydrogen-brazed assemblies or the last percent of conductivity. For busbar, tube and general electrical work C11000 is the economical choice.
Q: Which standards cover these grades?
ASTM B152, ASTM B187 and ASME SB-152 cover flat and bar products, ASTM B75 and ASTM B111 cover seamless pipe and heat exchanger tube, and EN 13601 covers copper rod and bar for electrical use.
