ETP (electrolytic tough pitch) copper is about 99.9% pure copper with a little oxygen. It has excellent electrical and thermal conductivity, so it is the standard copper for busbars, cable, electrical contacts and earthing parts.
Quick facts
- Purity
- About 99.90% copper minimum
- Electrical conductivity
- About 100% IACS or slightly more
- Oxygen
- About 0.02–0.04%
- Tempers
- Annealed (soft), half hard, hard
- Joining
- Soldering and brazing; avoid hydrogen-atmosphere brazing
- Common forms
- Busbar, strip, sheet, rod, wire
ETP, OFHC or DHP?
| Grade | Character | Used for |
|---|---|---|
| ETP (C11000) | High conductivity, contains a little oxygen | Busbars, cable, electrical parts |
| OFHC (C10200) | Oxygen-free, highest purity | Vacuum, hydrogen brazing, electronics |
| DHP (C12200) | Deoxidised with phosphorus, lower conductivity | Plumbing and heat-exchanger tubes, welding |
Typical uses
- Busbars and switchgear parts
- Electrical terminals, lugs and contacts
- Earthing strips and rods
- Heat sinks and heat-exchanger parts
Machining tips
- Pure copper is soft and gummy: sharp tools with high rake and good coolant
- Brass or tellurium copper machine far more easily if conductivity allows
- Deburr carefully; copper burrs are tough
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Questions
- Why can't ETP copper be brazed in hydrogen?
- Hydrogen reacts with the small amount of oxygen in ETP copper and can crack it (hydrogen embrittlement). Oxygen-free (OFHC) copper is used instead.
- What does 100% IACS mean?
- Conductivity compared with the International Annealed Copper Standard. ETP copper meets or slightly exceeds 100%.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 9 October 2026.