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What Distinguishes Pure Copper vs. Oxygen-Free Copper

When it comes to selecting a metal that can conduct both heat and electricity efficiently, copper is the obvious choice. That’s why it is considered the standard of electrical conductivity for other metals. In a home environment, copper is not as likely to corrode as it is in industrial settings, where factors such as oxidized acids, compounds of sulfur and ammonia, and oxidizing heavy-metal salts tend to speed up corrosion. This is why it’s often used as the base metal for all the electrical and thermal products we use in our daily lives.

For industrial applications, it’s important to protect against corrosion in more extreme environments—this is where oxygen-free copper can become an invaluable material. To help you make the right choice for your application, we discuss the differences between pure copper vs. oxygen-free copper and list the properties of each.

What Is Pure Copper?

When a metal has a minimum copper content of 99.3%, it is known as commercially pure copper. However, such coppers are very soft and ductile in nature. That’s why other alloying elements are often added to copper to optimize its properties for a wide range of usage. However, in terms of electrical conductivity, even 0.05% of arsenic impurity can decrease copper’s conductivity by 15%. In this regard, oxygen-free copper offers mechanical strength coupled with high conductivity, all in one.

What Is Oxygen-Free Copper?

Oxygen-free copper (OFC) is copper that has gone through an electrolytic refinement process to remove all but a trace level of oxygen. It’s the purest commercial copper grade available, containing 99.99% copper with a minimal amount of impurities, and is highly recommended for applications requiring superior conductivity and connectivity, such as superconducting wires, PCBs, X-ray tubes, vacuum interrupters, rotor bars, and motor coils.

Oxygen-free copper has:

  • A rich conductivity profile.
  • High immunity to hydrogen embrittlement.
  • Superior cryogenic properties.
  • Excellent malleability.

Oxygen-free copper is available in the following three grades:

  • C10100 (OFE): 99.99% pure copper with 0.0005% oxygen content
  • C10200 (OF): 99.95% pure copper with 0.001% oxygen content
  • C11000 (ETP): 99.9% pure copper with 0.02% to 0.04% oxygen content

Comparing Pure Copper vs. Oxygen-Free Copper

Let’s compare the purest oxygen-free copper grade (C10100) with Chromium Zirconium Copper (CuCrZr) that closely resembles pure copper (Cu: 98.6%-99.4%). The table below compares some important metal characteristics of pure copper vs. oxygen-free copper to help you acknowledge their application differences.

General Properties OFC CuCrZr
Cold formability Excellent Good
Hot formability Excellent Good
Annealing 700°F to 1200°F Below 1450°F
Electrical conductivity 101% IACS 82% IACS
Thermal conductivity (Btu/sq. ft/ft. hr./°F at 68°F) 226 187
Machinability rate 20% 20%


Machining Properties  OFC CuCrZr
Soldering Excellent Good
Brazing Excellent Fair
Gas shielding arc welding Good Fair
Oxyacetylene welding Fair Not recommended
Coated metal arc welding Not recommended Fair
Seam welding Not recommended Not recommended
Butt welding Fair Fair
Hot forgeability 65% Unknown


Corrosion Resistance OFC CuCrZr
Atmospheric Good Good
Hydrogen Embrittlement Excellent Good
Marine water Excellent Good
Stress crack Good Good
Electrolytic Good No data


Due to reduced oxygen content, OFC offers excellent formability and higher electrical conductivity than pure copper. Although there are some minor differences in machining characteristics between pure copper vs. oxygen-free copper, they display some common machining challenges.

Machining Challenges With Pure Copper Alloys

Pure copper and OFC offer exceptional conductivity and high corrosion resistance, but they are difficult to machine as compared to oxygen-bearing coppers. Copper alloys with high purity levels are highly ductile. The chips stick to the tool during machining and are hard to remove;  thus, the tool has to exhibit more force with each pass to get the job done. As a result, tool wear is also high.

To form needle-like, discontinuous chips while machining OFC, fabricators add chip-breaking elements such as lead, sulfur, and tellurium. However, these may reduce the electrical conductivity of the alloy if the elements are not used within certain specific requirements.

The machining properties of OFC are more or less similar to oxygen-bearing copper alloys with a homogeneous profile. Heterogenous copper alloys tend to have better machinability.

Purchase Precisely-Cut Metals For Any Application

Industrial Metal Service has been supplying a wide variety of metals to fabricators, including pure and oxygen-free copper alloys, for more than two decades. We also can provide exotic metals such as titanium, nickel, Invar, molybdenum, and Hastelloy for your unique applications. We offer unbeatable prices, whether you need new, mill-sourced metals or verified metal remnants.

Fabricators and machinists can also take advantage of our state-of-the-art industrial sawing equipment to receive precision-cut, machine-ready materials, saving on material waste, floor space, and costly in-house sawing setups.

Contact us today to discuss your copper requirements. We’ll make it easy for you to work with us.

Published by IMS Team

Industrial Metal Service has decades of experience and over 1.1 billion pounds of metal sold and recycled. Our founder, Jeff, has spent his life in the industry and prides himself on offering fair, efficient, trustworthy, knowledgeable, outstanding customer service. We offer metal salesmetal recycling pickup service, and other associated services, such as precise metal sawing, machinery teardown, and warehouse cleanupGive us a call and we’ll get it done.