Next to silver, copper is the most conductive material available, with copper wiring 66% more conductive than aluminum wires of the same size. To transfer the same amount of current in an 8 AWG copper wire, a 6 AWG aluminum conductor up to 25% thicker in size is required.

However, copper is prone to corrosion and can turn greenish in color when exposed to oxygen—this effect can be seen on old pennies or the Statue of Liberty. By removing the oxygen from the copper, oxygen-free copper (OFC) is produced, dramatically improving its corrosion resistance. Using OFC comes with obvious benefits of higher current flow, improved conduction efficiency, and reduced environmental strain.

Below, we detail the different oxygen-free copper grades and some of the benefits and challenges of using OFC so you can make the right purchase for your application.

Oxygen-Free Copper Grades and Their Benefits

Oxygen-free copper represents the copper material that has gone through electrolytic refinement to remove all (almost 99.99%) but a trace level of oxygen. By removing oxygen and other impurities, the copper attains superior conductivity and becomes less susceptible to corrosion.

Types of Oxygen-Free Copper

There are three oxygen-free copper grades, detailed below. 

• C10100
  C10100 is designated as OFE, or oxygen-free electronic, and achieves a minimum electrical conductivity rating of 101% IACS under annealed conditions. C10100 is recommended for applications requiring high ductility and electrical as well as thermal conductivity.
• C10200
  C10200 is 99.95% pure copper. It is an ideal choice when the material needs a strong resistance against stress corrosion cracking. It also has excellent conductivity, welding, and soldering characteristics, like C10100.
• C11000
  C11000 is also known as electrolytic tough pitch copper or ETP. Though it is 99.9% pure copper, ETP copper contains more oxygen than OFE copper, with OFE having less than 10 ppm of oxygen, whereas ETP contains a minimum of 150 ppm of oxygen. However, ETP is the most commonly used grade copper for its inherent fabrication qualities.

Below is a summary of the oxygen-free copper (OFC) grades, along with their oxygen contents, high purity levels, and applications.

OFC Grade	Oxygen Content	Purity	Application
C10100	0.0005%	99.99%	Automotive rectifiers Bus conductors Coaxial cables Transistor component base Cavity resonators Glass-to-metal seals
C10200	0.001%	99.95%	Electrical conductors Coaxial cables Billet mold tube Klystrons Heat sinks
C11000	0.02%- 0.04%	99.9%	Welding fixtures Lean-in wires Ground straps Anodes Bus conductors

Benefits of Using Oxygen-Free Copper

Using OFC can be beneficial for specific applications. Below, we explore some of these benefits in more detail.

Exceptional Electrical Conductivity

During the manufacturing of OFC, the copper is processed in the presence of carbon to remove any oxygen present. High purity, coupled with the absence of oxygen, allows more currents to pass through the same conductor size. Thus, OFC is specifically used for battery cables, induction coils, and space heaters.

High Thermal Capacity

Due to higher thermal conductivity, OFC elemental copper wires do not heat up as quickly as other metals, such as aluminum. As a result, they also have superior thermal strength and thermal conductivity. Industries heavily rely on them for high-temperature applications such as induction heating furnaces.

Excellent Resistance to Hydrogen Embrittlement

Oxygen-free coppers achieve excellent resistance against hydrogen embrittlement occurring under wet electrochemical environments. Because of its malleability, weldability, and lack of reactivity in oxygen-free waters, Finland is even using copper canisters to store nuclear waste inside an encapsulation plant.

Excellent Fabrication Properties

All oxygen-free copper grades are good for machining, with an excellent machinability rating of 20 (100 is more difficult to machine). They have excellent hot-working and cold-working properties. All grades are ideal for soldering, brazing, and gas shielding arc welding. However, spot welding and seam welding are not recommended.

Challenges with Using Oxygen-Free Copper

Among all of the oxygen-free copper grades, C101 differs from the rest in terms of its processing method, as the smelting and pouring of C101 are carried out in an oxygen-free environment. Considering the complexity of production, C101 coppers are the most expensive grade; thus, it is imperative to utilize C101 carefully, especially during the cutting process, to minimize waste. If you don’t have the required infrastructure to precisely cut C101 or the expertise to recycle waste to your advantage, it might be beneficial to outsource your metal sawing to a reliable metal supplier.

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