The main function of any automobile's radiator is to cool liquid that has been heated by the engine. A radiator's surface area is the most important factor in reducing temperature. Modern radiators use wide tubes with cross sections providing more surface area per cubic inch of coolant than older, copper radiators.
Material strength is one of the biggest differences between copper and aluminum. Copper tubes that carry coolant have to be thin to keep a copper radiator cooling efficiently. Copper is somewhat weak, and tubes need to be narrow to prevent internal pressure from swelling. Aluminum is stronger, which makes it easier to use wider tubes. Using wider tubes allows for more direct contact between fins and the tube, which increases the radiator's capacity to dissipate heat.
There are several benefits to both aluminum and copper. It is scientifically proven that copper transfers heat better than aluminum transfers heat. Copper is also easier to repair than aluminum in most situations. Aluminum, however, is generally 30 to 40 percent lighter than copper. Aluminum can also be polished to a mirror-like finish for those interested in a show appearance.
Neither material is resistant to corrosion. They must both be maintained properly for optimal performance. According to stockcarproducts.com, copper works well as a heat conductor "but solder required to bond the tubes to fin creates an insulation point that prevents some heat transfer. Aluminum tubes are welded rather than soldered to the aluminum tanks, providing a more efficient conductor for cooling efficiency."
Aluminum radiators traditionally use one-inch wide tubes, while copper radiators traditionally use one-half-inch tubes. In comparison, aluminum is more resistant to damage than copper. Copper is easier and cleaner to produce than aluminum and it is also much more easily recyclable. Nearly 10 percent of all copper scrap is from copper radiators.