Copper might stand as a viable contender to aluminum in radiator applications, but it could be a hard sell for auto radiator manufacturers, who say they are unlikely to switch back to copper-brass models from aluminum despite the strength and corrosion-resistance benefits offered by the relatively new CuproBraze technology.
Radiator manufacturers like Dana Holding Corp., Toledo, Ohio, ceased making copper-brass radiators in 1989, shifting its focus exclusively to aluminum. The change was primarily sparked by aluminum's big weight-savings advantage over copper-brass, which translates into better fuel efficiency.
Despite the development of CuproBraze, manufacturers don't see a shift coming anytime soon. "Even though they're touting it as a new technology, most of the heat exchanger people would say aluminum is now entrenched and brass would have a hard time kicking it out," said Ted Zielinski, technical director of the Thermal Products division of Dana's Automotive Systems Group.
Aluminum is used throughout the engine, and introducing a brass heat exchanger could cause some corrosion. "We don't like to mix metals," Zielinski said. Heavy-duty vehicle manufacturers also have shifted to aluminum, attracted by the lower cost of the metal vs. copper.
Even in developing countries like China, the issue of fuel efficiency likely will eventually drive the Chinese toward aluminum. China also is increasing production of aluminum, which would further favor aluminum heat exchangers.
But those aren't the only two metals on the table. Dana said it is exploring even lighter materials that also are heat efficient, strong and corrosion resistant. So far, the company has looked into magnesium and titanium, both of which are lighter than aluminum although the significantly higher cost of the two metals is prohibitive.
"Everywhere I look there's room to argue which one (copper or aluminum) is actually superior vs. one design or another," said James E. Burns, design engineer at Piedmont, S.C.-based Griffin Thermal Products Inc. "But it's a debate that will be going on probably for the rest of my life and probably my children's."
Like Dana, Griffin began a shift to aluminum in the late 1980s and ceased using copper in the early 1990s. The company has no plans to shift back anytime soon, noting that it's not cost-effective from a design and investment perspective.
Comparing a 20.3-millimeter flat oval geometry brass-type tube in a one-row CuproBraze radiator to an aluminum radiator construction with a 26-mm core thickness for the same engine shows that the aluminum radiator is approximately 40 percent lighter, Burns said.
Major manufacturers like Griffin that supply powertrain cooling systems also have made large capital equipment investments to produce and meet the needs of customers, he said, noting that major design changes in equipment and heat exchangers would be required to reverse these investments—not to mention convincing customers like car and truck manufacturers.
Griffin acknowledges that the tensile strength of raw aluminum isn't as strong as that of raw copper and that the CuproBraze technology shows promise in heat exchangers for non-standard heavy machinery. However, Burns points out that manufacturers also have been able to make durable aluminum products for the same applications.
Another deterrent the industry faces in switching back to copper is work under way to build hydrogen fuel cell powered vehicles and hydrogen power battery shells for vehicles, for which aluminum is a better candidate, he added.
Even Climex World SA de CV, a dedicated CuproBraze radiator company in Escobedo in the Monterrey metropolitan area of Mexico, acknowledges that the technology isn't a feasible alternative for passenger car radiators. "For those, aluminum is still the best option," Jorge Warnholtz, Climex World's plant manager, said.
However, the red metal seems to have found a niche market. The CuproBraze technology is ideally suited for the mining, off-road, construction, agriculture, heavy-duty truck and electric power industries. Climex is getting ready to sell replacement parts for such after-market heavy-duty vehicles, and CuproBraze products offer strong mechanical resistance given that they're subjected to extremely high temperatures as part of the brazing process, Warnholtz said.
Demand for conventional soft-soldered copper-brass radiators is showing signs of growth in the Caribbean, Mexican and North American after-markets. Proveedora de Herramientas y Accesorios para Radiador SA de CV, parent company of Climex, began exporting in 2004 and has witnessed growing copper-brass demand during the past two years, Warnholtz said. "The customers in the U.S. are seeing that the copper-brass radiator behaves better than the aluminum counterpart that the heavy-duty units were equipped with originally. Many people still like the repairability, they like the ruggedness and they like the copper-brass radiator better than the aluminum. People are beginning to switch back."
The company declined to specify its sales levels, although Warnholtz did say that the soft-soldered copper-brass radiators made by Climex World's parent company has grown 20 percent this year vs. 2007. He declined to disclose the number of units sold.