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External corrosion of automotive heat exchangers, mainly radiators, has in recent years become a problem in some cases. The reasons for the corrosion attacks are a combination of air pollution on one side and road salting or tropical marine climate on the other. This paper deals with actions taken to improve the corrosion resistance of copper/brass radiators. Rapid corrosion of the tubes due to dezincification which gave early radiator leakages was solved by introducing arsenic and phosphorous containing brass qualities (1). Corrosion of fins and solder has been tackled by different types of coatings (2, 3). Copper strips that are zinc coated before the fin production are a new product for large scale application (4). Solder coated strips have been used since many years but are expensive and heavy. Organic coatings applied on complete radiators have been tested for a couple of years. The black painting that is normally used on radiators does not give any corrosion prevention.

The copper industry has during the last couple of years developed two new joining techniques for copper/brass heat exchangers. The results are promising and they are likely to find industrial applications very soon. Laser welding can use a modified ordinary lock seam tube mill together with the laser. The welding speed can be at least the same as during normal lock seam tube production and the wall thickness as thin as the thinnest used in lock seam tubes. Results from laser welding of a new tube profile, “double tubes”, is also presented. Brazing instead of soldering is possible as new materials for brazing now are available. A cheap, non toxid low temperature brazing alloy based on the CuSnNiP system has been developed. Brazing can be done using a fluxless paste made from atomized powder. Both vacuum and inert gas furnaces can be utilized.

Three new technologies so improve copper and brass radiator production are now being pursued in the U.S.A.: Automated core baking significantly improves the reliability of soldered joints; zinc-base solders cars provide much higher mechanical properties and lighter weight than conventional lead alloys, with no “blooming corrosion” or toxicity hazards; and mechanically clinched brass tank-to-header joints promise better reliability than conventional soldered designs. These technologies, ready for commercial exploitation, will make available copper and brass radiators that are lighter, more durable, more efficient and lower in cost than today's products