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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.

For many years the tubing in automotive brake systems has been manufactured from low-carbon steel. One or more superficial coatings are applied after brazing to protect the steel substrate from corrosion, because steel has no inherent corrosion resistance to the road environment. Although coating composition has changed since the original hot-dip lead-tin coatings were used, coating flaws remain a problem. The addition of zinc-rich paints did little to improve the protection of the tube. Current aluminum-zinc coatings and added polyvinylfloride coatings are still inadequate to totally protect the steel tube. In a recent series of tests, 90-10 copper-nickel tube (UNS C70600) was fabricated into typical brake system “shapes” which were then attached to a test trailer and conveyed through various corrosive and mechanically abusive test track environments. The tests included holding the tubes in a high humidity chamber for a portion of each 24-hour test cycle.

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

At the 1965 SAE Mid-Year Meeting in Chicago, fleet operators commented on hydraulic brake tube failures. Since little factual information was available on the effects of service life on the performance of hydraulic brake lines, a program was initiated to obtain this information. Results of the program indicate that corrosive deterioration of the steel hydraulic brake tubing now being used on cars and trucks creates maintenance problems and can be a safety hazard. The investigation also showed that the performance of presently used brake tubing becomes highly erratic after four to six years in service. Age of the vehicle appears to be more significant than mileage relative to brake tube corrosion. However, there are so many variables which influence brake line corrosion that attempts to correlate the results of the investigation with any one factor, such as age, are difficult.