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. Good corrosion results have been found with several dip coatings (2, 3) without interfering with the heat performance of the radiators. The coating must be so thin and even that the airflow through the radiator is not blocked. The dip coatings had, however, some drawbacks. Equipment for large scale application was not commercially available, organic solvents gave environmental uncertainty and black colour was in some cases difficult to apply.
Lately, an electrophoretic coating (EC) has been developed and tested. The results are very promising and are reported here together with some earlier results with conventional dip coatings. Line technology concepts will be available during 1993.