The demands for longer lifetimes of cars have meant that the durability of radiators has also become more important, particularly with regard to the resistance to external corrosion due to environmental pollution. In this paper corrosion mechanisms, as well as some preventive measures for copper/brass radiators, are discussed.
The radiator is constructed basically of solder–coated flat brass tubes and copper fins. The tubes and fins are joined together with tinllead solder. Bimetallic contact points in joints and also pores and scratches are exposed to corrosive chloride and sulfur compounds. This can initiatiate corrosion damage, if corrosion prevention measures have not been taken into consideration.
Experiments have been made to evaluate the risks of bimetallic corrosion between copper, some brass alloys and soldering alloys on radiators. Experiments are based on electrochemical methods.
The corrosive environment was simulated with a water solution containing chlorides, corresponding to remainders of fluxing agents, marine atmosphere and road deicing salts, and also containing sulfur and nitrogen oxide compounds, corresponding to road environment pollutants.
As a practical method to increase the corrosion resistance of copper/brass radiators, an organic solvent acrylic type, low–curing, clear–lacquering method is introduced. Test results with sprayed epoxy coatings are also reported. Coatings, 5–10 μm thick, gave improved corrosion resistance in accelerated salt and sulfide spray test without any appreciable influence on the radiator heat dissipation. A lifetime of at least ten years for coated radiators is predicted.