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Technical Paper

Methods for Assessing the Corrosion Behaviour of Heat Exchanger Materials and Components

To determine the true galvanic compatibility of radiator components a test has been developed using a zero resistance ammeter (ZRA) technique, which measures the magnitude of the galvanic current between different materials, thus allowing specific corrosion rates to be calculated. It is believed that the use of the ZRA technique will help provide a better balance between sacrificial behaviour and thermal performance of fin alloys. In particular, it will be demonstrated that it is not necessary to make additions of zinc to the fin alloys to attain a sacrificial effect, which in the longer term may compromise the recyclability of radiator units.
Technical Paper

Development of an Understanding of the Critical Factors Influencing Waterside Corrosion Behaviour of Brazed Aluminium Radiators

The application of aluminium alloy materials for automotive heat exchangers, including engine cooling and air conditioning systems, is now widespread. To meet the industry demands of both extended service life and improved reliability for heat exchanger components, it is important that the critical factors influencing corrosion behaviour are properly understood, particularly with the trend towards downgauging of materials. To maximise resistance to waterside corrosion, manufacturers have adopted the approach of using an internal cladding, commonly a high purity or zinc - containing alloy, to provide sacrificial protection of the core material. Recent studies have shown that the presence of an internal cladding can, under certain conditions, promote rapid localised attack of the core alloy.
Technical Paper

Development of a Long Life Aluminium Brazing Sheet Alloy with Enhanced Mechanical Performance

The use of aluminium alloys for automotive heat exchangers has increased considerably in the last 15-20 years and, in parallel, new alloys have been developed to meet the increased demand for strength and improved corrosion resistance. A non-heat treatable Al-Mn alloy, X800, has been developed by Alcan to significantly increase the corrosion resistance of radiator tubes when subjected to typical service environments. The alloy development employed considerable microstructural understanding to provide heat exchanger manufacturers with an improved product that readily attained enhanced performance during any brazing cycle. A similar philosophy has been adopted to address the issue of increased mechanical performance, higher intrinsic sheet strength, both during and after brazing, provides the opportunity for sheet downgauging and thus lightweighting of components.