On the Corrosion Properties for Roll-Bonded One-Layer AA4045/AA3003 Modified Brazing Sheets for Automotive Heat Exchanger Application

The automobile industry continues to put pressure on the heat exchanger manufacturing sector to develop heat exchangers that are of less than average dimension, light, efficient, and as affordable as possible. During the service life, automotive heat exchangers are subjected to a variety of environments, including heating and cooling cycles, saltwater environment on the road surface, and mechanical loading. As a result, corrosion performance is critical, as perforation of the material could result in system failure. The corrosion behaviour of roll-bonded aluminium brazing sheets is significant since this is the most common mode of failure for automotive heat exchangers, especially with the trend toward lighter automotive parts. Furthermore, thermal treatments such as solution heat treatment, homogenization, and brazing alter the microstructure and, as a result, vary the corrosion behaviour. The qualities of the finished product, such as mechanical properties and corrosion resistance, are impacted by microstructural variation in AA3xxx that results in the development of manganese (Mn) bearing dispersoids during preheat treatment before rolling. The effect of homogenization temperature and duration on the microstructure of AA3xxx aluminium alloys has been studied, but more research is needed. The goal of this investigation was to see how different holding times during pre-heat treatments affect the corrosion behaviour of the AA4045/3003 modified brazing sheet used for automotive heat exchangers. The experimental plate samples were made from modified alloy 3003 and standard alloy 4045 in the cast and homogenised state. Accelerated laboratory corrosion tests are essential for ranking trial materials and ultimately qualifying an alloy for production. The corrosion behaviour of one-layer modified AA4045/3003 brazing sheets was examined in this chapter before brazing. The samples homogenized for 20 hours exhibited more corrosion resistance with a corrosion rate of less than 0.1 mm/y than those homogenized for longer times. The corrosion resistance deteriorated with an increase in the homogenization time. The corrosion propagation was attributed to potential differences between the brazing sheet, creating a galvanically driven perforation of the core material by the diffusion zone after accelerated salt spray testing (ASST) and electrochemical testing.