The Significance of Environment for Performance of Structural Adhesive Bonding

The development of a durable adhesive bonding technology for joining of aluminium automotive structures requires a full understanding of the importance of the environment on the chemistry of the adhesively bonded system. This paper describes the accelerated testing procedures used by Alcan to provide information on the significance of environmental factors on adherend surface, the bonding interface and adhesive and so establish the best combination of adhesive and surface pretreatment for good long term durability. The stress/humidity test provides information on adhesive and interface performance, while the neutral salt spray test illustrates durability and corrosion resistance of the pretreatment. Outdoor exposure testing provides the means of comparing the accelerated tests with real life durability. The paper demonstrates that by combining the results of all three test methods, a much greater degree of confidence in the overall compatibility and long term durability of a surface pretreatment/adhesive system can be achieved than by the use of a single test procedure alone.