THE EFFECT OF Zr CONVERSION COATINGS ON ADHESIVE BOND DURABILITY OF ALUMINIUM AUTO-BODY SHEET

摘要

As car manufacturers pursue their drive to reduce weight of vehicle structures, aluminium has received increased attention as a preferred material. Achieving the weight reduction that aluminium can provide without any loss in structural integrity has posed a distinct challenge. Structural adhesives are now playing an important role in reinforcing aluminium structures, and car manufacturers are finding that adhesive bonded aluminium structures meet the desired levels of torsional stiffness. Adhesive bonds with good initial strength can be easily produced but they lack durability. Acid pickling is well known to improve bond durability. The pickled surface has to be stable until bonding. Zr or Ti based conversion coatings are considered to be essential to enhance the stability of the pickled surface. The presence of a dry lubricant makes the material ready for conventional stamping. Compatibility of the dry lubricant and the adhesive is essential This paper shows that the effect of a Zr passivation on the properties of the oxide layers of EN 5182-0 and EN 6016-T4 is negligible and no effect on adhesive bond strength and durability has been found. The dry lubricant is compatible with the epoxy adhesive.