The influence of the nature of the surface oxide on the adhesive fracture energy of aluminium-bonded joints as measured by T-peel tests

Modification of aluminium alloy substrates microstructure and morphology by depositing new oxide layers on top of the metal surface has been investigated, with the aim of improving adhesion. The effect of treating the metal with boiling water or immersing it in a cerate bath has been studied by means of electron microscopy, contact angle measurements and peeling tests. The formation of pseudoboehmite layers or cerium conversion coatings both led to an increase in joint's adhesive fracture energy and more durable adhesive bonds with respect to joints obtained with “mechanically grinded only” substrates. Differences in the performance of the bonded joints has been discussed in terms of the possible formation of different microstructured interphases.