Work presented in this paper focuses on the critical aspects of the surface preparation of aluminium employed for the manufacture of aluminium-epoxy joints. The surface preparation procedure examined is currently employed by the Royal Australian Airforce (RAAF) for repairs requiring metal-to-adhesive bonding. The influence of each step in the surface preparation on the bond durability performance of the adhesive joint is examined by a combination of methods. Double-cantilever wedge-style adhesive joints are loaded in mode 1 opening and exposed to a humid environment. Together with analysis of the adherend and joint failure surfaces, the results show conclusively that adhesive bond durability is sensitive to the presence of contaminant and the roughness of the adherend surface. The presence of contaminant can interfere with the effectiveness of an organosilane coupling agent as a durability improver. A two-step bond degradation model was developed to describe qualitatively the observed bond durability performance and fracture data.