Hydrated oxide film growth on aluminium alloys immersed in warm water

The growth of hydrated oxide films on 2024 bare and 7075 clad aluminium alloys immersed in deionized water at temperatures of 40 and 50 °C for periods up to a couple of hours was studied using grazing angle FTIR, weight gain measurements, high resolution SEM and AFM. The results show that a porous oxide structure, likely to be very suitable for adhesive bonding, develops. The films formed at 50 °C are much thicker than those formed at 40 °C and contain significantly more pseudoboehmite; however, the porosity of the films appears to be comparable at both temperatures. In contrast with film growth studies reported for pure aluminium, the alloy systems do not appear to show an incubation period prior to hydrated oxide growth.