Ageing of aluminium oxide surfaces and their subsequent reactivity towards bonding with organic functional groups

An infrared reflection absorption spectroscopy investigation was performed of the changes that occur to a freshly prepared aluminium substrate upon ageing in ambient air and upon ageing in a clean, dry environment. Moreover, the bonding capacity of the oxide surfaces was evaluated after prior ageing, by adsorbing an aliphatic carboxylic acid and determining the amount of molecules that were capable of chemisorption with the oxide surface. Ageing in the ambient resulted in the adsorption of water and organic species on the oxide surface, which could not be removed using solvents. The adsorbed water caused hydroxylation and growth of the oxide layer. Because of the adsorbed species, the oxide surface was found to loose 60% of its initial bonding capacity during the first 20h of ageing. Ageing in a clean and dry environment resulted in considerably less changes to the oxide surface. Because of this, during the first 20h of ageing, the substrate was found to loose only 35% of its initial reactivity.