X-RAY PHOTOELECTRON-SPECTROSCOPY STUDY OF ALUMINUM SURFACES PREPARED BY ANODIZING PROCESSES

X-ray photoelectron spectroscopy was used to compare several pretreatments of aluminium surfaces used in aerospace and aircraft industry. These anodizing processes, which aim at preparing the metal surface for adhesive bonding or painting, all lead to the formation of an aluminium oxide layer. A set of aluminium samples representing the various steps of the processes was analysed by XPS. After curve fitting of the aluminium peak (Al 2p) and oxygen peak (O 1s) recorded at high energy resolution, and correction of charging effects, residual energy shifts between the spectra can be observed. This could be attributed to differences in the Fermi energy values between the treated aluminium surfaces. A classification based on this parameter of the relative Lewis acid-base character of these treated surfaces is proposed, The evolution of this parameter after exposure of the treated samples to a moist environment was also studied.