Acid-base properties of passive films on aluminum II. An X-ray photoelectron spectroscopy and X-ray absorption near edge structure study

The adhesion between metals and polymers has attracted much interest in recent years due to the increasing use of metal/polymer assemblies, for example, in the fields of packaging, architecture, and automotive manufacturing. Among the parameters controlling the adhesion properties of metal/polymer systems, the acid-base properties of both materials appear to play an important role. Two methods are proposed for assessing and quantifying the acido-basicity of passive films on metals: X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES). These techniques were used here to characterize the acid-base properties of a large set of passivated aluminum surfaces. Both XPS-monitored Fermi level shift and XANES formic acid and pyridine adsorption measurements were found in good agreement in the establishment of a relative basicity scale for the studied surfaces. Moreover, the results were cross-validated with those of the novel photoelectrochemical approach to the acid-base properties of aluminum surfaces presented in Part I.(1)