Characterization of aluminum surfaces after different pretreatments and exposure to silane coupling agents

X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to characterize surfaces of aluminum which have been pretreated by mechanical polishing, acid etching and alkaline etching, as well as given subsequent exposures to air and water. These surfaces can differ markedly with regard to their chemical compositions and topographical structures. Characterizations of these surfaces after exposures to three organosilanes, gamma -GPS, BTSE and gamma -APS, indicate that the amount of silane adsorbed in each case shows a tendency to increase both with the number of OH groups detected at the oxidized aluminum and with the surface roughness. The XPS data are consistent with the adhesion of gamma -APS occurring through H bonding, especially via NH3+ groups.