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

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