A combined atomic force microscopy (AFM)/X-ray photoelectron spectroscopy (XPS) study of organosilane molecules adsorbed on the aluminium alloy L157-T6

Abstract

Organosilanes are extensively used to promote the adhesion of surface coatings and adhesives to different substrates, including metals. The surface concentration and spatial distribution of the organosilane on a particular material are important factors in determining its efficiency as an adhesion promoter. The powerful combination of atomic force microscopy (AFM) with X-ray photoelectron spectroscopy (XPS) was adopted to characterise the adsorption of aminopropyltriethoxysilane (APS) on the Al alloy L157-T6. Complementary information on the distribution of the adsorbed APS was obtained using the force–volume (FV) approach in AFM. The combined AFM/XPS study revealed that the coverage and stuctural integrity of the APS film were dependent on the concentration of the silane in solution. Greater coverage and better structural integrity were obtained by adsorbing the APS film from a 3% silane (in methanol) solution than from a 6% solution.