XPS and AES characterization of hydrolysed γ-mercaptopropyltrimethoxysilane deposited on Al, Zn and Al-43.4Zn-1.6Si alloy-coated steel

In this paper Al, Zn and A1-43.4Zn-1.6Si (AlZn) alloy-coated steel have been treated with the organofunctional silane gamma-mercaptopropyltrimethoxysilane (gamma-MPS). The influence of different metal substrates on the structure and composition of the silane films was investigated with XPS and AES. The films were obtained by dipping the substrates in the silane solution followed by a blow-dry procedure in nitrogen gas. The results show that the surface concentration of the deposited silane is independent of the metal substrate and that the thickness of the silane film is non-uniform. The AES measurements indicate that the silane film covers the entire substrate surface and XPS analysis of the silane-treated substrate surfaces at different take-off angles indicates that the gamma-MPS molecule is randomly orientated. Also, the results show that the silane is well hydrolysed under the solution conditions used. Finally, in the zinc-containing silane-metal systems, i.e. the silane-treated AlZn and Zn substrates, the results indicate that the gamma-MPS molecules can bond to the substrate surfaces via the thiol group of the molecule. Copyright (C) 2004 John Wiley Sons, Ltd.