Analytical and microscopic characterisation of modified bis-[triethoxysilylpropyl] tetrasulphide silane films on magnesium AZ31 substrates

In this work solutions of bis-[triethoxysilylpropyl] tetrasulphide silane modified with cerium nitrate are used as pre-treatments for the AZ31 Mg alloy. The silane films formed after the pre-treatment of the metallic substrates were characterised by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films were studied before and after immersion in corrosive NaCl solutions in order to study the ageing of the silane film and to understand the role of the dopant in this process. The results demonstrate that the addition of cerium ions modifies the morphology of the surface film and leads to important changes in the film thickness and composition. Ageing in NaCl solutions decreases the film thickness and affects the chemistry of the surface film. (c) 2007 Elsevier B.V. All rights reserved.