The present work investigates the electrochemical behaviour of galvanised steel substrates pre-treated with bis-[trietboxysilylpropyl] tetrasulfide silane (BTESPT) solutions modified with SiO2 or CeO2 nanoparticles activated with cerium ions. The electrochemical behaviour of the pre-treated substrates was evaluated via electrochemical impedance spectroscopy in order to assess the role of the nanoparticles in the silane film resistance and capacitance. The ability of the Ce-activated nanoparticles to mitigate corrosion activity at the microscale level in artificial induced defects was studied via scanning vibrating electrode technique (SVET). Complementary studies were performed using potentiodynamic polarisation. The results show that the presence of nanoparticles reinforces the barrier properties of the silane films and that a synergy seems to be created between the activated nanoparticles and the cerium ions, reducing the corrosion activity. The addition of CeO2 nanoparticles was more effective than the addition Of SiO2 nanoparticles. (c) 2007 Published by Elsevier Ltd.