Homogeneous thick silica coatings were prepared onto metals substrates by Electrophoretic Deposition (EPD) using particulate sol-gel sols. The synthesis of the sols was performed by mixing tetraethoxysilane and methyltriethoxysilane under basic catalysis. The synthesis, storage and processing conditions were optimised, correlating the rheological properties of the sols with EPD performance and reliability. Homogeneous and crack-free coatings are obtained when both, the synthesis and the deposition, are performed under tight conditions avoiding the contact with room humidity. The maximum crack-free thickness of the sintered coatings was 12 mum, three times more than those obtained by dipping. (C) 2004 Kluwer Academic Publishers.