The work aims at investigating the corrosion behavior of AA2024-T3 substrates pretreated with sol-gel derived hybrid coatings. The hybrid sols were prepared by copolymerization of 3-Glycidoxypropyltrimethoxysilane (GPTMS), tetraethylortosilicate (TEOS) and tetran-propoxyzirconium (TPOZ). Coatings with Zr/Si atomic ratios of 1:9 and 1:4 were also prepared. During the synthesis process, there is formation of ZrO2 nanoparticles, which content depends on the temperature and time of the TPOZ hydrolysis/condensation reactions. The results show that the ZrO2 nanoparticles have diameters ranging between 40 and 200 nm. These particles are amorphous and they improve the corrosion protection of the sol-gel coatings. The presence of ZrO2 nanoparticles seems to have a pore blocking effect in the coatings with higher content of particles. (c) 2004 Elsevier B.V. All rights reserved.