In the present study, the effects of surface pretreatments of AA2024 aluminium alloy on the corrosion protection of the alloy using a sol–gel coating were investigated. It was revealed that the second phase particles that remain after etching and desmutting have a significant impact on the subsequent sol–gel coating which, in turn, influences the overall corrosion protection afforded to the substrate by the sol–gel coating. The removal of second phase particles in the surface region can be achieved by an alternative surface pretreatment using nitric acid. A significant improvement of corrosion protection of sol–gel coated AA2024 aluminium alloy was observed when the surface of the alloy was pretreated with nitric acid. Copyright © 2013 John Wiley & Sons, Ltd.