ZrO2 sol–gel pre-treatments doped with cerium nitrate for the corrosion protection of AA6060

Sol–gel coatings represent an alternative corrosion protection method to the chromate based systems which must be replaced. Recently, it was shown that ZrO2 based sol–gel coatings deposited on AA6060 can provide a good corrosion protection to AA6060. However, ZrO2 based sol–gel systems are not able to provide the self-healing effect which is instead the peculiar property of chromate conversion coatings. The structure of the ZrO2 based sol–gel systems does not contain species able to restore the barrier properties when defects or damages impair the coating protection. In this work, ZrO2 based sol–gel coatings containing cerium nitrate were deposited on AA6060 aluminum alloy in order to evaluate the corrosion inhibition provided by the incorporated cerium ions. The cerium nitrate was added to the starting sol based on zirconium alkoxide precursors. Three types of samples were produced: a non inhibited type consisting of 3 layers of ZrO2, an inhibited system consisting of two layers of ZrO2 with an intermediate layer doped with cerium nitrate and an inhibited system consisting of two layers containing cerium nitrate with a top layer of ZrO2.