Influence of inhibitor addition on the corrosion protection performance of sol-gel coatings on AA2024

Sol-gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability. In this work a certain number of corrosion inhibitors for AA2024 was used as additives to the hybrid sol-gel formulations in order to confer active corrosion protection without damaging the coating. The 8-hydroxyquinoline, benzotriazole and cerium nitrate were added at different stages of the synthesis process to understand the role of possible interaction of the inhibitor with components of the sol-gel system. The Scanning Vibrating Electrode Technique and Electrochemical Impedance Spectroscopy were employed as two main techniques to characterize the corrosion protection performance of the hybrid sol-gel films doped with inhibitors and to understand the mechanisms of corrosion protection. The results demonstrate that 8-hydroxyquinoline and cerium nitrate do not affect the stability of sol-gel films and confer additional active corrosion protection effect. In contrast to this, benzotriazole leads to deterioration of the corrosion protection properties of hybrid sol-gel films. (C) 2008 Published by Elsevier B.V.