Inhibitor-doped sol–gel coatings for corrosion protection of magnesium alloy AZ31

This work presents new anticorrosive coatings for the AZ31 magnesium alloy, based on hybrid sol–gel films doped with a corrosion inhibitor. The sol–gel coatings were prepared by copolymerization of 3-glycidoxypropyltrimethoxysilane and zirconium (IV) tetrapropoxide. 8-Hydroxyquinoline (8-HQ) was chosen as a corrosion inhibitor to be incorporated into the sol–gel films at two different stages of synthesis, either before or after hydrolysis of the sol–gel precursors.The effectiveness of 8-HQ for corrosion suppression on AZ31 was verified by Scanning Vibrating Electrode Technique. Electrochemical Impedance Spectroscopy was used to monitor the evolution of the substrate/film systems in the course of immersion in 0.005 M NaCl. The morphology and the structure of the sol–gel films were characterized with SEM/EDS and TEM techniques. The sol–gel films exhibit good adhesion to the metal substrate and prevent the corrosive attack during 2 weeks under immersion test.Results showed that addition of inhibitor into the sol–gel films enhances the corrosion protection of the magnesium alloy and does not lead to deterioration of the barrier properties of the sol–gel matrix.