Corrosion inhibition of magnesium by combined zirconia silica sol-gel films

The inhibition of Mg (AZ91D) corrosion by thin sol-gel films was studied. The sol-gel films were prepared by the traditional acid or base-catalyzed hydrolysis and condensation, and finally deposited by dip coating. Two different sol-gel monomers were used: phenyltrimethoxysilane (PTMOS) and zirconium(IV)tetra-1-propoxide (ZrTPO). Films were made of each of the individual monomers and by depositing first a PTMOS film followed by ZrTPO-based film. The corrosion inhibition of the films and their characterization were examined by different methods including potentiodynamic polarization, contact angle measurement, adhesion test, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). We found that while the ZrTPO-based film did not show a significant corrosion inhibition, the PTMOS-based film provided moderate protection. Interestingly, the combined film exhibited superior corrosion inhibition as compared with the other films. (C) 2008 Elsevier Ltd. All rights reserved.