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.