Anticorrosion Sol-Gel Coatings for Anodised Aluminium

摘要

This study results from the collaborative AVCOP-FP7 project, which aims at investigating the potential of nanostructured hybrid organic-inorganic sol-gel materials in the sealing process of anodised aerospace grade aluminium AA2024-T3. A range of hybrid materials prepared from hydrolysis and condensation reactions of organosilane and metal transition precursors have been synthesised, characterised and employed as coating systems for the anodic layer. In addition to the effect of the function group contained in the organosilane, emphasis has been placed on understanding the fundamental mechanism related to the nanostructuration of the metal transition complex and the subsequent effect this would provide to anti-corrosion performances. The corrosion and chemical resistance of the sealed anodic films has been evaluated and compared to conventional sealing technologies such as hydrothermal treatments. Field Emission Scanning Electron Microscopy was utilised to characterise the pore morphology of the anodic films and to determine the sealing mechanism. Accelerated exposure tests have been conducted including neutral salt spray, acidified salt spray and strong alkaline resistance. The synergistic anti-corrosion mechanism of the hybrid sol-gel and oxide film of the corrosion prone alloy was determined with and without the use of the sol-gel sealants. The technique described offers numerous opportunities for industrial applications.