Sol–gel sealing characteristics for corrosion resistance of anodised aluminium

Conventional anodising electrolytes based on sulphuric acid, oxalic acid and phosphoric acid have been used to form nanoporous layers on AA3003-H14 and sealed with silane based sol–gel sealers. It is shown that the sol–gel chemistries have varying levels of pore penetration depending on the synthesis conditions. The extent of sol–gel penetration and pore sealing is analysed by electron microscopy and energy dispersive X-ray spectroscopy. To describe the sealing phenomena observed a sol–gel penetration and sealing rating has been proposed to explain the interactions of the sol–gels with the pores of the anodised layers. The corrosion resistance of the sol–gel sealed anodised aluminium surfaces was evaluated using neutral salt spray testing and electrochemical impedance spectroscopy.