Effective corrosion inhibition performance of Ce3+ doped sol–gel nanocomposite coating on aluminum alloy

Abstract

Sol–gel nanocomposite coatings have been investigated for Alclad AA2024 as a potential replacement for the hazardous and banned hexavalent chromate conversion coatings. The sol–gel coatings were prepared using a sol obtained by the hydrolysis and condensation of methyltriethoxysilane and colloidal silica. They were doped with cerium nitrate inhibitor to provide active corrosion protection and were deposited by spray-coating method. The sol–gel process conditions were optimized to obtain smooth and homogenous crack free films. The chemical composition and microstructure of the coatings were studied using EDX and FESEM respectively. The effect of cerium nitrate concentration on the corrosion protection efficiency of the sol–gel coatings was evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy and salt spray tests. The results indicated that cerium nitrate doped coatings were more resistant to corrosion than undoped coating. The coatings doped with 6000ppm cerium nitrate rendered improved protection after longer immersions due to the inhibitive action of Ce3+.