A hybrid sol synthesized from an acid-catalyzed hydrolysis and condensation reaction of 3-glycidoxypropyltrimethoxysilane (GPTMS) and zirconium n-propoxide was used as a matrix nanocomposite sol. To this sol, 0.01？M？Ce3+ was added as an inhibitor to provide a self-healing coating system. The effect of an atmospheric air plasma surface pretreatment of aluminum alloy substrates prior to coating deposition of Ce3+-doped/undoped GPTMS-ZrO2 sol was studied with respect to corrosion protection. Coatings were generated by a dip coating technique employing a withdrawal speed of 5？mm/s and thermally cured at 130° C for 1？h. The coated Al surfaces were characterized using potentiodynamic polarization studies and electrochemical impedance spectroscopy. They were also subjected to accelerated corrosion testing using neutral salt spray test with 5% NaCl solution after creating an artificial scratch for more than 200 hours to assess the self-healing ability of coatings. It was observed that cerium (III) doping was effective for corrosion protection during long-term exposure to the electrolyte solution, and a plasma surface pretreatment of substrates prior to coating deposition of Ce3+-doped coatings improved the adhesion of coatings that provides enhanced corrosion protection along with self-healing ability exhibited in case of damages/scratches caused in the coating. 1. Introduction Aluminum and Al alloys are widely used in structural applications mainly in aircraft and automobile industries due to their light weight and high strength properties [1]. Aluminum alloys are very sensitive to corrosion when exposed to a chloride containing atmosphere. Although there are several surface engineering treatments available to prevent corrosion on Al/Al alloys, surface treatments that require low temperatures for post-treatment processing are recommended to prevent a deterioration of mechanical strength that occurs by dissolution of intermetallic particles during high temperature post-treatment [2]. Hybrid sol-gel coatings are the best alternatives as low temperature curable coatings that offer a barrier-type protection [3]. However, sol-gel coatings contain micropores, cracks and areas of low cross-link densities that provide pathways for diffusion of corrosive species to the coating metal interface [3]. In order to overcome these problems, the use of inhibitors in the coating is usually resorted to. Such coatings may not also be able to provide continued corrosion protection in the event of development of a crack in the coating. Hence, instead of providing a metal with just
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