Effect of titania nanoparticles loading in sol-gel films for corrosion protection of aluminum AA2024-T3 alloy in 3.5% sodium chloride solution

Abstract

Sol-Gel films modified with tiania (TiO2) was prepared and employed as a corrosion protective coating for aluminum Al2024 (UNS A92024) alloy in 3.5% sodium chloride solution. The morphology of the coatings was analyzed using field-emission scanning electron microscope (FESEM). The protective nature of the coating was evaluated using electrochemical polarization and impedance spectroscopy measurements. The results indicated that the modification of the sol-gel coating with TiO2 increased the corrosion resistance of the alloy. The insulating and non-permeable nature of the coating resulted in a slower rate of electrolyte penetration to the underlining of the coating. On the other hand, the presence of TiO2 allowed the modification of the sol-gel structure that ended with a high cross-linked structure. However, we found that increasing the Ti-content allowed high chance for galvanic corrosion that resulted in increasing the corrosion rate. The electrochemical impedance spectroscopy measurements provided an explanation for the increased corrosion resistance of the sol-gel coating containing TiO2. The surface morphology revealed changes imparted to the surface with and without coating before and after its exposure to the corroding medium.