Corrosion protection properties of silica coatings formed by sol–gel method on Al: The effects of acidity, withdrawal speed, and annealing temperature

• Silica films were prepared by sol–gel dip-coating method onto aluminum sheets.
• The characteristics of the films were studied as a function of coating parameters.
• The films derived from acidic sol had uniform morphology.
• The acid catalyzed film had better corrosion resistance than base catalyzed film.

In this research, silica films were coated onto aluminum sheets using the sol–gel dip-coating method from acidic and basic solutions containing (C2H5O)4Si, C2H5OH, H2O, and catalysts. NH3 and HNO3 were used as catalysts in the acidic and basic solutions, respectively. The characteristics of the films were investigated as a function of the sol catalyst, withdrawal rate, and heat treatment temperature. Morphology of the coatings was studied by scanning electron microscopy (SEM). Corrosion behavior of coated and uncoated aluminum sheets was measured in 0.1 M NaCl. Findings indicated that SiO2 coatings can offer proper protective properties against corrosive environments. Results also showed that conditions used to prepare the coatings significantly affect the morphology and thus, the corrosion protection of the silica films.