Taguchi design applied to process parameters optimization of sol–gel anticorrosive films

In order to obtain an anticorrosive film produced according to the sol–gel method for protection of steel alloys, some parameters of the process were tested, which resulted in a crackless film with effective corrosion protection. The parameters studied were sol formulation, aging time of the sol, withdrawal speed using dip-coating technique, and heat treatment temperature. After the conduction of preliminary experiments, the formulation with a molar ratio of TEOS:glycerol:NH₄OH of 3:3:1 was selected, due to the lack of cracks when analyzed with an optical microscope. The evaluation of the other parameters (aging time of the sol, withdrawal speed after the immersion in the sol using dip-coating technique, and heat treatment temperature) was realized with the help of a Taguchi design. Aiming for the evaluation of the effectiveness of the corrosion protection, experiments of accelerated corrosion in sulfuric acid aqueous solution were conducted. The samples covered with the film aged in 96 h, heat treated at 150 °C, and with withdrawal speed of 10 cm.min⁻¹ presented the most satisfactory results.