Hybrid organic–inorganic coatings are deposited on 304 stainless steel substrates by the sol-gel technique to improve the corrosion resistance. A titania-based nanostructured hybrid sol–gel coating is impregnated with three different microencapsulated healing agents (inhibitors) including cerium, Benzotriazole, and 8-Hydroxyquinoline. Field-emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS) are performed to investigate the barrier performance properties. The optimum conditions to achieve corrosion protective coatings for 304 stainless steel were determined. The Nyquist plots demonstrate that the activation time of the coating containing 8- Hydroxyquinoline (8H) as an organic healing agent shows improved behavior when compared to other coatings including cerium and Benzotriazole. Cerium as an inorganic healing agent is second and Benzotriazole (BTA) is third and minimum. An increase in the impedance parameters such as resistance and capacitance as a function of immersion time is achieved in a 3.5 wt% NaCl solution by using healing agents such as Benzotriazole. Actually, over the course of immersion, the barrier performance behavior of the coatings changes and reduction of the impedance observed from the coatings containing Ce and 8- Hydroxyquinoline (8H) discloses deterioration of the protection system after immersion for 96 h of immersion in the 3.5% NaCl solution. However, after 96 h of immersion time, the concentration of chloride ions is high and cause to increasing defects, micro cracks and hole on surface of hybrid titania nanostructured coating containing Ce and 8- Hydroxyquinoline (8H) by destroyed of coating, and also hybrid titania nanostructured coating containing Benzotriazole, released Benzotriazole from coating cause to improve the resistance of passive film, which created on the surface.
