Electrochemical Assessment of the Self-Healing Properties of Cerium Doped Sol-Gel Coatings on 304L Stainless Steel Substrates

The present work aims at assessing the corrosion behavior of 304L stainless steel substrates pre-treated with 3-glicidoxypropyltrimethoxy silane (GPTMS) solutions modified with cerium nitrate or cerium oxide nanoparticles. Furthermore, the work aims at evaluating the self-healing properties of the dopant in intact and artificially scratched silane films via natural salt spray tests, electrochemical impedance spectroscopy (EIS) and d.c. potentiodynamic polarization. The morphological features of the coated substrates were evaluated by atomic force microscopy (AFM) and optical microscopy. The results confirmed the formation of transparent cerium modified sol-gel films without any defect and cracks and revealed the formation of a comparatively smooth nanostructure surface with a small heterogeneity in coating thickness in the sol-gel coatings modified with Ce(NO3)(3)center dot 6H(2)O. Corrosion tests indicated that the CeO2 nanoparticles have good corrosion inhibition properties on scratched surfaces due to their ability to complex other species, therefore contributing for the stabilization of the passive film. In this way, these particles display an anodic inhibition mechanism. It was found that the positive impact, both in the barrier properties and corrosion inhibition, was significantly improved by modifying the silane solution with cerium nitrate. Presence of cerium nitrate, reinforces the barrier properties of the silane films, reducing the corrosion activity and self-healing the corroded areas.