Self-healing silane coatings of cerium salt activated nanoparticles

This work investigates the effect of cerium salt activated nanoparticles as nanoreservoirs on the self-healing properties of silane hybrid coatings deposited on electro-galvanized steel substrates. The substrates were pre-treated with 3–glycidoxypropyl-trimethoxysilane (GPTMS) and bisphenol A (BPA), modified with cerium ion-activated CeO2-ZrO2 and CeO2-SiO2 nanoparticles. The morphology of the coating before corrosion tests was examined using atomic force microscopy (AFM). The results indicate the formation of nanostructured surfaces with relatively uniform dispersion of nanoparticles in the silane coating containing CeO2-ZrO2 nanoparticles. The corrosion behavior of the sol-gel coatings was also investigated using salt spray tests, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests. During the salt spray test, the samples are exposed 600 h (or 25 days), revealing the improved resistance of the coated substrate containing CeO2-ZrO2 nanoparticles. Incorporation of activated CeO2-ZrO2 nanoparticles reduces the cathodic and anodic current density by one order of magnitude and shifts the corrosion potential to more positive values compared with the coating containing CeO2-SiO2 nanoparticles. Also, the EIS test results revealed higher impedance for the coating containing activated CeO2-ZrO2 nanoparticles. Corrosion tests results suggest that the activated CeO2-ZrO2 nanoparticles are more effective as nano-structured cerium ion reservoirs and can provide prolonged release of the inhibitor ions.