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)3.6H2O. 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

Evaluation of the corrosion inhibition performance of silane coatings filled with cerium salt-activated nanoparticles on hot-dip galvanized steel substrates

The present work investigates the morphological and electrochemical behavior of hot-dip galvanized (HDG) steel substrates that were pre-treated with 3-glycidoxypropyltrimethoxysilane (GPTMS) and bisphenol A (BPA) modified with cerium ion-activated CeO2 nanoparticles. The morphology of the coatings before and after the corrosion test was examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results indicated the formation of a comparatively smooth, nanostructured surface, with a small heterogeneity in the coating thickness. Microscopic observations also confirmed that the integral surface morphology of the silane coating filled with activated CeO2 nanoparticles was maintained after short-term corrosion tests (144 h). The corrosion behavior of the sol–gel coatings was investigated using natural salt spray tests, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests. The results showed that the presence of the nanoparticles reinforced the barrier properties of the silane films, and a synergy seemed to be created between the activated nanoparticles and the cerium ions, reducing the corrosion activity

Influence of the cerium concentration on the corrosion performance of Ce-doped silica hybrid coatings on hot dip galvanized steel substrates

The aim of this work was to investigate the effect of the cerium concentration on the morphology and anticorrosion performance of cerium-silane hybrid coatings on hot dip galvanized (HDG) steel substrates. 3-glycidoxypropyltrimethoxysilane (GPTMS) and bisphenol A (BPA) were employed as precursors to prepare the sol-gel based silane coating. Cerium nitrate hexahydrate was added to the silane coatings as dopant in five different concentrations. The morphology of the coatings before and after the corrosion test was examined by scanning electron microscopy (SEM), indicating an effect of the cerium concentration. Very low and very high cerium concentrations deteriorate the corrosion inhibition in the sol-gel matrix and consequently, there is an optimum concentration of cerium nitrate. Accelerated salt spray testing showed that corrosion near an artificial scratch is blocked efficiently by high cerium nitrate contents, whereas uniform corrosion is inhibited effectively with comparatively low ceria contents. Electrochemical studies indicate a general beneficial effect of the incorporation of cerium nitrate, although the performance of the coated substrate depends on the cerium nitrate content. The results of electrochemical impedance spectroscopy (EIS) and electrochemical polarization confirmed that the corrosion resistance of the coatings initially increases and then decreases as the cerium concentration goes up. Optimal corrosion resistance was obtained at a cerium concentration of 0.05 M

The corrosion resistance of 316L stainless steel coated with a silane hybrid nanocomposite coating

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Effects of activated ceria and zirconia nanoparticles on the protective behaviour of silane coatings in chloride solutions

This work investigates the effect of CeO2 and ZrO2 nanoparticles on the corrosion protection performance of non-inhibited and cerium inhibited silane coatings in 3.5% and 5% NaCl solutions on electro-galvanized steel substrates. Atomic force microscopy (AFM) results show relatively uniform coating thickness and varying nanoparticle distribution depending on coating composition. The corrosion behaviour of the sol–gel coatings revealed that CeO2-ZrO2 nanoparticles reinforce the barrier properties of the silane films and seem to act as nano-reservoirs providing a prolonged release of cerium ions. This prolonged release of inhibitor from oxide nanoreservoirs confers longer protection to the metallic substrate

Effects of ceria nanoparticle concentrations on the morphology and corrosion resistance of cerium-silane hybrid coatings on electro-galvanized steel substrates

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