Steel protection using sol-gel coatings in simulated concrete pore solution contaminated with chloride

This work compares the anticorrosion features of polysiloxane hybrid films deposited on carbon steel substrates by dip-coating. To assess the influence of the components, sol-gel coatings were prepared from condensation and polymerization of TEOS and MPTS, TEOS and MTES, TMOS and MPTS or TMOS and MTES mixtures in three molar ratios. The corrosion protection of the coatings was evaluated by means of polarization curves and electrochemical impedance spectroscopy measurements. The coatings' thickness was quantified by field emission-scanning electron microscopy. The results indicate that all the coatings improved the corrosion resistance of carbon steel in an alkaline environment contaminated with 3 wt.%NaCl solution and show that the protective properties of the coating were especially improved when MTES was added to the formulations and when the TMOS/MPTS mixture was used, probably due to a highly cross-linked network and a greater coating thickness, capable of delaying the corrosion process.