Steel corrosion in simulated carbonated concrete pore solution its protection using sol–gel coatings

• The nature of the reagents had a greater influence than the molar ratio.
• TMOS/MTES hybrids were the most protective against corrosion in SCCP solution.
• These hybrids had a greater adherence to the steel and a branched structure.
• Molar ratio of 2 of this formulation showed the best anticorrosion properties.

The corrosion features of polysiloxane hybrid films deposited on carbon steel substrates by dip-coating are compared. Sol–gel coatings were prepared by condensation and polymerization of TEOS/MPTS, TEOS/MTES, TMOS/MPTS and TMOS/MTES mixtures in three molar ratios to assess the influence of their components. The corrosion protection of the coatings was evaluated by means of polarization curves and electrochemical impedance spectroscopy measurements. Coating thickness and composition were quantified by field emission scanning electron microscopy equipped with an EDX analyzer. The results show that all the coatings improved the corrosion resistance of carbon steel in a carbonated synthetic solution, with especially improved protective properties in the case of the TMOS/MTES mixture. These best properties could be due to a highly cross-linked network and greater adhesion to the metallic surface, restricting the corrosion attack.