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Abstract
The protection of metals from their surrounding environment is usually achieved by deposition of protective coatings on the metal surface to establish a physical barrier against aggressive ions. The corrosion behaviour of hybrid organic–inorganic coatings for carbon steel embedded in carbonated ordinary Portland cement (OPC) and alkali activated fly ash (AAFA) mortars was studied, after different periods of immersion in a 3 wt.% sodium chloride solution using electrochemical techniques. Hybrid organic–inorganic films employed as protective coatings have been prepared via sol–gel using several silicon compounds: 3-methacryloxy-propyltrimethoxysilane or methyltriethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) precursors using a molar ratio of 1 and deposited on carbon steel substrates by dip-coating. The corrosion potential (Ecorr) values were higher and the current density (icorr) values were lower for AAFA mortars, indicating that the coatings were more efficient against rebar corrosion in this system than in OPC mortars. On the other hand, the hybrids synthesised with TEOS/MTES and TMOS/MTES for carbon steel embedded in carbonated AAFA mortars showed the lowest icorr values. This enhanced protection could be due to a structure denser and more compact and greater adhesion to the metallic surface.