Abstract
Hybrid sol-gel coatings, named U(X):TEOS, based on ureasilicate matrices (U(X)) enriched with tetraethoxysilane (TEOS), were synthesized. The influence of TEOS addition was studied on both the structure of the hybrid sol-gel films as well as on the electrochemical properties. The effect of TEOS on the structure of the hybrid sol-gel films was investigated by solid state Nuclear Magnetic Resonance. The dielectric properties of the different materials were investigated by electrochemical impedance spectroscopy. The corrosion behavior of the hybrid coatings on HDGS was studied in chloride-contaminated simulated concrete pore solutions (SCPS) by polarization resistance measurements. The roughness of the HDGS coated with hybrids was also characterized by atomic force microscopy. The structural characterization of the hybrid materials proved the effective reaction between Jeffamine® and 3-isocyanate propyltriethoxysilane (ICPTES) and indicated that the addition of TEOS does not seem to affect the organic structure or to increase the degree of condensation of the hybrid materials. Despite the apparent lack of influence on the hybrids architecture, the polarization resistance measurements confirmed that TEOS addition improves the corrosion resistance of the hybrid coatings (U(X):TEOS) in chloride-contaminated SCPS when compared to samples prepared without any TEOS (U(X)). This behavior could be related to the decrease in roughness of the hybrid coatings (due TEOS addition) and to the different metal coating interaction resulting from the increase of the inorganic component in the hybrid matrix.
Highlights
Corrosion of reinforcement is one of the major causes of damage of reinforced concrete structures (RCS) worldwide [1,2,3,4,5,6]
Structural features of the hybrid materials were investigated by multinuclear solid state Nuclear Magnetic Resonance (NMR)
13C CPMAS spectra of the hybrid samples with and without TEOS are shown in Figure 4 and the Structural features of the hybrid materials were investigated by multinuclear solid state NMR
Summary
Corrosion of reinforcement is one of the major causes of damage of reinforced concrete structures (RCS) worldwide [1,2,3,4,5,6]. The durability requirements, in harsh environments such as marine and industrial, are not always achieved [5,7,8,9,10]. The major causes for corrosion of reinforcement in concrete are carbonation of concrete due to concrete acidification after reaction with atmospheric carbon dioxide, and/or the presence of chloride ions. Chloride ions can penetrate the porous structure of concrete and reach the steel [6]. A recurrent malpractice is the use of chloride-contaminated coarse aggregates and water constituents leading to the presence of chloride ions in the concrete since the beginning [11,12].
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