Investigation of the protective effect of inorganic coating with corrosion inhibitor against deterioration of structural damages

Abstract

The most widely used method for the protection of reinforced concrete and masonry is through coatings, either inorganic or organic. Inorganic coatings based on water glass present various advantages, which are very important when used in old structures. Their microcrystalline texture results in admirably aesthetic appearance and the lower absorption of sun radiation causes no change of coloration, consequently when repainting it is not possible to distinguish between old and new coating. They do not flake off, build up algae or microorganisms or have organic solvents, hence bringing out pollution. Inorganic coatings also react chemically with the concrete surface strengthening the substrate, as opposed to organic coatings, which need a stable substrate. However, they are less protective against chloride diffusion and carbonation than organic coatings. For that reason, inorganic coatings are combined with three different corrosion inhibitors based on calcium nitrite, aminoalcohols and alkanolamines. All these inhibitors can be used either as admixtures or applied on the surface of the construction. For the evaluation of the performance of the coating and the inhibitors in the presence of chloride ions, the following methods were used: measurement of the corrosion potential and the mass loss of the reinforcing bars, measurement of the carbonation depth in the mortars and the strain gauge technique for corrosion measurements. Results proved that when the inorganic coating is combined with the corrosion inhibitors, particularly as admixtures, there is a significant protective effect followed by lower corrosion rate.