Enhancing corrosion resistance in reinforced concrete structures by using innovative eco-friendly composite pigments

Abstract

This is the first study to look into the use of modified feldspars as anticorrosive pigments in the coatings industry. Herein, novel anticorrosive composite pigments were prepared by the chemical deposition of thin films of different oxides (e.g., zinc oxide and vanadium oxide with doloresite phase) on the surface of feldspar, which comprises 80% of the whole structure. A new vanadium oxide (e.g., doloresite) was chosen due to its IV oxidation state and excellent anticorrosive characteristics. ZnO is also well-known for its high resistance to corrosion. Firstly, the synthesis of the composite pigments was done, and then, they were characterized via XRD, SEM/EDX, XRF, and TGA. The composite pigments were incorporated into solvent-based epoxy coatings to evaluate their anticorrosive performance on reinforced concrete steel. Their corrosion resistances were determined using linear polarization resistivity and electrochemical impedance spectroscopy techniques. The physico-mechanical properties of the dry coats containing the prepared composite pigments were also evaluated. The results revealed that the polarization resistivity (Rpo) of coatings containing Zn/F ranged from 5900 to 3900 Ohm.cm2 and that of V/F ranged from 7077 to 5500 Ohm.cm2, while the resistivity of uncoated rebar was from 1900 to 1300 Ohm.cm2. These results confirm that these novel pigments (e.g., ZnO/feldspar and doloresite/feldspar) could provide high corrosion resistivity for concrete structures that are immersed in chloride-laden environments. These composite pigments will be eco-friendly with a low impact on humans and the environment as they contain very low concentrations of heavy metals, besides their high efficiency and economic feasibility.