Novel Ca-SLS-LDH nanocomposites obtained via lignosulfonate modification for corrosion protection of steel bars in simulated concrete pore solution

Abstract

A novel nanocomposite (Ca-SLS-LDH) of Ca-Al-layered double hydroxides (Ca-LDH) modified with sodium lignosulfonate (SLS) was synthesized using hydrothermal synthesis method. Mechanistically, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analysis revealed that SLS modified the nanocomposite by adsorbing onto the surface of Ca-LDH. The specific surface area of Ca-SLS-LDH was larger and the average particle size was smaller than that of Ca-LDH. This enabled the Ca-SLS-LDH to bind chlorides more effectively and is hence suitable for application in reinforced concrete. Ca-SLS-LDH binds to chlorides through ion exchange and surface adsorption, which is similar to the binding mechanism of Ca-LDH to chlorides.Ca-SLS-LDH efficiently controlled the corrosion of carbon steel in simulated concrete pore (SCP) solution and had a stronger inhibitory effect compared to unmodified LDHs at equal concentrations. Ca-SLS-LDH improved the resistance to corrosion by binding more chlorides in SCP solution. In addition, it may be due to the anti-corrosion effect of SLS on steel bars, thereby delaying the initiation of corrosion.