Chloride removal and corrosion inhibitions of nitrate, nitrite-intercalated Mg Al layered double hydroxides on steel in saturated calcium hydroxide solution

Abstract

Abstract The aim of this study is to evaluate the chloride removal and corrosion inhibitions of NO3−, NO2− intercalated Mg Al layered double hydroxides (LDH) on steel in saturated calcium hydroxide solution by a comparative experiment. Mg-Al-LDH intercalated with NO2− was synthesized by anion exchange in the host material, Mg-Al-NO3 LDH, which was prepared by a coprecipitation method. The chloride equilibrium isotherm, corrosion potential and polarization resistance of steel (decided by electrochemical impedance spectroscopy (EIS)) in the solution were measured. Besides, scanning electron microscopy (SEM), X-ray diffraction instrument (XRD) and infrared spectroscopy were applied to observe the morphologies and microstructures of LDH. The results indicate that the LDH intercalated with NO3−, NO2− have excellent chloride removal capacities. Compared to LDH-NO3, the maximum chloride uptake amount for LDH-NO2 is relatively lower. However, the corrosion of steel for LDH-NO2 has a higher chloride threshold level. The dual effects, i.e., the uptake of chloride ion as an absorbent and the release of NO2− ions as an inhibitor, contribute to the better inhibition effect for LDH-NO2.