Evaluation of Corrosion Inhibition of NO_(2)^(-) Intercalated LDHs on Steel Coated by Cement Paste

The purpose of this study is to apply the steel coated by cement paste to evaluate the corrosion inhibition of NO_(2)^(-) intercalated Mg-Al layered double hydroxides(LDHs),which was prepared by a conventional calcination-rehydration method.The chloride equilibrium isotherm,open-circuit potential(OCP)and electrochemical impedance spectroscopy(EIS)of steel in the saturated Ca(OH)_(2) solution contaminated by chloride ions were measured.The microstructures of as-obtained LDHs and cement paste containing the LDHs were observed by scanning electron microscope(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and mercury intrusion porosimetry(MIP).It is found that the technique using the steel coated by the cement paste layer containing the LDHs to represent the steel in real concrete can be applied to accurately evaluate the corrosion inhibition performance of NO_(2)^(-) intercalated LDHs in a short duration.The addition of NO_(2)^(-) intercalated Mg-Al LDHs can improve the absorption capacity of Cl^(-) and the anti-corrosion property of cement paste layer.The combination actions of the refinement of pore structure,uptake of chloride ions and release of inhibitive NO_(2)^(-) contribute to the better corrosion protection property of cement paste layer.Moreover,a schematic mechanism of chloride intrusion for the steel specimen with cement paste layer is developed.