Phosphate loaded layered double hydroxides for active corrosion protection of carbon steel

Layered double hydroxides (LDHs) can serve as corrosion inhibitor reservoirs. In the present work, hydrotalcite-like LDHs were synthesized and employed as host matrixes for the release of phosphate. The morphological and structural properties of the as-prepared LDH-PO4 were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The PO43- adsorption uptake was successfully confirmed by the XRD results. The corrosion resistance of the coating with LDH-PO4 was investigated by electrochemical impedance spectroscopy (EIS), which was approximately 1 order of magnitude higher than that of the blank coating after immersion for 168 h. Results of the scanning Kelvin probe technique revealed that the potential of LDH-PO4 coating was higher and smoother than that of the blank coating after exposure to 0.5 M NaCl solution. This effect is attributed to the release of PO43- that forms a phosphate protective film in the scratched region.