Hexacyanoferrate-Intercalated Layered Double Hydroxides as Nanoadditives for the Detection of Early-Stage Corrosion of Steel: The Revival of Prussian blue

This work describes the synthesis and characterization of Zn-Al and Mg-Al layered double hydroxides (LDHs) intercalated with hexacyanoferrate. X-ray diffraction, infrared spectroscopy and scanning electron microscopy indicated a successful intercalation of hexacyanoferrate in the sub-micrometer sized platelet-like particles. Release studies of hexacyanoferrate from LDHs found that the anion is released depending on the concentration of NaCl and under alkaline conditions. When placed in contact with carbon steel under corrosive conditions, the formation of Prussian blue was detected. Furthermore, the application of potentiodynamic polarization and electrochemical impedance spectroscopy revealed that hexacyanoferrate has a detrimental effect on the corrosion of carbon steel, while when intercalated in LDHs this effect is minimized. Overall, these findings open perspectives for the application of these materials as smart nanoadditives in coatings for corrosion detection.