Enhancement corrosion resistance of Mg-Al layered double hydroxides films by anion-exchange mechanism on magnesium alloys

This investigation describes synthesis and anion exchange of Mg-Al layered double hydroxides (LDHs), with the aim of achieving fabrication and clarifying the enhancement anti-corrosion properties of LDHs composite films on the magnesium alloys. Herein Mg-Al-NO3 LDHs films on the magnesium alloy substrate were fabricated by facile hydrothermal method. Tungstate anions (WO32-) and DL-methionine (Met) anions were intercalated into the LDHs interlayer by virtue of the anion-exchange reaction. The characterization of Mg-Al-NO3 LDHs, LDHs-WO3 and LDHs-Met through employing X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared (FT-IR). The smart release ability of the inhibitive spices from LDHs were examined by polarization, EIS and mass loss tests in 3.5 wt% NaCl solution. The result demonstrates that the magnesium alloy could be effectively protected by the Mg-Al-NO3 LDHs, LDHs-WO3 and LDHs-Met films. The reason is that due to the formed LDHs film itself acts as a good barrier, coupled with the anion exchange capacity of the LDHs films, they can capture a part of the chloride ions and release the inhibitive anion to form Mg compounds accumulation on the surface defects.