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

Abstract 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.