Mg-Al layered double hydroxide as surface pretreatment for applying organic coating on AZ31 Mg alloy

R. Malekkhouyan1, M. Olivier1,2

1Materials Science Department, UMONS-University of Mons
2Materia Nova asbl

Mg-Al layered double hydroxide (Mg-Al/LDH) was synthesized on the surface of an anodized AZ31 Mg alloy substrate via in-situ hydrothermal treatment. Morphology, chemical composition, and crystalline structure were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The corrosion resistance of the coatings was investigated by H2 evolution, salt spray, and electrochemical impedance spectroscopy (EIS). LDH was synthesized as the surface pretreatment method for applying organic coating on the substrate. Therefore, the epoxy coating was applied on the LDH sample for assessing the compatibility and effectiveness of LDH on the corrosion properties of the substrate. The corrosion resistance of the LDH/epoxy on the substrate was investigated by EIS and salt spray tests. The layered and crystalline structure of LDH as well as the improved corrosion resistance of the substrate (with LDH) was observed in the SEM micrographs, XRD diagrams, and electrochemical tests, respectively. The results related to the LDH/epoxy samples revealed enhanced corrosion protection of the coating due to the synergic effect of LDH and epoxy coating on the substrate. The figure below explains the procedure used for preparation of samples.