Combining the 8-hydroxyquinoline intercalated layered double hydroxide film and sol-gel coating for active corrosion protection of the magnesium alloy

8-hydroxyquinoline (8-HQ) intercalated layered double hydroxides (LDH) film as underlayer and sol-gel layer was combined for active corrosion protection of the AM60B magnesium alloy. The LDH, LDH/sol-gel, and LDH@HQ/sol-gel coatings were analyzed using the scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS) methods. The SEM images showed that the surface was entirely coated by the LDH film composed of vertically-grown nanosheets. The same morphology was observed for the LDH/sol-gel and LDH@HQ/sol-gel coatings. Also, almost the same topography was observed for both composite coatings except that the LDH@HQ/sol-gel coating had relatively higher surface roughness. Although the LDH film had the same impedance behavior as the alloy sample in 3.5wt% NaCl solution, its corrosion resistance was much higher, which could be due to its barrier properties as well as to the trapping of the chloride ions. Similar to the LDH film, the corrosion resistance of the LDH/sol-gel composite diminished with increasing the exposure time. However, its values were much higher than that of the LDH film, which was mainly related to the sealing of the solution pathways. The LDH@HQ/sol-gel composite showed much better anti-corrosion properties than the LDH/sol-gel coating due to the adsorption of the 8-HQ on the damaged areas through the complexation.

Automated summary

The combination of 8-hydroxyquinoline (8-HQ) intercalated layered double hydroxides (LDH) film and sol-gel layer can be used for active corrosion protection of magnesium alloy. The LDH film exhibits higher corrosion resistance, while the LDH@HQ/sol-gel composite shows better anti-corrosion properties.