LDH conversion films for active protection of AZ31 Mg alloy
B. Pillado (Universidad Complutense de Madrid)
B. Mingo (The University of Manchester)
R. del Olmo (Military University of Technology, Universidad Complutense de Madrid)
E. Matykina (Universidad Complutense de Madrid)
Agnieszka Kooijman (TU Delft - Team Arjan Mol)
Yaiza Gonzalez Gonzalez Garcia (TU Delft - Team Yaiza Gonzalez Garcia)
R. Arrabal (Universidad Complutense de Madrid)
M. Mohedano (Universidad Complutense de Madrid)
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Abstract
Zinc aluminium (Zn-Al) and lithium aluminium (Li-Al) – layered double hydroxides (LDH) coatings with incorporated inhibitors (Li−, Mo− and W−based) were successfully synthesized on AZ31 Mg alloy. Zn−Al LDH W and Li−Al LDH Li showed the highest corrosion resistance and were selected for further evaluation. SEM cross−section examination revealed a bi−layer structure composed of an outer part with loose flakes and a denser inner layer. XRD, FTIR, and XPS analysis confirmed the incorporation of the inhibitors. Post−treatments with corrosion inhibitors containing solutions resulted in the selective dissolution of the most external layer of the LDH coating, reducing the surface roughness, hydrophilicity and paint adhesion of the layers. Active corrosion properties were confirmed by SVET evaluation for the Zn−Al LDH W coating. The proposed active corrosion mechanism involves the ion−exchange of aggressive Cl− ions, deposition of hydroxides and competitive adsorption of W−rich corrosion inhibitors.
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