Abstract
A super-hydrophobic anti-corrosion film was facilely prepared via in situ growth of layered double hydroxides (LDHs) on the etched AZ31 magnesium alloy and then modification by 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane (PFOTMS) in this work. The morphology, structure, composition, surface roughness and water contact angles (WCA), and the anti-corrosion performance of the samples were investigated. The results revealed that the micro/nano hierarchical surface morphology of the films was composed of island structures obtained after chemical etching and MgAl-LDH nanowalls grown in situ. The best hydrophobicity (CA = 163°) was obtained on the MgAl-LDHs with the maximum surface roughness. Additionally, the potentiodynamic polarization, electrochemical impedance spectroscopy, and immersion test indicated that the super-hydrophobic LDH films provided better corrosion resistance to AZ31 magnesium alloy due to the double-protection derived from the LDHs and super-hydrophobic properties. Furthermore, the contact angle could be kept at above 140° after dipped in 3.5 wt% NaCl solution for 6 days.
Highlights
Magnesium alloys have been applied in automotive, aerospace fields, and military equipment on a large scale because of low density, high thermal conductivity, good electromagnetic shielding, and easy recyclability (Xie et al, 2018; Yao et al, 2020; Yang et al, 2021)
The results demonstrated that the superhydrophobic layered double hydroxides (LDHs) films improved significantly the corrosion resistance of Mg alloy and displayed excellent stability of super-hydrophobicity in corrosive liquid
The hexagonal plate-like LDH nanosheets grown on the surface of AZ31 Mg alloy were observed in SEM images of the high resolution
Summary
Magnesium alloys have been applied in automotive, aerospace fields, and military equipment on a large scale because of low density, high thermal conductivity, good electromagnetic shielding, and easy recyclability (Xie et al, 2018; Yao et al, 2020; Yang et al, 2021). It has been reported that these above methods needed to use expensive equipment, and the formed coatings showed a porous structure This coatings prepared via the above methods only can provide a passive physical barrier function (Bocchetta et al, 2021), which cannot significantly improve the corrosion resistance. Wang and co-workers (Wang et al, 2020) obtained the load-inhibitors MgAl-LDH films on the porous anodized Mg alloys via in situ growth method and post-sealing it by a super-hydrophobic coating, showing active corrosion protection property. LDH nanosheets was formed on etched AZ31 surface by in situ hydrothermal crystallization method, which provided a micro/ nanostructure for the preparation of super-hydrophobic surface. The results demonstrated that the superhydrophobic LDH films improved significantly the corrosion resistance of Mg alloy and displayed excellent stability of super-hydrophobicity in corrosive liquid
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