Abstract
Double doped layered double hydroxide thin films were developed directly on the aluminum substrate in two steps: Initially cerium-based MgAl-layered double hydroxide (LDH) were synthesized directly on the anodic aluminum surface via the in situ growth method, and were then modified with the stearate anions through an ion-exchange mechanism to achieve compact multifunctional protective thin films. The structural and morphological characteristics of the developed LDH films were investigated, and the surface contact angle measurements (CA) and self-cleaning properties were analyzed. The obtained double doped LDH film displayed the superhydrophobic characteristic with a water contact angle of ~155°. Furthermore, the superhydrophobic behavior of LDH on exposure to UV radiation (λ = 310 nm) was examined to evaluate outdoor applications. Long-term Electrochemical Impedance Spectroscopy (EIS) analysis was performed to understand the corrosion resistance properties. The introduction of double doped LDHs demonstrates significantly higher corrosion resistance properties than only cerium-modified LDHs and has shown superior stability against 0.1 M NaCl solution.
Highlights
IntroductionIn recent years, layered double hydroxide (LDH)-based coating systems have been thoroughly investigated to substitute the traditional chromate coating systems in order to protect aluminum alloys [7,8]
A wide range of divalent metal cations was used to develop M-Al-layered double hydroxide (LDH) (M = Li, Ca, Mg, Zn, Ni, etc.) on the aluminum alloys, and the corrosion resistance properties were investigated for LiAl-LDHs [9], MgAl-LDHs [10], ZnAl-LDHs [11], CaAl-LDHs [12], NiAl-LDHs [13], where LDHs have shown the following key features: (a) Active protection due to LDH anion-exchange capabilities; (b) self-healing characteristics; and (c) barrier effect, which inhibits the diffusion of corrosive species to the underlying metal
MgAl-LDHs and Ce-LDHs showed hexagonal platelet structures intercalation of stearate groups induced considerable stress inside the framework and grown perpendicular to the substrate and distributed randomly on the surface
Summary
In recent years, layered double hydroxide (LDH)-based coating systems have been thoroughly investigated to substitute the traditional chromate coating systems in order to protect aluminum alloys [7,8]. A wide range of divalent metal cations was used to develop M-Al-LDH (M = Li, Ca, Mg, Zn, Ni, etc.) on the aluminum alloys, and the corrosion resistance properties were investigated for LiAl-LDHs [9], MgAl-LDHs [10], ZnAl-LDHs [11], CaAl-LDHs [12], NiAl-LDHs [13], where LDHs have shown the following key features: (a) Active protection due to LDH anion-exchange capabilities; (b) self-healing characteristics; and (c) barrier effect, which inhibits the diffusion of corrosive species to the underlying metal.
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