Key Takeaways & Executive Findings
- •• A novel LDH-W/PFDTMS composite coating on Mg alloy provides superior corrosion resistance, with no corrosion signs after 15 days in 3.5 wt% NaCl solution. • The coating exhibits excellent superhydrophobicity and self-cleaning properties against water and common beverages, confirmed by contact angle and water-repellency tests. • The synthesis method is mild (low temperature, atmospheric pressure) and simple, offering a cost-effective approach for Mg alloy protection. • The study demonstrates the potential of LDH-based composite coatings as environmentally friendly alternatives to traditional chromate coatings.
Abstract
We have developed a superhydrophobic and corrosion-resistant LDH-W/PFDTMS composite coating on the surface of Mg alloy. This composite comprised a tungstate-intercalated (LDH-W) underlayer that was grown at low temperature (relative to hydrothermal reaction conditions) under atmospheric pressure and an outer polysiloxane layer created from a solution containing perfluorodecyltri-methoxysilane (PFDTMS) using a simple immersion method. The successful intercalation of tungstate into the LDH phase and the following formation of the polysiloxane layer were confirmed through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the LDH-W film, both before and after the PFDTMS modification, was evaluated using electrochemical impedance spectroscopy (EIS), Tafel curves, and immersion experiments. The results showed that Mg coated with LDH-W/PFDTMS exhibited significantly enhanced corrosion protection compared to the unmodified LDH-W film, with no apparent signs of corrosion after exposure to 3.5wt% NaCl solution for 15 d. Furthermore, the LDH-W/PFDTMS coating demonstrated superior superhydrophobicity and self-cleaning properties against water and several common beverages, as confirmed by static contact angle and water-repellency tests. These results offer valuable insights into preparing superhydrophobic and corrosion-resistant LDH-based composite coatings on Mg alloy surfaces under relatively mild reaction conditions.
1. Introduction
Mg alloys are notable for their excellent physicochemical properties, making them popular in various industries, including automotive [1–2], aerospace [3–5], electronics [6–7], and biomedical [1–3]. Despite their advantages, their low corrosion potentials (−1.5 V vs. SHE (standard hydrogen electrode)) render them highly susceptible to corrosion, limiting their wider application. Designing suitable surface coatings is an effective way to suppress corrosion. Common surface treatments for Mg alloys mainly include chemical conversion films [4–8], metal plating [9–11], micro-arc oxidation [12–17], and organic coatings [18–20]. Among these, layered double hydroxides (LDHs) have attracted much attention recently owing to their environmental friendliness, low cost, and simple preparation process, positioning them as potential alternatives to traditional, carcinogenic chromate coatings.
However, LDH layers inherently contain micro/nanopores that can act as diffusion channels for aqueous corrosive agents, thereby requiring appropriate post-treatment to enhance corrosion resistance. A typical method involves the deposition of additional layers onto the LDH surface to fill and seal these pores. For example, Ni–P alloys have been used to fill the porous structure of the LDH film, while organic layers have been applied to cover the microdefects on the LDH surface [21–22]. Superhydrophobic surfaces offer an effective method for improving corrosion protection through their outstanding self-cleaning and water-repellency capabilities, which prolong the penetration of corrosive media to the metal substrate [23–24]. Typical superhydrophobic coatings exhibit micro/nanorough structures with a low surface energy [25]. Although numerous methods for preparing such coatings have been reported, most emphasize the micro/nanorough structure and low surface energy. For example, composite coatings prepared by spraying SiO2-modified polydimethylsiloxane on the microarc oxidized coating have demonstrated sustained superhydrophobicity in acid, alkali, high/low temperature, and UV radiation exposure, leading to impressive corrosion resistance in neutral solutions [26]. Another approach involved the development of dodecyltrimethoxysilane-modified Mg(OH)2 superhydrophobic coating through electrodeposition, reaching a contact angle of (165.1 ± 2.1)° and decreasing the corrosion current density by three orders of magnitude compared to that of the uncoated AZ31 Mg alloy [27]. The LDH film comprises many perpendicularly grown nanosheets and exhibits a micro/nanoscale rough structure. The post-treatment process for pore closure should mainly focus on imparting low surface energy to the coating. Silanization is a low-cost and effective method for achieving low surface energies in coatings. During this process, silanol groups (Si–OH) generated by ...
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Wenxi Zhang, Zhangzelong Zhuo, Dan Xu, Liang Wu, Zhihui Xie (2025). Superhydrophobic and corrosion-resistant siloxane-modified MgAl–LDHs coatings on magnesium alloy prepared under mild conditions. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-2927-3
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Frequently Asked Questions
What is the main innovation of this study?
The study develops a superhydrophobic and corrosion-resistant LDH-W/PFDTMS composite coating on Mg alloy using mild conditions (low temperature and atmospheric pressure), which significantly enhances corrosion resistance and provides self-cleaning properties.
How was the corrosion resistance evaluated?
Corrosion resistance was evaluated using electrochemical impedance spectroscopy (EIS), Tafel curves, and immersion experiments in 3.5 wt% NaCl solution for 15 days.
What are the key properties of the LDH-W/PFDTMS coating?
The coating exhibits superior superhydrophobicity, self-cleaning properties, and significantly enhanced corrosion protection compared to unmodified LDH-W film.
Why is the mild preparation condition important?
Mild conditions (low temperature and atmospheric pressure) make the synthesis process simpler, more energy-efficient, and more practical for industrial application compared to traditional hydrothermal methods.
What is the significance of using LDH-based coatings?
LDH-based coatings are environmentally friendly, low-cost, and simple to prepare, offering a potential alternative to carcinogenic chromate coatings for Mg alloy corrosion protection.
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