This study presents a novel approach to improving the anticorrosive performance of AZ31 Mg alloy by exploiting the role of the hydration reaction to induce interactions between Quinolin-8-ol (8HQ) molecules and the porous MgO layer formed via plasma electrolytic oxidation (PEO). The AZ31 Mg alloy, initially coated with a PEO layer, underwent a dipping treatment in an ethanolic solution of 0.05 M 8HQ at 50 ℃ for 3 h. The results were compared with those from a different procedure where the PEO layer was subjected to a hydration reaction for 2 h at 90 ℃ before immersion in the 8HQ solution under the same conditions. The hydration treatment played a crucial role by converting MgO to Mg(OH)₂, significantly enhancing the surface reactivity. This transformation introduced hydroxyl groups (−OH) on the surface, which facilitated donor-acceptor interactions with the electron-accepting sites on 8HQ molecules. The calculated binding energy (E_binding) from DFT indicated that the interaction energy of 8HQ with Mg(OH)₂ was lower compared to 8HQ with MgO, suggesting easier adsorption of 8HQ molecules on the hydrated surface. This, combined with the increased number of active sites and enhanced surface area, allowed for extensive surface coverage by 8HQ, leading to the formation of a stable, flake-like protective layer that sealed the majority of pores on the PEO layer. DFT calculations further suggested that the hydration treatment provided multiple active sites, enabling effective contact with 8HQ and rapid electron transfer, creating ideal conditions for charge-transfer-induced physical and chemical bonding. This study shows that hydration and 8HQ treatments significantly enhance the corrosion resistance of Mg alloys, highlighting their potential for advanced anticorrosive coatings.

The passivation of magnesium (Mg)-based alloys is an electrochemical behavior. The formation of a protective surface film results in passivation. The composition of this surface layer is influenced by the substrate alloy, which in turn affects the passive behavior. Recent studies have examined the composition of the surface film when Mg alloys undergo corrosion. Most of these studies have focused on the presence of Mg hydroxide (Mg(OH)₂) and MgO in the layer. However, a systematic examination of the impact of alloying elements on the stability of the passive layer is lacking. The essential question for developing a corrosion-resistant Mg-based alloy with passive protection is: which are the best and most efficient elements that can form a passive layer when alloyed with Mg? Passivity in a Mg alloy could be achieved by using a non-equilibrium technique to supersaturate the matrix phase with a high concentration of a strong passivating element. This review paper examines and explores the potential of creating a passive Mg-based alloy using metallurgical methods, like alloying and purification. Additionally, this paper explains key concepts about the passivity of Mg alloys and proposes possible methods to create a passive Mg alloy.

Advanced hybrid materials with unique properties are essential for addressing the demands of increasingly complex applications. Despite their importance, the self-assembly of layered double hydroxides (LDH) with metallic oxide nanoparticles and dicarboxylic acids is constrained by a limited understanding of the formation mechanisms and difficulties in evaluating their anticorrosive performance. In this study, we developed a novel anticorrosive system by intercalating CeNiLDH with a complex of vanadium pentoxide (V₂O₅) nanoparticles and (2E)-but-2-enedioic acid ((2E)-BDA) on a MgO layer created through plasma-electrolysis of AZ31 Mg alloy. This system was compared with LDH films intercalated with either V₂O₅ or (2E)-BDA alone. The intercalation of LDH with V₂O₅ and (2E)-BDA resulted in a flower-like structure, while modification with their complex led to a more compact, cloud-like formation. These cloud-like structures, driven by enhanced absorption and robust hydrogen bonding throughout the hierarchical network, effectively suppress corrosion by delaying the movement of corrosive anions. This was reflected in a polarization resistance of 1.51 × 10¹⁰ Ω·cm², which is approximately two orders of magnitude times higher than the resistance of the unmodified LDH film (3.41 × 10⁸ Ω·cm²). Additionally, the corrosion current density (i_corr) of the VOBDA sample showed a decrease by four orders of magnitude compared to the unmodified LDH sample, emphasizing the superior anticorrosive performance of this hybrid coating. Density functional theory (DFT) was used to elucidate the bonding and formation mechanisms between LDH and the inorganic-organic complex.

Corrosion is a pervasive phenomenon affecting materials across a multitude of scales, from the atomic to the macroscopic. This review paper presents a comprehensive examination of the methodologies employed in the analysis of magnesium corrosion, including electrochemical, non-electrochemical and analytical approaches, emphasizing the need for a diverse array of analytical tools to understand the complex interplay between corrosion, microstructure, and the dissolution mechanisms of magnesium alloys. The research showcases the utility of specific tools like SEM/EDS and SKPFM for targeted site analysis, while XPS and FTIR provide a broader perspective on specimen surfaces. The paper also discusses the value of in-situ analysis techniques, which allow for the real-time observation of corrosion processes, offering a dynamic view of the emergence and evolution of corrosion products. These in-situ methods stand in contrast to ex-situ analyses, which only permit post-experimental evaluation. By highlighting the capabilities of various analytical tools, from those that reveal surface layer details to those that probe deeper structures, and from those that detect primary elements to those that trace minute quantities of impurities, this study underscores the intricate nature of corrosion and the critical role of advanced analytical techniques in fostering a deeper understanding of material degradation. The findings advocate for the increased application of in-situ analysis in magnesium corrosion research, as it provides a more immediate and accurate depiction of corrosion dynamics, potentially leading to more effective corrosion prevention and control strategies.

The difficulty in achieving a balance between photocatalytic efficiency and chemical robustness has been a barrier to the broad use of MgO as a versatile material, mainly because of its restricted surface activity. To overcome this, a novel surface modification technique is proposed. It involves the integration of highly stable SnO₂ and WO₃ nanoparticles, which are known to enhance surface activity. This approach aims to achieve an optimal balance between efficiency and stability by finely tuning the structure-surface reactivity relationship. The technique utilizes a plasma electrolytic oxidation (PEO) method. In this method, both the AZ31 Mg alloy substrate and SnO₂/WO₃ precursors undergo simultaneous oxidation. This is induced by high-energy plasma generated through high voltage. The results demonstrate that this process yields a MgO layer with a homogeneous dispersion of SnO₂ and WO₃ nanoparticles, significantly enhancing its overall performance. Corrosion measurements demonstrated enhanced electrochemical stability against chloride ions. The dual incorporation resulted in a hybrid film exhibiting a corrosion current density value of 7.57 × 10⁻¹¹ A/cm² and a high outer layer resistance of 5.17 × 10⁷ Ω.cm². Additionally, the dual incorporation of SnO₂ and WO₃ nanoparticles enhances the photocatalytic activity of AZ31 Mg towards tetracycline degradation. This results in a photocatalytic efficiency of 89.54% within 2 h of exposure to visible light using the BA-W-Sn sample, which outperforms other samples. This integrated strategy enables the study to contribute significantly to expanding the practical applications of MgO-based materials. It does so by simultaneously enhancing their photocatalytic activity and chemical stability.

Magnesium (Mg) is a widely used and attractive metal, known for its unique physical and chemical properties, and it has been employed in the manufacture of many practical materials. Layered Double Hydroxides (LDHs), particularly Mg-based LDHs, rank among the most prevalent two-dimensional materials utilized in separation processes, which include adsorption, extraction, and membrane technology. The high popularity of Mg-based LDHs in separation applications can be attributed to their properties, such as excellent hydrophilicity, high surface area, ion exchangeability, and adjustable interlayer space. Currently, polymer membranes play a pivotal role in semi-industrial and industrial separation processes. Consequently, the development of polymer membranes and the mitigation of their limitations have emerged as compelling topics for researchers. Several methods exist to enhance the separation performance and anti-fouling properties of polymer membranes. Among these, incorporating additives into the membrane polymer matrix stands out as a cost-effective, straightforward, readily available, and efficient approach. The use of Mg-based LDHs, either in combination with other materials or as a standalone additive in the polymer membrane matrix, represents a promising strategy to bolster the separation and anti-fouling efficacy of flat sheet mixed matrix polymer membranes. This review highlights Mg-based LDHs as high-potential additives designed to refine flat sheet mixed matrix polymer membranes for applications in wastewater treatment and brackish water desalination.

Magnesium (Mg) alloys are lightweight materials with excellent mechanical properties, making them attractive for various applications, including aerospace, automotive, and biomedical industries. However, the practical application of Mg alloys is limited due to their high susceptibility to corrosion. Plasma electrolytic oxidation (PEO), or micro-arc oxidation (MAO), is a coating method that boosts Mg alloys' corrosion resistance. However, despite the benefits of PEO coatings, they can still exhibit certain limitations, such as failing to maintain long-term protection as a result of their inherent porosity. To address these challenges, researchers have suggested the use of inhibitors in combination with PEO coatings on Mg alloys. Inhibitors are chemical compounds that can be incorporated into the coating or applied as a post-treatment to further boost the corrosion resistance of the PEO-coated Mg alloys. Corrosion inhibitors, whether organic or inorganic, can act by forming a protective barrier, hindering the corrosion process, or modifying the surface properties to reduce susceptibility to corrosion. Containers can be made of various materials, including polyelectrolyte shells, layered double hydroxides, polymer shells, and mesoporous inorganic materials. Encapsulating corrosion inhibitors in containers fully compatible with the coating matrix and substrate is a promising approach for their incorporation. Laboratory studies of the combination of inhibitors with PEO coatings on Mg alloys have shown promising results, demonstrating significant corrosion mitigation, extending the service life of Mg alloy components in aggressive environments, and providing self-healing properties. In general, this review presents available information on the incorporation of inhibitors with PEO coatings, which can lead to improved performance of Mg alloy components in demanding environments.

This study presents a facile and rapid method for synthesizing novel Layered Double Hydroxide (LDH) nanoflakes, exploring their application as a photocatalyst, and investigating the influence of condensed phosphates' geometric linearity on their photocatalytic properties. Herein, the MgO film, obtained by plasma electrolysis of AZ31 Mg alloys, was modified by growing an LDH film, which was further functionalized using cyclic sodium hexametaphosphate (CP) and linear sodium tripolyphosphate (LP). CP acted as an enhancer for flake spacing within the LDH structure, while LP changed flake dispersion and orientation. Consequently, CP@LDH demonstrated exceptional efficiency in heterogeneous photocatalysis, effectively degrading organic dyes like Methylene blue (MB), Congo red (CR), and Methyl orange (MO). The unique cyclic structure of CP likely enhances surface reactions and improves the catalyst's interaction with dye molecules. Furthermore, the condensed phosphate structure contributes to a higher surface area and reactivity in CP@LDH, leading to its superior photocatalytic performance compared to LP@LDH. Specifically, LP@LDH demonstrated notable degradation efficiencies of 93.02%, 92.89%, and 88.81% for MB, MO, and CR respectively, over a 40 min duration. The highest degradation efficiencies were observed in the case of the CP@LDH sample, reporting 99.99% for MB, 98.88% for CR, and 99.70% for MO. This underscores the potential of CP@LDH as a highly effective photocatalyst for organic dye degradation, offering promising prospects for environmental remediation and water detoxification applications.

Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite (HAp) has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.

A novel inorganic-organic layer with outstanding corrosion resistance in a 3.5wt.% NaCl solution was fabricated by taking advantage of the unique interactions between coumarin (COM) molecules and the porous layer formed on Mg alloy. To achieve this aim, the AZ31 Mg alloy coated via microarc oxidation (MAO) coating was placed in an ethanolic solution of COM for 6 and 12 h at 25 ℃. By reducing the surface area exposed to the corrosive species, the donor-acceptor complexes produced by the particular interactions between the COM and MAO surface would successfully prevent the corrosion of Mg alloy substrate. The MAO layer would provide the ideal sites for the charge-transfer-induced physical and chemical locking, leading to uneven organic layer nucleation and crystal growth with a thatch-like structure. To evaluate the formation mechanism of such hybrid composites and highlight the key bonding modes between the COM and MAO, theoretical simulations were conducted.