ATR-FTIR in Kretschmann configuration integrated with electrochemical cell as in situ interfacial sensitive tool to study corrosion inhibitors for magnesium substrates

Titanium-based hybrid coatings grown using ALD/MLD onto AZ31 screw-like supports for implantable systems

Atomic/molecular layer deposition (ALD/MLD) is ideally suited for addressing the challenges faced by the new generation biomedical technologies through surface and interface modification with organic-inorganic hybrid coatings, which are emerging as an alternative to inorganic coatings. In this study, we present a feasible strategy for modifying the surface of magnesium alloy (AZ31) screw-like substrates with titanium-based hybrid coatings, using titanium tetraisopropoxide as the metal-bearing precursor, and a simple aliphatic bi-functional alcohol, such as ethylene glycol, as the organic precursor. Results demonstrated that the titanium-based hybrid coating was evenly distributed without obvious defects on the AZ31 screw-like substrates while providing physical protection. In addition, the cytocompatibility of the titanium-based hybrid coating was validated through the cytotoxicity assay, revealing its potential for future biomedical applications.

Carbon dots on LAPONITE® hybrid nanocomposites: solid-state emission and inter-aggregate energy transfer

This study delves into the photoluminescent characteristics of solid-state hybrid carbon dots/LAPONITE® (CDLP). These hybrid materials were synthesized using the hydrothermal method with a precise pH control set at 8.5. The LAPONITE® structure remains intact without structural collapse, and we detected the possible deposition of carbon dots (CDs) aggregates on the clay mineral's edges. The use of different concentrations of citric acid (10-, 6-, 2- and 1-times weight/weight of LAPONITE® mass, maintaining the 1 : 1 molar ratio with ethylenediamine) during synthesis results in different CDs concentrations in CDLP-A (low precursors concentration) and CDLP-D (high concentration) with an amorphous structure and average size around 2.8-3.0 nm. The CDLP displayed visible photoluminescence emission in aqueous and powder, which the last underwent quenching according to lifetimes and quantum yield measurements. Low-temperature measurements revealed an enhancement of the non-radiative pathways induced by aggregation. Energy transfer modelling based on Förster-Dexter suggests an approximate mean distance of 9.5 nm between clusters of CDs.

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys-A Review: Part III-Corrosion Inhibitors and Combining Them with Other Protection Strategies

Owing to the unique active corrosion protection characteristic of hexavalent chromium-based systems, they have been projected to be highly effective solutions against the corrosion of many engineering metals. However, hexavalent chromium, rendered a highly toxic and carcinogenic substance, is being phased out of industrial applications. Thus, over the past few years, extensive and concerted efforts have been made to develop environmentally friendly alternative technologies with comparable or better corrosion protection performance to that of hexavalent chromium-based technologies. The introduction of corrosion inhibitors to a coating system on magnesium surface is a cost-effective approach not only for improving the overall corrosion protection performance, but also for imparting active inhibition during the service life of the magnesium part. Therefore, in an attempt to resemble the unique active corrosion protection characteristic of the hexavalent chromium-based systems, the incorporation of inhibitors to barrier coatings on magnesium alloys has been extensively investigated. In Part III of the Review, several types of corrosion inhibitors for magnesium and its alloys are reviewed. A discussion of the state-of-the-art inhibitor systems, such as iron-binding inhibitors and inhibitor mixtures, is presented, and perspective directions of research are outlined, including in silico or computational screening of corrosion inhibitors. Finally, the combination of corrosion inhibitors with other corrosion protection strategies is reviewed. Several reported highly protective coatings with active inhibition capabilities stemming from the on-demand activation of incorporated inhibitors can be considered a promising replacement for hexavalent chromium-based technologies, as long as their deployment is adequately addressed.

Organo-metallic electrolyte additive for regulating hydrogen evolution and self-discharge in Mg–air aqueous battery

Metal–air battery with cutting-edge electrolyte modification technologies.

Na2SnO3 functions as outstanding magnesium alloy passivator by synergistic effect with trace carboxymethyl chitosan for Mg–air batteries for standby protection

Coordination of Na2SnO3 with trace carboxymethyl chitosan contributes to standby protection and high utilization efficiency of the AZ61 anode.

Evaluation of the Protection Ability of a Magnesium Hydroxide Coating against the Bio-Corrosion of Concrete Sewer Pipes, by Using Short and Long Duration Accelerated Acid Spraying Tests

The Microbiologically Induced Corrosion (MIC) of concrete sewer pipes is a commonly known problem that can lead to the destruction of the system, creating multiple public health issues and the need for costly repair investments. The present study focuses on the development of a magnesium hydroxide coating, with optimized properties to protect concrete against MIC. The anti-corrosion properties of the respective coating were evaluated by using short and long duration accelerated sulfuric acid spraying tests. The coating presented satisfying adhesion ability, based on pull-off and Scanning Electron Microscopy (SEM) analysis measurements. The surface pH of the coated concrete was maintained at the alkaline region (i.e., >8.0) throughout the duration of all acid spraying tests. The consumption of the coating, due to the reaction (neutralization) with sulfuric acid, was confirmed by the respective mass and thickness measurements. The protection ability of this coating was also evaluated by recording the formation of gypsum (i.e., the main corrosion product of concrete) during the performed tests, by X-ray Diffraction (XRD) analysis and by the Attenuated Total Reflectance (ATR) measurements. Finally, a long duration acid spraying test was additionally used to evaluate the behavior of the coating, simulating better the conditions existing in a real sewer pipe, and the obtained results showed that this coating is capable of offering prolonged protection to the concrete substrate.

Sonochemical decontamination of magnesium and magnesium-zirconium alloys in mild conditions

UNGG cladding nuclear wastes constitute a huge volume of Mg-based materials that raises economic and safety concerns, particularly due to their radioactivity coupled to the potential generation of H₂ gas under deep underground disposal. Their significant decontamination would result in more secure and less expensive storage, with a better containment of the separated long-lived radioisotopes that could enter in a classical channel. Sonication of genuine UNGG cladding materials and simulants at 345 kHz in 0.01 M oxalic acid solution (20 °C) allowed the structuring of their surfaces with the observation of homogeneously distributed craters of 20-40 µm in diameter. After a thorough characterization and comparison of the ultrasound effects generated at the surface, the various samples were artificially contaminated and characterized before sonication. The complete and rapid sonochemical decontamination of Mg-based materials was then observed, in addition to the removal of the carbon layer promoting corrosion on the inner UNGG cladding. The extension of sonication allows the neo-formed brucite (Mg(OH)₂) and zirconium-based phases to accumulate on the surface, thus contributing in a slight but continuous surface recontamination process. This phenomenon results from the re-adsorption of uranyl cations from the solution which can be avoided by optimizing the duration of treatment.

Smart Functionalization of Ceramic-Coated AZ31 Magnesium Alloy

Providing materials with smart functionalities such as self-healing properties is primarily a domain for organic materials, although their applicability is restricted to mild environments and loads because of poor thermal and mechanical properties. This work seeks to achieve the active functionalities obtained in organic materials but in ceramics, which are much more heat resistant and robust. Ceramic coatings were produced by plasma electrolytic oxidation (PEO), which is an environmentally friendly technique that offers an alternative to potentially carcinogenic treatments used widely in the automotive and aircraft industries to protect light alloys against corrosion. The active functionalization was achieved by incorporating corrosion inhibitors encapsulated into halloysite nanotubes (HNTs) into the PEO coatings. This allowed controlled release of active agents when detecting environmental pH changes associated with the corrosion initiation of the metal substrate. Three corrosion inhibitors-vanadate, molybdate salts, and 8-hydroxyquinoline (8-HQ)-were assessed within the PEO-HNT system and demonstrated considerable improvements in the corrosion resistance by decreasing the kinetics of both anodic and cathodic reactions. For immersion times up to 72 h, vanadate offered a consistently higher corrosion resistance, which was followed by molybdate, whereas the positive effect of 8-HQ was time-limited. The improvement in corrosion resistance was associated with the combined enhancement of the barrier and active protection properties of ceramic coatings. All coatings containing corrosion inhibitors were capable of providing self-healing to small scratches, whereas only vanadate could partially restore a more severe damage.