2D Nanomaterials Reinforced Organic Coatings for Marine Corrosion Protection: State of the Art, Challenges, and Future Prospectives

Solvent-Assisted Ligand Exchange of the 2D Zeolitic Imidazolate Framework (ZIF-L): Fine-Tuning the Facet Ligands for Anticorrosive Coatings

The cohybridization of metal-organic frameworks (MOFs), particularly zeolitic imidazolate framework-8 (ZIF-8), with two-dimensional (2D) nanomaterials has emerged as a promising approach to enhance both the barrier properties and active corrosion protection of epoxy (EP)-based coatings. However, the widespread use of these hybrid systems is hindered by environmental concerns associated with toxic methanol used in ZIF-8 synthesis, the limited accessibility of active sites, and the high production costs of 2D nanomaterials. Therefore, there is growing interest in developing alternatives that integrate the beneficial properties of MOFs and 2D materials while offering lower costs, greater environmental compatibility, and increased active site accessibility. Herein, a 2D leaflike zeolitic imidazolate framework (ZIF-L) was utilized as a low-cost, environmentally friendly alternative to ZIF-8 with dual functionality for active and barrier protection properties. The hydrophilicity of ZIF-L was fine-tuned through a facet ligand exchange with benzotriazole (BTA), which acted as both a surface modifier and a corrosion inhibitor. This solvent-assisted ligand exchange was validated by X-ray photoelectron spectroscopy (XPS) analysis. The BTA loading in BTA@ZIF-L was determined to be 14.43 wt %. Incorporating 1 wt % BTA@ZIF-L pigment into the EP matrix resulted in a higher cross-linking density compared to both blank/EP and ZIF-L/EP coatings, yielding ultrahigh impedance values (∼1011 Ω cm2) at the lowest frequency, even after 4.5 months of immersion in a 3.5 wt % NaCl solution. Additionally, the active corrosion inhibition capability of the BTA@ZIF-L/EP coating was demonstrated through electrochemical impedance spectroscopy (EIS) analysis of scratched coatings, showing a 130% increase in the total resistance relative to blank/EP, which was further validated by salt spray testing.

Review of Layered Double Hydroxide (LDH) Nanosheets in Corrosion Mitigation: Recent Developments, Challenges, and Prospects

Layered double hydroxides (LDHs) are a typical class of two-dimensional nanomaterials that present numerous possibilities in both scientific and practical applications. LDHs, with a layered structure and unique interlayer ion-exchange properties, can be utilized to prepare various functional coatings, showing great potential in the field of marine corrosion protection. In this review, the preparation approaches and properties of LDHs are first briefly introduced. Subsequently, various protection types based on LDH-based composite coatings for marine corrosion protection are highlighted, including physical barriers, self-healing, chloride trapping effects, and hydrophobic effects, respectively. Furthermore, critical factors influencing the anti-corrosion performance of composite coatings are discussed in detail. Finally, remaining challenges and future prospects for LDH-modified composite coatings in corrosion protection are proposed. This review provides a distinctive perspective on fabricating LDH-enhanced corrosion-resistant materials, contributing toward the development of multifunctional, intelligent anti-corrosion coatings for diverse applications.

Phononic origin of resonance in atomic scale fatigue of MoS2

Previous researchers have conducted extensive investigations on the impact of various working conditions on fatigue damage. However, further research is still needed to understand the underlying mechanism of how the excitation frequency of cyclic loading affects the fatigue life. This article systematically discloses the phononic origin of atomic scale fatigue resonance, focusing on single-layer molybdenum disulfide (SL MoS2) as a prototypical material. We first devise a method to initiate free vibration in the SL MoS2 system by applying an initial condition, enabling the measurement of its natural vibration period and calculation of natural frequency. When excitation frequency matches natural frequency and its harmonics, primary and sub-harmonic resonances occur, leading to a notable decrease in fatigue life. Moreover, when the excitation frequency approaches but has not yet reached the natural frequency, the beat vibration phenomenon occurs, characterized by periodic changes of amplitude. The excitation amplitude and frequency exert pivotal influences on determining the vibration amplitude and the onset of vibration instability. Finally, the phonon behaviors across varying excitation frequencies and different fatigue stages are investigated. During resonances, excited phonons are not only distributed at the excitation frequency, but also at the harmonics of the natural frequency. This resonance effect causes a significant amplification of lattice vibrations, accompanied by more phonons being excited, resulting in a faster entry into the vibrational instability stage. Our study offers valuable insights into regulating the fatigue performance of nanomaterials, thus playing a significant guiding role in the application of nanomaterials.

Robust Damage-Sensing and Corrosion-Warning Polymeric Coatings: a New Approach to Visually Monitor the Degradation Dynamics of Coated Mg-Alloys

Corrosion and degradation of magnesium (Mg) alloy result in serious damage and limit its application in new-energy automobile industry. Considerable protective coating is proposed, yet it is hindered by the difficulties in avoiding and visually monitoring coating micro-damage and localized metal corrosion. Herein, a novel anticorrosion coating system with autonomously monitoring multiple levels of damages in coated Mg-alloy system, is proposed. In this design, the top layer of coating consists of polymethyl methacrylate (PMMA) microcapsules containing crystal violet lactone (CVL) and polyurethane resin dispersed with SiO2 nanoparticles. Upon surface damage, the presence of SiO2 triggers the chromogenic reaction of CVL liberated from ruptured microcapsules, resulting in an immediate blue coloration to highlight coating damage. Meanwhile, the primer coating incorporates PMMA microcapsules with a phenolphthalein (PHP) core, which timely reveals alkaline corrosion pits at Mg alloy/coating interface by generating pink coloration. Furthermore, the microcapsules-embedded coating exhibits superior corrosion resistance. The failure evolution dynamics of coating-Mg system, including both the external coating damage and internal localized corrosion, can be visually indicated. This work provides an innovative strategy to tailor and monitor the degradation of coated Mg alloys, thereby presenting promising prospects for application in automotive anticorrosion engineering.

Surface-Modification Strategy to Produce Highly Anticorrosive Ti3C2Tx MXene-Based Polymer Composite Coatings: A Mini-Review

MXenes are a group of novel two-dimensional (2D) materials with merits such as large specific surface area, abundant surface-functional groups, high chemical activity, excellent mechanical properties, high hydrophilicity, and good compatibility with various polymers. In recent years, many novel high-performance organic anticorrosion coatings using MXenes as nanofillers have been reported and have attracted widespread attention. As the first successfully prepared MXene material, Ti3C2Tx is the most extensively studied and typical member of the MXene family. Therefore, it is taken as the representative of its family, and the status of Ti3C2Tx MXene/epoxy resin (EP) and MXene/waterborne polyurethane (WPU) polymer anticorrosive composite coatings is reviewed. Firstly, the structure, characteristics, and main synthesis methods of MXenes are briefly introduced. Then, the latest progress of four surface-modification strategies to improve the dispersion, compatibility, stability, and anti-aggregation properties of MXenes, namely functionalization grafting, orientation regulation, heterostructure nanocomposite design, and stabilization and greening treatment, are analyzed and summarized. Finally, the current challenges and future opportunities regarding MXene-based corrosion-resistant organic composite coatings are discussed prospectively.

A Multifunctional Coating with Active Corrosion Protection Through a Synergistic pH- and Thermal-Responsive Mechanism

This article aims to develop CeO2 nanocontainer-constructed coating with a synergistic self-healing and protective nature through a simple mechanical blending technique to manage metal corrosion. The proposed coating exhibits excellent corrosion resistance, which is primarily attributed to the combination of thermal-driven healing and active corrosion inhibition. Paraffin wax and 2-polybenzothiazole-loaded CeO2 nanotubes (CeO2-MBT) are directly doped into epoxy coating to perform such a multifunctional role. CeO2 nanocontainers and encapsulated corrosion inhibitor MBT can be released by pH triggers to achieve instant corrosion inhibition upon the surface of metal substrate. In addition, any physical defects in the coating are responsively repaired by heating incorporated paraffin wax to regain structural integrity and consequent barrier function. Corrosion protection efficiency remains sufficient even after ten cycles of damage and healing. Such a multiple-functional coating strategy provides an alternative pathway toward efficient and sustainable performance to tackle corrosion-related challenges of metal components in both short-term and long-term services.

Effect of Glycerol Stearates on the Thermal and Barrier Properties of Biodegradable Poly(butylene Adipate-Co-Terephthalate)

Two types of glycerol stearates, glycerol monostearate (GMS) and glycerol tristearate (GTS), were added into poly(butylene adipate-co-terephtalate) (PBAT), with the aim to improve their water vapor barrier properties. The effects of the two small molecules on microstructure, chain mobility, and surface hydrophobicity were amply assessed via both experimental and simulation methods. The incorporation of the modifiers at small loadings, 5 wt% of GMS and 1 wt% of GTS, resulted in substantial improvements in water vapor barrier properties, while a further increase in the modifier content resulted in deterioration. The optimal water vapor permeability reached values of 2.63 × 10-13 g·cm/(cm2·s·Pa) and 6.55 × 10-13 g·cm/(cm2·s·Pa), which are substantially lower than the permeability, 8.43 × 10-13 g·cm/(cm2·s·Pa), of neat PBAT. The water vapor permeability of PBAT/GMS blends was also proven to be time-dependent and dramatically decreased with time, mainly due to the migration process of small molecules, forming a waterproof layer. The barrier improvement results are assumed to be related to the hydrophobic effect of glycerol stearate and are largely dependent on the content, polarity, compatibility, and dispersion of modifiers. In addition, the incorporation of modifiers did not largely sacrifice the mechanical strength of PBAT, which is advantageous in mulch film applications.

Pearl-Inspired Intelligent Marine Hetero Nanocomposite Coating Based on "Brick&Mortar" Strategy: Anticorrosion Durability and Switchable Antifouling

Corrosion activities and biofouling pose significant challenges for marine facilities, resulting in substantial economic losses. Inspired by the "brick&mortar" structure of pearls, a novel nanocomposite coating (Pun-HJTx) with long-lasting anticorrosion and intelligent antifouling modes is fabricated by integrating a compatible MoS2/MXene heterostructure as the "brick" into a polyurea-modified PDMS (Pun) acting as "mortar." Notably, the presence of multiple hydrogen bonds within the coating effectively reduces the pinholes resulted from solution volatilizing. In the dark, where fouling adhesion and microbial corrosion activities are weakened, the MoS2/MXene plays a role in contact bactericidal action. Conversely, during daylight when fouling adhesion and microbial corrosion activities intensify, the coating releases reactive oxygen species (such as hydroxyl radicals and superoxide ions) to counteract fouling adhesion. Additionally, the coating exhibits multisource self-healing performance under heated or exposed to light (maximum self-healing rate can reach 99.46%) and proves efficient self-cleaning performance and adhesion strength (>2.0 Mpa), making it highly suitable for various practical marine applications. Furthermore, the outstanding performance of the Pun-HJT1 is maintained for ≈180 days in real-world marine conditions, which proving its practicality and feasibility in real shallow sea environments.