Understanding localized corrosion under atmospheric droplets is critical, yet previous studies have mostly focused on single-droplet systems or general trends, leaving the role of individual droplets within multi-droplet environments yet to be explored. Here, we present a fully automated, image-based, data-driven framework for analyzing corrosion progression under thousands of droplets simultaneously. Using time-resolved optical imaging and pre-trained large vision models for droplet segmentation, we construct per-droplet color features and propose a probability-based representation of corrosion product formation in inner and outer regions of interest. This approach overcomes the limitations of binary classification by capturing the continuous and spatially heterogeneous nature of corrosion product formation. Applied to carbon steel exposed to over 1500 pre-sprayed 1 M NaCl droplets of various sizes, the method reveals that the probability of corrosion product presence strongly depends on droplet size, with larger droplets more likely to exhibit products both under and around the droplet footprint. Moreover, corrosion products in the outer region can appear independently of under-droplet corrosion, suggesting a role for inter-droplet interactions. By transforming raw imaging data into physically meaningful per-droplet metrics, this work offers a scalable platform for investigating localized corrosion kinetics and morphology in complex, real-world droplet populations, opening new opportunities for connecting droplet formation and population behavior to local and overall atmospheric corrosion rates.

The search for non-toxic alternatives to hexavalent chromium based corrosion inhibitors requires a comprehensive understanding of the factors critical to effective corrosion protection. Key considerations include the evolution of corrosion inhibition with inhibitor concentrations and exposure times, the inhibition efficacy in the presence and following absence of inhibitors, and the stability of inhibition upon polarisation. In our electrochemical comparison of promising organic molecules with sodium dichromate, we found that even top-performing candidates can lead to premature conclusions if such critical factors are overlooked. While organic molecules can match the inhibition performance of chromates under specific conditions, this can be misleading when considering concentration, time, and polarisation dependent behaviour. Initial high performance can also be deceptive in dynamic environments, as we observed that the inhibition provided by most organic molecules drastically decreases when the inhibitor is absent in the electrolyte. These observations call for broader comprehensive inhibitor robustness studies that take into account factors including time, concentration, stability, and polarisation effects in inhibitor efficacy analysis.

This research provides detailed insights into the correlation of microstructural and morphological characteristics of a Cr/CrN multilayer coating deposited onto steel and its corrosion behavior, by examining its local surface electronic properties, nanomechanical behavior, and electrochemical activity in a 3.5 % NaCl solution. A key focus of the study is the influence of physicochemical surface evolution on nano-mechanical properties of Cr/CrN coating. This is investigated by correlating electrochemical data from electrochemical impedance spectroscopy (EIS) with findings from X-ray photoelectron spectroscopy (XPS) and nanoindentation analysis. The integrated approach shed light on physicochemical evolution of the coating, and its resistance to corrosion in demanding environments.

Chromium coatings, famed for their superior wear and corrosion resistance, are a critical component in countless industrial processes. However, the longevity of these coatings in aggressive corrosive environments continues to be a significant hurdle, even with recent advances in deposition technology and microstructural improvements. An advanced thin dense chromium (TDC) coating, with a near-nanocrystalline structure and unique morphology, naturally forms a non-conductive nano-bilayer oxide. This passive and protective layer effectively moderates electrical charge transfer, offering superior corrosion resistance. X-ray photoelectron spectroscopy (XPS) shows significant Cr³⁺ oxide layer formation, distinguished by multiplet splitting, after 7 days in a 0.6 M NaCl solution. The unique characteristics of this non-conductive bilayer oxide structure promote its growth and densification, leading to vertical differential charging in the O1s electron energy region. This effect arises from the enhanced resistivity of the oxide layer. Electrochemical impedance spectroscopy (EIS) confirmed these findings, showing a substantial increase in charge transfer resistance at the chromium metal/bilayer oxide interface, reaching 1.01 MΩ. Scanning Kelvin probe force microscopy (SKPFM) analysis shows that both TDC nodules and their boundaries exhibit high surface potential and work function. However, after exposure to NaCl media, these values are moderately reduced, likely due to diminished electrical surface charge distribution.

The increasing concentration of CO2 is a serious concern for the environment. Electrochemical conversion of CO2 into valuable products, including fuels, offers a viable solution and helps close the carbon-neutral cycle. Metal-organic framework (MOF) composites, due to their high porosity, large surface area, and significant chemical tunability, are considered to be a promising class of catalyst materials for the CO2 reduction reaction (CO2RR). This chapter focuses on the fundamentals of CO2RR and mechanism of the reaction followed by discussing the recent advancements in MOF composite electrocatalysts for CO2RR including MOF-supported electrocatalysts, conductive-supported MOF composites, graphene and carbonous MOF composites, MOF-MXenes, MOF-polymers, and polyoxometalate.

The development of advanced catalysts with innovative nanoarchitectures is critical for addressing energy and environmental challenges such as the electrochemical CO₂ reduction reaction (CO₂ RR). Herein, the synthesis of an innovative copper–sulfur planar structure, Cu–S–BDC, within a metal–organic framework (MOF) catalyst is presented, which demonstrates 100% selectivity toward formate as the sole carbon product. Structural analysis and surface characterizations reveal that Cu–S–BDC exhibits quasi-2D inorganic building units, with Cu bonded to two S-CH (Formula presented.) groups and one BDC linker, while carboxylate groups adopt a bridging coordination mode. This unique arrangement not only imparts remarkable structural stability but also enhances the electronic properties of the MOF, as evidenced by a narrow bandgap of 1.203 eV that facilitates efficient charge transfer and increased electrochemical current density in CO (Formula presented.) RR. Notably, it offers a Faradaic efficiency of 92% for formate at an overpotential as low as −0.4 V versus the reversible hydrogen electrode (RHE) in an aqueous electrolyte of 1 m KOH, as well as a current density of −25.8 mA cm² at −0.9 V versus RHE, averaged over 24 h of electrolysis. This study highlights a fresh perspective in the field of MOF electrocatalysts by demonstrating that engineering the metal coordination environment can significantly enhance the electronic properties and consequently improve the electrocatalytic performance of these materials.

Eliminating hexavalent chromium-based corrosion inhibitors from structural aircraft coatings remains a significant challenge, primarily due to the lack of reliable accelerated test methods. This study evaluates the performance of various structural aircraft coatings under different exposure conditions, i.e. outdoor exposure, cyclic salt spray testing and in-service conditions, supplemented by environmental sensors. Quarterly inspections and scanning electron microscopy were used to evaluate corrosion damage. The findings highlight a lack of correlation between accelerated testing and outdoor exposure testing, likely driven by disparities in salt deposition, UV-radiation, time of wetness and temperature cycling. Additionally, galvanic couples between skin and fasteners remain difficult to protect, with chromate-based systems offering limited inhibition and alternative systems struggling to protect such complex assemblies. However, in lap-joints, alternative coatings outperformed chromate-based counterparts, likely due to their polymer matrices providing improved barrier properties, hence limiting access of electrolyte to the coating-aluminium alloy interface.

Kelvin probe force microscopy (KPFM) is a highly advanced technique offering notable surface sensitivity and high lateral resolution, ranging from micrometres to the sub-nanometre scale. This scanning probe technique effectively detects local electrical surface potential (ESP), influenced charge distribution, and work function differences, making it essential for studying biological and biochemical processes, from single molecules to complex cellular structures. By enabling nanometre-resolution analysis under simulated conditions, KPFM provides crucial insights into the physicochemical evolution, functionality, and structural organization of biomolecular systems. Recent advancements have significantly expanded KPFM's capabilities, revealing ESP characteristics in diverse biological entities, including single proteins, DNA strands, lipid films, fibrils, and complex neuronal structures. The technique also facilitates the study of biomolecular nanolayers on advanced nanomaterials like gold nanoparticles and carbon nanotubes, enhancing its role in bio-nanotechnology. Such versatility highlights KPFM's transformative potential in elucidating biomolecular interactions at unprecedented resolutions. This review critically analyses recent advancements, addresses ongoing challenges in measuring ESP in biological samples, and highlights emerging strategies to improve resolution and sensitivity. Additionally, KPFM's implications in diagnostics, biosensing, tissue engineering, therapeutics, drug screening, and Alzheimer's research are explored, establishing it as a powerful tool at the intersection of nanotechnology and biomedical innovation.

There is no denying that the world is heading towards an era powered by green energy resources. The need for highly efficient devices for sustainable energy storage and utilization is vital in transitioning towards the full-time realization of renewable energy for our society. In the last four decades, there have been groundbreaking developments in the large-scale commercialization of Li-ion batteries, electric vehicles, and solar power, all made possible by an in-depth understanding of the science of materials. Theoretically, there exists no problem in the production of green hydrogen, as oxides of Ir, Rh, and Pt, and the elements themselves, are excellent catalysts for the electrochemical hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) with fast kinetics. Thus, more work remains to be done in the area of green energy material technology. The problem lies with the critical availability and cost of these materials, which is the underlying motivation for finding alternative energy materials and technologies. This energy transition era presents us with an opportunity to expand our horizons and knowledge in chemical engineering, materials science, and allied fields through two-dimensional (2D) nanomaterials. These materials exhibit intriguing characteristics in contrast to their bulk counterparts, coupled with interchangeable electronic properties depending on the synthesis methodologies employed. The chapter begins by introducing the family of graphene nanosheets and expands into a discussion of advanced 2D families, such as transition metal dichalcogenides (TMDs), MXenes, transition metal oxides (TMOs), and hexagonal boron nitride (h-BN).

A 2D finite element model is developed to simulate the protection of active protective coatings in a defect. The leaching kinetics, inhibitor-electrolyte reactions and electrochemical surface reactions on homogenized AA2024-T3, are considered. Changes in local oxygen distribution, pH, and current density over time are validated using surface scanning micro-probe techniques. The limitations posed by the prediction of surface current density at the metal interface using a FEM model with a homogenized microstructure are identified and addressed. The validated FEM is then used to predict inhibitor concentration and pH dependent on the initial inhibitor pigment concentration in an organic coating.

Chromium-based functional coatings (CFCs) are widely recognized for their outstanding wear and corrosion resistance across diverse industrial sectors. However, despite advancements in deposition techniques and microstructural enhancements, many contemporary CFCs remain vulnerable to degradation in highly corrosive environments. For the first time, this research delivers a thorough characterization of the corrosion resistance of advanced CFCs, focusing on the performance of a 5 μm thin dense chromium (TDC) coating. These TDCs exhibit a distinctive, uniform nodular microstructure, characterized by approximately 3.6 μm nodules composed of defect-free near-nanocrystalline grains (227 ± 75 nm) plus enhanced electrochemical nobility. This structure promotes the rapid formation of a stable, dense bilayer oxide, resulting in a remarkably low corrosion susceptibility, effectively impeding both charge transfer and mass transport, particularly the diffusion of Cl^- ions. Furthermore, the coating sustains an exceptionally high polarization resistance over extended exposure times in aqueous NaCl electrolyte. These findings offer critical insights into the design of CFCs optimized for extreme environmental durability.

The stability of inhibiting layers on AA2024-T3 intermetallic particles (IMPs) during re-immersion in saline following an initial immersion in a Ce(III)-containing electrolyte was investigated using in situ reflected light microscopy. Re-immersion behaviour varied due to differences in IMP composition, spatial distribution, and Ce(III) precipitation. IMPs were grouped into four categories based on whether their activity was high or low during both the immersion and re-immersion stages. Majority of the high activity particles during re-immersion had low activity during immersion. Longer immersion times (up to 72 h) and a brief delay in inhibitor supply (30 s) reduced re-immersion activity by increasing Ce(III) coverage. These findings suggest that corrosion protection systems promoting greater Ce(III) precipitation may enhance re-immersion stability.

Medical devices contribute to the carbon footprint generated by the healthcare sector. The development of implants and biomaterials using recycled waste materials promotes sustainable advances in tissue engineering. Additively manufactured (AM) bone-substituting biomaterials with multifunctional properties, e.g., biodegradability, antibacterial and osteogenic potential, can contribute to sustainable healthcare. Biodegradable biomaterials eliminate secondary surgeries to remove implants, reduce post-surgical complications, and enhance patient recovery, thus decreasing the energy usage and waste associated with medical treatments. Herein, we present porous iron (Fe) scaffolds incorporating 20 vol% waste-derived eggshell particles for bone substitution. The Fe-eggshell scaffolds were fabricated using direct ink writing (DIW) technique and underwent post-AM heat treatment. During sintering, the eggshell's main component – CaCO₃, transformed into CaO. Atomic diffusion between α-Fe and CaO phases resulted in the formation of Ca₂Fe₂O₅ phase at the interface. The scaffolds were 70 % porous and displayed a biodegradation rate of 0.11 mm/year. The mechanical properties were comparable to trabecular bone and the scaffolds endured 3 million loading cycles at 0.7σ_y in r-SBF. The scaffolds showed apatite-forming ability, evidenced by the formation of (carbonaceous) hydroxyapatite, which are conducive to preosteoblast adhesion, proliferation, and differentiation. RT-qPCR analysis confirmed the osteogenic potential of the specimens as evidenced by the upregulated expression of osteopontin and osteocalcin as compared to Ti6Al4V controls. Furthermore, the scaffolds exhibited bactericidal activity (>3.9-log CFU reduction) against methicillin-sensitive and multidrug-resistant strains of Staphylococcus aureus and delayed their biofilm formation. Our research showcases the exceptional multifunctionality of DIW Fe-eggshell composite scaffolds for the sustainable development of orthopedic biomaterials. Statement of significance: We aim to improve the biofunctionalities and sustainability of biodegradable bone substitutes, by developing the extrusion-based 3D printed porous Fe composite scaffolds containing eggshell-derived CaO bioceramics. Our results demonstrated that Fe-eggshell scaffolds exhibited hydroxyapatite-forming ability in simulated body fluid, having mechanical properties in the range of trabecular bone even after 4 weeks biodegradation, supported the proliferation of preosteoblasts and upregulated the expression of osteogenic genes. Moreover, the scaffolds were bactericidal against methicillin-sensitive and multi-drug resistant strains Staphylococcus aureus and delayed their biofilm formation.