Co/WS2 and Co/WC composite coatings were electrodeposited from sulfate-based baths containing 0.5-10 g L-1 WS2 and 2-15 g L-1 WC particles. The influence of particle concentration on the structure, hardness, and tribological properties of the coatings was investigated. A hybrid Co/WC-WS2 coating was also synthesised to combine the high hardness of WC with the solid-lubricating properties of WS2. The morphology of cobalt changed from pyramidal to blade-like and finally to a porous structure consisting of rounded particulates with increasing WS2 content. Nodular and cauliflower-like morphologies were observed for Co/WC and Co/WC-WS2 coatings. Hardness decreased with the addition of WS2, from 330 HV for pure cobalt to 204 HV at 10 g L-1 WS2, whereas the addition of WC increased the hardness up to 530 HV at 10 g L-1 WC. The hybrid coating exhibited a hardness of 502 HV, reflecting a balance between WC strengthening and WS2 lubrication. Wear tests revealed that only the coatings prepared in baths containing 5 and 10 g L-1 WS2 particles exhibited lower wear resistance than pure cobalt. The hybrid coating delivered the best performance, with wear loss approximately 2.87 times lower than that of pure cobalt and approximately 1.25 and 1.37 times lower than those of the most wear-resistant 1 g L-1 WS2- and 10 g L-1 WC-reinforced coatings, respectively. Abrasion remained the dominant wear mechanism.
This research evaluates the functionalisation of AISI 304 stainless steel via surface engineering, including oxy-nitrocarburising and electrodeposition from ethylene glycol-based electrolytes to produce silver, copper, nickel, and chromium-cobalt oxide coatings. Utilising an Analytic Hierarchy Process (AHP) framework, the study systematically compares two standardised methodologies: ASTM E2562 -based dynamic biofilm assay and JIS Z-2801 for static contact activity. The multi-criteria analysis integrates experimental data with operational parameters like reproducibility, robustness, and cost. Results demonstrate that both standards effectively discriminate between treatments, though nickel and chromium-cobalt coatings achieve superior performance against microbial colonisation. AHP reveals a preference for ASTM E2562-based dynamic biofilm assay when prioritising environmental representativeness in hydrodynamic systems. By validating these strategies through structured decision-making, this work provides a robust engineering approach for selecting antimicrobial finishes, optimising resource allocation for high-performance components in marine and industrial sectors.
This study proposes a bio-inspired strategy to fabricate seashell-like micro-textures on Ti-6Al-4V alloy surfaces using laser surface texturing (LST), aiming to enhance surface properties. Inspired by the spiral patterns of seashells, laser parameters namely frequency (F), spiral pitch (SP) and scanning speed (SS) were used to create controlled surface textures on Ti-6Al-4V alloy surface. Results showed that increasing SS and F reduced mean Sa (arithmetic mean height, & micro;m), leading to smoother and more uniform surface topographies. Conversely, increasing SP leads to higher mean Sa and increased surface area. Surfaces with greater SP demonstrated increased Sdr (developed interfacial area ratio, %) values, indicating higher surface complexity. The high SS and SP combination effectively achieved hydrophobic surfaces with low mean surface energy. This work introduces an innovative and sustainable approach for developing functional surfaces, offering potential benefits in marine, biomedical and industrial applications.
This study focusses on optimising High-Velocity Oxy-Fuel (HVOF) spraying parameters to enhance NiCrFeSiAlBC coatings on AISI 316L stainless steel. The effects of nozzle geometry and spray distance on microstructural, mechanical, and tribological properties are systematically evaluated. Coatings produced using 4-inch and 8-inch (100 and 200 mm) nozzles are characterised via scanning electron microscopy (SEM), X-ray diffraction (XRD), and image-based porosity analysis. Vickers microhardness testing (3 N load) and ball-on-flat wear tests (10 N, 5000 cycles, alumina counter-body) assess mechanical performance. Results show that the 4-inch (100 mm) nozzle significantly improves coating integrity, hardness, and wear resistance. Additionally, spray distances of 330, 350, and 370 mm are investigated, with 350 mm providing the best balance of coating quality and adhesion due to enhanced thermal transfer and particle flattening. These findings underscore the importance of optimising nozzle design and spray distance to improve the performance and durability of HVOF coatings in demanding industrial environments.
Ginkgo biloba leaf extract was evaluated as a natural corrosion inhibitor for carbon steel in a simulated concrete pore solution containing 3.5 wt% NaCl and saturated Ca(OH)2 at pH 13.5. Open-circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarisation were used to clarify concentration-dependent interfacial evolution. The extract showed a distinct concentration effect. During early exposure, all extract-containing systems exhibited lower impedance than the blank, indicating initial disturbance of natural passivation. With prolonged immersion, the systems gradually diverged. In the 100-500 mg/L range, the adsorbed layer showed limited coverage and stabilisation, and the 300 and 500 mg/L systems were more prone to form loose, defect-rich composite films. The 700 and 1000 mg/L systems developed more stable inhibitor-passive composite films after interfacial rearrangement. Among them, 1000 mg/L showed the highest impedance, the highest film and total electrode-process resistances, the lowest equivalent film capacitance, and the best overall long-term inhibition performance.
The properties of metallic matrix materials can be modified by the addition of different types of composite materials (ceramic, polymer and carbide). Electrodeposition is a vital technique for producing metal matrix composites. This work shows that Ni matrix composite coatings with uniformly distributed different-sized particles were successfully fabricated by different electroplating techniques from the deep eutectic solvent (DES) known as Ethaline. Particulate dispersions are generally more stable in DES media than in aqueous electrolytes because of the higher viscosity and more favourable wetting characteristics (surface tension). This work demonstrates, by characterisation from electrochemical methods and electron microscopy, that Ni matrix composite coatings with uniformly distributed microparticles of cBN and Cr3C2, of different sizes, were successfully developed by using simple electroplating facilitated by the Ethaline-based DESs either in suspension or as a paste. The work of this study is reported in two parts. In part one, here, the electrochemical characterisation and temperature dependence of the nickel-based DES solutions containing different fractions of the microparticles, both cubic boron nitride (cBN) and chromium carbide (Cr3C2), are presented. The electrochemical fabrication in DES of the composites and characterisation of the resultant coatings are discussed. Consequently, the viable route to generating such particulate composites in a DES electrolyte has been demonstrated. In part two,a detailed hardness and wear study of composite coatings of nickel containing cBN, Cr3C2 particles, together with mixed systems, is presented. This will appear in a subsequent issue of this journal.
Electrodeposition is a vital technique for producing a metal matrix composite. In part one of this work, the authors showed that Ni matrix composite coatings with uniformly distributed different-sized particles were successfully fabricated by different electroplating techniques from Ethaline DES. Here, it is shown that the size of the particles had a significant influence on the tribology of the Ni composite coatings. The maximum contents of micro-sized Cr3C2 particles incorporated into the Ni matrix were between 11.11% and 22.2% in weight. Further, Ni-cBN-Cr3C composite coatings exhibited a higher wear resistance than Ni-cBN composite coatings. Additionally, the friction coefficient of the composite coatings to the third phase (Ni-cBN-Cr3C2) decreases when Cr3Cr2 has been incorporated between cBN particles. The wear tracks of the two coating layers have been examined using SEM, and the images of morphology show that the wear tracks of the first and second layers have no wear, and the wear tracks appear very shallow. EDX analysis was performed on these areas, and the concentration of Fe element in the wear track of the Ni-cBN layer is significantly higher than that of the Ni-cBN-Cr3C2 layer. This indicates that the residual Fe from the steel ball is greater on the first layer surface during the wear test. Consistently, the grinding balls were significantly worn; the diameters of wear scars from the first and second layers are 1645 and 1530 mu m, respectively. These also suggest that cBN from this layer has a stronger cutting action on the steel ball than cBN with Cr3C2 layers. This work demonstrates that Ni matrix composite coatings with uniformly distributed microparticles of different sizes were successfully developed by using electroplating from Ethaline-based DESs..
As semiconductor devices continue to scale down, achieving reliable copper electroplating for high-aspect-ratio TSVs has become increasingly critical. In via filling, competitive adsorption among suppressors, accelerators, and levelers governs bottom-up behaviour. This study investigates how the molecular weight of polyethylene glycol (PEG) modulates such interactions in acidic copper sulfate baths containing SPS and either a dye-type leveler (DL) or a non-dye leveler (NDL). Electrochemical analyses (LSV, EQCM) were employed to quantify adsorption/transport effects, and TSV filling tests established process outcomes. PEG-2000 enabled void-free bottom-up filling in the SPS/PEG/NDL system, whereas higher-molecular-weight PEGs slowed filling and generated voids. In SPS/PEG/DL baths, voids formed regardless of PEG molecular weight, indicating insufficient suppression near via entrances. EQCM showed that low-molecular-weight PEG permits stronger NDL adsorption, while high-molecular-weight PEG inhibits leveler adsorption. Overall, PEG molecular weight emerges as a key lever for tuning suppressor-leveler balance and TSV filling performance.
This study presents the development and optimisation of linseed oil-filled poly(urea-formaldehyde) (PUF) microcapsules for protective coatings on galvanised steel. The microcapsule size was successfully reduced to approximately 2 & micro;m by increasing the stirring rate and minimising emulsification time during in-situ polymerisation. The synthesised microcapsules were characterised using SEM, particle size analysis, FTIR and TGA to confirm morphology, size distribution and chemical integrity. Polyester coatings incorporating varying microcapsule concentrations (0, 1, 3 and 5 wt.%) were applied to galvanised steel panels and evaluated for self-healing and corrosion resistance. Performance assessments included SEM-EDX, electrochemical impedance spectroscopy (EIS), salt spray testing (SST) and scanning Kelvin probe (SKP) analysis. Results indicate that coatings with 3 wt.% microcapsules exhibited optimal self-healing efficiency and superior corrosion protection, while higher concentrations led to agglomeration and reduced adhesion. These findings demonstrate that size-reduced PUF microcapsules with linseed oil can significantly enhance the durability and protective performance of galvanised steel coatings, offering a promising approach for advanced smart coating applications.
In this study, Zn-W films were developed on 316L stainless steel via chronopotentiometric electrodeposition to improve its protective performance. Zinc was employed for its ability to form a passive layer, while tungsten was incorporated to enhance mechanical strength and durability. A citrate-based electrolyte was used to facilitate co-deposition, overcoming the challenges of direct tungsten electrodeposition. Deposition was conducted within a current density range of -35 to -50 mA cm-2, as identified from cyclic voltammetry. X-ray diffraction confirmed the formation of hcp Zn-W phase with crystallite sizes of 15-22 nm, indicating microstructural refinement due to tungsten incorporation. The resulting films exhibited a smooth, compact and flower-like morphology. Energy-dispersive spectroscopy (EDS) analysis indicated that the coatings were predominantly Zn-rich, with a maximum Zn content of similar to 97.62 wt.% obtained at -35 mA cm-2. At higher current densities, the Zn content decreased slightly, while the maximum tungsten incorporation reached similar to 3.28 wt.%. The coatings exhibited an average thickness of similar to 1.5 & micro;m, confirming the formation of a uniform and continuous layer over the substrate. Open-circuit potential measurements indicated passive layer formation. Tafel analysis showed the highest polarisation resistance (Rp) of 223 Omega cm & sup2; at -35 mA cm-2.
