Step-by-Step Tuning of Tribological and Anticorrosion Performance of Zinc Phosphate Conversion Coatings through Effective Integration of Spherical P-Doped MoS2 Nanoparticles.

Surface coatings with enhanced mechanical stability, improved tribological performance, and superior anticorrosion performance find immense application in various industrial sectors. Herein, we report the development of multifunctional composite zinc phosphate coatings by the effective integration of a structurally and morphologically tuned P-doped MoS2 nanoparticle additive (3P-MoS2) into the zinc phosphate matrix to offer attractive characteristics suitable for industrial applications. The integration of spherical nanoparticles as additive leads to the formation of homogeneous and compact coatings with a densely packed crystalline microstructure having enhanced microhardness, distinctive leaf-like morphology, and comparatively smooth topographical features. The attractive lubricity of the additive (3P-MoS2), coupled with its spherical morphology, facilitates a transition from sliding to rolling friction and contributes significantly toward the performance enhancement of the tuned composition of the composite zinc phosphate coating (0.3-PMS). Thus, the tuned 0.3-PMS coating delivers the lowest specific wear rate (1.334 × 10-5 mm3/Nm) and coefficient of friction (0.114) that significantly outperform bare-zinc phosphate coating. Further, the electrochemical corrosion study results indicate the improvement in corrosion resistance behavior of the composite zinc phosphate coatings with reduced corrosion current density (icorr) and charge transfer resistance (Rct) values, as compared to the bare-zinc phosphate coating. The effect of passivation in conjunction with the barrier protection characteristics of the composite coatings induced by the optimal composition of the integrated additive nanoparticles (3P-MoS2) can efficiently prevent the infiltration of corrosive ions and thereby significantly reduce the rate of corrosion.

Tuning of Electrode Surface for Enhanced Bacterial Adhesion and Reactions: A Review on Recent Approaches.

The study of bacterial adhesion and its consequences has great significance in different fields such as marine science, renewable energy sectors, soil and plant ecology, food industry, and the biomedical field. Generally, the adverse effects of microbial surface interactions have attained wide visibility. However, herein, we present distinct approaches to highlight the beneficial aspects of microbial surface interactions for various applications rather than deal with the conventional negative aspects or prevention strategies. The surface microbial reactions can be tuned for useful biochemical or bio-electrochemical applications, which are otherwise unattainable through conventional routes. In this context, the present review is a comprehensive approach to highlight the basic principles and signature parameters that are responsible for the useful microbial-electrode interactions. It also proposes various surface tuning strategies, which are useful for tuning the electrode characteristics particularly suitable for the enhanced bacterial adhesion and reactions. The tuning of surface characteristics of electrodes is discussed with a special reference to the Microbial Fuel Cell as an example.

Development of Antibacterial V/TiO2-Based Galvanic Coatings for Combating Biocorrosion.

Recently, TiO2 crystals have been modified by transition-metal dopants with different physicochemical structures to attain distinguished properties. Considering the similar ionic sizes of V4+ (0.058 nm) and Ti4+ (0.061 nm), vanadium in the +4 state can be effectively incorporated into the crystal lattice of TiO2 to tune the band gap energy by creating an impurity energy level (V5+/V4+) below the conduction band (2.1 eV) and retaining the anatase phase. In vanadium-incorporated TiO2 (V/TiO2), V4+ is a good dopant candidate as it can increase the lifetime of the charge carrier and reduce the electron-hole recombination rate, which results in high antibacterial activity under visible light irradiation. The present study explores the V/TiO2-based hot-dip zinc coating with enhanced electrochemical properties and long-term stability for combating biocorrosion. All the composites and the coatings are characterized by different techniques, including X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive X-ray analysis, confocal laser scanning microscopy, optical surface profilometry, and X-ray photoelectron spectroscopy. The biofilm formation assay and the cell viability assay reveal that the tuned composition of the V/TiO2-based hot-dip zinc coating effectively kills the adherent bacteria and inhibits biofilm formation on the surface. The high-charge-transfer resistance (225.67, 223.63, and 242.35 Ω cm2) and the high-inhibition efficiency (92.24, 92.30, and 92.02%) of the tuned composition of the V/TiO2-based hot-dip zinc coating confirm its efficient and sustainable antibiocorrosion performance and long-term stability even after an exposure period of 21 days in different bacterial environments. With the inherent antibacterial properties and antibiocorrosion performance of the developed V/TiO2-based hot-dip zinc coating, the mild steel substrates can find potential application in different fields, including aquatic and marine environments.

Tuning of the electrocatalytic characteristics of PANI/Fe2O3 composite coating for alkaline hydrogen evolution reaction.

The paper reports a simple and cost-effective strategy for the development of a stable and reproducible PANI/Fe2O3 composite coating as an efficient electrode for the electrocatalytic alkaline hydrogen evolution reaction (HER). The surface characteristics of the developed PANI/Fe2O3 composite coatings are tuned to achieve high hardness (510 HVN), thickness (26 µm), porosity, and surface roughness (Sa = 3.760 µm). The PANI/Fe2O3 composite coating with tuned surface characteristics (PANI/Fe2O3-2GL) facilitates the effective conduction of electrons from a highly conducting polymer to a metal. This increases the electron density on the coating surface and enhances the active surface area, which effectively enhances the hydrogen adsorption efficiency on the coating surface to improve HER activity. The composite coating exhibits enhanced HER activity with low overpotential (110 mV) and high exchange current density (95.32 mA cm-2). The mechanism of HER on the coating surface follows the Volmer-Heyrovsky reaction with the Heyrovsky step as the rate-determining step. The stability of the composite coating under aggressive reaction conditions even after long-term HER confirms its competency with commercial electrocatalysts.