Artichoke Extract as an Eco-Friendly Corrosion Inhibitor for Zinc in 1 M Hydrochloric Acid Solution

Artichoke extract (AE) was studied as the corrosion inhibitor for zinc in 1 M HCl utilizing chemical and electrochemical methods. The adsorption isotherm of Artichoke extract on Zn surface accords with Langmuir adsorption isotherm. The inhibition efficiency increases with increasing the extract's concentration and decreases with the rise in the medium's temperature. The inhibition efficiency reached a value of 93.2% at 300 ppm of extract. This extract may be forming a film and acts as a barrier, which minimizes the contact area between zinc surface and HCl solution. Artichoke extract acts as a mixed inhibitor in HCl solution. Thermodynamic parameters of activation and adsorption were determined and explained. The adsorption parameters also obeyed the Langmuir adsorption isotherm, and the sign of the free energy of adsorption showed a spontaneous process. The surface morphology of zinc metal was examined by employing various techniques. Also, the biological effect of the Artichoke extract was studied. Theoretical studies of quantum mechanics and molecular dynamics simulations studies were carried out on the Artichoke extract compounds, and the results agree with the experimental one. The efficiencies marked from all employed techniques were in perfect correspondence, demonstrating the validity of these procedures.

Anodic ZnO Microsheet Coating on Zn with Sub-Surface Microtrenched Zn Layer Reduces Risk of Localized Corrosion and Improves Bioactivity of Pure Zn

Zinc-based alloys are emerging as an alternative to magnesium- and iron-based alloys for biodegradable implant applications, due to their appropriate corrosion performance and biocompatibility. However, localized corrosion occurring on the zinc surface, which is generally associated with restricted mass transport at specific surface sites, such as in confined crevices, declines mechanical strength and can lead to the failure of implant materials. In order to improve corrosion behavior and bioactivity, we explore the effect of a ZnO microsheet coating fabricated on pure Zn via anodic oxidization. Samples were characterized with Scanning Electron Microscope (SEM) (including Energy Dispersive Spectroscopy (EDS), X-ray Photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD)). The microstructured surface consists of parallel Zn trenches on the bottom and ZnO/Zn3O(SO4)2 sheets on the top. This layer shows favorable Ca-phosphate precipitation as well as bovine serum albumin (BSA) adsorption properties. Electrochemical experiments indicate an increased corrosion resistance of surface-modified Zn by the presence of BSA in simulated body fluid. Most noteworthily, localized corrosion that has been previously observed for pure Zn in BSA-containing electrolytes does not occur on the Zn/ZnO-coated surface.

Morphological Study of Zinc-Oxide Nanorods Grown by Hot Water Treatment Suitable for Solar Cells Conversion Efficiency Enhancement

Zinc-oxide (ZnO) nanostructures including nanorods are currently considered as a pioneer research of interest world-wide due to their excellent application potentials in various applied fields especially for the improvement of energy harvesting photovoltaic solar cells (PSC). We report on the growth and morphological properties of zinc-oxide (ZnO) nanorods grown on the surface of plain zinc (non-etched and chemically etched) plates by using a simple, economical, and environment-friendly technique. We apply hot water treatment (HWT) technique to grow the ZnO nanorods and varies the process parameters, such as temperature and the process time duration. The morphological, and elemental analysis confirm the agglomeration of multiple ZnO nanorods with its proper stoichiometry. The obtained nanostructures for different temperatures with different time duration showed the variation in uniformity, density, thickness and nanonorods size. The ZnO nanorods produced on the etched zinc surface were found thicker and uniform as compared to those grown on the non-etched zinc surface. This chemically etched Zinc plates preparation can be an easy solution to grow ZnO nanorods with high density and uniformity suitable for PSC applications such as to enhance the energy conversion efficiency of the photovoltaic (PV) solar cells towards the future sustainable green earth.

Sodium Lingo-Sulfonate and Sodium Dodecyl-Sulfate Mixtures Influence on Zinc Concentrate Pressure Leaching and Zinc Electro-Winning

This paper is describing an investigation of sodium lingo-sulfonate and sodium dodecyl-sulfate mixtures influence on zinc concentrates high temperature oxidative pressure leaching and zinc electro-winning. For this purpose, surfactants concentration at leaching tests was varied from 200 to 800 mg∙l-1. It was established that the maximum zinc extraction (99 %) at leaching was achieved in the presence of mixture containing 800 mg∙l-1 lignosulfonate and 200 mg∙l-1 sodium dodecyl-sulfate. Therefore, this mixture can be recommended for high temperature oxidative pressure leaching of zinc concentrates. Sulfur-sulfide pellets formation also was observed at a low lingo-sulfonate concentration (200 mg∙l-1) in a mixture with sodium dodecyl-sulfate. This phenomenon can lead to emergency shut down of autoclave. It was observed that the mixture usage of 800 mg∙l-1 lignosulfonate and 200 mg∙l-1 sodium dodecyl-sulfate had no significant impact on zinc current efficiency, it was in the rage of 92-93 %. The mixture usage of 200 mg∙l-1 lignosulfonate and 600 mg∙l-1 sodium dodecyl-sulfate allowed to increase current efficiency up to 95 %. Increasing sodium dodecyl-sulfate concentration in mixtures with lignosulfonates leads to decrease of current efficiency, to formation of deep pores and defects on cathode zinc surface.

The Influence of Dimethyl Sulfoxide as Electrolyte Additive on Anodic Dissolution of Alkaline Zinc-Air Flow Battery

The present work describes the effects of dimethyl sulfoxide (DMSO) in KOH aqueous electrolyte on the performance of a zinc-air flow battery. Aqueous electrolytes containing 7 M KOH and (0 to 20)% v/v DMSO were studied revealing a critical role of DMSO on the dissolution and deposition of zinc. The anodic zinc dissolution process was studied via cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy (EIS). The presence of DMSO showed improved zinc dissolution performance with the highest peak of zinc dissolution being the electrolyte containing 5% v/v DMSO. Tafel analysis demonstrated a significant decrease in polarization resistance and an increase in corrosion rate due to the introduction of DMSO to the electrolyte. This suggests that DMSO has the ability to suspend zinc oxide in the electrolyte, thus preventing passivation of the zinc surface. EIS results revealed that by adding DMSO to the electrolyte, charge transfer resistance increased. This is attributed to the formation of passive layers having arisen from DMSO adsorption, the formation of zincate ions in the vicinity of the zinc surface, and the deposition of discharged products. A difference in Nyquist plots was observed for 20% v/v DMSO/KOH and 0% v/v DMSO/KOH electrolytes implying non-Debye relaxation behavior taking place due to the surface effects. The electrolytes were implemented in a zinc-air flow battery. Maximum power densities of 130 mW/cm2 (5% v/v DMSO) and 125 mW/cm2 (20% v/v DMSO) were obtained and were observed to be about 43% and 28% higher than that of the DMSO-free electrolyte. Results indicated that when 20% v/v DMSO was added to KOH solution, there was 67% zinc utilization efficiency (550 mAh/g) which provided 20% improvement in discharge capacity. Further, the battery with 20% v/v DMSO demonstrated excellent cyclability. Overall, DMSO shows great promise for enhancement of zinc dissolution/deposition in zinc-air batteries.

Kinetics of Zinc Corrosion in Concrete as a Function of Water and Oxygen Availability

This paper studies the effect of water as an oxidation agent and also of oxygen on zinc corrosion kinetics in active state in concrete, using high-sensitivity electrical resistance sensors. It was proven that zinc corrosion in active state is strongly affected by the presence of water at its surface. Zinc corrosion in real concrete in the absence of water can be misinterpreted as salt passivity. The presence of oxygen results in an increase of zinc corrosion rate, however at pH 12.6, passivity can occur. It was verified that corrosion products consisting primarily of Ca[Zn(OH)3]2·2H2O cannot effectively passivate zinc surface in concrete, even after 1800 h of exposure and zinc, or hot-dip galvanized steel can corrode at an unacceptable corrosion rate (more than 4 µm·a−1).

Improved Discharge Capacity of Zinc Particles by Applying Bismuth-Doped Silica Coating for Zinc-Based Batteries

Corrosion and discharge behavior of battery-grade zinc particles coated with a silica layer doped with bismuth was investigated and compared with untreated zinc powder. Electrochemical investigations were carried out in half-cell configuration. The electrolyte was 6 M KOH in excess. Coated zinc particles provided a discharge capacity of 737 mAh g−1 (89.9% DoD) versus 633 mAh g−1 (77.2% DoD) of untreated zinc particles after a dwell time of 1 h in KOH. The silica coating reduced the direct contact of the zinc surface with the electrolyte and thus minimized the hydrogen evolution reaction, which led to an increased discharge capacity. Additionally, bismuth doping enhanced conductivity within the silica coating and increased zinc utilization. Those coated zinc particles inhibited corrosion, i.e., corrosion efficiency reached 87.9% compared to uncoated zinc. Additionally, the coating achieved a capacity retention of 90.9% (670 mAh g−1) after 48 h dwell time in 6 M KOH. The coatings were prepared by sol-gel technology and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface determination.