Zinc electrodeposition from a chloride-free non-aqueous solution based on ethylene glycol and acetate salts

The microstructure and protective properties of electroplating zinc films on NdFeB from a chloride-free nonaqueous bath

The traditional aqueous electroplating of zinc film causes significant corrosion of NdFeB during the electroplating process, which is accompanied by hydrogen evolution reactions. In this study, electroplating zinc film is carried out from a chloride-free nonaqueous bath using zinc acetate (Zn(OAc)2) as the main salt, sodium acetate (NaOAc) as the conducting salt, and ethylene glycol (EG) as the solvent. The electrochemical properties of the EG bath with Zn(OAc)2 and NaOAc are characterized by means of cyclic voltammetry (CV) and linear sweep voltammetry (LSV) together with a Hull cell test on brass. The results of the experiment show that the Zn(OAc)2 concentration, current density, and temperature significantly impact the deposition behavior of zinc. Moreover, the open circuit potential (OCP) test and scanning electron microscopy (SEM) results demonstrated that the corrosion of NdFeB in the EG bath containing 0.7 M Zn(OAc)2 and NaOAc is effectively inhibited compared to when using the traditional aqueous zinc plating bath. A dense zinc film with a metallic appearance is successfully deposited on the NdFeB surface from the EG bath containing 0.7 M Zn(OAc)2 and NaOAc at 6 mA cm-2 and 60 °C. Comparative experiments demonstrate that the as-deposited Zn film exhibits superior protective performance and exerts less damage to NdFeB compared to the aqueous electroplating film.

Influence of Electrolyte Choice on Zinc Electrodeposition

Zinc electrodeposition serves as a crucial electrochemical process widely employed in various industries, particularly in automotive manufacturing, owing to its cost effectiveness compared to traditional methods. However, traditional zinc electrodeposition using aqueous solutions faces challenges related to toxicity and hydrogen gas generation. Non-aqueous electrolytes such as ionic liquids (ILs) and deep eutectic solvents (DESs) have gained attention, with choline-chloride-based DESs showing promise despite raising environmental concerns. In this study, zinc electrodeposition on mild steel was investigated using three distinct electrolytes: (i) halide-free aqueous solutions, (ii) chloride-based DES, and (iii) halide-free acetate-based organic solutions. The study examined the influence of deposition time on the growth of Zn on mild steel substrates from these electrolytes using physical characterization techniques, including scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that glycol + acetate-based non-aqueous organic solutions provide an eco-friendly alternative, exhibiting comparable efficiency, enhanced crystalline growth, and promising corrosion resistance. This research contributes valuable insights into the impact of electrolyte choice on zinc electrodeposition, offering a pathway towards more sustainable and efficient processes. Through a comprehensive comparison and analysis of these methods, it advances our understanding of the practical applications of zinc electrodeposition technology.

Electrolysis energy efficiency of highly concentrated FeCl2 solutions for power-to-solid energy storage technology

An electrochemical cycle for the grid energy storage in the redox potential of Fe involves the electrolysis of a highly concentrated aqueous FeCl2 solution yielding solid iron deposits. For the high overall energy efficiency of the cycle, it is crucial to maximize the energy efficiency of the electrolysis process. Here we present a study of the influence of electrolysis parameters on the energy efficiency of such electrolysis, performed in an industrial-type electrolyzer. We studied the conductivity of the FeCl2 solution as a function of concentration and temperature and correlated it with the electrolysis energy efficiency. The deviation from the correlation indicated an important contribution from the conductivity of the ion-exchange membrane. Another important studied parameter was the applied current density. We quantitatively showed how the contribution of the resistance polarization increases with the current density, causing a decrease in overall energy efficiency. The highest energy efficiency of 89 ± 3% was achieved using 2.5 mol L−1 FeCl2 solution at 70 °C and a current density of 0.1 kA m−2. In terms of the energy input per Fe mass, this means 1.88 Wh g−1. The limiting energy input per mass of the Fe deposit was found to be 1.76 Wh g−1.

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Electrodeposition of ZnNi Alloys from Choline Chloride/Ethylene Glycol Deep Eutectic Solvent and Pure Ethylene Glycol for Corrosion Protection

The present work follows the trend to develop non-aqueous electrolytes for the deposition of corrosion resistant ZnNi alloys. It investigates the use of the choline chloride/ethylene glycol (1:2 molar ratio) eutectic mixture and of pure ethylene glycol as solvents for ZnNi electroplating. The electrochemical behavior of Zn and Ni is investigated via cyclic voltammetry, and potentiostatic ZnNi deposition is performed. Ni content is found to be precisely tunable in the 10–20% wt range, which presents the highest industrial interest for corrosion protection. ZnNi coatings obtained are characterized from the morphological and phase composition point of view. Evidence of the formation of a metastable γ ZnNi phase is observed for both choline chloride/ethylene glycol and pure ethylene glycol. Finally, potentiodynamic corrosion tests are performed to assess their corrosion properties.

Potential Application of Ionic Liquids for Electrodeposition of the Material Targets for Production of Diagnostic Radioisotopes

An overview of the reported electrochemistry studies on the chemistry of the element for targets for isotope production in ionic liquids (ILs) is provided. The majority of investigations have been dedicated to two aspects of the reactive element chemistry. The first part of this review presents description of the cyclotron targets properties, especially physicochemical characterization of irradiated elements. The second part is devoted to description of the electrodeposition procedures leading to obtain elements or their alloys coatings (e.g., nickel, uranium) as the targets for cyclotron and reactor generation of the radioisotopes. This review provides an evaluation of the role ILs can have in the production of isotopes.

Progress in Electrodeposition of Zinc and Zinc Nickel Alloys Using Ionic Liquids

Zinc (Zn) and zinc–nickel (Zn–Ni) electrodeposition has been widely used in many industries, such as automotive and aerospace, for corrosion protection of steel components owing to their excellent corrosion resistance. Conventional zinc and zinc–nickel electrodeposition is performed in different types of aqueous baths (acid and alkaline). Such electrolytes suffer from certain drawbacks such as hydrogen gas evolution, low coulombic efficiencies, and environmental toxicity. Electrodeposition of Zn and Zn–Ni alloys from ionic liquids has gained significant attention in aerospace and automotive sectors owing to the different environments they provide for electrodeposition. This paper reviews the progress in deposition of zinc and zinc-nickel alloys in non-aqueous systems, especially ionic liquids. In addition, the challenges and technological developments associated with the Zn and Zn–Ni deposition on different substrates and the factors that need to be considered while electroplating at an industrial scale are discussed.