Alkaline Zincate Solutions Research Articles

Effect of Structure of Organic Additives on Electrodeposition Behavior of Zn from Alkaline Zincate Solution and Its Crystal Morphology

Effect of Structure of Organic Additives on Electrodeposition Behavior of Zn from Alkaline Zincate Solution and Its Crystal Morphology

Corrosion Resistance of Zn–Ni Alloy Films Electroplated in Alkaline Zincate Solutions Containing a Brightener

Corrosion Resistance of Zn–Ni Alloy Films Electroplated in Alkaline Zincate Solutions Containing a Brightener

Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solutions Containing Various Brighteners and its Microstructure

Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solutions Containing Various Brighteners and its Microstructure

Electrodeposition Behavior of Zn-Ni Alloy from Alkaline Zincate Solutions Containing Various Brighteners and its Microstructure

The effect of brighteners on the deposition behavior of Zn–Ni alloys ant its microstructure was investigated. Zn–Ni alloys were electrodeposited on Cu electrode at 10–5000 A·m−2, 105 C·m−2, 308 K in unagitated zincate solutions containing various brighteners. Although the degree of suppression of hydrogen evolution was different depending on the kind of brightener, the transition current density at which the deposition behavior shifted from normal to anomalous was almost same in solutions containing brighteners. The current efficiency for alloy deposition significantly decreased with an addition of brighteners which had suppression effect on the Zn deposition. Since the brighteners more suppressed the Ni deposition than Zn deposition, the Ni content in deposited films decreased with an addition of brighteners. When the brightener of a straight-chain polymer composed of a quaternary ammonium cation (PQ) which can suppress the diffusion of ZnO22− and Ni ions in solution was added, the Ni content in deposited films increased with increasing current density at high current density region. This is attributed to that Zn which is preferentially deposited over Ni earlier reached the diffusion limitation of ZnO22− ions and Ni deposition didn’t reach the diffusion-limited current density. When both PQ and a quaternary ammonium salt with a benzene ring were added in solution, the films obtained at the diffusion-limited current density of ZnO22− ions exhibited the smooth surfaces composed of fine crystals. With an addition of brighteners to increase the overpotential for deposition, the γ-phase (intermetallic compound of Ni2Zn11) of the deposited films was formed easily.

Synergistic Effect of Brightener and Solution Temperature on the Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solution

Synergistic Effect of Brightener and Solution Temperature on the Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solution

Effect of Solution Temperature on Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solution

Effect of Solution Temperature on Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solution

Synergistic Effect of Brightener and Solution Temperature on the Electrodeposition Behavior of Zn-Ni Alloy from Alkaline Zincate Solution

Synergistic Effect of Brightener and Solution Temperature on the Electrodeposition Behavior of Zn-Ni Alloy from Alkaline Zincate Solution

Effect of Solution Temperature on Electrodeposition Behavior of Zn-Ni Alloy from Alkaline Zincate Solution

Effect of Solution Temperature on Electrodeposition Behavior of Zn-Ni Alloy from Alkaline Zincate Solution

Relation between Faradic Yields, Hydrogen Evolution and Pulsed Currents: Morphological and Fe Content Control in Zn and ZnFe Coatings

Long-term protection of metallic parts from atmospheric exposure is an important challenge and one of the most frequent way to ensure their corrosion resistance is the application of sacrificial zinc alloys coatings [1]. Among the various zinc electroplating baths, the alkaline zincate solutions has gained a wide range of applications thanks to its simple bath composition, good dispersion and efficient coverage ability. Nevertheless, its efficiency is very low in absence of additives, which affects the performances of the coatings by modifying the crystal growth and therefore the structural and mechanical properties. This is a result from the competition between dihydrogen production and the reduction of the metallic species present in the bath.The present study deals with the optimization of ZnFe sacrificial coating on steel and aluminum substrate in the frame of the ATLAS project -Alternative TechnoLogies for improved Anticorrosion Solutions- managed by the IRT M2P. After the analysis of the electrochemical behavior of the ZnFe electrolyte patented by the Coventya company and the UTINAM institute, pulsed currents will be implemented to extend the versatility of the coatings. Indeed, pulsed currents are known to act on various parameters such as improving the faradic yield or modifying morphologies and structures [2].The determination of a first panel of pulsed sequences (average current densities, cathodic peak current, cathodic pulse time and off-time) have been based on transient curves analysis from a zincate bath. Three sequences have been selected as they resulted in very different patterns in terms of electrochemical behavior and coatings characteristics. These sequences have been replicated and compared to DC current in several electrolytes, from the zincate bath to the commercial formula. For each set of parameters, the faradic yield has been measured and compared to the hydrogen generated during the electrolysis distributed between the absorbed one (measured by hot extraction) and the dihydrogen released into the reactor atmosphere (measured by mass spectrometry with a dedicated set- up). It is interesting to note that the obtained values strongly depend on pulsed sequences as well as electrolytes composition. Coatings were systematically produced and characterized. Morphology was observed using SEM and microstructure determined from XRD diffractograms: preferential orientation and crystal lattice and crystalline phases. The latest has required a specific methodological development.Finally, the identification of nucleation parameters by model simulation has been undertaken to describe the mechanisms involved in the first steps of zinc electrodeposition [3].[1] B. Chatterjee, « Electrodeposition of Zinc Alloys », p. 31.[2] X. Zhang, K. Tsay, J. Fahlman, and W. Qu, « Journal of Energy Storage, 26 p. 100966 (2019)[3] A. Milche, Electrochimica Acta, 48 p.2903-2913 (2003)

Effect of Reaction Product of Epichlorohydrin and Imidazole on the Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solution

Effect of Reaction Product of Epichlorohydrin and Imidazole on the Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solution

In Situ Observation at the Surface of Zinc in Alkaline Solution under Pulsed Current by Holographic Interferometry

Horizontal upward-facing zinc anode surfaces combined with Ni(OH)2/NiOOH cathodes in 1.95 M KOH aqueous solution were electrochemically dissolved and deposited with pulsed current. The morphological variations of zinc oxide were examined as a function of pulse width at three different locations on the anode surface using ex situ SEM observation. The particle size of zinc oxide varied with pulsed current for different pulse periods. Then, the transient variations in electrolyte for refractive index profiles along the axis perpendicular to the zinc anode were in situ measured under pulsed current using holographic interferometry. The oscillating layers of the refractive index profile were observed and related to a duplex diffusion layer model proposed by Ibl. Much more fine set up of SOC can be anticipated by combining the present results with HEV control (ECU) system.

Effect of Additives on Electrodeposition of Zinc from Alkaline Zincate Solution and Their Synergy Mechanism

Effect of Additives on Electrodeposition of Zinc from Alkaline Zincate Solution and Their Synergy Mechanism

Effect of Reaction Product of Epichlorohydrin and Imidazole on the Electrodeposition Behavior of Zn-Ni Alloy from Alkaline Zincate Solution

Effect of Reaction Product of Epichlorohydrin and Imidazole on the Electrodeposition Behavior of Zn-Ni Alloy from Alkaline Zincate Solution

Pulsed Current Vs. Organic Additives on Electrodeposition from Zincate Bath

Among the various zinc electroplating baths, alkaline zincate solution has gained a wider range of applications thanks to its simple bath composition, good dispersion and efficient coverage ability. Nevertheless, alkaline zincate solution cannot be used as such and it is necessary to introduce additives to control the process performances [1]. Otherwise, efficiency is extremely low, and the properties of the coatings are disappointing. Additives can modify the crystal growth and therefore the structural and mechanical properties, the corrosion resistance, and the appearance of coatings [2]. In the absence of additives, the main problem is low efficiency, resulting from the competition between dihydrogen production and the reduction of the metallic species present in the bath.Therefore, pulsed currents constitute an attractive way to eliminate the need for organic additives by significantly improving the Faradic yield. In this study, the influence of various pulsed current sequences versus the addition of organic additives is observed in the characteristics of the coatings as well as in the process execution. A key point in the determination of the pulse sequence is the study of the transient curves with a zincate bath. This allows for the identification of the most influential parameters on dihydrogen production, with direct consequences on the process mechanisms.By knowing the τD i.e. diffusion time preceding hydrogen reduction, it is possible to design pulse sequences with limited gas production. This is confirmed by mass spectrometry measurements which quantify the total dihydrogen production for each pulse sequence. Fig 1.The coating’s characterization consists in SEM analysis topographic pictures and preferential orientations and grain sizes determined through XRD. Results confirm the interest of pulsed currents versus organic additives for zincate baths.[1] J. L. Ortiz-Aparicio, Y. Meas, G. Trejo, R. Ortega, T. W. Chapman, et E. Chainet, « Effects of organic additives on zinc electrodeposition from alkaline electrolytes », J Appl Electrochem, vol. 43, no 3, p. 289-300, mars 2013, doi: 10.1007/s10800-012-0518-x.[2] L. Yuan, Z. Ding, S. Liu, W. Shu, et Y. He, « Effects of additives on zinc electrodeposition from alkaline zincate solution », Transactions of Nonferrous Metals Society of China, vol. 27, no 7, p. 1656-1664, juill. 2017, doi: 10.1016/S1003-6326(17)60188-2. Figure 1

Effect of Organic Additives on the Electrodeposition Behavior of Zn from an Alkaline Zincate Solution and Its Microstructure

Effect of Organic Additives on the Electrodeposition Behavior of Zn from an Alkaline Zincate Solution and Its Microstructure

Effect of Organic Additives on Electrodeposition Behavior of Zn from Alkaline Zincate Solution and Its Micro Structure

Effect of Organic Additives on Electrodeposition Behavior of Zn from Alkaline Zincate Solution and Its Micro Structure

Al2O3 Coatings on Zinc for Anti-Corrosion in Alkaline Solution by Electrospinning

The severe corrosion accompanied with hydrogen evolution reaction has become the main obstacle restricting the utilization of zinc as an electrode in alkaline batteries. Al2O3 coating helps control the corrosion of zinc in alkaline solution. Herein, a stable Al2O3 coating is fabricated through facile electrospinning from Al(NO3)3 as an efficient anti-corrosion film on zinc. The electrospinning technique facilitates uniform dispersion of Al2O3 particles, therefore the corrosion inhibition efficiency could be up to 88.5% in this work. The Al2O3 coating prevents direct contact between zinc and the alkaline solution and minimize hydrogen evolution. Further, the effects of the thickness of Al2O3 coating on corrosion behavior of zinc are investigated through hydrogen evolution reaction, Tafel polarization, and impedance test. The results show that the thicker Al2O3 coating possessed better corrosion inhibition efficiency due to the higher corrosion resistance and lower porosity. The 18 μm Al2O3 coating on zinc provides corrosion current density of 60.6 mA/cm2, while the bare zinc substrate delivers as much as 526.3 mA/cm2.This study presents a promising approach for fabricating Al2O3 coating for corrosion-resistant applications.

Research into the Influence of Process Parameters on the Efficiency of Zinc Electrolysis from Alkaline Solutions

The effect of the main zinc electrolysis parameters from an alkaline zincate solution on the current efficiency and power consumption is studied in laboratory conditions. The zinc concentration (initial and final), current density, and temperature are chosen as variable parameters. Both model (prepared from standard reagents) and actual electrolytes are used. The latter is prepared by leaching the calcined middling product of zinc-bearing dusts processing of ferrous metallurgy. It is shown that the current efficiency can be rather high (higher than 90%) even at the initial zinc concentration in the alkaline electrolyte of 10 g/dm3. However, low current loads (100–400 A/m2) are required in this case, the use of which is unreasonable for industrial electrolysis with the formation of powdered metal, because the actual current density decreases with the development of a cathode deposit surface even lower than the limiting diffusion current of complex ions. The growth of enlarged dendrites with the formation of short-circuited segments in the interelectrode space is expected in this case, which will decrease the current efficiency of zinc. Large-scale laboratory studies on zinc electrolysis from the actual zincate solution make it possible to determine the most power-efficient (with the highest current efficiency of zinc and lowest power consumption) process parameters; notably, the current density is 1000–2000 A/m2, the electrolyte temperature is 50–80°C, the initial zinc concentration is 20–50 g/dm3, and the residual zinc concentration is no lower than 15 g/dm3. A high current efficiency (85–95%) and applied power consumption (2.28–3.20 kW h/kgZn) will be provided under these conditions. The maximal current efficiency (higher than 90%) for the “depleted” zincate solution with a zinc content of 10 g/dm3 is implemented at current density j = 125 A/m2 close to the diffusion current density (of about 95.7 A/m2). The current efficiency considerably decreases at j > 500 A/m2, which is caused by intense hydrogen evolution. When performing studies for the enlarged electrolysis cell, the formed cathode deposit is evaluated qualitatively (by visible crystal sizes).

Effect of Stannum Ion on the Enhancement of the Charge Retention of Single-Flow Zinc–Nickel Battery

This study aims to discuss the effect of stannum ion (potassium stannate) in alkaline zincate solution on the deposition/dissolution behavior of zinc anode for single-flow zinc–nickel battery (SFZNB). Physical analysis is conducted using scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) technologies. The electrochemical performance of the battery is tested using cyclic voltammetry and galvanostatic techniques. Results show that adding potassium stannate in alkaline solution promotes crystal seed formation and grain growth and substantially improves the charge retention of the battery. The battery is charged to 18.75 mAh·cm−2 (based on the area of the electrode) at current density of 10 mA·cm−2 and set aside for 12 h. Then, the battery using electrolyte with 0.1 mol·L−1 potassium stannate has a discharge capacity of 15.20 mAh·cm−2 (coulomb efficiency of 81.1%). Moreover, the control sample has a discharge capacity of 11.25 mAh·cm−2 (coulomb efficiency of 60.0%). Thus, the present work provides a simple approach to restrain the SFZNB from self-discharge.

RESEARCH OF THE INFLUENCE OF TECHNOLOGICAL PARAMETERS ON EFFICIENCY OF ZINC ELECTROLYSIS FROM ALKALINE SOLUTIONS

The effect that the main parameters of zinc electrolysis from an alkaline zincate solution have on current efficiency and power con­sumption was studied in laboratory conditions. Zinc concentration (initial and final), current density and temperature were chosen as variable parameters. The study used both model electrolytes (prepared using standard reagents) and real ones produced by leaching the calcined middling product obtained when processing zinc-bearing dusts of ferrous metallurgy. It was shown that the current efficiency of zinc can be quite high (more than 90 %) even at an initial zinc concentration in the alkaline electrolyte of 10 g/dm 3 . However, this requires low current loads (100—400 A/m 2 ) that are impractical in industrial electrolysis used to produce powdered metal, since the actual current density decreases as the cathode deposit surface develops and may fall below the limiting diffusion current of complex ions. In this case, the growth of enlarged dendrites is expected with the formation of «short-circuited» sections in the interelectrode space, which as a whole will reduce the zinc current efficiency. Larger-scale laboratory studies focused on zinc electrolysis from a real zincate solution made it possible to determine the most energy-efficient (with the highest zinc current efficiency and the lowest power consumption) process parameters: current density — 1000—2000 A/m 2 ; electrolyte temperature — 50—80 °С; initial zinc concentra­tion — 20—50 g/dm 3 ; residual zinc concentration — not less than 15 g/dm 3 . These conditions will ensure high current efficiency (85 — 95 %) and electric power consumption (2,28—3,20 kW-h/kg Zn ). For the «depleted» zincate solution with a zinc content of 10 g/dm 3 , the highest current efficiency (more than 90 %) is achieved at a current density of 125 A/m 2 , close to the diffusion current density j = = 95,7 A/m 2 . With j > 500 A/m 2 , the current efficiency is significantly lower due to the intensive hydrogen release. A qualitative evalu­ation of the resulting cathode deposit was made (by the visible dimensions of crystals) in studies on an enlarged electrolytic cell.