Zinc-nickel Alloy Coatings Research Articles

Hydrogen Permeation Study on Zinc-Nickel Coated Ultra-High Strength Martensitic Steels

Cadmium coatings are conventionally electrodeposited on ultra-high strength steels (UHSS) used in aerospace application to provide corrosion protection. Zinc-nickel alloy coatings are being studied as an alternative to cadmium coatings as the latter exhibits environmental and health concerns. The electrodeposition of zinc-nickel alloy is accompanied by hydrogen evolution reaction, resulting in hydrogen incorporation into the coating and further inward diffusion into the steel substrate. Presence of hydrogen in UHSS leads to hydrogen embrittlement and can be detrimental to the properties. To avoid this, outgassing of the coated parts are carried out.In this work, the diffusion of hydrogen through zinc-nickel coated and uncoated UHSS was investigated using the Kelvin-probe based detection technique. The charging of hydrogen in the samples was carried out using either an electrochemical or hydrogen gas-based charging. A comparative study between the electrochemical and gas-based charging techniques was carried out. The influence of coating morphology on the permeation was studied to understand the influence of morphology on outgassing efficiency. The diffusion coefficients were derived from multi-step permeation measurements performed by varying activity at the entry side. This project has received funding from the Clean Sky 2 Joint Undertaking (JU) under grant agreement No 101007712. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Clean Sky 2 JU members other than the Union.

Electrolytic deposition of zinc-nickel alloy coatings with organic addition

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

An investigation on corrosion properties of bright Zn‐Ni alloy coated mild steel

AbstractIn the present work, the electrodeposition of Zn–Ni alloy from Sulfate bath was carried out in presence of a novel brightener (CG), the condensation product of Cysteine Hydrochloride and Glutaraldehyde. The corrosion studies were carried out using Electrochemical Impedance spectroscopy and Potentiostatic techniques. They confirmed an increase in corrosion resistance and protection ability of bright zinc–nickel alloy coatings. Surface morphology was studied using SEM, FTIR, and reflectance spectroscopy that revealed fine‐grained nature of Zn‐Ni alloy crystallites. X‐ray diffraction studies were used for phase identification and preferred orientation of Zn–Ni alloy crystallites. The preferred orientation of the Zn‐Ni alloy crystallites along (630) planes was configured for bright appearance of the coating. CG was successful in giving an even, homogeneous, refined, and bright Zn‐Ni alloy deposit.

Zinc-nickel alloy coatings: electrodeposition kinetics, corrosion, and selective dissolution. A review

A review of the literature is devoted to the patterns of the electrodeposition of zinc-nickel alloys including the kinetics of cathodic reduction of zinc, nickel, and zinc-nickel alloys in ammonium chloride, sulphate, and glycinate deposition electrolytes. We studied the data on the effectiveness of the corrosion resistance of zinc-nickel coatings and summarised the principal patterns of selective dissolution of the Zn-Ni alloys. The role of the addition of glycine to an ammonium chloride deposition electrolyte was determined in the modification of the morphological and anticorrosive properties of the coatings.

Electroplating and Physicochemical Properties of Zinc–Nickel Alloy Coatings from Ammonium Oxalate Electrolytes

Electroplating of zinc−nickel alloy coatings (3–16 at % Ni) on Type 17G1S-U steel from ammonium oxalate baths is studied. The effects that the ratio of alloy components has on the coating’s corrosion resistance and structure and the electroplating kinetic parameters are revealed. Applying zinc–nickel alloy coatings leads to a nearly sevenfold decrease in the corrosion rate compared to zinc-only coatings. The microhardness of high-alloy nickel coatings increases by a factor of 1.8 compared to their low-alloy zinc–nickel counterparts.

USING ZINC-NICKEL ALLOY IN THE ZINC DEPOSITION TECHNOLOGY

Introduction. More negative potential of zinc coatings provides effective protection of the steel substrate from corrosion damage. To increase the chemical resistance to corrosion processes, zinc coatings are necessarily post-treated, i.e. by chromate treatment. The disadvantages of the latter are the use of toxic compounds of Cr (VI) and removing a significant layer of zinc coating (up to 2 μm). The aim of the study was to substantiate the choice of electrolyte for zinc electrodeposition mostly meeting modern requirements, and to replace the chromate film with a thin layer of zinc-nickel alloy. Materials and research methods. The measurements were carried out in a tree-electrode cell using a PI-50.1 potentiostat with a saturated silver chloride reference electrode. The values of the electrode potentials in the graphs are shown by this electrode. Zinc coatings were deposited from chloride, ammonina and alkaline electrolytes with two versions of organic additives. Zinc-nickel alloy coating was prepared from an ammonina-glycinate electrolyte. Results. Chloride and ammonium electrolytes are characterized by high current outputs, close to 100%, in almost the entire range of current densities from 1 to 4 A/dm2. The current efficiency decreases with current density increasing in alkaline electrolytes. It is due to the greater uniformity of metallic coatings. The throwing power in the studied electrolytes was estimated usingHull cell with a sectional cathode. The ratio of the maximum and minimum weight increments in individual sections of the cathode in indicates a higher throwing power of alkaline electrolyte. Due to the high protective properties of zinc-nickel alloy coatings, it is proposed to obtain a thin layer (0.5-0.7 µm) of the zinc-nickel coating from the ammoniz-glycinate electrolyte instead of chromate passive film during the process of zinc electrodeposition.

Role of the newly synthesized brightener in modification of surface properties of Zn-Ni alloy electrodeposited on steel substrate

In the present study, a new brightener was synthesized by condensation of salicylaldehyde and cysteine hydrochloride (SC). To examine the influence of SC on the nucleation mechanism of Zn-Ni alloy, electrodeposition, cyclic voltammetric and chronoamperometric studies were carried out. The model of Schariffker and Hills was used to analyze current transients which explained the electrocrystallization process of Zn-Ni alloy. It is revealed that Zn-Ni electrocrystallization process in presence of SC is regulated by instantaneous nucleation mechanism. The corrosion studies were done for the bright and dull zinc-nickel alloy coatings in 3.5 wt.% NaCl solution, using potentiodynamic polarization and electro­chemical impedance spectroscopic techniques. The phase structure, surface morphology and brightness of the deposit were characterized by means of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and reflectance studies. These studies revealed the role of SC in producing a bright Zn-Ni alloy coating on mild steel substrate and also showed its improved corrosion resistant nature.

Electrochemical behaviour and analysis of Zn-Ni alloy anti-corrosive coatings deposited from citrate baths

Zinc-Nickel alloy coatings have been widely used to improve the corrosion resistance of steels. Electrodeposition of zinc-nickel alloy films on a steel plate under various deposition conditions is studied. The effects of plating variables such as bath composition, pH and current density on the coating composition, morphology and corrosion property have been systematically investigated. The zinc and nickel ions in plating baths are stabilized using complexing agent potassium citrate. Increasing the molar concentration of potassium citrate extends the pH of nickel hydroxide and zinc oxide precipitation. The morphological properties and crystalline phase structure of the deposited alloy coatings are examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The analyses reveal that the coatings deposited from citrate bath contain γ-NiZn3 and γ-Ni2Zn11 alloy phases. These phases improve the corrosion resistance of the steel plate. Electrochemical behaviour analyses of the Zn-Ni film illustrated by electrochemical impedance spectroscopy (EIS) measurement revealed that the sample (a) deposited from 0.0326M citrate bath at acidic pH shown higher impedance modulus than non-citrate bath coated samples, which improved anti-corrosive properties of the coatings. This study confirms that uniform Zn-Ni coating with smaller grain sizes has better anti-corrosive properties.

Zinc–Nickel Alloy Electrodeposition: Characterization, Properties, Multilayers and Composites

The alloy coatings such as zinc–nickel are used to improve the lifetime of zinc sacrificial coatings. zinc–nickel alloy coating has a longer history than other zinc alloy coatings and is considered as the most corrosion resistive zinc alloy. One of the important properties of this type of coatings is the ductility properties of coated steel pieces; as after thermal treatment and shaping operations, the corrosion resistance is enhanced up to an optimal level. Because of such properties, this alloy is investigated in coating the pieces such as connecting bolts, brake system components, and fuel system. Resistance to heat, ultraviolet light, hydraulic fluids, and fuels are other characteristics of such coatings. The use of zinc–nickel alloy coatings is growing in the bolts and threaded parts industry. Since these coatings do not prevent galvanic corrosion in contact with aluminum, they are widely used in industries that deal with aluminum bodies. However, the zinc–nickel alloys are considered as the most expensive coatings. These alloys are coated both by acidic and alkaline baths that provide different coating properties. This paper reviews the studies conducted on zinc–nickel alloy coatings, analyzing baths and their properties, the effect of different parameters on electrodeposition, as well as Zn–Ni multilayer and composite coatings and their properties.

Исследование состава и структуры цинк-никелевых покрытий, осажденных из слабокислого электролита на железный подслой

Zinc-nickel alloy coatings have great advantages over many monometallic coatings. However, their use in practice is limited due to the complex mechanism of processes that is studied insufficiently. The paper is devoted to the investigation of the electrolysis parameters on zinc-nickel coating composition and structure during еlectroplating at the iron underlayer of copper substrate from weakly acidic chloride electrolyte. The chemical composition of the electrolyte was monitored by dichromatometriс and complexometric titration. Study of phase composition was performed using an X-ray diffractometer Rigaku Ultima IV. Gross composition was measured using a scanning electron microscope JEOL JSM-6460LV. It was found that аn increase of the current density increases the rate of deposition of the alloy. Increase of temperature leads to an increase of the proportion of nickel in the alloy, and an increase in the nickel deposition rate. Zinc deposition rate is not affected by temperature. Moreover, an abnormal codeposition of the alloy was observed in the entire investigated range of temperatures and current densities. As the temperature changes, The surface of the micro-relief changes with increasing temperature, the grain size becoming smaller and the surface smoother. X-ray analysis of the coatings showed that they are a homogeneous nickel-base solid solution. Сoating structure corresponds best to the face-centered cubic lattice.

Corrosion Behavior of Reverse-Pulse Electrodeposited Zn-Ni Alloys in Saline Environment

The study investigates the relationship of the reverse-pulse electrodeposited zinc-nickel alloy coatings’ characteristics and their corrosion behaviors in a saline environment, using both anodic polarization and electrochemical impedance analysis. The introduction of anodic pulsation gives deposits of more refined grain sizes and increased nickel contents, resulting in improvement of the corrosion resistance. High anodic current densities employed in the reverse-pulse electrodeposition, however, modulate crystallographic orientations of the grains, introduce porosity to the structure, and hence adversely affect the corrosion resistance of the coating deposits.

Research to the Corrosion Resistance of the Alkaline Zinc-Nickel Alloy Plates

The zinc-nickel alloy coatings were electrodeposited by changing the concentration of the NiSO4 • 6H2O in the plating bath. The scanning electron microscopy (SEM) was used to observe the coating’s surface morphology. The EDS was applied to test the coating’s nickel content. The corrosion resistance was studied by using the Tafel curves, AC impedance spectra and the neutral salt spray test. The results showed that: The coating’s nickel content could reach 12.56% when the NiSO4 • 6H2O concentration was 8g/L in the bath and the coating was very smooth, dense and bright. Its corrosion potential was low and its corrosion reaction resistance was best with red rust time up to 46d, so it had good corrosion resistance. But when the NiSO4 • 6H2O concentration was changed, the coatings’ corrosion resistance would be more or less changed.

Effects of deposition temperature on electrodeposition of zinc–nickel alloy coatings

Zinc–nickel alloy coatings were electrodeposited on carbon steel substrates from the ammonium chloride bath at different temperatures. The composition, phase structure and morphology of these coatings were analyzed by energy dispersive spectrometer, X-ray diffractometer and scanning electron microscopy respectively. Chronopotentiometry and potentiostatic methods were also employed to analyze the possible causes of the composition and structure changes induced by deposition temperature. It has been shown that both normal and anomalous co-deposition of zinc and nickel could be realized by changing deposition temperature under galvanostatic conditions. The abrupt changes in the composition and phase structure of the zinc–nickel alloy coatings were observed when deposition temperature reached 60°C. The sharply decrease of current efficiency for zinc–nickel co-deposition was also observed when deposition temperature is higher than 40°C. Analysis of the partial current densities showed that the decrease of current efficiency with the rise of deposition temperature was due to the enhancement of the hydrogen evolution. It was also confirmed that the ennoblement of cathodic potential was the cause for the increase of nickel content in zinc–nickel alloy coatings as a result of deposition temperature rise. The good zinc–nickel alloy coatings with compact morphology and single γ phase could be obtained when the deposition temperature was fixed at 30–40°C.

Effect of diethanolamine and triethanolamine on the properties of electroplated Zn–Ni alloy coatings from acid bath

AbstractIn the present work, zinc–nickel alloy coatings have been produced under direct current conditions from an acid bath with different concentrations of diethanolamine (DEA) and triethanolamine (TEA). The produced coatings were analysed through chronopotentiometry, microhardness, X‐ray diffraction and MEB techniques. The compositional analysis of the films showed that the Zn–Ni electrodeposition is anomalous for all the systems. Ethanolamines augmented the anomalous behaviour. The hindering in the Ni (II) reduction will be more effective due to complexation of Ni (II) catalyst with ethanolamines. Electrochemical and structure analysis of deposits indicated the presence of γ and highly Zn‐enriched phases. The presence of these additives resulted also in coatings with finer grains. The behaviour of modified Zn–Ni alloy coatings in corrosion solution of 3% NaCl was investigated through potentiodynamic polarisation and electrochemical impedance spectroscopy. It was found that the obtained Zn–Ni/3 mM TEA alloy exhibited better corrosion resistance compared to pure Zn–Ni alloy electrodeposited at similar conditions. © 2012 Canadian Society for Chemical Engineering

Investigation of high-performance acid zinc nickel electrolyte

Zinc nickel alloy coatings are increasingly demanded by the automotive industry due to their highly improved corrosion protection over pure zinc and other zinc alloy coatings. To produce zinc nickel coatings with a nickel incorporation of 12 to 16%, mainly alkaline zinc nickel electrolytes are used in the plating industry. Continuous improvements in the field of acidic zinc nickel alloy electrolytes now meet the needs of the automotive industry while being advantageous in specific fields of application. In this paper, zinc nickel coatings deposited from alkaline as well as from ammonium-free acid zinc nickel electrolytes are investigated. The morphology is evaluated by scanning electron microscopy; the texture is investigated by focused ion beam, and X-ray diffraction patterns identify the structure of the coating. The corrosion protection of the zinc nickel coatings and the adhesion of the zinc nickel coatings have been bench-marked. For applications on fasteners, the coefficients of friction have been measured and compared.

Electrochemical corrosion behavior in NaCl medium of zinc–nickel alloys electrodeposited under applied magnetic field

The electrochemical codeposition of zinc–nickel alloy coatings from sulfate bath has been carried out under low and high applied magnetic field. The influence of alloy structural parameters upon corrosion behavior is discussed. It has been found that the magnetically induced convection modifies the phase composition, promoting the zinc phase in spite of the γ-Ni 5Zn 21. Low magnetic field acts also on the morphology of the deposits by reducing the grain size and the average roughness R a. For alloy obtained with low magnetic field superimposition, surface morphology modification has no significant effect on corrosion behavior whereas for low nickel content alloy, the modification of phase composition, induced by applied magnetic field, favours higher polarization resistance. When high magnetic field amplitude is involved, the phase composition modifications are the same that for low applied B and the morphology is not largely modified. In this case, the hydrogen reduction current dramatically decreases that leads to a large shift of the corrosion potential. It is suggested that the surface reactivity of electrodeposited alloys depends on the magnetically induced convection that is efficient during the codeposition process.

Study on corrosion resistance of electroplating zinc–nickel alloy coatings

AbstractElectrodeposited zinc–nickel alloy coatings have been widely adopted for surface treatment of automobile body steel sheet for high corrosion resistance. The corrosion behavior of the coatings has been related with the components of nickel, and the zinc–nickel alloy passive coatings have much higher corrosion resistance than that of zinc–nickel alloy coatings. In the present paper, the corrosion resistance behavior of the zinc–nickel alloy coatings obtained by new process and formulation has been studied by means of the electrochemistry test and neutral salt spray test. And it is discovered that the properties of corrosion resistance of zinc–nickel alloy passive coatings were better than that of zinc passive coatings, Cadmium passive coatings and alloys of electrodeposited cadmium–titanium. The components of corrosion productions, in terms of X‐ray diffraction (XRD), are mainly ZnO, ZnCl2 · 4Zn(OH)2 and small quantity of 2ZnCO3· 3Zn(OH)2. The component of zinc–nickel alloy coatings has been investigated with Glow Discharge Optical Emission Spectrometry (GDA‐750). And it is found that as the thickness of zinc–nickel alloy coatings increases, the component of zinc increases from beginning to end, but the peak value of nickel appears and an enrichment of nickel in the coatings comes into being. Because the electrodeposited zinc–nickel alloy coatings exhibit different alloy phases as a function of their alloy composition, in this paper, the crystal structure changing with the different component of nickel has been studied in terms of XRD. The result shows that electrodeposited zinc–nickel alloy has different phases: α‐phase, a solid solution of zinc in nickel with an equilibrium solubility of about more than 79% nickel; γ‐phase, an intermediate phase with a composition Ni5Zn21; η‐phase, a solid solution of nickel in zinc with less than 5% nickel; and δ‐phase (Ni3Zn22) appeared from η‐phase to α‐phase with increasing content of nickel. Copyright © 2009 John Wiley & Sons, Ltd.

Tin–Manganese Alloy Electrodeposits: II. Corrosion Performance Studies

The corrosion performance of tin–manganese alloy electrodeposits either immersed in a quiescent sodium chloride solution or exposed to neutral salt spray (NSS) was studied. The results obtained were then compared with those for conventional pure zinc and zinc–nickel alloy electrodeposits with or without chromate passivation treatment. It was found that tin–manganese alloy electrodeposits provided much longer sacrificial protection against the corrosion of mild steel substrates than zinc–nickel alloy coatings, although they were inferior to pure zinc coatings. The prolonged sacrificial property was attributed to the high polarization resistance of tin–manganese alloy electrodeposits as revealed by linear polarization resistance techniques, which would only allow the corrosion and the consequent ennoblement of these coatings to proceed at a slow rate. The result of NSS tests indicated that tin–manganese alloy electrodeposits, with a time to red rust of about , were as good as chromated zinc–nickel alloy coatings but far outperformed pure zinc coatings and nonchromated zinc–nickel coatings. The high corrosion resistance of tin–manganese alloy electrodeposits without any passivation treatment suggests that they may be an environmentally friendly replacement to zinc alloy coatings, which need toxic chromate conversion coatings for corrosion-resistance enhancement.

Deposition of Nanocrystalline Zinc-Nickel Alloys by D.C. Plating in Additive Free Chloride Bath

Nanocrystalline zinc-nickel alloy coatings were electro-deposited in chloride bath containing ZuCl 2 (50-200 gL -1 ), NiCl 2 .6H 2 O (50-200 gL -1 ) and H 3 BO 3 (40 gL -1 ) at45°C. The initial alloy composition, as investigated by voltammetry, chronopotentiometry or EDX analysis, exhibited a pronounced dependence on the composition of plating bath. However, the alloy composition tended to approach an upper limit of 18 atomic percent when deposits grew thicker, for most of the plating bath compositions. The process was clearly the anomalous codeposition, which was considered to be due to the formation of an adsorbed layer of Zn(OH) 2 containing nickel cations, as an intermediate product, whose composition determines the composition of the electro-deposited alloy. The electro-deposited coatings comprised of single-phase structure of γ-phase (Nι 5 Zn 21 ) for about 12-18 atomic percent nickel and a mixture of γ- and η-phases (hcp) for nickel atom percent below 8. The grain size decreased from about 50nm to 20nm with decrease in nickel content away from the stoichiometric composition of Ni 5 Zn 21 along with a decrease in hardness from about 450KHN to 150KHN. The decrease in hardness with a decrease in grain size seems attributable to the grain boundary sliding as predominant deformation mechanism. Anodic dissolution of the alloys involved pronounced dezincification, forming α-phase (fcc) that dissolved at the end.

Zinc-Nickel alloy coatings electrodeposited by pulse current and their corrosion behavior

Steel in subtropical monsoon regions encounters severe atmospheric corrosion. In an attempt to provide better corrosion protection, zinc-nickel alloys were electrodeposited on steel by pulse current. Some electric variables (average current density and pulse cycle) and bath temperature on chemical compositions and grain size of coatings were studied. Next, zincnickel alloys electrodeposited on steel were prepared for atmospheric corrosion tests. In addition, the determination of the chemical compositions and the grain size of the Zn-Ni alloy coatings were conducted by scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS) and scanning probe atomic force microscope (AFM). Furthermore, Tafel plots were employed to evaluate the alloy corrosion behavior.