Zn Ni Alloy Coatings Research Articles

Physicochemical, Morphological and Anticorrosive Properties of Electrodeposited ZnNi Alloy Coating

Corrosion in its many forms is a major problem for many types of materials, extending from machining to manufacturing and daily use. In fact, it affects practically all engineering projects, from the biggest to the smallest: energy production, construction, transport, medical sector, electronics, etc. Consequently, corrosion generates both economic and environmental problems. To prevent corrosion and preserve materials' durability, several protection methods can be applied. These included protection by applying a coating on the metal surface. In this context, Zinc based alloy coatings have attracted much interesting scientific community because of their excellent mechanical and anti-corrosive properties. In the present work, ZnNi coatings were electrodeposited on steel substrates using a chloride bath containing ammonium salts. The effect of some experimental parameters, namely, potential and metal ion concentration ratio on the deposition kinetics of ZnNi system as well as on its physicochemical, morphological and anticorrosive properties has been investigated. For this purpose, an appropriate experimental work was performed by using both electrochemical (cyclic voltammetry, chronoamperometry, open circuit potential, potentiodynamic polarization) and nonelectrochemical (SEM-EDX) analysis methods. Based on the obtained results, it has been revealed that simultaneous codeposition of both elements Zn and Ni is possible in our experimental conditions. However, deposition kinetics exhibited a strong dependence on explored parameters. Also, morphological aspect and chemical composition of deposits are strongly influenced by metal ion concentration ratio. Investigation of corrosion behaviour confirms the protective effect of coatings acted as a sacrificial anode. Furthermore, increasing Ni content in the deposits induces a significant enhancement in corrosion resistance. Thus, Zn-Ni alloy coatings prepared from the Ni(II)-rich bath exhibited better corrosion resistance.

Effect of complexing agent on iron base zinc-nickel alloy coating

The influence of four complexing agents on corrosion resistance of Zinc-Nickel (Zn-Ni) alloy coating was investigated. The current density and plating time were determined by Hull and rectangular tank experiments. The effects of triethanolamine, potassium sodium tartrate, tetraethylenepentamine and sodium citrate on the properties of iron-based Zn-Ni alloy coatings were studied under the same electroplating process. The surface morphology, structure, elemental composition and corrosion resistance of Fe-base Zn-Ni alloy coatings with different complexing agents were analyzed. The surface and morphology of the coating were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The anticorrosive properties of the coating were evaluated by electrochemical electrode and electrochemical impedance spectroscopy (EIS). The self-corrosion current density of triethanolamine is 2.927e-005A·cm−2, the rate of corrosion is minimal, rendering the material highly resistant to corrosion; the surface remains flat and exhibits a dense texture. The content of potassium, sodium, Zn and Ni in tartrate increased, thus reducing the corrosion resistance and flatness of the coating. The self-corrosion current density was 9.400e-005A·cm−2. The surface was rough and uneven, and there were a large number of large concave and convex defects. The complexing agent enhances the adhesion and corrosion resistance of the coating, improves the optical and mechanical properties of the coating, adjusts the durability and stability of the coating, increases the crystal packing density, increases the coating thickness, improves the adhesion with the substrate interface, and optimizes the uniformity of grain distribution. These factors are the key factors that determine the corrosion behavior of Zn-Ni coatings. In the process of electroplating, the addition of complexing agent can improve the quality of the coating, and suitable complexing agent can obtain smooth and bright coating at the same time, make the corrosion resistance of the coating higher.

Nickel partitioning in ZnNi coatings (Ni less than 4 wt.%) and its effect on the coating corrosion behaviour

ABSTRACT ZnNi alloy coatings with low Ni content (1–4 wt.% Ni) were electrodeposited over mild steel. Ni addition changed the coating morphology from faceted to hillock, decreased the crystallite size, and shifted the basal plane texture to higher energy (011) texture. Zn-1.5 wt.% Ni coating exhibited significantly improved corrosion resistance, even better than the pristine Zn coating. The corrosion resistance properties, however, degraded considerably as the Ni content increased (2.7 and 3.7 wt% Ni). The high corrosion resistance of the Zn-1.5 wt.% Ni coatings was due to the presence of nearly basal texture, low coating strain and evolution of stable γ-phase in the Zn matrix. The corrosion rate for higher Ni addition increased due to high energy surface texture and higher coating strain.

Barrel electroplating of Zn-Ni alloy coatings from a modified deep eutectic solvent

ABSTRACT Here the authors report the electroplating of Zn-Ni alloy on mild steel components from a modified deep eutectic solvent (DES), Ethaline, through a combination of barrel-plating and pulse-plating processes. The Ethaline electrolyte, a eutectic mixture of choline chloride (ChCl) and ethylene glycol (EG), was modified with propylene carbonate (PC) as a co-solvent together with the addition of boric acid to control deposit morphology and to suit the barrel plating system. A coating of γ-phase Zn-Ni alloy with 12–16% Ni was formed uniformly on mild steel screws and small components and the coating performed well as a sacrificial anti-corrosion layer. These findings are reported as part of an Innovate UK funded collaboration between university and industry partners, and included here are also the results of a scale-up pilot demonstrator system installed at E.C. Williams Ltd. (UK). It is concluded that the barrel plating of components using these materials and methods is very effective on a medium-scale and that the specification and performance of the coating is comparable with that from aqueous media. However, further development of this process may be limited by low current efficiency and the high relative cost of DES media.

Effect of Ni Concentration on the Surface Morphology and Corrosion Behavior of Zn-Ni Alloy Coatings

This research work aims to develop electrodeposited Zn-Ni alloy coatings with controlled dissolution tendencies on a mild steel substrate. The varying Ni concentration in the electroplating bath, i.e., 10, 15, 20 and 25 g·L−1, affected the surface morphology and electrochemical properties of the deposited Zn-Ni alloy coatings. SEM and EDS analysis revealed the resulting variation in surface morphology and composition. The electrochemical behavior of different coatings was evaluated by measuring the open circuit potential and cyclic polarization trends in 3.5 wt.% NaCl solution. The degradation behavior of the electrodeposited Zn-Ni coatings was estimated by conducting a salt spray test for 96 h. The addition of Ni in the coating influenced the coating thickness and surface morphology of the coatings. The coating thickness decreased from 38.2 ± 0.5 μm to 20.7 ± 0.5 μm with the increase in Ni concentration. Relatively negative corrosion potential (<−1074 ± 10 mV) of the Zn-Ni alloy coatings compared to the steel substrate (−969 mV) indicated the sacrificial dissolution behavior of the Zn-rich coatings. On the other hand, compared to the pure Zn (26.12 mpy), ~4 times lower corrosion rate of the Zn-Ni coating (7.85 mpy) was observed by the addition of 25 g·L−1 Ni+2 in the bath solution. These results highlighted that the dissolution rate of the sacrificial Zn-Ni alloy coatings can effectively be tuned by the addition of Ni in the alloy coating during the electrodeposition process.

Comparative Study of Electrodeposited Zn and Zn–Ni Alloy Coatings for Improved Corrosion Protection in Chloride Medium

The anti-corrosive Zn and Zn–Ni alloy coatings were electrodeposited on different copper substrates using an optimized sulphate electrolyte bath by conventional Hull cell method with glycine as an additive. The composition and surface morphology of the coatings were dependent on the current density. The co-deposition of Zn and Ni in Zn–Ni alloy showed anomalous behaviour, wherein, the deposition of less noble metal (Zn) was preferred over the more noble (Ni) metal. Anticorrosion properties of the coatings were experimented by electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques in 3.5% NaCl medium. The Zn–Ni alloy exhibited 3 times better corrosion resistance than pure Zn coating under the same deposition conditions.

Influence of the microstructure of Zn–Ni coatings on hydrogen effusion characteristics

This study reports about the influence of the microstructure of electroplated Zn–Ni alloy coatings, especially the extent and characteristic of existing microcracks within, on hydrogen effusion characteristics at room temperature (RT) and 200 °C. For comparison, the behavior of an electroplated Zn coating was also investigated. The microstructures of the Zn and Zn–Ni coatings were examined by means of scanning electron microscope (SEM) and optical microscope (OM). These results were correlated with the hydrogen effusion profiles, which were determined by using a carrier gas hot extraction (CGHE) technique. In addition, a silver decoration method was applied to visualize the hydrogen effusion paths within the coatings. First both Zn–Ni electroplating processes exhibit less hydrogen absorption compared to Zn. In addition the microstructure of the Zn–Ni coatings, especially the characteristic and magnitude of the microcracks, significantly influences the hydrogen effusion characteristics. By using the silver decoration method according to (Schober in MTA 14:2440-2442, 1983) it could be proofed that for Zn–Ni hydrogen primary effuses along the microcracks and the interfaces of pustules within the coating. But the microcracks seem to promote the hydrogen effusion much more than the interfaces of the pustules.

Improvement of corrosion resistance of Zn-Ni alloy coatings by anodizing in selected alcoholic solutions

The subject of this investigation is the anodic treatment of galvanic Zn-Ni alloy coatings in alkaline solutions of selected alcohols and their characterization. The process was carried out galvanostatically at an anodic current density in the range 0.06–6.25 A/dm2 for 2–60 minutes. The characterization of the formed coatings was based on the morphological studies (OM), determination of the chemical and phase composition (XPS and GIXD), as well as film thickness (UV–vis spectroscopic ellipsometry) and corrosion investigations (EIS). It was found that the coatings have a mixed oxide-alkoxide passive character with the alkoxide-rich layer on the top. The anodic oxidation led to the coloration of the alloy; various colors (beige, blue, and violet) could be obtained depending on the process parameters. The colors were strongly related to the thickness of the films, which is similar to the passive layers found on valve metals (e.g. titanium). The thickest of the conversion coatings had ca. 250 nm. The EIS investigations showed the improvement of corrosion resistance of the substrate after the anodic treatment.

Electrodeposition of composition controllable Zn[sbnd]Ni coating from water modified deep eutectic solvent

Because of the anomalous co-deposition, the preparation of Ni content controllable ZnNi sacrificial coatings with excellent corrosion resistance from aqueous solutions is a great challenge. In this paper, a novel method was developed to deposit Ni content controllable ZnNi coating by adding appropriate water (0–7 wt%) to the deep eutectic solvent. It was found that the electrochemical windows of ChCl-2urea deep eutectic solvent were nearly unchanged when the water content was <5 wt%. The Ni content in ZnNi alloy can ranged from ~96 wt% to ~4 wt% by regulating the water content and deposition potential. The Zn alloy coating with ~14 wt% Ni and single γ phase exhibited the best protective effects to carbon steel, which was deposited from reline-5 wt% water at −1.2 V. Deep eutectic solvent-water system provides a promising way of preparing ZnNi alloy coatings with controlled composition and excellent corrosion resistance.

Structural, Micromechanical and Tribological Characterization of Zn–Ni Coatings: Effect of Sulfate Bath Composition

Zn and Zn–Ni alloy coatings were electrodeposited on mild steel from sulfate-based bath containing Sn as additive. The effect of Ni content on the microstructure, morphology, microhardness and the tribological behavior of these coatings were studied and discussed. Adding Sn in the sulfate bath had a significant effect on the surface morphology, particularly on the Zn–8 wt% Ni coatings. By increasing the Ni concentration from 8 to 14 wt%, the X-ray patterns showed that the phase structure of Zn–Ni alloy coatings was changed from η-phase Ni3Zn22 to γ-phase Ni5Zn21. The plastic deformation and delamination were found to be wear mechanisms for the investigated coatings. While the Zn–14 wt% Ni alloys had the best wear resistance, Zn films had the most severe wear volume loss and the highest friction coefficient.

INFLUENCE OF NICKEL CONCENTRATION ON THE CHARACTERISTICS OF THE ELECTROPLATING Zn-Ni ALLOY

Zn-Ni alloy electroplating behaves as anodic coating but has better mechanical properties in comparison with pure Zn coatings. Hence, Zn-Ni coating is accepted as an environmentally friendly alternative to cadmium coatings which is very toxic during producing and use. In this paper, Zn-Ni alloys were electrodeposited from sulfate electrolyte baths at various ratios of Ni2+/Zn2+. Influences of nickel concentration on the plating process were investigated. The composition, morphology and structural properties of the thin films were analyzed by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) measurements. Electrochemical behaviour of the plated thin films was characterized by open circuit potential and potentiodynamic polarization curves. It was seen that the optimum condition for Zn-Ni electroplating was at temperature of 50 °C, current density of 5 A/dm2, anode - cathode distance of 2.5 cm with stirring. Current efficiency of the plating process and characteristics of the Zn-Ni alloy coatings depended much on the nickel concentration in the plating bath. The best properties were found for the electroplated alloy coating with nickel content in the range of 12 - 14 %.

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

Anticorrosive coatings are a useful approach for protecting steel structures/machinery against corrosion. Electrodepositions of zinc and zinc–nickel alloy films on steel substrates under various conditions from baths containing potassium citrate were studied. The effects of electroplating variables such as bath composition and current density on the coating composition, morphology, corrosion and mechanical properties were systematically investigated. The electrochemical and mechanical behaviour of Zn–Ni deposits obtained at 60 mA cm−2 from the citrate bath exhibited a lower corrosion current (Icorr) and a less negative corrosion potential (Ecorr) compared to pure Zn and Zn–Ni alloy coatings from the non-citrate bath. The crystallite size of the Zn–Ni coating deposited from the citrate bath was 35.40 nm, and the Ni content of the coating was 8.3 wt%. The morphological properties and crystalline phase structure of the alloy coating were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The topographical structure of the coatings was analyzed by atomic force microscopy (AFM). The dominant γ-NiZn3 (815) and γ-Ni2Zn11 (330) (631) plane orientations in the zinc–nickel alloy films improved the corrosion resistance. Zn–Ni films with smaller grain size and uniform coating had an increased impedance modulus and improved corrosion resistance.

Deposition potential effect on surface properties of Zn–Ni coatings

ABSTRACTThe electrodeposition of Ni–Zn alloy coatings at different deposition potentials from a sulphate bath was studied by means of chronoamperometry, anodic linear stripping voltammetry, X-ray diffraction and atomic force microscopy. Corrosion behaviour of Zn–Ni alloys in 3.5 wt-% NaCl solution was examined by anodic polarisation and electrochemical impedance spectroscopy. Results indicated that the nickel content in the deposit is enhanced with more negative deposition potential, where the average surface roughness decreased. Electrochemical measurements obtained by anodic polarisation and impedance spectroscopy revealed that Zn–Ni alloy coatings obtained at more negative potential present best corrosion resistance.

Studies on surface treatment of electrodeposited Ni–Zn alloy coatings using saccharin additive

Ni–Zn alloy coatings were electrodeposited galvanostatically at room temperature. Saccharin (0 to 1.8 g L−1) was added in the deposition bath as an additive agent. The effects of varied saccharin content addition on the physical properties of Ni–Zn alloy coatings were studied. The Ni–Zn alloy coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic absorption spectroscopy (AAS), atomic force microscopy (AFM), contact angle, electrochemical impedance study (EIS), salt immersion test, friction coefficient, and wear resistance tribology techniques. The XRD study confirmed the formation of Ni–Zn alloys with mixed phases of Ni–Zn alloy depending upon the saccharin content addition. The AAS analyses based on varied saccharin addition confirmed Ni–Zn alloy composition between 64:36 and 22:78 at.%. The effects of varied saccharin addition on physical properties like stress, strain, microstructure, topography, wettability, wear, and corrosion resistance were studied. The optimized 1.6 g L−1 saccharin addition in the deposition bath with Ni–Zn composition as 25:75 at.% possesses highly enhanced surface properties like compact, smooth microstructure, and increased corrosion resistance with reduced friction coefficient value.

Effects of humidity on the sliding wear properties of Zn–Ni alloy coatings

Formation of nanocrystalline ZnO film on sliding wear tracks at high humidity levels reduces the wear.

Multilayered Zn-Ni alloy coatings for better corrosion protection of mild steel

A simple aqueous electrolyte for the deposition of anti-corrosive Zn-Ni alloy coatings was optimized using conventional Hull cell method. The corrosion protection value of the electrodeposited coatings at a current density (c.d.) range of 2.0–5.0Adm−2 has been testified in 5wt% NaCl solution, as representative corrosion medium. The electrochemical behavior of the coatings towards corrosion was related to its surface topography, elemental composition and phase structure using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, respectively. Among the monolithic coatings developed at different c.d.’s, the coating obtained at 3.0Adm−2 was found to be the best with least corrosion current (icorr) value. Further, the corrosion protection efficacy of the monolayer coatings were improved to many folds through multilayer coating approach, by modulating the cyclic cathode current densities (CCCD’s). The composition modulated multilayer (CMM) Zn-Ni alloy coating with 60 layers, developed from the combination of CCCD’s 3.0 and 5.0Adm−2 was found to be the best with 3 fold enhancement in corrosion protection efficiency. The formation of multilayer coatings was confirmed using cross-sectional SEM, and the experimental results are discussed with tables and figures.

Comparative study on structure, corrosion properties and tribological behavior of pure Zn and different Zn-Ni alloy coatings

Zn and Zn-Ni alloy coatings were electrodeposited from sulfate based electrolytes. The effect of alloys Ni content on morphology, microstructure, corrosion properties, microhardness and tribological behavior of these coatings were investigated and the results were compared with Zn film. According to X-ray diffraction patterns, different intermediate phases (η-Ni3Zn22, γ-Ni5Zn21, β-Zn-Ni) were formed by increasing the coatings Ni content from 11 to 17 wt%. Polarization and EIS results revealed that all the alloy coatings had better corrosion resistance than the Zn film. Zn-14 wt%Ni coating had the least corrosion current density and maximum polarization resistance between all the samples. Microhardness of the coatings was improved by increasing their Ni percentage to 17%. However, Zn-14 wt%Ni coating had the lowest wear loss and friction coefficient, while Zn film had the worst wear resistance between all the coatings.

Electrodeposition of ZnNi Alloys from Ethylene Glycol/Choline Chloride Based Ionic Liquid

Zinc alloys containing transition metals (Ni, Co and Fe) have attracted the attention because of their high corrosion resistance [1,2]; particularly high is the interest of ZnNi system for practical application. In addition, electrodeposition of ZnNi alloys is generally described as anomalous codeposition (Brenner [3]). In this work ZnNi electrodeposition from ionic liquid system is studied; particular attention is paid to the formation Zn rich alloys (15-25 % Ni). The plating bath consists of 1 choline chloride: 2 ethylene glycol containing metal salts in different concentration. All the electrodepositions have been carried out at constant temperature T=70°C on steel. Codeposition of ZnNi is studied by means of potentiostatic electrodeposition. Compositional and morphological analysis are performed to evaluate the effect of the plating conditions and bath formulation. Electrochemical characterization of the solution is performed for those baths compositions allowing the formation of \U0001d6fe-phase ZnNi. Metastable \U0001d6fe-ZnNi with short-range order has been observed with XRD analysis; thermal treatment are carried out to evaluate phase reorganization. [1] R Fratesi, G Roventi. Corrosion resistance of Zn-Ni alloy coatings in industrial production, Surface and Coatings Technology. 82 (1996) 158. [2] R Ramanauskas, P Quintana, L Maldonado, R Pomés, MA Pech-Canul. Corrosion resistance and microstructure of electrodeposited Zn and Zn alloy coatings, Surface and Coatings Technology. 92 (1997) 16. [3] A Brenner. A. Electrodeposition of Alloys. Vol. 1, General Survey, Principals, and Alloys of Copper and of Silver, (1963).

Mechanisms and influences of electro-brush plating micro-force on coatings performances

Abstract

Characterization of the influence of Ni content on the corrosion resistance of electrodeposited Zn–Ni alloy coatings

Abstract The electrodeposition of Zn–Ni alloy coatings containing less than 11% Ni was performed in a sulfuric acid bath. We investigated the influence of the Ni content in the electrodeposit on the corrosion behavior of the alloy in detail, focusing mainly on the evolution of internal stress. The initial corrosion rates of specimens before salt spray testing were closely related to the internal stress and the Zn–6 wt% Ni coating showed better corrosion resistance than those of the other investigated coating due to the smallest internal stress. However, it was shown that the amount of residual Ni and a concentration reversal between Zn and Ni at the Zn–Ni/steel interface became more significant as the corrosion proceeded. In addition, closely packed nodular grains with hairline cracks and the formation of electrochemically noble γ-Ni 5 Zn 21 phase were observed at the highest Ni concentration of 10 wt%. And the cross-sectional distributions of alloying elements were more homogeneous with increasing Ni content in the deposit. Electrochemical test results with the resulting specimens with different salt spray testing times were also presented. At the highest Ni concentration, the sacrificial property to steel substrate was maintained with extended testing time, showing minimal corrosion current density. Regarding Zn–Ni alloy coatings for automotive applications, a decrease in corrosion depth with increasing Ni content after long-term exposure to salt spray was observed, indicating improved perforation resistance.