Corrosion Resistance Of Zinc Coatings Research Articles

Temperature dependence of deposition behavior and corrosion resistance of zinc coatings electroplated on copper substrates from ethaline electrolyte

Temperature dependence of deposition behavior and corrosion resistance of zinc coatings electroplated on copper substrates from ethaline electrolyte

Rapid Electrodeposition and Corrosion Behavior of Zn Coating from a Designed Deep Eutectic Solvent

This work aimed to develop a new type of deep eutectic solvent containing high concentrations of zinc ions as an electrolyte to improve the electrodeposition rate for zinc plating. Two typical deep eutectic solvent systems, choline chloride (ChCl)–urea and ChCl–ethylene glycol (EG), were combined to prepare a stable electrolyte at room temperature with a zinc ion concentration up to 2 M. Cyclic voltammetry experiments of the electrolyte at different temperatures were conducted. The effects of key electrodeposition parameters (bath temperature and current density) on the morphology, structure, and corrosion resistance of zinc coatings deposited on mild steel were investigated. It was found that the crystal orientation of the as-deposited zinc particle is related to the electrodeposition temperature and current density. The experimental results show that the zinc coating deposited at 60 °C and the current density of 4 mA·cm−2 exhibited the most compact and crack-free morphology, thus had the optimum corrosion resistance property.

Effect of Alumina Sol on Formation and Properties of Electrodeposited Zinc Coatings on NdFeB Magnet

Al2O3-contained zinc coatings with enhanced protective and mechanical performances were prepared on NdFeB magnets by in situ electro-deposition methods from the zinc plating baths containing alumina sol. The positively charged alumina sol particles migrate to the NdFeB cathode and then gel along with zinc on the cathode surface, which changes the electro-deposition process of zinc. As a result, the surface morphology and phase structure of the zinc coating is significantly changed. The incorporation of alumina particles achieves a denser zinc coating with a smaller grain size and the hardness is well improved. By increasing alumina sol concentration in the plating bath, the micro-hardness and wear resistance of the zinc coatings gradually increased. What's more, the alumina sol addition also improved the corrosion resistance of zinc coatings. When 20 wt. % alumina sol is added, the corrosion potential of the zinc coating is positively shifted for 168 mV and the corrosion current was more than one order magnitude lower than the blank one. Therefore, this approach shows great promise to obtain alumina-contained zinc coatings with enhanced anti-corrosion properties and mechanical properties.

Impact of Bi and Sn on Microstructure and Corrosion Resistance of Zinc Coatings Obtained in Zn-AlNi Bath

The paper presents results of studies on the impact of bismuth and tin additions to the Zn-AlNi bath on microstructure and corrosion resistance of hot dip galvanizig coatings. The structure at high magnifications on the top surface and cross-section of coatings received in the Zn-AlNiBiSn bath was revealed and the microanalysis EDS (energy dispersion spectroscopy) of chemical composition was determined. The corrosion resistance of the coatings was tested relatively in a neutral salt spray test (NSS), and tests in a humid atmosphere containing SO2. Electrochemical parameters of coatings corrosion were determined. It was found that Zn-AlNiBiSn coatings show lower corrosion resistance in comparison with the coatings received in the Zn-AlNi bath without Sn and Bi alloying additions. Structural research has shown the existence of precipitations of Sn-Bi alloy in the coating. It was found that Sn-Bi precipitations have more electropositive potential in relation to zinc, which promotes the formation of additional corrosion cells.

Efecto de la composición química del baño en la microestructura y resistencia a la corrosión de los recubrimientos de zinc por inmersión en caliente: Una revisión

Los recubrimientos metálicos son métodos ampliamente utilizados para la protección contra la corrosión de aleaciones metálicas, siendo el proceso de cincado por inmersión en caliente uno de los que presenta mayor evolución a nivel industrial. El objetivo de este trabajo es realizar una revisión bibliográfica sobre la influencia de la adición de elementos aleantes en el baño, en la microestructura y en el comportamiento a la corrosión de recubrimientos de zinc obtenidos por la técnica de inmersión en caliente. Se estableció que la composición química de los baños galvanizados influye en las características microestructurales de los recubrimientos y en su comportamiento a la corrosión. La mejora de la resistencia a la corrosión de los recubrimientos de zinc se produce por la adición a los baños de elementos generalmente más activos que el zinc, tales como el magnesio o el aluminio que permiten la formación de capas pasivas que retardan el proceso corrosivo.

Influence of Chloride and Sulfate Ions on Electrodeposition, Wettability and Corrosion Resistance of Zinc Coatings Produced from Gluconate Solutions

Electrodeposition of zinc from slightly acidic gluconate solutions was investigated. Cyclic voltammetric measurements showed inhibition of a cathodic process by sulfate ions. Chronoamperometric study combined with a speciation of individual solutions indicated instantaneous zinc nucleation interrupted by concurrent hydrogen coevolution and release of zinc cations from ZnSO4 complexes. Morphology of coatings was strongly affected by deposition potentials and a type of zinc salt. Sulfate anions hindered zinc deposition, enhanced development of (100) crystallographic plane and increased cathodic current efficiency. In a presence of chloride ions, zinc growth toward bulk electrolyte and development of (002) crystallographic base plane of hexagonal structure were preferred. Water contact angles (WCA) of zinc deposited from chloride-containing baths revealed the highest values of 131–135°, while the highest WCAs of coatings obtained from sulfate bath reached only 112–119°. Moderately rough and hydrophobic as-plated zinc coatings were characterized by slightly improved corrosion resistance in both neutral and acid solutions.

Effect of CeO2 addition on pack cementation zinc coatings on Mg–4Y–4Al magnesium alloy

Zinc coatings on as-cast Mg–4Y–4Al magnesium alloy were prepared by the zinc packed powder diffusion coating treatment, and the effect of CeO2 addition in the zincizing agent on the microstructure and electrochemical properties of the zinc coatings was investigated by OM, XRD, SEM, EDS and electrochemical workstation. The experimental results reveal that the microstructure of the zinc coatings is that the primary block α-Mg solid solution distributes on the continuous eutectic matrix composed of MgZn and intergranular α-Mg solid solution. The addition of CeO2 can increase the diffusion efficiency of Zn atoms into the alloy substrate. The thickness, compactness and corrosion resistance of zinc coatings increased first and then decreased with the increase of CeO2 addition from 0 to 9%. When the CeO2 content is 3%, the zinc coating gets the maximum thickness (about 1200 μm), and the corrosion current density reduced one order of magnitude than that of the substrate.

Influence of the pH and Stirring Speed of the Electrodeposition Bath in the Performance of Zinc and Zinc-Nanocomposite Coatings

With the increase of environmental restrictions, chromium and cadmium-based coatings have been replaced by zinc layers. These coatings can be obtained through electrodeposition, whose industrially established pH range is from 5.0 to 5.8, and stirring speed is uncontrolled, which has led to part rejections. In addition, the corrosion resistance of zinc coatings is inferior to cadmium and chromium coatings, which has boosted the research of zinc composite coatings. The proposed work presents the performance of zinc-bentonite composite coatings in regards to corrosion relating to pH variation and stirring speed. The samples were degreased for 5 minutes in a commercial degreasing solution at a temperature of 55 °C, with magnetic stirring and, posteriorly, submitted to a pickling process with a duration of 1 to 2 minutes in a commercial bath, followed by a washing process with deionized water. The electrolyte used for electrodeposition was a zinc bath with a chemical composition of 85 g/l ZnCl2, 210 g/l KCl and 25 g/l H3BO3. For the zinc-bentonite electrodepositions 20 g/l of bentonite nanoparticles was added to the bath. Zinc and zinc-bentonite coatings were characterized by scanning electron microscopy, open circuit potential and potentiodynamic polarization. This work shows that a 5.2 pH is the most recommended for the zinc electrodeposition process. Potentiodynamic polarization tests indicated that pure zinc coatings developed in the stirring speed of 380 rpm and zinc-bentonite produced in the stirring speed of 710 rpm showed the best results.

The corrosion resistance of zinc coatings in the presence of boron-doped detonation nanodiamonds (DND)

The effect of detonation nanodiamonds, doped with boron (boron-DND) in detonation synthesis on the process of zinc electrochemical deposition from zincate electrolyte is investigated. It is shown that the scattering power (coating uniformity) increases 2-4 times (depending on the concentration of DND-boron electrolyte conductivity does not change, the corrosion resistance of Zn- DND -boron coating increases 2.6 times in 3% NaCl solution (corrosion currents) and 3 times in the climatic chamber.

Corrosion Resistance of Zinc Coatings With Aluminium Additive

Abstract This paper is focused on evaluation of anticorrosion protection of inorganic metal coatings such as hot-dipped zinc and zinc-galvanized coatings. The thickness and weight of coatings were tested. Further, the evaluation of ductile characteristics in compliance with the norm ČSN EN ISO 20482 was processed. Based on the scratch tests, there was evaluated undercorrosion in the area of artificially made cut. Corrosion resistance was evaluated in compliance with the norm ČSN EN ISO 9227 (salt-spray test). Based on the results of the anticorrosion test, there can be stated corrosion resistance of each individual protective coating. Tests were processed under laboratory conditions and may vary from tests processed under conditions of normal atmosphere.

Enhancement of Corrosion Resistance of Zinc Coatings Using Green Additives

In the present work, morphology, microstructure, and electrochemical behavior of Zn coatings containing non-toxic additives have been investigated. Zn coatings were electrodeposited over mild steel substrates using Zn sulphate baths containing four different organic additives: sodium gluconate, dextrose, dextrin, and saccharin. All these additives are ``green'' and can be derived from food contents. Morphological and structural characterization using electron microscopy, x-ray diffraction, and texture co-efficient analysis revealed an appreciable alteration in the morphology and texture of the deposit depending on the type of additive used in the Zn plating bath. All the Zn coatings, however, were nano-crystalline irrespective of the type of additive used. Polarization and electrochemical impedance spectroscopic analysis, used to investigate the effect of the change in microstructure and morphology on corrosion resistance behavior, illustrated an improved corrosion resistance for Zn deposits obtained from plating bath containing additives as compared to the pure Zn coatings.

Structure Analysis of Zn-Al-Mg Coating on Steel Wire

Abstract The corrosion resistance of zinc coatings is determined primarily by the thickness of the coating but varies with the severity of environmental conditions. In case of zinc-based alloys for steel coating the phase type and its quantity developed upon solidification determines corrosion resistance as well. In this paper the phase quality and evolution along thickness of the Zn-Al-Mg coating layer was studied by x-ray diffraction analysis. During investigation the coating was removed in controlled manner in several steps. Each individual step of removal was followed with x-ray diffraction measurement and subsequent analysis of x-ray diffraction patterns.

The influence of Si addition in 55AlZn bath on the coating structures obtained in the batch hot-dip metallization

One of the methods of increasing the corrosion resistance of zinc coatings is the application of zinc and aluminium alloy baths in the metallization process. The coatings obtained are characterized by much better corrosion resistance thanks to the combination of aluminium properties, i.e. the barrier protection provided by naturally created aluminium oxides, with the capacity to protect the steel substrate, which is characteristic of zinc coatings. Zinc coatings with 55 wt. % Al and an addition of Si have gained industrial importance. The introduction of a third alloying component into the metallization bath is a technological addition, the aim of which is to reduce and possibly inhibit the aluminium diffusion towards the substrate. The article presents the results of the examination of coatings obtained in a 55AlZn bath at varied parameters of the technological process, as well as the specification of silicon addition influence on the structure and chemical composition of the coatings, and on the kinetics of growth. The coatings were obtained in three temperatures: 620, 640 and 660°C, and the process was conducted in a 55 wt. % Al bath with Si content of 0, 0.8 and 1.6 wt. % respectively, the remaining content was Zn. For the purposes of evaluating the microstructure and thickness of the coatings obtained, examinations on a light microscope were conducted. In order to determine the chemical composition of the coatings obtained, an EDS analysis was conducted. Quantitative examination of the chemical composition was carried out on the selected cross-sections of samples with coatings considered to be representative ones, using a SEM with a microanalysis system. Moreover, the linear distribution of elements on the cross-sections of the chosen coatings was determined. It is possible to state that the addition of silicon to 55AlZn baths allows reducing the uncontrolled growth of a layer. The layers obtained are more uniform, continuous and they show good adhesion to the substrate.

Corrosion resistance of zinc electrodeposited from acidic and alkaline electrolytes using pulse current

AbstractCorrosion resistance of zinc coatings was investigated in an accelerated corrosion test in a condensation chamber. Zinc was electrodeposited from alkaline and acidic electrolytes using direct current (DC) or pulse current (PC). The zinc coating was subsequently protected against corrosion with a chrome (III) layer. Morphology and structure of the coatings was investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) before and after the corrosion test. Corrosion resistance of alkaline zinc coatings electrodeposited with DC and PC under test conditions was found to be comparable. The corrosion resistance of zinc coatings deposited from acidic electrolytes by PC was lower in comparison with corrosion resistance of zinc coatings deposited using DC.

Zinc-and aluminum-based protective coatings obtained in a fluidized bed

Sherardizing and zinc-aluminizing Ct3 steel in a fluidized bed are considered. Microhardness, microbrittleness, porosity, and corrosion resistance of zinc coatings are analyzed.

Corrosion Resistance of Zinc Coatings Obtained in High-Temperature Baths

We present the results of investigation of the technology of application of coatings in zinc baths at temperatures different from the standard temperatures of the process of galvanization. The corrosion resistance of the coatings is determined under the action of neutral salt mist and sulfur dioxide in the case of condensation of moisture. With the help of galvanization at elevated temperatures of 540–560°C, it is possible to obtain coatings of constant thickness with improved structure and higher corrosion resistance as compared with the coatings obtained at standard temperatures.

Corrosion Resistance of Zinc Coatings Deposited from Electrolytes by a Pulse Current

We present the results of rapid tests of single- and multilayer zinc coatings electrodeposited by currents of various forms from full- and low-concentration weak-acid electrolytes. For diluted electrolytes, we established the formation of coatings whose protective capability is 20–25% higher independently of the form of current. The corrosion resistance of single-layer sediments obtained with the use of a pulse current is greater than that obtained by a direct current by a factor of 1.5. The corrosion resistance of multilayer coatings is greater than that for massive one-layer ones by a factor of 2–2.5.

Corrosion Resistance of Zinc-alloy Coated Steel in Construction Industry Environments

SummaryConsiderable efforts are being made to improve the corrosion resistance of zinc coatings by alloying and application of compatible conversion coating treatments. These new systems have the potential for reliable and cost effective protective coatings on steel used in construction applications.The present investigations have been concerned with:(i) development of a simple sensor that can be used to determine corrosion rates of zinc alloy coated steel in the macro/micro climates found in and around buildings and other structures.(ii) determination of the compatibility and corrosion rates of zinc alloy coatings in contact with cementitious materials and preservative treated timber.This paper describes the rationale for the investigations and the experimental techniques used, with a summary of the principle results and conclusions.

Corrosion resistance of Zn-Ni alloy coatings in industrial production

The corrosion behaviour of chromated zinc and chromated Zn-Ni alloy coatings, obtained from different industrial plants, was studied by means of salt spray tests and electrochemical tests in aerated 0.6 M NaCl solution. At almost neutral pH values, all the chromated Zn-Ni coatings show better corrosion resistance than conventional chromated zinc coatings. The acidity causes a decrease in the corrosion resistance of both chromated zinc and chromated Zn-Ni alloy; at low pH values the corrosion resistance of zinc coatings is better than that of alloy coatings because of depolarization of the cathodic reaction (hydrogen reduction), owing to the lower overvoltage of hydrogen reduction on nickel. The morphology of corrosion attack in both chloride environments is also reported.

Corrosion resistance of zinc coatings produced from a sulfate bath

Corrosion resistance of zinc coatings produced from a sulfate bath