Cadmium Coatings Research Articles

ЭЛЕКТРОХИМИЧЕСКОЕ ЛЕГИРОВАНИЕ ЦИНКОВЫХ ПОКРЫТИЙ ХРОМОМ И НИКЕЛЕМ ИЗ ГЛИЦИНАТНЫХ РАСТВОРОВ

The purpose of this work is the electrochemical alloying of zinc coatings with chromium and nickel from electrolytes containing heteronuclear complexes. Zinc coatings are widely used to protect steel products from corrosion in the atmosphere of various climatic zones. To increase corrosion resistance, zinc coatings are chromated or phosphated. An effective way to increase the corrosion resistance of the coatings under study is their alloying with other metals. Obtaining such coatings makes it possible to reduce their thickness and increase their service life, solve environmental problems when replacing cadmium. The kinetics of the process on zinc and steel electrodes has been studied by removing cathode polarization curves. It is suggested that the absence of characteristic current peaks on the polarization curves is due to the convergence of the electrode potentials of individual metal ions recovering from heteronuclear compounds, as well as the concomitant discharge reaction of proton donors. X-ray fluorescence analysis has shown that in the studied range of current densities 1-5 A/dm2, the content of alloying metals in the coating reaches 1.4% for chromium and 9.8% for nickel. The obtained data on the elemental composition of zinc coatings indicate an abnormal co-deposition of zinc with nickel. Chromium in coatings is observed at higher current densities of 4-5 A/dm2.The data obtained in this work can be used in electroplating in the development of processes for alloying zinc coatings with chromium and nickel in order to replace cadmium coatings.

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.

The Influence of Cadmium Plating of 60S2A Steel in Cyanide-Free Electrolytes on Its Strength Characteristics and Some Properties of Cadmium Coatings

The Influence of Cadmium Plating of 60S2A Steel in Cyanide-Free Electrolytes on Its Strength Characteristics and Some Properties of Cadmium Coatings

Effects of laser energy on the surface quality and properties of electrodeposited zinc-nickel-molybdenum coatings

As a substitute for toxic cadmium coatings in the aerospace industry, zinc-nickel coatings have excellent application prospects, and their properties can be improved by adding molybdenum. In this study, laser-assisted electrodeposition is used to improve the surface quality and properties of Zn–Ni–Mo coatings, with investigation of how laser energy in the range of 0–21.1 μJ affects their element content, surface morphology, crystal phase, microhardness, residual internal stress, and corrosion resistance. The laser irradiation accelerates the electrodeposition, refines the grain size, improves the hydrogen adsorption, and reduces the residual tensile stress, and a laser energy of 15.4 μJ gives the highest Ni and Mo contents and the lowest Zn content, as well as the optimum surface morphology, microhardness, residual internal stress, and corrosion resistance of the coating.

COMPLEX FORMATION IN THE SYSTEM ZINC (II)-CHROMIUM (III) -COBALT (II)-GLYCINE-WATER

The study of complex formation processes is the scientific basis for the development of electrolytes in electroplating. The data on complexation in the zinc (II)–chromium (III)–cobalt (II)–glycine–water system were obtained. The study of complex formation in the zinc (II)-chromium (III)-cobalt (II)-glycine-water system is relevant due to the possibility of developing electrolytic galvanizing processes and obtaining appropriate coatings with high corrosion resistance. In addition, the alloying of zinc electroplating coatings with chromium, cobalt makes it possible to replace the use of toxic cadmium coatings and use their smaller thicknesses. The solutions were thermostated at 25 °C. The HI 2215 pH/ORPMeter was used to measure pH. The spin-lattice relaxation time T1 was measured on a pulsed NMR spectrometer "Minispecmq20" with a frequency of 19.75 MHz. The constants of the formation of complexes and their accumulation shares were calculated according to the CPESSP program. The paper presents data on previously conducted studies of chromium(III)–water, zinc(II)–glycine–water, chromium(III)–glycine–water and zinc(II)–chromium(III)–glycine–water systems. Data on complexation in the chromium (III)-cobalt (II)-glycine-water system were obtained. The formation of a heteronuclear complex CrCoGly83- has been established. The compositions of heteronuclear compounds, their accumulation fractions and formation constants were established: CrCoZn(HGly)5Gly34+ (lgK= 2.31±0.01); CrCoZn(HGly)3Gly52+ (lgK= -1.36±0.05) and CrCoZn(HGy)2Gly6+ (lgK= -4.23±0.09). The maximum proportion of accumulation of heteronuclear complexes, as studies have shown, is observed in the pH range of 2...6. In this paper, considerations are made about the electrochemical reactivity of heteronuclear compounds. In particular, it is noted that the electrochemical reduction of more electronegative metals, if they are in a heteronuclear complex, should occur with less overvoltage of the reaction. For citation: Berezin N.B., Chevela V.V., Mezhevich Zh.V., Ivanova V.Yu. Complex formation in the system zinc (II)-chromium (III) -cobalt (II)-glycine-water. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 31-36. DOI: 10.6060/ivkkt.20236606.6789.

Antibacterial efficiency of cadmium thin films deposited by the thermionic vacuum arc

Antibacterial efficiency of cadmium thin films deposited by the thermionic vacuum arc

INFLUENCE OF SURFACTANTS ON THE SCATTERING ABILITY OF SULPHATE ELECTROLYTES OF CADMIUM PLATING AND THE QUALITY OF CADMIUM COATINGS

The effect of surfactants - calcium phenolate (phenolates of tertiary aminophenols), which has a significant size (1286 g/mol) and high activity (adsorbability) in electrolytes and has a positive effect on the scattering ability of the cadmium electrolyte, as well as on the quality of cadmium coatings was studied in this work. In the work, the usual parameters of the cadmium electrodeposition process, such as electrolyte composition, current density, temperature, and deposition time were used. The quality of the obtained cadmium coatings by using a new surfactant in the process of electrocrystallization of cadmium was determined on a JSM-6490LV scanning electron microscope with INSAEnergu energy dispersive microanalysis and HKL-Basic structural analysis systems with a useful magnification of 300.000.

Failure of Jet Engine Fuel Control Unit Originated by Corrosion of Cadmium Coating

Since 2015 the barometric fuel units of the aircraft jet trainer fleet were featured by an anomalous increase in the rate of failures, all caused by the presence of debris in the jet fuel system. Cadmium and sulfur based composition of debris observed in the fuel control unit revealed that they were originated by a reaction of jet fuel’s sulfur compounds with cadmium protection coating of few components in the unit. Analysis carried out on jet fuel samples did not find any value out of the specification and therefore further investigations were conducted on the cadmium coating process. Two fuel pumps were examined: a degradation of cadmium coating was observed on every components of both pumps, proportionally to their flight hours.A brown-yellow gelatinous deposit was found into the pumps components, mainly composed by hydrocarbons, cadmium, sulfur and carboxylic salts. The investigation on the cadmium surface treatment process revealed the anomalous absence of the chromate conversion coatings: it was responsible of cadmium availability in the fuel flow, causing the cadmium plating detachment that finally resulted in the solid particles production.

Subtleties Behind Hydrogen Embrittlement of Cadmium-Plated 4340 Steel Revealed by Thermal Desorption Spectroscopy and Sustained-Load Tests

Thermal desorption spectroscopy (TDS) and sustained-load tests were used to investigate hydrogen embrittlement (HE), hydrogen profiles and the impact of the baking delay of cadmium-plated 4340 steel-notched bars. The results show a tremendous concentration of hydrogen in the cadmium coatings (200 to 1500 ppma) that does not contribute to HE. Hydrogen in manganese sulfide (MnS) traps was also found not to contribute to HE. The total hydrogen concentration measured by TDS is thus not suitable to determine an embrittlement threshold. Subtracting hydrogen in cadmium and MnS traps from total hydrogen allowed finding a true critical hydrogen concentration threshold of 0.6 ppma (0.01 ppmm). No impact of the baking delay was found.

СВОЙСТВА ЗАЩИТНЫХ ГАЛЬВАНИЧЕСКИХ ПОКРЫТИЙ ДЛЯ ЗАМЕНЫ КАДМИЯ НА СТАЛЬНЫХ КРЕПЕЖНЫХ ДЕТАЛЯХ (обзор) Часть 2. Водородное охрупчивание и фрикционные характеристики

The paper considers the options for replacing the electroplated single-layer toxic cadmium coatings with zinc-based compositions, as well as multi-layer coatings. Their tribological characteristics and tendency to hydrogenation of the protected metal during coating and operation are considered. Conclusions are drawn about the shortcomings of existing technologies and promising directions of research in this area. Thus, the most preferred composition for replacing a cadmium coating is a nickel-zinc coating with nickel content of 12% (by weight), but a tin-zinc coating has the lowest value of the coefficient of friction, close to the value for cadmium.

The effect of indole on kinetics of electrodeposition and morphology of cadmium and nikel coatings

The effect of indole on kinetics of electrodeposition and morphology of cadmium and nikel coatings

Pulse Electroplating of Zinc/Nickel Alloy from a Deep Eutectic Solvent (DES)

Electrodeposition of metal coatings such as nickel, zinc, tin, chromium and cadmium for the purposes of corrosion protection has been a core interest of the electrochemical community for more than one hundred years. Cadmium has been a favourite for military and aerospace applications because of the combination of good corrosion protection and lubricity. However, cadmium salts are very toxic and hazardous and so the use of cadmium coatings is now proscribed in all but the most demanding of applications. Alternatives to cadmium coatings have included aluminium and more recently zinc nickel alloys. The latter is more accessible via aqueous methods but requires rigorous control and monitoring of bath conditions in order to maintain the composition and quality of the coating. An alternative to aqueous electrolytes is a derivative of ionic liquids that feature eutectic mixtures of quaternary ammonium salt and hydrogen bond donor. These have become known as deep eutectic solvents (DSE). Here we have used a DES to produce coherent and adherent coatings of zinc nickel alloy in an electrochemical study and in pre-commercialisation scale-up trials. In a digital controlled pulse-plating method, alternative forward (deposition) and reverse (stripping) currents, are applied to adjust the deposit composition and morphology, as has been demonstrated in film plating from aqueous electrolytes. This report focuses on pulse-plating γ-Zn11Ni2 alloy from a eutectic mixture of choline chloride (ChCl) and ethylene glycol (EG), also known by the commercial name of Ethaline. The effect of pulse shape and frequency on deposit morphology and crystal structure were analysed and compared with coatings derived from constant current (DC) plating methods, through Hull cell tests, XRD, and SEM/EDX measurement. The deposit composition is shown here to be dependent on the average current density, the surface morphology is not sensitive to the pulse frequency, while dendritic growth is shown to be suppressed by pulsed current. We show that the crystal grain size can be controlled according to the pulse shape and frequency. By choosing a certain shape and frequency, the pulse-plating in the DES can provide improved coating qualities and improved process control. Additionally, we have extended the laboratory investigation to pre-commercial scale-up trials with a commercial electroplating company (EC Williams, UK). This project is funded by an Innovate UK action and is entitled Cadmium Replacement Using Pulse-Plating and Ionic Liquids (CRUPPAIL). Barrel-plating trials using pulse and reveres pulse methods on small components such as screws have given even adherent coatings, Figure. The combination of pulse methods and DES electrolyte give a levelling effect, Figure (a), and good throwing power in confined geometries, Figure (b). Figure: Scanning electron micrographs of Zinc Nickel alloy (85:15%) deposited using DES and pulse-plating on mild steel substrates, (a) sheet, (b) screws. Figure 1

CONDITIONS OF ZINC-NICKEL ALLOY FORMATION FROM AMMONIA-GLYCINATE LOW-CONCENTRATED ELECTROLYTE

Introduction. Zinc-nickel alloys coatings are considered to replace cadmium coatings. The corrosion resistance of the zinc-nickel alloy depends on the phase composition of the coating. Thus, the alloy coatings with nickel content of 8–14 wt. % (mainly the γ-phase) are characterized by corrosion resistance 5 times greater than zinc coatings. In turn, the composition and structure of the coatings is determined by the conditions of their production, primarily by the type of electrolyte and electrolysis modes. The aim of the work is to determine the effect of the low concentration ammonium glycinate electrolyte composition on electrode processes during the formation of coatings with a zinc-nickel alloy. Materials and research methods. The kinetics of electrode processes on zinc and nickel samples with surface area from 1 to 5 cm2 in ammonia-glycine electrolyte was studied by analyzing polarization dependencies using a PI-50.1 potentiostat with three electrode cell. A saturated silver chloride electrode was used as a reference electrode, and the potentials are given according to this electrode. Voltammograms were obtained at a potential scan rate of 50 mV/s. The pH value of the electrolytes was monitored using CT-6020A pH meter. Results. The effect of pH value of a mixed ammonium-amino acid electrolyte on the kinetic regularities of electrode processes during the nickel and zinc codeposition was determined by the polarization method. The shape of the polarization dependences of alloy deposition allows suggesting the presence of two limiting stages – electrochemical and diffusion. When pH of the electrolyte increases the alloy deposition occurs with greater overvoltage on both nickel and zinc electrodes. The zinc codeposition with nickel begins at potentials more negative than –1.2 V. Thus, it is possible to obtain zinc-nickel alloys with the necessary protective characteristics by changing the conditions of electrolysis.

Effect of Deep Eutectic Solvent Composition on the Corrosion Behavior of Electrodeposited Cadmium Coatings on Carbon Steel

Effect of Deep Eutectic Solvent Composition on the Corrosion Behavior of Electrodeposited Cadmium Coatings on Carbon Steel

FEATURES OF FRACTURE OF METAL ITEMS (HARDWARE) MADE OF STEEL 30KhGSA

The reasons for destruction of fasteners made of steel 30KhGSA are analyzed. It is shown that in case of destruction of bolts in the package connecting frame elements, damage of bolts results from fretting corrosion, attributed to mutual friction between bolts and elements of skin, belt and tape. Fretting corrosion develops in the sites where cadmium coating of bolts is damaged upon friction. The occurrence of fracture in the belt, skin and tape is promoted by break-in scuffing of the openings and corrosion damages (fretting corrosion) triggering the intergranular fracture, most severe in the skin and tape. The reason for damage arises from structural and technological factors: increased stresses present in the package, micro-displacements of the mating parts, violation of the cadmium coating, insufficient corrosion protection and environmental impact. Destruction of self-locking nuts made of 30KhGSA steel with anti-corrosion cadmium coating used in the assembly of the auxiliary gas turbine engine is attributed to their significant overheating, i.e., the impact of molten coating on the surface of loaded nuts and the penetration of the liquid metal into the base material along the grain boundaries. The use of cadmium coatings in operation of steel parts at a temperature exceeding (even briefly) the melting temperature of Cd ( T melt = 320.9°C), under conditions of contact with stressed metal due to the Rebinder effect, leads to a sharp loss of strength and premature failure of the part. Study of the destruction of galvanized bolts made of 30KhGGSA steel during the repeated-static testing revealed that several factors contribute to the onset of fatigue multiple site damage: presence of the rough risks; sandblasting, performed before galvanizing using large sand fractions, which contribute to the premature origin of cracks; areas with deposits formed upon coating with a loose adhesion of the layer. The presence of a large number of pits along with the fatigue grooves indicates to high load of the bolt material upon operation. The study was carried out using optical and scanning electron microscopy and X-ray microanalysis.

Synthesis of Porous Tungsten from Tungsten–Cadmium Film Coatings

Solid solutions (alloys) with a Cd concentration of 50.3–76.3 at % were synthesized for the first time in the form of coatings by ion–plasma sputtering and codeposition of ultrafine W and Cd particles. When coatings were formed by tungsten and cadmium nanolayers, the components dissolved mutually to produce solid solutions of one metal in the other. A solid solution of cadmium in tungsten was synthesized at Cd concentrations up to 60.9 at %. At a cadmium concentration of 68.6 at % in the coating, the crystalline structure of cadmium with an admixture of amorphous tungsten was produced. At 800°C, tungsten evaporated from tungsten–cadmium coatings to form porous tungsten. The results of examination of materials fabricated on the basis of porous tungsten are planned to be used in practice.

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 %.

ФАЗОВЫЙ СОСТАВ И МОРФОЛОГИЯ ПОВЕРХНОСТИ Ni,Zn СПЛАВА, ЭЛЕКТРООСАЖДЕННОГО ИЗ СУЛЬФАТНО АММОНИЙНОГО РАСТВОРА

Хронопотенциометрическим и рентгенофазовым анализом показано, что никель-цинковое покрытие толщиной 1.1 мкм, осажденное на гладкую никелевую пластину в потенциостатических условиях Ek = -1.050 В из сульфатно-аммонийного электролита, содержит интерметаллические фазы NiZn и NiZn3. При помощи сканирующей электронной микроскопии установлено, что Ni,Zn-сплав осаждается равномерно по всей поверхности электрода, и молярное соотношение Ni и Zn составляет 1:4. По данным атомно-силовой микроскопии размер частиц дисперсного никеля составляет 40‑60 нм.
 
 Результаты исследований получены на оборудовании Центра коллективного пользования научным оборудованием ВГУ

New NbCd2 Phase in Niobium–Cadmium Coating Films

Solid solutions in the form of alloy coatings have been obtained for the first time in the Cd concentration range of 64.5% using ion-plasma sputtering and the codeposition of Nb and Cd ultrafine particles. This supports thermal fluctuation melting and the coalescence of fine particles. A coating of niobium and cadmium layers less than 2 nm thick at 68 at % Cd results in the formation of a new phase identified as NbCd2. The tetragonal fcc phase with lattice parameters a = 0.84357 nm and c = 0.54514 nm forms directly during film coating. XRD data for the identification of the intermetallic compound have been determined. The thermal stability of the NbCd2 intermetallic compound is limited by 200°C. The properties of the synthesized NbCd2 phase are typical of semiconductors.

Comparison of fretting behaviour of electrodeposited Zn-Ni and Cd coatings

Zn-Ni is a primary replacement candidate for cadmium in the aerospace industry. However, tribological behaviours of these coatings are not well understood, despite the importance in their applications. This study compares the fretting behaviour of Zn-Ni and cadmium coatings, a hard and a soft coating. As the mechanical properties are different, coatings were compared under similar contact stresses and normal loads. Under similar contact stresses, Zn-Ni wore severely due to gross slip in the contact at high displacement amplitude. For cadmium, wear occurred through ejection of the coating from the contact, which became more severe when the displacement amplitude increased. Under similar normal loads, Zn-Ni remained in the stick regime and there was minor wear in the contact.