Galvanic Bath Research Articles

Structure characterization of nanocrystalline Ni–W alloys obtained by electrodeposition

Ni–W coatings of different tungsten content (2–50wt%) were electrodeposited on a steel substrates from an aqueous complex sulfate–citrate galvanic baths, under controlled hydrodynamic conditions in a Rotating Disk Electrode (RDE) system. The optimum conditions for the electrodeposition of crack-free, homogeneous nanocrystalline Ni–W coatings were determined on the basis of the microstructure investigation results. The XRD structural characterizations of Ni–W alloy coatings obtained under different experimental conditions were complemented by SEM and TEM analysis. Results of the study revealed that the main factor influencing the microstructure formation of the Ni–W coatings is the chemical composition of an electrolyte solution. X-ray and electron diffraction patterns of all nanocrystalline Ni–W coatings revealed mainly the fcc phase structure of an α-Ni(W) solid solution with a lattice parameter increased along with tungsten content. The use of additives in the plating bath resulted in the formation of equiaxial/quasifibrous, nanocrystalline Ni–W grains of an average size of about 10nm. The coatings were characterized by relatively high tensile residual stresses (500–1000MPa), depending on the electrodeposition conditions. Ni–W coatings exhibited weakly pronounced fiber type 〈110〉 crystallographic texture, consistent with the symmetry of the plating process. Coatings of the highest tungsten content 50wt% were found to be amorphous.

Dynamic set-up rules for hybrid flow shop scheduling with parallel batching machines

An S-stage hybrid (or flexible) flow shop, with sequence-independent uniform set-up times, parallel batching machines with compatible parallel batch families (like in casting or heat treatments in furnaces, chemical or galvanic baths, painting in autoclave, etc.) has been analysed with the purpose of reducing the number of tardy jobs (and the makespan); in Graham’s notation: FPB(m1, m2, …, mS)|p-batch, . Jobs are sorted dynamically (at each new delivery); batches are closed within sliding (or rolling) time windows and processed in parallel by multiple identical machines. Computation experiments have shown the better performance on benchmarks of the two proposed heuristics based on new formulations of the critical ratio (CRsetup) considering the ratio of allowance set-up and processing time in the scheduling horizon, which improves the weighted modified operation due date rule.

Performance of Inductors Attached to a Galvanizing Bath

By taking a galvanizing bath with inductors from an Iron and Steel Co., Ltd as an example, the distributions of Lorentz force and generated heat in the inductor are simulated. As a result, the zinc flow and the temperature distribution driven by the Lorentz force and the generated heat in the inductor of a galvanizing bath are simulated numerically, and their characteristics are analyzed. The relationship of the surface-weighted average velocity at the outlet and the temperature difference between the inlet and the outlet and the effective power for the inductor is studied. Results show that with an increase in effective power for the inductor, the surface-weighted average velocity at the outlet and the temperature difference between the inlet and the outlet increase gradually. We envisage this work to lay a foundation for the study of the performance of the galvanizing bath in future.

An isogeometric variational multiscale method for large-eddy simulation of coupled multi-ion transport in turbulent flow

Electrochemical processes, such as electroplating of large items in galvanic baths, are often coupled to turbulent flow. In this study, we propose an isogeometric residual-based variational multiscale finite element method for multi-ion transport in dilute electrolyte solutions under turbulent flow conditions. In other words, this means that the concepts of isogeometric discretization and variational multiscale methods are successfully combined for developing a method capable of simulating the challenging problem of coupled multi-ion transport in turbulent flow. We present a comprehensive three-dimensional computational method taking into account, among others, coupled convection–diffusion-migration equations subject to an electroneutrality constraint in combination with phenomenological electrode-kinetics modeling. The electrochemical subproblem is one-way coupled to turbulent incompressible flow via convection. Ionic mass transfer in turbulent Taylor–Couette flow is investigated, representing an important model problem for rotating-cylinder-electrode configurations. Multi-ion transport as considered here is an example for mass transport at high Schmidt number (Sc=1389). An isogeometric discretization is especially advantageous for the present problem, since (i) curved boundaries can be represented exactly, and (ii) it has been proven to provide very accurate solutions for flow quantities when being applied in combination with residual-based variational multiscale modeling. We demonstrate that the method is robust and provides results which are in good agreement with direct numerical simulation results as well as empirical mass-transfer correlations reported in literature.

Structure and Properties of Electrolytic Zn-Mn Coatings Deposited by the Galvanostatic Method

The Zn-Mn coatings were deposited under galvanostatic conditions from a sulfate galvanic bath. The influence of thiocarbamide additions in the bath on surface morphology, chemical and phase composition and corrosion resistance of the electrolytic Zn-Mn coatings was investigated. On the basis of these investigations it was found that Zn-Mn coatings can be obtained by the galvanostatic method. Morphology and chemical composition of the electrolytic Zn-Mn coatings depend on the thiocarbamide concentration in the galvanic bath. XRD investigations of obtained coatings showed a single phase structure (α-Mn1.08Zn2.92). The additions of thiocarbamide improve the protective properties of the Zn-Mn coatings.

RESEARCH INTO THE INFLUENCE OF THE ACOUSTIC FIELD ON THE EFFICIENCY OF REMOVING AEROSOLS / AKUSTINIO LAUKO ĮTAKOS AEROZOLIO ŠALINIMO EFEKTYVUMUI TYRIMAS

The paper presents the methods for reducing harmful aerosols from galvanic baths polluting the environment under conditions when air flow helps in forming an acoustic field above the bath. The findings show that the level of air humidy is the lowest when aerosols are removed with the help of a side exhauster. Side effects on acoustic coagulation may occur. Aerosol coagulates when elevated above the liquid and returns to liquid not dispersed in the evironment. The article introduces active suckers in accordance to their form and effectiveness collecting pollutants. The dependence of humidity on temperature is analyzed under the impact of external factors such as sucking, blowing and sucking or blowing, sucking and an acoustic field. The paper also discusses data on the dependence of sound pressure and looks at the level of frequency distribution. Santrauka Atliktas kenksmingų garų (aerozolio), patenkančių į aplinką nuo galvaninių vonių, tyrimas, kai jiems šalinti naudojamas aktyvintasis šoninis siurbtuvas su oro srautu, kuris suformuoja akustinį lauką virš vonios. Parodyta, kad oro drėgnumas kinta nereikšmingai esant skysčio temperatūroms iki 85 ºC, kai kartu su siurbimu naudojami aeroakustiniai srautai, dėl kurių pasireiškia akustinė koaguliacija. Nustatyta, kad aerozoliui pakilus virš skysčio, vyksta koaguliacija, ir jis, nepasklidęs į aplinką, sugrįžta į skystį. Aptariami aktyvintieji šoniniai siurbtuvai pagal formą ir efektyvumą surenkant teršalus. Analizuojama drėgnumo priklausomybė nuo skysčio temperatūros, veikiant išoriniams veiksniams: siurbimui; siurbimui ir pūtimui; siurbimui, pūtimui ir akustiniam laukui. Atlikta sukuriamo akustinio lauko parametrų analizė: garso slėgio intensyvumo ir garso slėgio lygio pasiskirstymas dažnio srityje.

Interaction of refrigerants with contents of acid baths applied in chemical and electrochemical processing of aircraft equipment parts

Chemistry and aftereffects of the processes proceeding when a refrigerant (ethylene glycol or diethylene glycol) enters galvanic acid baths were studied.

ChemInform Abstract: Chromium(VI) Galvanic Bath: Chemical Treatments and Possible Recycling Ways of the Obtained Sludges

AbstractReview: 24 refs.

Experimental design in the electrodeposition process of porous composite Ni–P + TiO 2 coatings

In this paper, an environmentally friendly electroplating process of the composite Ni–P + TiO 2 coatings was developed. Such coatings were prepared by in situ codeposition of Ni–P with TiO 2 powder (anatase) on a polycrystalline copper substrate from the nickel-plating bath in which titanium dioxide particles were held in suspension. The codeposition was carried out under galvanostatic conditions on a rotating disc electrode. To optimize the production conditions of the Ni–P coatings modified with TiO 2 by the method of mathematical statistics, the Hartley's polyselective quasi D optimum plan of experiments was used. The relationship between the percentage content in the electrodeposited composite Ni–P + TiO 2 coatings ( z) and the electrodeposition parameters like cathodic current density ( j dep), bath temperature ( T) as well as content of TiO 2 powder suspended in the galvanic bath ( c), has been described by the adequate cubic polynomial equation and illustrated graphically. Based on the Hartley's plan it can be stated that the maximal TiO 2 content of 28.7 at.% in the Ni–P + TiO 2 coating can be obtained for the following optimal parameters of the electrodeposition process: j dep = 0.05 A cm −2, c = 99 g dm −3 and T = 40 °C. The chemical and physical characteristics of the coating obtained under such optimum conditions, have been presented. The deposit exhibits the presence of TiO 2 particles embedded into the amorphous Ni–P matrix. It has been ascertained that embedding of TiO 2 powder to the amorphous Ni–P matrix leads to the production of deposits with large surface area. Such electrochemical codeposition method may be a good alternative in the field of porous composite coatings used in gas evolution.

Effect of temperature and pH of ammonium galvanic bath on the properties of Zn-Co alloy coatings

The results of investigations on Zn-Co coatings obtained electrochemically in acidic and neutral ammonium baths are presented. The chemical composition, morphology and surface roughness of received coatings were determined together with the current efficiency. It was found that the coatings morphology depends on the process parameters. In the case of neutral bath the increase of bath temperature resulted in decrease of cobalt contents in the coatings, whereas it was not practically observed for acidic baths. It was also observed that surface roughness of the Zn-Co coatings decreased with the increase of temperature for both types of baths. It was also found that the grain size of coatings obtained in neutral bath depends on pH of bath.

Reactive wetting of high Mn steels during continuous hot-dip galvanizing

An electrobalance was used to study the reactive wetting of a series of Mn-containing steels ranging in composition from 0.14 wt.% to 5.1 wt.% Mn by a 0.20 wt.% dissolved Al continuous galvanizing bath as a function of immersion time, alloy Mn content and annealing atmosphere pO 2. It was found that the wetting force for the 1.4–5.1 wt.% Mn alloys was significantly less than that for the 0.14 wt.% Mn alloy due to the formation of a significant MnO layer on the higher Mn alloys. For all alloys and process atmospheres, reactive wetting and the formation of a well-developed interfacial Fe–Al intermetallic layer was achieved with the wetting force being directly related to the thickness of the external MnO layer. The wetting force was a strong function of the process atmosphere pO 2, which was in turn strongly related to the thickness of the external MnO layer. A reactive wetting model in which the motion of the triple line and the wetting force is limited by the oxide layer thickness is proposed.

Study of the influence of sonication during the electrod­eposition of nickel matrix nanocomposite coatings on the protective properties

The interest in the electrocodeposition has been revived due the development of new nanotechnology methods for the production of nano-particles. The codeposition of nanoparticles might enhance the mechanical properties of composite deposits without penalizing the corrosion resistance and avoid the formation of an abrasive third body during the wear process. On the other hand, the volume fraction of codeposited nano-particles is generally low and usually inversely proportional to their size. Many efforts have been done in order to improve the codeposition rate of nanoparticles. Most of the research on nickel composites is focused on the electrodeposition process or on the mechanical and wear properties rather than on the corrosion resistance. In this work, the protective properties of nickel matrix nanocomposite coatings have been studied by means of potentiodynamic curves and electrochemical impedance spectroscopy. Two different nanopowders, i.e., silicon carbide and alumina, were added to a Watts type galvanic bath in order to deposit the nanocomposites coatings on steel substrate. Ultrasonic vibrations have been considered as new process parameter to improve the dispersion of the powder into both the plating bath and metal matrix coating and to substitute pitting control agents for the production of defect-free coatings. Unique, functional properties of composite coatings are derived not only from the presence of the particles dispersed in the bulk of the metallic matrix but also on the matrix microstructural changes induced by the interaction between particles and electrocrystallization process. It has been demonstrated that the codeposition of the silicon carbide particles induces an important microstructural refinement. On the contrary, the aluminum oxide powder is strongly agglomerated and only under ultrasonic vibrations can be dispersed. Ultrasounds have a positive effect not only in hindering the porosity but also in dispersing the ceramic powder and increasing the codeposition rate leading thus to the production of protective and very refined coatings. Moreover, the better dispersed powder induces an improvement also in the corrosion protection leading to the formation of a more stable and resistant passive nickel oxide.

CeO 2–TiO 2 mixed oxide incorporated high performance hot dip zinc coating

The greatest limitation in using zinc coated steel in industrial environments is the biofilm formation and greater dissolution rate of zinc. If initial bacterial adhesion to the coating surface is inhibited, biofilm formation will be prevented. In the present work, effective corrosion resistance and better antifouling characteristics for the coatings was achieved by the incorporation of CeO 2–TiO 2 mixed oxides. Based on the performance of the coatings during physicochemical and electrochemical characterization, the concentration of the mixed oxide in the bath was optimized as 0.40 wt.% CeO 2 + 0.10 wt.% TiO 2. The interior layers of the mixed oxide incorporated coatings exhibited greater stability towards corrosion. The morphological results from SEM and AFM analyses reveal the structural refinement and better quality of mixed oxide incorporated coatings. The incorporation of the CeO 2–TiO 2 mixed oxide into the galvanic bath yielded coatings with effective barrier protection, better corrosion resistance, good antifouling characteristics and improved surface quality. The coating was non porous in nature and have potential scope for high industrial utility.

Wear-resistant nanostructured platinum–titanium anodes: II. STM and STS measurements on ECAPTA specimen that operated for 35 years

The results of STM and STS measurements carried out on surfaces of wear-resistant Pt-Ti anodes obtained by waste-free electrocontact oxidation are discussed. In this way, a thin (0.5–2 μm) coating of electrocontacted-alloyed platinum-titanium anodes (ECAPTA) is formed. The effect of the anodic treatment in an electrolyte, which serves as a buffer in galvanic gilding, on the surface of a model ECAPTA specimen is determined and the nature of the surface properties of a specimen, which has operated for 35 years in a galvanic bath for gold electroplating, is clarified. It is found that, as a result of the anodic dissolution, most of the applied EATP coating dissolves in 2–2.5 years; however, a nanolayer involving platinum and titanium atoms is formed on the surface and preserves the activity for decades. Properties and the amount of the layer, which differs in the electrophysical characteristics from the original ECAPTA, provide the effective operation of the anode covered with such a modified component under conditions of industrial gold electroploting. A supposition is made about the formation mechanism of a surface that is electrocatalytically active with respect to the target technological process and exclusively corrosion-resistant and stable. The nanoscale dispersion of the main surface parameters down to the atomic resolution limit, and the time-dependent dynamics of the properties, which seems to be a fundamental feature of any surface in heterogeneous processes, are discussed.

The Influence of Sodium Molybdate on the Properties of Zn-Ni Layers Obtained by Electrolytic Deposition

This study was undertaken in the aim to try the limit of extraction of Zn from Zn-Ni system. The aim was realized by the addition of MoO42- ions into the galvanic bath containing Ni2+ and Zn2+ ions. Zn-Ni-Mo layers were deposited under galvanostatic conditions on (OH18N9) austenitic steel substrate. The influence of Na2MoO4 concentration in a bath on the surface morphology, chemical and phase composition and the corrosion resistance of obtained layers, was investigated. The properties of Zn-Ni-Mo layers were compared to the properties of electrolytic Zn-Ni layer. Structural investigations were performed by the X-ray diffraction (XRD) method. The surface morphology and chemical composition and surface chemical elements distribution of deposited layers were studied using a scanning electron microscope. Electrochemical corrosion resistance investigations were done by classical Stern method and electrochemical impedance spectroscopy. The potentiodynamic curves in the range of  0.05V to the potential of open circuit, were obtained. On the base of these curves the parameters like corrosion potential- Ecor, corrosion current density- icor and the polarization resistance- Rp were determined. These values served as a measure of the corrosion resistance of obtained layers. Results of impedance investigations were presented on the Nyquist Z”= f (Z’) and the Bode log Z = f (log) and  = f (log), diagrams. On the basis on this research, it was exhibited that surface morphology, chemical composition of Zn-Ni-Mo layers are dependent on Mo contents. The optimal content of Na2MoO4 in the bath for the sake of corrosion resistance in 5% NaCl, is found to be 1.2 gdm-3.

Al 2O 3–ZrO 2 mixed oxide composite incorporated aluminium rich zinc coatings for high wear resistance

Corrosion resistance and wear resistance are the two important parameters for high performance of zinc galvanic coating. In the present work, the improvement of these two characteristics was achieved by the incorporation of Al 2O 3–ZrO 2 mixed oxide composite in the coating. Al 2O 3–ZrO 2 mixed oxide composite was synthesized from ZrOCl 2·8H 2O. Aluminium rich zinc coatings with high sliding wear resistance was developed from a galvanic bath containing the mixed oxide. Based on the performance of the coating during physicochemical and electrochemical characterization, the concentration of mixed oxide composite in the bath was optimized as 0.50 wt% Al 2O 3–0.50 wt% ZrO 2. While rich in Al–metal content in the coating caused high corrosion resistance, the incorporation of the mixed oxide improved structural characteristics of the coating resulting in high wear resistance also. The coating was nonporous in nature and even the interior layers had high stability. The coatings have potential scope for high industrial utility.

Stress corrosion cracking of structural steels immersed in hot-dip galvanizing baths

Failures during hot-dip galvanizing are occasionally, but they are important because of the high responsibility of the evolved structures. Traditionally two processes have been related with this phenomenon: liquid metal assisted cracking and hydrogen embrittlement. Hydrogen influence is discarded after the hydrogen concentration tests performed in this paper. Besides, crack characterization tests on steel CT specimens which are immersed in liquid galvanization bath with Zn, 1.1% Sn and 0.1% Bi at 450 °C are detailed. The main obtained results were three: 1. The value of the threshold stress intensity factor, K th, which is the lowest value to produce cracking; 2. The subcritical crack propagation rate (d a/d t) II; and 3. The failure assessment diagram (FAD) of the steel for two different load conditions. Microscopy revealed intergranular propagation and the existence of an intermetallic compound, the FeSn, at the crack tips. As a final result, the authors propose the key points of a qualitative failure model which consists of a first step of accumulation of Sn and Pb in crack tips, a second step of production of FeSn compound, and a final step of FeSn cracking due to accumulated stresses.

STUDY OF COMPETITIVENESS BETWEEN METAL IONS IN SOLUTION IN THE TREATMENT OF SYNTHETIC EFFLUENTS OF PHOSPHATIZATION LINES CONTAINING IRON, NICKEL AND ZINC IONS BY ELECTRODIALYSIS

Using the electrodialysis in treatment of rinsewater, two other solutions are obtained: one concentrated, which can be returned to the galvanic bath; and the other diluted, which has perfect conditions to be reused in a closed circuit as rinsewater. The aim of this work was to evaluate the competitiveness between metallic ions (iron, niquel and zinc) during the electrodialysis technique as a method for treatment of wastewater produced by the phosphatization process. Experiments were conduced with different rinsewater composition and Nafion® 450 and Selemion® AMP membranes. The results obtained show correlation between percentual extractions, current efficiency and the presence of metallic ions in solution.

Optimization and comparison of chemical and electrochemical hydride generation for optical emission spectrometric determination of arsenic and antimony using a novel miniaturized microwave induced argon plasma exiting the microstrip wafer

Continuous flow (CF) chemical hydride generation (CHG) and electrochemical hydride generation (ECHG) directly coupled to a novel 40 W, atmospheric pressure, 2.45 GHz microwave microstrip Ar plasma exiting a microstrip wafer has been developed for the emission spectrometric determination of As and Sb using a miniaturized optical fiber spectrometer and a CCD-array detector. The experimental conditions for both procedures were optimized with respect to the relative net intensities of the As I 228.8 nm and Sb I 252.8 nm lines and their signal-to-background intensity ratios. Additionally, the susceptibility to interferences from Cd, Co, Cr, Cu, Fe, Ni, Pb and Zn and other hydride-forming elements in the determination of As and Sb using the CHG and ECHG techniques was investigated in detail. Under the optimized conditions, it was found that ECHG is more prone to interferences compared to CHG. The detection limits (3 σ) of As (6 ng mL −1) and Sb (7 ng mL −1) obtained for the ECHG–MSP–OES method are about three times lower than in the case of the CHG–MSP–OES method due to a two-fold lower amount of H 2 introduced into the MSP in case of the ECHG, resulting in a better plasma stability and reduced background level. The linearity ranges for both calibration curves to a concentration of up to 5 μg mL −1 and a precision between 2% and 7% (2 μg mL −1 and 0.050 μg mL −1 of As and Sb, respectively) were found for both methods. The developed ECHG–MSP–OES method was validated for As through the analysis of a certified coal fly ash standard reference material (NIST SRM 1633a) after sample dissolution. The derived concentration (140 ± 8 μg g −1) was found to agree well with the certified data (145 ± 15 μg g −1). The method was also successfully applied to the analysis of both a galvanic bath sample, which contained Sb and was spiked with As, and a tap water sample spiked with both analytes. Recovery rates of 99–101% and a Sb concentration of 6.6 μg mL −1 in the galvanic bath sample were revealed. The latter value showed a good agreement with the data obtained from ICP-OES analysis, which was also used for validation purpose.

Reaction of 316L stainless steel with a galvanizing bath

Type 316L stainless steel (316L SS), commonly used as pot roll material, was tested in an industrial Zn–Al galvanizing bath, with an effective Al content of 0.2 wt.%. Samples welded to the supporting roll arms and sides of the sink roll experienced heavy dross buildup. Samples placed at locations away from the incoming strip generally experienced much less dross buildup. Dross particles within the buildup on samples attached to supporting roll arms were small in size but numerous while particles on samples welded to the sides of the sink roll were much larger. SEM-EDS analyses indicated that the buildup consisted of two layers. The inner layer was the product of the corrosive reaction of 316L SS with the bath metal, and the outer layer was formed by dross particles built up on the inner reaction layer. The intermetallic phase, which formed at the reaction front of the samples was the inhibition compound Fe2Al5 containing some Mo and Cr. The formation of this intermetallic layer provided a thermodynamically favourable base for the attachment and further buildup of suspended dross particles on the sample surfaces.