Sulfuric Acid Bath Research Articles

Electrochemical codeposition of arsenic from acidic copper sulfate baths: The implications for sustainable copper electrometallurgy

• The main source of arsenic contamination is codeposition during the nucleation stage. • Convection and concentrated Cu(II) electrolytes mitigate arsenic contamination. • The reduction of As(III) to metallic As does not occur readily. • Fast removal of As(III) possible by copper-arsenic codeposition. Copper producers face increased demand associated with increasing complexity in feedstock composition, including high amounts of impurity metals. In this work, linear sweep voltammetry was used to study the electrodeposition behavior of copper and arsenic, define strategies for the production of grade A copper, and the removal of arsenic from complex electrolytes. Our results show that the copper concentration is a key parameter to control in the electrodeposition process. The continuous deposition of arsenic from the electrolyte requires copper in solution (≤10 g L −1 Cu(II) for 2 g L −1 As(III)) to form copper arsenides . The deposition of metallic arsenic does not occur readily. Conversely, the use of a concentrated Cu(II) solution (e.g. 40 g L −1 ) resulted in grade A copper from an electrolyte with a maximum of 2 g L −1 As(III) under galvanostatic control at a current density of – 42 mA cm −2 . Time-of-Flight Secondary Ion Mass Spectrometry depth profile measurements on copper deposits revealed that arsenic contamination was entirely concentrated near the substrate side of the deposit and progressively decreased further into the deposit. The codeposition of arsenic occurred along with the initial copper nucleation, when the electrochemical potential for electrodepostion under galvanostatic control is temporarily lower. These findings provide important insights for future sustainable copper electrodeposition technologies from complex feedstocks.

Deposition of Cu-based composite coatings on mild steel substrate via electrodeposition method

The mild steel (MS) is a commonly used material in various structural industries due to its low cost and good strength (relatively lower than other processed steel). But, poor corrosion resistance, relatively low hardness, and wear resistance lead to a limit of its application. To enhance these properties, surface engineering with coating are preferred. The present article investigates the synthesis, microstructural and mechanical properties of copper-based electrodeposited coatings on the mild steel. The direct current (DC) power source is used to deposit the pure copper and copper-based composite reinforced with carbonaceous materials, such as graphene (Gr), graphite (Gt), and carbon nanotubes (CNTs). The coatings were deposited using two types of bath containing reinforcement, non-cyanide alkaline glycerol complex and acidic (sulphuric acid) bath. Various deposition parameters, such as bath temperature, time, current density, pH, and stirring of electrolyte were used to get an optimised uniform coating. The wetting agent was added with carbonaceous particles to make it mix and distribute uniform in the electrolyte. The cube-shaped morphology of copper crystals was witnessed in the electrodeposited coatings along with the plate-like structures of graphene and graphite. The morphology and chemical composition of the deposited coatings were analysed with the help of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) respectively. The microhardness and elastic modulus of the electrodeposited coatings were measured using instrumented microindentation test. Among the composite coatings, copper/graphite (Cu/Gt-MS) coating showed the superior hardness of ∼ 5 GPa, due to the uniform distribution of reinforcement.

Electrodeposition of Cu-Ag Alloy Films at n-Si(001) and Polycrystalline Ru Substrates

Electrodeposition of Cu-Ag films from acidic sulfate bath was conducted at n-Si(001) and polycrystalline Ru substrates. Significant nucleation overpotential of 0.4 V is observed with the Cu-Ag bath at n-Si(001) substrate, whereas the electrodeposition of Cu-Ag at Ru substrate is influenced by Ru oxides at the surface. Incomplete coverage of Si substrate by Cu-Ag deposit was observed from the deposition systems without Ag(I), or with 0.1 mM Ag(I), comparing with the compact Cu-Ag film obtained with the deposition bath containing 0.01 mM Ag(I). Layered and faceted Cu-Ag deposit was observed at small Cu deposition overpotential with the Ru substrate. Phase composition of the Cu-Ag deposits at n-Si(001) substrate from electrolyte with various Ag(I) concentrations is examined by XRD. Limited solubility of Ag (0.4 at.%) was observed in fcc-Cu until phase separation occurs. The classical model for nucleation kinetics in electrodeposition was used to examine the potentiostatic transients of the Cu-Ag electrodeposition at n-Si(001) substrate.

Estimating electrodeposition properties and processes: Cu-Ag alloy at n-Si(001) and Ru substrates from acidic sulfate bath

In alloy electrodeposition, estimations of the initial transient and the potential vs. composition trend of the film system is important for material design, deposition procedure and the deposit characterization. However, solving the diffusion-migration-convection problem based on common simulation methods is often too burdensome and too resource-consuming for ordinary tasks in the context of alloy electrodeposition works. In this work, based on a stagnant diffusion layer model, we have proposed simple estimates on (1) the potential-composition curve, (2) the thickness of the initial deposit, and (3) the time interval to reach the steady state deposition. These estimates were validated by using a Cu-Ag acidic sulfate electrolyte, which upon electrodeposition results in an immiscible Cu-Ag alloy, both at n-Si(001) or at polycrystallline Ru substrates. The limiting current of Cu-Ag electrodeposition is compared with the numerical results given by Selman and Newman in 1970s [17], whereas the film composition deposited at the limiting current from various electrolyte constitutions is compared with the model suggest by Brenner based on stagnant diffusion layer model [21]. The proposed estimation methods show good agreement with the observed values, despite being highly simplified, since they are compared with the actual mass-transfer problem of ions under convection and migration.

Corrosion Behavior of AA2055 Aluminum-Lithium Alloys Anodized in the Presence of Sulfuric Acid Solution

The aim of this work was to evaluate the corrosion behavior of the AA2055 Aluminum-lithium alloy anodized in a sulfuric acid (H2SO4) bath, varying the current density of 0.19 and 1 A·cm−2 and why the sealing solution was water (H2O) and sodium dichromate (Na2Cr2O7). Anodized samples were exposed to a 10 vol.% H2SO4 solution and the electrochemical technique used was electrochemical impedance spectroscopy. Scanning electron microscopy and X-ray photoelectron spectroscopy were employed to characterization of the anodizing layer, determinate morphology and thickness of coatings. The Na2Cr2O7 sealing solution tends to increase the charge transfer resistance and produces a more homogeneous and compact passive oxide layer, and imparts a corrosion inhibition protection to the AA2055. SEM observations indicated that the morphology and thickness of the anodic films formed on AA2055 aluminum-lithium alloy anodized have the best results for both current densities.

Migration and formation of an iron rich layer during acidic corrosion of concrete with no steel reinforcement

The present study aimed to study the formation, enrichment, and relocation of iron-rich regions in the corroded area of concrete blocks, made without rebar, subjected to severely corrosive highly acidic conditions. In this work, three different concrete mix designs (a proprietary ready-mixed concrete, and laboratory made mortar and concrete) were corroded under induced accelerated conditions in sulfuric acid solutions at pH 1 for a duration of one to six months, in the absence of reinforcement (i.e. rebar) or iron-oxidizing bacteria. A variety of physicochemical and mechanical techniques were applied to monitor and assess the corrosion progress, and physical and chemical changes in the corroded samples. Results indicated a pronounced presence of iron rich layer (iron oxide/hydroxide) at the border of the corrosion front and the transition zone in all mix designs in the form of a ring. While existing papers in the literature describe the iron coming from the rebar, the only source of mobile iron in this experiment was from the iron oxide (Fe2O3) already in the cement. This zone (in a form of a ring) had an average iron content of 2.0 wt% and moved away from the surface to the center of the samples submerged in a sulfuric acid bath with the increase of immersion time, and it was accompanied by hairline cracks. The movement of this zone was in the same direction as sulfate (from acidic media) ingress and the opposite direction of calcium ion leaching, (Ca leaching). The rate of corrosion, the hardness and the compressive strength of concrete are mostly affected by the concrete mix design, the iron-ring enrichment and relocation had no significant impact on them. Detection of the iron-rich zone is an indication of the depth of corrosion at advanced stages in concrete products.

Porous PEDOT:PSS Particles and their Application as Tunable Cell Culture Substrate

AbstractDue to its biocompatibility, electrical conductivity, and tissue‐like elasticity, poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) constitutes a highly promising material regarding the fabrication of smart cell culture substrates. However, until now, high‐throughput synthesis of pure PEDOT:PSS geometries was restricted to flat sheets and fibers. In this publication, the first microfluidic process for the synthesis of spherical, highly porous, pure PEDOT:PSS particles of adjustable material properties is presented. The particles are synthesized by the generation of PEDOT:PSS emulsion droplets within a 1‐octanol continuous phase and their subsequent coagulation and partial crystallization in an isopropanol (IPA)/sulfuric acid (SA) bath. The process allows to tailor central particle characteristics such as crystallinity, particle diameter, pore size as well as electrochemical and mechanical properties by simply adjusting the IPA:SA ratio during droplet coagulation. To demonstrate the applicability of PEDOT:PSS particles as potential cell culture substrate, cultivations of L929 mouse fibroblast cells and MRC‐5 human fibroblast cells are conducted. Both cell lines present exponential growth on PEDOT:PSS particles and reach confluency with cell viabilities above 95 vol.% on culture day 9. Single cell analysis could moreover reveal that mechanotransduction and cell infiltration can be controlled by the adjustment of particle crystallinity.

Influence of zinc sulfate concentration in baths on the structure, morphology and tribocorrosion properties of Fe-Zn alloy coating

To address the glazing issue of impregnated diamond bit in drilling hard and compact rock formations, Fe-Zn alloys were electrodeposited from acid sulfate baths and the surface morphology , phase composition, microhardness and tribocorrosion property of the deposits were studied. As the ZnSO 4 concentration increased from 0 g/L to 20 g/L, the morphology of deposits changed from fine-grained clusters to triangular based pyramids, and finally to granular grains. α phase, η phase and a mixture of α phase and η phase were identified in Fe-Zn coatings. And the microhardness of the deposits is influenced by the Zn content and grain size of Fe-Zn alloy. Furthermore, tribocorrosion behaviors of the deposits were investigated in NaCl solutions by electrochemical measures (potentiodynamic polarization, electrochemical current noise) with an abrasion-corrosion rig. Results of tribocorrosion tests showed that the primary form of the material loss was pure mechanical wear , except the deposit obtained at 20 g/L ZnSO 4 , whose mass loss due to corrosion-induced abrasion contributed most to its total material loss. The degradation mechanism of Fe-Zn deposits was also detailed in this paper. • Fe-Zn alloy was electrodeposited from an acid bath with improved stability. • The morphology of Fe-Zn deposits changed with the variation of phase structure. • Fe-Zn coating with 20% Zn provided the best combination of hardness and mass loss. • The wear mechanism of Fe-Zn deposits in silica slurry with NaCl was discussed.

On the temperature dependent magnetization in dual-phase Co nanowires confinedly electrodeposited inside nanoporous alumina membrane

The present paper reports the temperature dependent magnetization in dual-phase Co nanowires electrodeposited inside nanoporous alumina membrane. The Co nanowires were grown inside the nanochannels of the alumina membrane using an acidic sulphate bath (pH 3). Phase analysis, in combination with magnetic measurements, confirmed the mixed-phase structures as hcp and fcc-Co. The dominant fcc-Co phase appears with a minor hcp-Co phase having major c-axis orientation perpendicular to the nanowire axis. The role of phase structures and the interplay of magnetic anisotropies have been discussed to understand the temperature dependent magnetization of these dual-phase Co nanowires embedded inside alumina membrane. The temperature dependent reorientation of easy magnetization axis and the resulting magnetic properties could be ascribed to the magneto-structural coupling for such confinedly grown Co nanowires.

Electrodeposition of Zn-Co Alloy from an Acid Sulphate Bath Containing Triethanolamine and Thiaminehydrochloride

Electrodeposition of Zn-Co alloy from an acid sulphate bath has been carried out in this research work. The effects of metal ion ratio in the bath, pH current density, temperature, stirring, thickness and concentrations of triethanolamine and thiaminehydrochloride on the alloy composition and on cathodic current efficiency have been investigated. The deposition potentials of Zn-Co alloy are less noble of zinc and cobalt. The structure of Zn-Co alloy was investigated by X-ray diffraction indicates zinc structure. The surface morphology of alloy deposits is found to depend on the percentage of cobalt in the alloy. Under the optimum operating conditions, Zn-Co alloy deposition follows anomalous co-deposition.

Physico-Chemical Properties of Zn-Fe Alloy Deposits from an Acid Sulphate Bath Containing Triethanolamine

The composition, properties, structure and morphology of electrodeposited Zn-Fe alloy deposits obtained from an acid sulphate bath containing triethanolamine have been investigated. A bath containing less zinc (20%) produced an alloy deposit with higher zinc content (80%), i.e. anomalous co-deposition process. The composition of alloy remained constant with pH of the plating bath and thickness of the alloy deposit. The cathodic current efficiency depends on plating variables. The shift in deposition potentials of Zn-Fe alloy is a chief cause in the co-deposition process to produce alloy of varying composition. Phase structure determination by X-ray diffraction studies showed a wide variety of inter metallic phases. Zn-Fe alloy showed a superior corrosion resistance than zinc coatings. An alloy containing greater than 40% Fe showed a good paintability. Hardness of the alloy deposits increased with increase in iron content in the alloy. Smooth, uniform and fine grained deposits were obtained for the Zn-Fe alloy containing 20% Fe.

Physico-Chemical Properties of Zn-Ni Alloy Deposits from an Acid Sulphate Bath Containing Ethanolamines

The composition, properties, structure and morphology of electrodeposited Zn-Ni alloy deposits obtained from an acid sulphate bath have been investigated. A bath having higher percentage of nickel (50%) produced an alloy deposit with low percentage of nickel (12%), the percentage of nickel in the alloy deposit increases with current density up to 40 A.dm-2, with further increase in current density, the percentage of nickel shows a downward trend, increase in temperature of the plating bath increases the percentage of nickel in the alloy deposit. The hardness of the alloy deposits increases with increase in nickel content in the alloy, the phase structure of alloy deposit shows the presence of α, η, δ and γ phases. The morphology of Zn-Ni alloy deposits shows uniform and finer grained structure.

Part I: Ni-Co alloy foils electrodeposited using ionic liquids

The Ni-Co alloy co-electrodeposit from a sulfate bath including two new ionic liquids 1-methyl-3-(2-oxo-2-((2,4,5 trifluorophenyl) amino) ethyl)-1H-imidazol-3-ium iodide [MOFIM]I and 1-(4-fluorobenzyl)-3-(4-phenoxybutyl) imidazol-3-ium bromide [FPIM]Br as additives was characterized using the SEM, EDS, EDS mapping, XRD, AFM and microhardness measurement techniques. The resultant surface morphologies in acidic sulfate baths on a copper substrate demonstrated that both the [MOFIM]I and [FPIM]Br additives served as effective leveling agents. The Ni-Co alloy co-deposit morphology in the [MOFIM]I bath was more enhanced (non-grained coating, Ra of 28 nm and Rt of 35.5 nm) than that in the [FPIM]Br bath (grain size 225 nm, Ra of 51. 1 nm and Rt of 65.7 nm) owing to the molecular structure. The co-deposition of Co and Ni from the acidic baths was of the anomalous type. Moreover, the anomalous behavior of the Ni-Co co-deposition was alleviated after [MOFIM]I and [FPIM]Br were introduced in the bath. To determine the optimal bath conditions, the cathodic current efficiency (CCE%) value was calculated during the Ni-Co alloy co-electrodeposition process under three different compositions and different operating conditions. Under the composition of Ni 70% and Co 30% (Ni70%-Co30% alloy deposit), the CCE% values increased considerably, with maximum values of 99.8% and 97.07% in the baths including [MOFIM]I and [FPIM]Br, respectively.

STUDY OF Zn–Co ALLOY COATINGS MODIFIED BY NANO- TiO2 PARTICLES INCORPORATION

The purpose of this paper is to investigate the effect of TiO2 nanoparticles contents on structural properties, microhardness and corrosion resistance of Zn-Co alloy coating and ZnCo-TiO2 composite coatings is electrodeposited on steel substrate in the acid sulfate bath, The smaller grain size of the composite coatings is observed in the presence of TiO2 and it is confirmed by the images of scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The corrosion performance of coating in the 3 % NaCl as a corrosive solution is investigated by potentiodynamic polarization and electrochemical impedance spectroscopy EIS methods. It is found that the incorporation of nanoparticules in Zn–Co alloy coating have better corrosion resistance and the values of Rct and Zw increase, while the values of Cdl decrease with the increasing of nanoparticules

Zn–Ni compositionally modulated multilayered alloy coatings for improved corrosion resistance

ABSTRACT Zinc–Nickel monolayer (single layer) and compositionally modulated multilayer alloy coatings were developed on to mild steel from acidic sulphate bath; and their corrosion performance were studied using potentiodynamic polarization and electrochemical impedance spectroscopy methods. The coating layers were formed galvanostatically by single bath technique, using square current pulses and triangular current pulses. For the best efficiency of the deposits against corrosion, the switched cathode current density and the number of layers were optimized. Under optimized conditions, Zn–Ni multilayer alloy coatings were produced at the current density 3.0/5.0 A dm−2 having 300 layers were ∼65 (square) and ∼48 (triangular) times more corrosion resistant respectively than the single layer alloy coating of the same thickness. Scanning electron microscopy has been employed to investigate, the formation of multilayer alloy coatings as well as the morphology of the surface before and after corrosion studies.

Characterization of Anodic Films Produced on Anodized AA1050 Aluminum Alloy: Effect of Bio-additive

In this study, AA1050 aluminum alloy samples were anodized in sulfuric acid baths containing different amounts of environmentally friendly bio-additive (eggshell particles). The morphological, chemical, and structural characteristics of the resulting films were investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques, respectively. Wear and corrosion resistance of the coatings were evaluated by pin-on-disk and potentiodynamic polarization tests, respectively. The results showed that amorphous films containing less amount of sulfur would be deposited as the concentration of eggshell particles in bath increases. Moreover, coatings with more surface roughness values containing fewer microcracks would be produced in baths containing more eggshell particles. In addition, thicker films with more corrosion and wear resistance values were produced in baths including higher concentrations of eggshell particles. Those samples that were anodized in baths containing eggshell particles exhibited more corrosion and wear resistance in comparison to conventionally anodized ones.

Production of Copper Powder by Electrodeposition with Different Equilibrium Crystal Shape

The copper powder is electrodeposited from copper sulfate pentahydrate (CuSO4·5H2O) and sulphuric acid (H2SO4) bath. The polarization study is carried out to get an indication of limiting current density or deposition potential. Solutions are prepared with different concentrations of CuSO4·5H2O, i.e., from 0.015 to 0.35 M. Additives like sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) are used during electrodeposition. To elucidate the effect of additive on the copper electrodeposition, an equal concentration of SDS and CTAB is used for a particular concentration of CuSO4·5H2O. The examination of surface topography is carried out with the help of a scanning electron microscope. In the absence of additive, the morphology is a honeycomb like structure. However, the deposits are dendritic in nature in the presence of the additive. The smallest constituent in the dendrites is different for both the additive added solutions. In the case of CTAB, the smallest constituent is a flower like structure where microspheres of copper are embedded with nanosheets. On the other hand, the faceted crystal appears for SDS added solution. SHAPE V 7.4 software is used to draw the equilibrium crystal shape. In summary, it is concluded that the dissimilarity in the smallest constituent of dendritic morphology is associated with the concentration of the surfactant.

Characteristics and tribological behavior of the hard anodized 6061-T6 Al alloy

Abstract The hard anodizing process is one of the best choices to achieve high wear resistance in a 6061-Al alloy, which is commonly used in marine and aerospace applications. In this study, the hard anodizing process was performed by applying several current densities at different times. Two types of electrolytes containing various concentrations of sulfuric acid or oxalic acid were used as the bath. The microhardness of the coatings was measured. Morphology, thickness, and structure of the samples were investigated through a scanning electron microscope (SEM), and an X-ray diffractometer (XRD). Surface roughness and tribological behavior of the optimum samples were also examined. The results revealed that there was an optimum value for the electrolyte concentration, as well as the hard anodizing current density and time at which the hardest coating was obtained. All the oxide films had an amorphous structure. Doing the hard anodizing at 35 mA/cm2 in a sulfuric acid bath for 50 min resulted in a uniform and crack-free coating. The weight loss of this oxide film was 50 and 21 times lower than the substrate and the coating obtained in an oxalic acid bath at the optimum conditions, respectively.

Effect of graphene addition on composition, morphology and corrosion behavior of ZnNiFe-graphene composite coatings

Graphene reinforced, Zn-rich, Zinc-Nickel-Iron (ZnNiFe-G) coatings were deposited on mild steel substrate by electrolyzing the Zn-Ni-Fe acidic sulphate bath containing different amounts of dispersed graphene layers. Effect of graphene incorporation on composition, microstructure, morphology and electrochemical corrosion performance of coatings was investigated. X-ray diffraction studies revealed ZnNiFe coatings consists η Zn, γ Ni2Zn11 and Fe phases but the concentration of γ Ni2Zn11 phase increased with increasing graphene content in the coating. Incorporation of graphene enhanced the coating compactness and reduced the micro-pores and surface defects. Presence of graphene increased the Ni and Fe content in the coatings. The electrochemical corrosion behavior of the composite coatings was determined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Increase in γ Ni2Zn11 phase concentration, compact and defect free ZnNiFe-G composite coatings exhibited >50% better corrosion resistance performance when compared to the corrosion resistance exhibited by the graphene free Zn-Ni-Fe coating. Among the ZnNiFe-G coatings, the composite coating with combination of highest Ni and graphene content showed the best corrosion resistance performance.

Electro-Chemical Deposited Cu-Ni Binary and Cu-Ni-Mn Ternary Alloys from Sulphate Bath for Anti-Corrosive Coating Applications in Brine Environment: Effect of Corrosion Behaviour, Polarization Studies, Morphological and Structural Characterizations

Electrochemical preparation of binary alloy of Cu-Ni from acid sulphate bath containing citric acid using Potentiostatic method. The effects of alloy composition were monitored. Copper is widely used in industry, because of its good thermal conductivity and mechanical characteristics. The accumulation of Nickel & Manganese to Copper enhances itspotency, vigour, toughness, endurance, permanence&also the corrosion-resistanceas well asattrition. Corrosion controls of metal have technical environmental and economical importance. The Cu-Ni-Mn alloyswere used commercially for decorative and protective purpose and also in marine applications. The thin film coating characterized by SEM, EDAX and XRD shows morphological, compositional and structural properties of alloys respectively.