Electrodeposition of Sn-Mn Layers from Aqueous Citrate Electrolytes (original) (raw)
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Electrodeposition of Sn and Co coatings from citrate solutions
2001
Optimal conditions for Sn and Co codeposition were achieved in slightly acid citrate solutions containing no excess of ligand. Sn±Co coatings were deposited with amounts of Co ranging from 15 to 86 mass %. Bright deposits were obtained when the Co content exceeded 76%. These coatings may be considered as solid solutions of tin in a-Co and b-Co. The b-Sn phase is predominant in the case of coatings containing less Co. Voltammograms of the partial processes of Sn(II) and Co(II) reduction may be described quantitatively with the proviso that SnL 2) and CoLH) are electrically active complexes.
Hydrometallurgy, 2013
Recently an increasing interest in deposition of electrolytic Mn has been observed. Part of the experimental data published earlier (in the journals of the former Soviet Union), but unfamiliar to western researchers because of the inaccessibility of the literature is presented and compared. The following results were reported in these papers that were inaccessible to Western researchers: larger crystals of γ-Mn were obtained from chloride electrolytes than from sulfate electrolytes; the crystal structure of α-Mn phase was observed by XRD when Mo K α radiation was used; the influence of Zn, Cd and Cu impurities on microhardness of Mn coatings was complex; successful deposition of γ-Mn was possible at temperature as high as 80°C from "ultra pure" sulfate electrolyte containing ammonium ion; the phase of deposited Mn from pure electrolytes was influenced by the cathode-substrate, but increase in current density allowed eliminating the influence of the cathode-substrate leading to the deposition of α-Mn coatings.
We studied the effect of anode substrates such as pure lead (Pb), lead antimony (Pb-Sb), and lead-silver (Pb-Ag) on the structural and electrochemical properties of electrolytic manganese dioxide (EMD). X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and chemical analyses were used to determine the structural and chemical characteristics of the EMD samples. The charge–discharge profile was studied in 9 M KOH using a galvanostatic charge-discharge unit. In all the substrates the current efficiencies were more than 99% except with Pb-Sb where it was 90%. Results revealed the nature of the substrate strongly affected the morphology of the deposited material which in turn affected the electrochemical properties of the EMD samples. XRD analyses revealed that the nature of the anode did not affect the crystal structure of the deposited EMD and all the samples were predominantly γ-MnO 2 , which is electrochemically active for energy storage applications. The E...
Manganese electrodeposition from urea-rich electrolyte
Macedonian Journal of Chemistry and Chemical Engineering, 2015
Pure manganese coatings were prepared on the steel (AISI 4340) electrode by non-conventional electrodeposition method, in the presence of 8 mol dm-3 of urea as a plating additive. The influence of urea on the electrodeposition of Mn was investigated by linear sweep voltammetry. The morphology of the coatings was studied by scanning electron microscopy (SEM), and their elemental composition by energy dispersive X-ray spectrometry (EDS). The results showed that the presence of urea in the solution enhanced both the reduction of water and Mn2+ ions, however it also increased the current efficiency for metal reduction for around 20 %. Moreover, urea improves the characteristics of Mn deposits, i.e. their adhesiveness, porosity, compactness, and appearance. Except from oxygen as a part of Mn corrosion product at the coatings' surface, no carbon or nitrogen incorporation was detected in the deposits by EDS.
2015
Different techniques were used to illustrate the effect of manganese concentration on the composition and microstructure of Zn-Ni-Mn films. Zn-Ni-Mn alloys electrodeposited from aqueous sulfate media, under acidic conditions was investigated. According to the obtained results the Zn-Ni-Mn showed greater corrosion resistance than Zn-Ni alloy under similar conditions. Galvanostatic measurements for electrodeposition, cyclic voltammetry (CV) were used to the anodic and cathodic behavior of alloy to study the potential ranges. Anodic linear sweep voltammetry (ALSV) technique was used for the phase structure determination. It is obvious that increasing the manganese concentration results in decreasing the grain size and the coating is uniform and homogenous. The corrosion test was performed by the potentiodynamic anodic polarization method. The corrosion resistance of the coating films was increased with increasing Mn ions in the electrolyte. Under these experimental conditions the elect...
Manganese deposition without additives
Surface & Coatings Technology, 2007
A new method was developed to deposit high quality manganese coatings from MnSO 4 aqueous solution without any additives (sulphur or selenium compounds). The method was by pre-electrolysis of the plating bath. Thereafter, the plating of manganese proceeded. High cathode current efficiency (71%) was obtained. Studies showed that deposition time and current density influence the current efficiency of manganese deposition.
Manganese metallurgy review. Part III: Manganese control in zinc and copper electrolytes
Hydrometallurgy, 2007
Manganese is often associated with zinc and copper minerals, and can build up in the processing circuits. Part III of the review outlines the current practice and new developments to get a better understanding of manganese behaviour and control in electrowinning of zinc and copper, and identifies suitable methods and processes to control manganese.
Coatings
Manganese coatings are excellent for the cathodic protection of steel against corrosion. Although manganese is more electrochemically active than widely used protective coatings of zinc, the exceptional resistance of manganese coatings in neutral and basic media is determined by the film of insoluble corrosion products, which forms on the surface of manganese and greatly suppresses its further corrosion. It is known that the electrodeposition process of Mn coatings from sulphate electrolytes is positively affected by some additives of chalcogenide (S, Se and Te) compounds in the electrolyte. However, a more detailed study on the corrosion properties of Mn coatings electrodeposited from sulphate bath with Te(VI) additive is lacking. In this work, the measurements of free corrosion potential and potentiodynamic polarization in a neutral NaCl solution, as well as the corrosion resistance properties of obtained Mn coatings, were evaluated in a salt spray chamber. It was obtained that th...
The influence of anion type in electrolyte on the properties of electrodeposited ZnMn alloy coatings
Surface and Coatings Technology, 2013
Zn\Mn alloy electrodeposition on steel electrode, in electrolytes containing chloride or sulfate anions, was investigated by chronopotentiometry. Galvanostatically obtained electrodeposits were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and atomic absorption spectrophotometry (AAS). It was found that Zn 2+ and Mn 2+ ion reduction occurred at higher overpotentials in sulfate bath, leading to a higher Mn content in the deposit and smaller crystallites as compared to the chloride electrolyte. AFM images of deposits revealed that with the increase in deposition current density, bigger agglomerates formed in both electrolytes, leading to higher roughness and heterogeneity of the samples. In relation to this observation, the Zn\Mn coatings were deposited at current densities of up to 80 mA cm −2 because at higher current densities the samples from sulfate electrolyte were non adherent and dendritic. Depending on the deposition current density, the XRD patterns of the Zn\Mn deposits produced from chloride electrolyte indicated that the coatings were formed of either ηor ε-Zn\Mn phase, while the coatings obtained from sulfate bath consisted of ε-Zn\Mn phase. The linear polarization method showed that Zn\Mn alloys deposited from sulfate electrolyte exhibited higher corrosion resistance in NaCl corrosive media.
Surface and Coatings Technology, 2016
Zn-Mn coatings were electrodeposited at fixed applied potential on steel substrate from an acidic chloride bath containing 4-Hydroxybenzaldehyde (4-HB) and Ammonium Thiocyanate (NH 4 SCN) as additives. Voltammetric and Electrochemical Quartz Crystal Microbalance (EQCM) studies were carried out to study the related electrochemical system in order to determine the optimal deposition conditions. Several parameters such as deposition potential, plating bath composition and additives were investigated with regard to the Mn content in the final coatings. The composition, morphology and crystallographic structure of the coatings were studied using Atomic Absorption Spectroscopy (AAS), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD). In addition, the corrosion behavior of the Zn-Mn alloys was investigated by means of potentiodynamic polarization curves and polarization resistance (R p) measurements. Manganese contents of 11 wt% were obtained with plating baths without additives and increased up to 17 wt% Mn in presence of both additives. The 17 μm-thick coatings obtained from the bath with additives consisted of a compact and smooth ε-Zn-Mn hexagonal close-packed (HCP) single phase with a fiber texture along the 〈110〉 direction. By contrast, coatings deposited from additive-free electrolytes were rough with a dendritic morphology and consisted of a single ε-Zn-Mn phase. Zn-Mn coatings deposited in absence of additives were found to provide lower protective ability than Zn coatings, presumably due to their dendritic morphology and rough surface. Oppositely, better corrosion protection was obtained for coatings deposited in presence of additives compared to pure Zn coatings.