Piotr Ozga

Electrodeposition of Zn-Ni protective coatings from sulfate-acetate baths

Abstract The electrodeposition conditions for Zn–Ni alloys from sulfate–acetate electrolytes have been studied with the view of preparing protective coatings. The influence of electrolyte composition (different [Ni(II)]/[Zn(II)] ratios, pH, buffer), cathode current density, cathode potential and hydrodynamic conditions on the composition of coatings, cathode current efficiency and corrosion resistance were determined. For all of the conditions examined, strong inhibition of nickel reduction with simultaneous increase in the rate of zinc discharge characteristic of an anomalous system, have been observed. The Zn(II) discharge becomes diffusion-controlled at more negative cathode potentials, whereas the partial nickel current densities are independent of electrode rotation speed. Consequently, nickel content and current efficiency are reduced with decreasing thickness of the diffusive layer. An increase in pH above 3.3 causes a significant catalysis of Zn–Ni deposition with a simultaneous decrease of the nickel in coatings. This effect may be related to the formation and increasing concentration of Zn(II) and Ni(II) acetate complexes in this condition. The Zn–Ni coatings obtained (5–18% Ni) characterise improved corrosion resistance in comparison to Zn layers deposited under the same conditions.

Effect of complex formation on the diffusion coefficient of CuII in citrate solution containing NiII and MoVI

An attempt has been made to account for the differences in the values of the observed diffusion coefficient of CuII at a transition from a separate reduction to a codischarge with Ni and Mo. For this purpose experiments were carried out in a wide range of pH for various electrolyte compositions, combining them with the analysis of species occurring in these solutions and with the analysis of different models of mass transport to the cathode surface. The observed results indicate that in the range pH = 6–8, the changes in the values of the limiting currents of Cu occurring in the presence of nickel ions are associated with the formation of a inert heteronuclear complex [CuNi(cit)2]4−. The obtained results also help to account for the differences in the value of the diffusion coefficient of CuII obtained in such electrolytes by other researchers. They also form a basis for the preparation of optimum bath compositions and for further explanation of the electrodeposition mechanism of NiCu and NiCuMo alloys.

Influence of structural factor on corrosion rate of functional Zn–Ni coatings

Abstract The electrocrystallization processes of Zn–Ni coatings from weakly acid sulfate solutions with the addition of citrate and acetate complexing compounds have been compared. The deposition kinetics and the influence of electrolyte composition on the Zn–Ni alloy composition and on some physicochemical properties (corrosion resistance, texture, phase composition, morphology) were determined. It was found that the properties of coatings obtained under the same operating conditions in electrolytes with the same [Ni(II)]/[Zn(II)] concentration ratio and pH but containing different complexing agents were different. The composition of the deposits and their texture as well as phase structure were found to depend on the complexing species present. Coatings deposited from acetate solutions are richer in Ni than those from citrate solutions. The corrosion resistance of a Zn–Ni alloy depends in practice on the percentage of Ni, but in sulfate–citrate electrolytes, layers containing less Ni were obtained with the same corrosion resistance as Ni-rich coatings deposited from acetate solution. The corrosion current decreases more rapidly with increasing Ni content. This effect is connected mainly with phase composition. In citrate solutions practically single-phase (hexagonal η) deposits were obtained which provide better protection with a lower corrosion rate in comparison with alloys consisting of three phases (hexagonal η, monoclinic δ, regular γ) deposited from acetate baths.

Pulse electrodeposition of NiCuMo alloys

Abstract Pulse plating of NiCuMo alloy has been investigated using a series of planned experiments. A domain of pulse parameters has been defined where the coating quality is optimal. The current efficieny and the Mo content can be larger than in d.c. deposition especially at low average current density. Only the copper content in the deposited alloy can be described by a linear function of the pulse parameters (average current density, frequency and duty cycle). Owing to complex kinetics and interactions during the codischarge, the molybdenum and nickel contents do not obey simple analytical dependences on pulse parameters.

Photochemical silver nanoparticles deposition on sol–gel TiO2 for plasmonic properties utilization

This paper shows investigations on silver nanoparticles deposition using simple photochemical method on sol–gel coated titania. The influence of titania substrate, silver precursor concentration, light intensity and irradiation time are considered as a factors determining the microstructure. The average diameter of the particles and surface coverage are calculated from SEM microstructure investigations and confirmed by AFM imaging. The crystalline phase in titania layers were determined by TEM and Raman spectroscopy. The optical measurements of absorbance and absorption were shown indicating that there was no absorption of the light used in experiment even though deposition of nano silver was confirmed. Finally, the plasmonic properties were simulated for the model particles by finite difference time domain method. Possible application of obtained structure was proposed.

Effect of Zinc Sulphide Concentrate Composition and Roasting Temperature on Magnesium Distribution in Zinc Calcine

Abstract Magnesium is present in zinc calcine in two major forms. The first is a solid solution of zinc and magnesium oxides Zn 1− z Mg z O and the second one is a solid solution of zinc, magnesium and ferrous ferrites Zn x Mg y Fe 1− x − y Fe 2 O 4 . A thermodynamic analysis of equilibrium Zn and Mg distribution among the above oxide and ferrite phases as a function of temperature and relative Zn, Mg and Fe contents in the ZnS concentrates has been carried out. The derived relations are presented in the form of nomograms for 950, 1000 and 1050°C. These data have been found to be fairly close to those observed in industrial zinc calcine. The nomograms make it possible to assess the Zn and Mg distributions in the oxide and ferrite phases already at the stage of establishing the composition of ZnS concentrates. Taking into account that Zn−Mg oxide is easily soluble in H 2 SO 4 solutions, whereas Zn−Mg−Fe ferrite is sparingly soluble, the nomograms may be helpful in optimizing the leaching parameters and in the selection of a method of controlling magnesium concentration in zinc electrolyte. Some data illustrating the solutions of the latter problems applied in Polish zinc refineries are presented.

Lecithin suspensions for electrophoretic deposition on stainless steel coatings

Lecithin is a mixture of phospholipids (PLs) that are found in living organisms. It gained the interest as a bio- and hemocompatible modifying agent for biomaterials. In this paper, we focused on the elaboration of a simple and well-described technology of metals coating with low-cost substance that could be useful in biomaterials industry. We studied the utility of lecithin suspension for stainless steel coating by electrophoretic deposition method. Our goal was to find a relationship between the conditions of lecithin suspension preparation, obtained suspension properties (vesicles size and structure, zeta potential, electrophoretic mobility) and lecithin coating features (topography, roughness). We found that final pH value, zeta potential and electrophoretic mobility of lecithin suspensions were not altered by initial solution pH value. However, the presence of hydrated Na+ ions forced forming of large multi-layered vesicles. We obtained uniform lecithin coatings with the use of electrophoretic deposition, which has a great potential to be used in a large scale.