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Belgrade, Serbia
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Tomic M.V.,University of Sarajevo | Petrovic M.M.,Institute of Materials Research and Engineering of Singapore | Stankovic S.,National University of Singapore | Stankovic S.,University of Belgrade | And 3 more authors.
Journal of the Serbian Chemical Society | Year: 2014

Electrochemically deposited Zn-Ni-Co alloys under various deposition conditions were investigated using atomic absorption spectroscopy for determination of chemical composition, atomic force microscopy for surface morphology analysis, and electrochemical impedance spectroscopy for determination of corrosion properties. The influence of alloying elements ratio, [Co2+]/[Ni2+], in the chloride deposition solution, as well as deposition current density, on the chemical content, morphology and corrosion properties of ternary alloys was studied. The plating solutions used were with the same overall metal concentration, free of additives and deposition was carried out at room temperature. It was shown that deposition of ternary alloy coatings was of anomalous type and that a ratio of nickel to cobalt ions in the plating solution, as well as deposition current density, has a significant influence on the chemical composition and corrosion stability of these coatings. Presence of both Ni and Co was beneficial for their corrosion stability. It was shown that morphology and porosity were important factors in corrosion stability of these coatings. The coating deposited from the solution with higher [Co2+]/[Ni2+] ion ratio at 8 A dm-2 was made up of the smallest crystalline aggregates, had small surface roughness and porosity, and was with quite uniform distribution of agglomerates and it showed the best corrosion stability.


Tomic M.V.,University of Sarajevo | Petrovic M.M.,Institute of Materials Research and Engineering of Singapore | Petrovic M.M.,National University of Singapore | Stankovic S.,University of Belgrade | And 2 more authors.
Journal of the Serbian Chemical Society | Year: 2015

Electrochemically deposited Zn-Ni-Co alloys under various deposition conditions were investigated using atomic absorption spectroscopy for the determination of the chemical composition, atomic force microscopy for surface morphology analysis, and electrochemical impedance spectroscopy for determination of corrosion properties. The influence of the ratio of the alloying elements, [Co2+]/[Ni2+], in a chloride deposition solution, as well as the deposition current density, on the chemical content, morphology and corrosion properties of the ternary alloys was studied. The plating solutions used were with the same overall metal concentration, free of additives and the deposition was realized at room temperature. It was shown that the deposition of the ternary alloy coatings was of anomalous type and that the ratio of nickel to cobalt ions in the plating solution, as well as the deposition current density, had a significant influence on the chemical composition and corrosion stability of these coatings. The presence of both Ni and Co was beneficial for their corrosion stability. It was shown that morphology and porosity were important factors in the corrosion stability of these coatings. The coating deposited from the solution with higher [Co2+]/[Ni2+] ratio at 8 A dm-2 was made up of the smallest crystalline aggregates, had a small surface roughness and porosity, and was with quite uniform distribution of agglomerates and it exhibited the best corrosion stability. © 2015, Serbian Chemical Society. All rights reserved.


Bucko M.,University of Belgrade | Rogan J.,University of Belgrade | Stevanovic S.I.,ICTM IEC | Peric-Grujic A.,University of Belgrade | Bajat J.B.,University of Belgrade
Corrosion Science | Year: 2011

The effects of a deposition current density (c.d.) on the corrosion behaviour of Zn-Mn alloy coatings, deposited from alkaline pyrophosphate solution, were investigated by atomic absorption spectrophotometry (AAS), X-ray diffraction (XRD), atomic force microscopy (AFM), optical microscopy, electrochemical impedance spectroscopy (EIS) and measurement of corrosion potential (Ecorr). XRD analysis disclosed that zinc hydroxide chloride was the main corrosion product on Zn-Mn coatings immersed in 0.5moldm-3 NaCl solution. EIS investigations revealed that less porous protective layer was produced on the alloy coating deposited at c.d. of 30mAcm-2 as compared to that deposited at 80mAcm-2. © 2011 Elsevier Ltd.


Bajat J.B.,University of Belgrade | Stankovic S.,University of Belgrade | Jokic B.M.,University of Belgrade | Stevanovic S.I.,ICTM IEC
Surface and Coatings Technology | Year: 2010

Electrochemically deposited Zn-Co alloys under various deposition conditions were investigated using atomic absorption spectroscopy (AAS) for determination of chemical composition, anodic linear sweep voltammetry (ALSV) and X-ray diffraction (XRD) for phase structure determination, SEM and AFM for surface morphology analysis, and polarization measurements for determination of corrosion properties. The influence of deposition current density and composition of deposition solution on the phase structure, morphology and corrosion properties of Zn-Co alloys were studied. The plating baths used were with low metal concentration, free of additives and deposition was carried out at room temperature, since the aim of the work was to investigate only the influence of different deposition current densities using economically favorable deposition parameters. It was shown that the ratio of cobalt to zinc ions in the plating bath strongly affects the chemical content and phase structure, as well as the morphology and corrosion stability, of Zn-Co alloys. The single-phased Zn-Co alloys showed the best corrosion stability. The alloys deposited at the highest current density from plating bath with the lower ratio of cobalt to zinc ions, as well as the one deposited at the intermediate current density from bath with higher ratio of cobalt to zinc ions, exhibited the lowest corrosion rates. It was also shown that the deposit having smaller crystallite grains (obtained at higher current density), among two alloy deposits having the same chemical content and phase structure, yielded lower corrosion rate. © 2010 Elsevier B.V.


Bajat J.B.,University of Belgrade | Popic J.P.,ICTM IEC | Miskovic-Stankovic V.B.,University of Belgrade
Progress in Organic Coatings | Year: 2010

One of the most important factors in corrosion prevention by protective coatings is the coating adhesion loss under environmental influence. Thus, adhesion strength is often used when characterizing protective properties of organic coatings on a metal substrate. In order to improve the adhesion of organic coating the metal substrate is often pretreated in some way. In this work, the adhesion of polyester coatings on differently pretreated aluminium surface (by anodizing, with and without sealing, by phosphating and by silane film deposition) was examined. The dry and wet adhesion of polyester coatings were measured by a direct pull-off standardized procedure, as well as indirectly by NMP test. It was shown that under dry test conditions all polyester coatings showed very good adhesion, but that aluminium surface pretreated by silane film showed superior adhesion. The overall increase of wet adhesion for polyester coating on aluminium pretreated by silane film was maintained throughout the whole investigated time period. The different trends in the change of adhesion of polyester coatings were observed for different aluminium pretreatments during exposure to the corrosive agent (3% NaCl solution). The highest adhesion reduction was obtained for polyester coating on aluminium pretreated with phosphate coating. The corrosion stability of polyester coated aluminium was investigated by electrochemical impedance spectroscopy in 3% NaCl solution. The results confirmed good protective properties of polyester coating on aluminium pretreated with silane film, i.e. greater values of pore resistance and smaller values of coating capacitance were obtained in respect to other protective systems, whereas charge-transfer resistance and double-layer capacitance were not measurable during 2 months of exposure to a corrosive agent. © 2010 Elsevier B.V.


Bucko M.,University of Belgrade | Rogan J.,University of Belgrade | Stevanovic S.I.,ICTM IEC | Stankovic S.,University of Belgrade | Bajat J.B.,University of Belgrade
Surface and Coatings Technology | Year: 2013

ZnMn 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 Zn2+ and Mn2+ 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 ZnMn coatings were deposited at current densities of up to 80mAcm-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 ZnMn deposits produced from chloride electrolyte indicated that the coatings were formed of either η- or ε-ZnMn phase, while the coatings obtained from sulfate bath consisted of ε-ZnMn phase. The linear polarization method showed that ZnMn alloys deposited from sulfate electrolyte exhibited higher corrosion resistance in NaCl corrosive media. © 2013 Elsevier B.V.

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