Electrodeposition of zinc–cobalt alloy from a complexing alkaline glycinate bath

Ortiz-Aparicio, José Luis; Meas, Y.; Trejo, G.; Ortega, R.; Chapman, Thomas W.; Chaînet, Eric; Ozil, P.

doi:10.1016/j.electacta.2007.01.010

Cited by 74 publications

(50 citation statements)

References 40 publications

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“…Because of this fact, the cobalt content in the zinccobalt alloys produced from aqueous plating baths is usually low. The electrodeposition of Zn-Co alloys with a controlled morphology and composition has been investigated as a consequence of their observed improved corrosion resistance [7][8][9][10][11]. It is well known that additives which are often organic compounds yield deposits with suitable properties.…”

Section: Introductionmentioning

confidence: 99%

Effects of thiourea and urea on zinc–cobalt electrodeposition under continuous current

2007

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The effect of thiourea and urea on zinc-cobalt alloys obtained from chloride baths under continuous current deposition are described and discussed. The deposit morphology was analyzed using Scanning Electron Microscopy (SEM) and an X-Ray Diffraction (XRD) was used to determine the preferred crystallographic orientations of the deposits. The use of additives does not refine the grain size of the Zn-Co alloy and an especially porous alloy was produced in the presence of urea. The preferred crystallographic orientations of zinc-cobalt alloys do not change in the presence additives. Zinc-cobalt alloys were without texture in the presence and absence of additives. Also, in the absence of additive and in the presence of urea, the XRD lines of the Zn-Co alloys are slightly shifted with respect to the pure zinc XRD lines, whereas, in the presence of thiourea, the XRD lines are not shifted. The alloy composition was examined using Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF). The percentage of cobalt in the alloy decreases slightly from 1.04 to 0.91 wt.% in the presence of urea and in the presence of thiourea it increases from 1.04 to 7.70 wt.%. Voltammetric studies show that thiourea increases the reduction rate of cobalt. This explains the increase in cobalt percentage in the alloy in the presence of thiourea.

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Section: Introductionmentioning

confidence: 99%

Effects of thiourea and urea on zinc–cobalt electrodeposition under continuous current

2007

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“…1), the equilibrium potential of cobalt reduction moves toward more negative values at about -870 mV versus SCE and the growth of the deposited layer increases gradually when the potential shifts to more negative values. The transition of reduction potential to more negative values could be due to the formation of Coglycine complex species [28,29]. During potential scan in positive direction in cyclic voltammogram of cobalt, the anodic peak at the potential of about -570 mV versus According to cyclic voltammogram of Zn 2?…”

Section: Resultsmentioning

confidence: 97%

“…reduction. Many researches [8,[29][30][31][32] have attributed this behavior to the underpotential deposition (UPD) of zinc on cobalt. A peak at potential -1070 mV versus SCE is located on the anodic part of the Zn-Co cyclic voltmmogram that shows oxidation and dissolution of the deposited alloy.…”

Section: Resultsmentioning

confidence: 98%

Electrochemical studies of zinc–cobalt alloy coatings deposited from alkaline baths containing glycine as complexing agent

Gharahcheshmeh

Sohi

2010

J Appl Electrochem

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Co-deposition of Zn-Co alloy coatings that were electrodeposited from weakly alkaline glycine solutions has been studied by cyclic voltammetry. Scanning electron microscopy (SEM), energy depressive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were used to study surface morphology, chemical composition, and phase structure of the coatings. Corrosion behavior of the coatings was also studied using potentiodynamic polarization tests in 3.5 wt% NaCl solution. Cyclic voltammetry results showed that in Zn-Co deposition from an alkaline bath in the presence of glycine, cobalt deposited at a potential near to that of zinc together with successful co-deposition of Co and Zn. It was also shown that reduction-oxidation (redox) reactions of Zn-Co alloy deposits were quasi-reversible and resulted in deviation of electrodeposited alloys from the equilibrium phase diagrams. The corrosion resistance of the deposits was also highly influenced by the composition and morphology of the coatings. Overall, Zn-Co deposit containing 0.89 wt% Co showed that the highest corrosion resistance among the coatings that was due to its single phase structure and fine morphology.

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“…It is possible that glycine and (NH 4 ) 2 SO 4 affect the formation of the barrier film in the region of active dissolution by forming complexes with ions from the dissolving coating and thus facilitate the dissolution process. At this electrolyte pH stronger complexation between glycine and Cr ions (than glycine-Zn ions) is expected [29], leading to complete dissolution of the residual C x -(Zn, Cr) phase in the transpassive region; thus the anode maximum is better pronounced. The shape of the voltammogram is apparently related to the alloy composition.…”

Section: Effect Of Combination Of Additives On Co-deposition Of Cr Anmentioning

confidence: 95%

Deposition of Zn–Cr alloy coatings from sulfate electrolyte: effect of polypropylene glycol 620 and glycine and combinations thereof

et al. 2008

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The effect of polypropylene glycol with molecular mass 620 (PPG 620) and glycine as additives in electrodeposition of Zn-Cr alloy coatings from acidic sulfate electrolyte containing (NH 4 ) 2 SO 4 and H 3 BO 3 , at ambient temperature, without agitation is investigated. PPG 620 inhibits the Zn reaction causing significant proximity of the deposition potentials of Zn and Cr, and a co-deposition at a less negative potential of -1.8 V (vs. Hg/Hg 2 SO 4 ) as compared to the case when polyethylene glycol 1500 (PEG 1500) is used. Depending on the deposition conditions, alloy coatings containing up to 23 mass % Cr can be obtained. Glycine itself does not facilitate the co-deposition of Cr and Zn. Added to the electrolyte containing PPG 620, glycine causes a decrease of the Cr content in the alloy. However, the alloy coatings deposited in the presence of both additives are denser, have better overall appearance and good adherence to the steel substrate. Moreover, glycine increases the buffer capacity of the electrolyte. At short deposition times, the alloy coatings consist mainly of bcc C x -(Zn, Cr) phase with lattice parameter about 3.035 (3) Å and mean crystallite size of the order of 25 nm. Cr content in the coatings can be controlled by changing the concentration of Cr(III) and pH of the electrolyte as well as the current density. Depending on the working conditions, the cathode current efficiency is within 35-55%.

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Electrodeposition of zinc–cobalt alloy from a complexing alkaline glycinate bath

Cited by 74 publications

References 40 publications

Effects of thiourea and urea on zinc–cobalt electrodeposition under continuous current

Effects of thiourea and urea on zinc–cobalt electrodeposition under continuous current

Electrochemical studies of zinc–cobalt alloy coatings deposited from alkaline baths containing glycine as complexing agent

Deposition of Zn–Cr alloy coatings from sulfate electrolyte: effect of polypropylene glycol 620 and glycine and combinations thereof

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