Electrodeposition behavior of zinc-nickel-iron alloys from sulfate bath.Abstract The present work is directed at collecting the properties of Zn-Ni and Zn-Fe alloys in one alloy via the electrodeposition e·lec·tro·de·pos·it
tr.v. e·lec·tro·de·pos·it·ed, e·lec·tro·de·pos·it·ing, e·lec·tro·de·pos·its
To deposit (a dissolved or suspended substance) on an electrode by electrolysis.
The substance so deposited. of Zn-Ni-Fe ternary (programming) ternary - A description of an operator taking three arguments. The only common example is C's ?: operator which is used in the form "CONDITION ? EXP1 : EXP2" and returns EXP1 if CONDITION is true else EXP2. alloy. Electrodeposition of ternary Zn-Ni-Fe alloy was investigated and compared with the characteristics of Zn-Ni electrodeposits. The electrodeposition was performed from a sulfate sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl). bath onto a steel substrate. Structural analysis by X-ray diffraction (XRD XRD X-Ray Diffraction
XRD X-Ray Diode ) method revealed that the Zn-Ni-Fe alloys consisted of a mixture of zinc, and ([gamma]-[Ni.sub.2][Zn.sub.11]) and ([Fe.sub.3][Ni.sub.2]) phases. The study was carried out using electrochemical electrochemical /elec·tro·chem·i·cal/ (-kem´i-k'l) pertaining to interaction or interconversion of chemical and electrical energies.
adj. methods such as cyclic voltammetry Cyclic voltammetry is a type of potentiodynamic electrochemical measurement. In a cyclic voltammetry experiment, a voltage is applied to a working electrode in solution and current flowing at the working electrode is plotted versus the applied voltage to give the cyclic and galvanostatic for electrodeposition, while anodic an·ode
1. A positively charged electrode, as of an electrolytic cell, storage battery, or electron tube.
2. The negatively charged terminal of a primary cell or of a storage battery that is supplying current. linear polarization In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation. See polarization for more information. resistance and anodic linear sweeping voltammetry techniques were used for the corrosion study. Surface morphology morphology
In biology, the study of the size, shape, and structure of organisms in relation to some principle or generalization. Whereas anatomy describes the structure of organisms, morphology explains the shapes and arrangement of parts of organisms in terms of such and chemical composition of the deposits were also examined by using scanning electron microscopy electron microscopy
Technique that allows examination of samples too small to be seen with a light microscope. Electron beams have much smaller wavelengths than visible light and hence higher resolving power. and atomic absorption spectroscopy In analytical chemistry, Atomic absorption spectroscopy is a technique for determining the concentration of a particular metal element in a sample. Atomic absorption spectroscopy can be used to analyse the concentration of over 62 different metals in a solution. , respectively. It was found that the obtained Zn-Ni-Fe alloy exhibited more preferred surface appearance and better corrosion resistance without adding any organic brighteners to the plating bath in comparison to Zn-Ni alloy that electrodeposited at similar conditions. Results obtained revealed that the increase in corrosion resistance of ternary deposits is not only attributed to the formation of ([gamma]-[Ni.sub.2][Zn.sub.11]) phase, but also to iron codeposition and formation of ([Fe.sub.3][Ni.sub.2]) phase.
Keywords Electrodeposition, Phase structure. Surface morphology, Corrosion resistance, Ternary Zn-Ni-Fe alloy
Zn-Ni alloy coatings have attracted much attention because they possess higher corrosion resistance and better mechanical characteristics in comparison with zinc and other zinc alloy coatings. (1-10) Although the literature concerning ternary alloys is very limited in comparison with that of binary alloys, it has been found that Zn-Ni-Fe alloys are valuable for their leveling action. (11) It has been observed that the addition of Fe to Zn-Ni alloy led to the formation of a ternary Zn-Ni-Fe alloy, which, when deposited from a chloride bath, improved both the appearance of the alloy and its corrosion resistance. (12) In addition. Zn-Ni-Fe alloy has been found to be useful as a source in a hydrogen evolution reaction. (13) Electrodeposition of these alloys has attracted considerable attention because they exhibit the phenomena of "anomalous a·nom·a·lous
1. Deviating from the normal or common order, form, or rule.
2. Equivocal, as in classification or nature. codeposition." This term, introduced by Brenner, (14) is used to describe the preferential pref·er·en·tial
1. Of, relating to, or giving advantage or preference: preferential treatment.
2. deposition of the less noble metal (i.e., Zn) to the more noble metal (Ni or Fe). In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke"
put differently , the reduction of Ni or Fe is inhibited while the deposition of Zn is enhanced when compared with their individual deposition rates. Several theories have been forwarded by various researchers, (15-21) but the most widespread one, and subject of controversy, is the so-called "hydroxide hydroxide (hīdrŏk`sīd), chemical compound that contains the hydroxyl (−OH) radical. The term refers especially to inorganic compounds. suppression mechanism" (HSM (1) (Hierarchical Storage Management) The automatic movement of files from hard disk to slower, less-expensive storage media. The typical hierarchy is from magnetic disk to optical disc to tape. ). This model, initially proposed by Dahms and Croll (15) for the Ni-Fe alloys, suggests that the discharge of more noble ions (i.e., [Ni.sup.2+]) is hindered by the formation of Fe[(OH).sub.2] in respective electrolytes, due to local pH rise, on the catalyst surface and. therefore, inhibits the codeposition of Ni. Tsuru el al. (22) have supported HSM theory by producing a normal deposition from a methanol methanol, methyl alcohol, or wood alcohol, CH3OH, a colorless, flammable liquid that is miscible with water in all proportions. Methanol is a monohydric alcohol. It melts at −97. bath and showed that anomalous behavior occurs when water is added to the electrolyte electrolyte (ĭlĕk`trəlīt'), electrical conductor in which current is carried by ions rather than by free electrons (as in a metal). . Recently, the hydroxide oscillation Oscillation
Any effect that varies in a back-and-forth or reciprocating manner. Examples of oscillation include the variations of pressure in a sound wave and the fluctuations in a mathematical function whose value repeatedly alternates above and below some concept was proposed, (23) according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. which the thickness of the hydroxide layer changes periodically and the hydrogen reduction and cobalt deposition takes place when the hydroxide layer is depleted de·plete
tr.v. de·plet·ed, de·plet·ing, de·pletes
To decrease the fullness of; use up or empty out.
[Latin d .
In contrast, Gomes and Valles (24) have disagreed and objected to the HSM theory. They observed that an increase in the solution pH promotes the normal codeposition of Zn-Co alloys. However, Chassaing and Wiart (25) and Miranda et al. (26) found high Ni deposition at higher pH values during Zn-Ni electrodeposition in chloride and sulfate medium and suggest that the deposition of Ni is activated with an increase in solution pH of the Zn-Ni system, which is in contradiction with HSM.
Two other papers on NiFe electrodeposition propose different mechanisms. The mechanism of Lieder and Biallozor (27) assumes that [Ni.sup.2+] discharges first to form a thin layer which chemisorbs water to form adsorbed Ni[(OH).sup.+], and competition between the [Ni.sup.2+] and [Fe.sup.2+] to occupy active sites leads to the preferential deposition of Fe. Matlosz (28) uses a two-step reaction mechanism involving adsorbed monovalent monovalent /mono·va·lent/ (-va´lent)
1. having a valency of one.
2. capable of combining with only one antigenic specificity or with only one antibody specificity. intermediate ions for both electrodeposition of iron and nickel, as single metals, and combines the two to develop a model for codeposition. Anomalous effects are assumed to be caused by preferential surface coverage due to differences in Tafel rate constants for electrodeposition.
The Sasaki and Talbot proposed model (29) extends the one-dimensional diffusion diffusion, in chemistry, the spontaneous migration of substances from regions where their concentration is high to regions where their concentration is low. Diffusion is important in many life processes. modeling of Grande and Talbot, (30) a supportive or interpretive in·ter·pre·tive also in·ter·pre·ta·tive
Relating to or marked by interpretation; explanatory.
in·terpre·tive·ly adv. , rather than a predictive, model of electrodeposition. A main contribution of this model is the inclusion of hydrogen adsorption adsorption, adhesion of the molecules of liquids, gases, and dissolved substances to the surfaces of solids, as opposed to absorption, in which the molecules actually enter the absorbing medium (see adhesion and cohesion). and its effects on electrodeposition. Zech et al. (31) concluded that codeposition of iron group metals leads to a reduction of the reaction rate of the nobler component and an increase of the reaction rale rale (rahl) crackle; a discontinuous sound consisting of a series of short sounds, heard during inhalation.
amphoric rale of the less noble component compared to single metal deposition.
In the present work, it was felt that it would be interesting to collect the properties of Zn-Ni and Zn-Fe alloys in one alloy via the electrodeposition of Zn-Ni-Fe ternary alloy. The electrodeposition of ternary Zn-Ni-Fe alloy from sulfate electrolytes as well as surface morphology and corrosion resistance were studied. In addition, a comparison was made between Zn-Ni and Zn-Ni-Fe alloys obtained under the same conditions. The results of the experimental approach were based essentially on the analysis of the cyclic cyclic /cyc·lic/ (sik´lik) pertaining to or occurring in a cycle or cycles; applied to chemical compounds containing a ring of atoms in the nucleus.
cy·clic or cy·cli·cal
1. voltammograms and galvanostatic measurements during the electroplating electroplating: see plating.
Process of coating with metal by means of an electric current. Plating metal may be transferred to conductive surfaces (e.g., metals) or to nonconductive surfaces (e.g. . For corrosion study, the anodic linear sweep voltammetry and linear polarization resistance were used.
The standard bath compositions for Zn-Ni-Fe deposits are given in Table 1. The sulfate salt concentrations in the baths for separate deposits, (a) Zn, (b) Ni, (c) Fe, and (d) Zn-Ni alloy, are (a) 0.10 M Zn[SO.sub.4]. (b) 0.10 M NiS[SO.sub.4] (c) 0.10 M Fe[SO.sub.4], and (d) 0.10 M Zn[SO.sub.4], and 0.10 M NiS[SO.sub.4], respectively. The electrolytes used for electrodeposition of different deposits were freshly prepared using Analar grade chemicals without further purification purification, in religion, the ceremonial removal of what the religion deems unclean. The usual agents of purification are water (as in baptism), bodily alteration (as in circumcision), and fire. and dissolved in appropriate amount of doubly distilled water Noun 1. distilled water - water that has been purified by distillation
H2O, water - binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 degrees centigrade and boils above 100 degrees centigrade; .
Table 1: Basic bath composition of ternary Zn-Ni-Fe alloy electrodeposition Bath composition Concentration (M) Zinc sulfate 0.1 Nickel sulfate 0.1 Ferrous sulfate 0.1 Sodium sulfate 0.2 Boric acid 0.2 Sulfuric acid 0.01
The electrolytic cell electrolytic cell
1. A cell containing an electrolyte through which an externally generated electric current is passed by a system of electrodes in order to produce an electrochemical reaction.
2. was used for the present work as detailed in reference (32). Before each run, the cell was cleaned with chromic/sulfuric mixture, washed with single and doubly distilled water, and filled with the 50 [cm.sup.3] of the electroplating solution. The electrodeposition process was performed on pure steel rod of cross-sectional area 0.196 [cm.sup.2] at pH = 2.5 and current density 5.0 mA [cm.sup.-2] for 10 min at 30[degrees]C.
For electrochemical methods (cyclic voltammetric behavior, galvanostatic measurements, linear polarization resistance, and anodic sweeping voltammetry techniques), an EG&G Potentiostat/Galvanostat Model 273A, controlled by a PC using Corrosion Analysis Software Model 352, was used. All cyclic voltammetry experiments were initiated at 0 V in a negative direction, and reversed at -1.2 V in a positive direction at 0 V at a scan rate The number of times per second an image capture or display device samples its field of vision. See scan line and horizontal scan frequency. See also scan technology. of 5 mV [s.sup.-1].
Anodic sweeping voltammetry analysis is employed effectively for the in situ In place. When something is "in situ," it is in its original location. characterization of the electrodeposition process and products of the galvanostalically obtained electrodeposits on the steel substrate. For anodic sweeping voltammetry, the galvanostatic deposition was carried out for 10 min to obtain a thin deposit. The analysis was performed right after the galvanostatic depositions in 0.5 M [Na.sub.2][SO.sub.4] + 0.05 M EDTA EDTA: see chelating agents. solution.
The surface morphology of the deposit was evaluated by a Scanning Electron Microscope scan·ning electron microscope
n. Abbr. SEM
An electron microscope that forms a three-dimensional image on a cathode-ray tube by moving a beam of focused electrons across an object and reading both the electrons scattered by the object and (JSM-5500 LV, SEM, JEOL JEOL Japan Electron Optics Laboratory . Japan). X-ray diffractometry (XRD). X'Pert Pro PANalytical, was used to identify the phases of Zn-Ni-Fe alloys deposited. Steel and copper sheets cathodes, of widths 1.0 cm and 1.0 cm in length, were used for XRD and SEM analysis, and chemical and EDX EDX Energy Dispersive X-Ray (Spectroscopy)
EDX Electronic Data Exchange
EDX Extended Data Register
EDX Event-Driven Executive (IBM Series/1 OS)
EDX Event-Based Data Exchange (UPNet) analysis, respectively. To steel and copper sheets provided with a narrow strip of about 1 [cm.sup.2] area, clamp clamp (klamp) a surgical device for compressing a part or structure.
rubber dam clamp a metallic device used to retain the dam on a tooth.
n. terminals were attached for electrical contact Noun 1. electrical contact - contact that allows current to pass from one conductor to another
tangency, contact - (electronics) a junction where things (as two electrical conductors) touch or are in physical contact; "they forget to solder the contacts" . To determine its composition, the deposit (32) was stripped in 30% (v/v) HCl solution, then diluted di·lute
tr.v. di·lut·ed, di·lut·ing, di·lutes
1. To make thinner or less concentrated by adding a liquid such as water.
2. To lessen the force, strength, purity, or brilliance of, especially by admixture. with doubly distilled water up to 100 [cm.sup.3] and analyzed to ascertain the Zn, Ni, and Fe contents in the deposited alloy using Atomic Absorption Spectroscopy (Variian SpectrAA 55).
The values of electrochemical corrosion measurements of the coatings. [E.sub.corr], the corrosion potential, [I.sub.corr], the corrosion current, [R.sub.p], the polarization polarization
Property of certain types of electromagnetic radiation in which the direction and magnitude of the vibrating electric field are related in a specified way. resistance, and corrosion rate, were obtained and represented in Table 2.
Table 2: Values of Zn, Ni, and Fe amount in the deposit, total mass of the deposit, content (Zn, Ni, and Fe), current efficiencies (Zn, Ni, Fe, Zn-Ni, and Zn-Ni-Fe deposits), thickness, and electrochemical corrosion measurements of the deposit on copper (2 [cm.sup.2]) deposited galvanostatically from a bath containing (a) 0.10 M Zn[SO.sub.4], (b) 0.10 M Ni[SO.sub.4], (c) 0.10 M Fe[SO.sub.4], (d) 0.10 M Zn [SO.sub.4] and 0.10 M Ni[SO.sub.4], (e) 0.10 M Zn[SO.sub.4], 0.10 M Ni[SO.sub.4], and 0.1 M Fe[SO.sub.4], with 0.01 M [H.sub.2][SO.sub.4], 0.20 M [Na.sub.2][SO.sub.4], and 0.20 M [H.sub.3]B[O.sub.3] at 5 mA [cm.sup.-2] for 10 min at 30[degrees]C Parameter Deposit (a) Zn (b) Ni (c) Fe (d) (e) only only only Zn-Ni Zn-Ni-Fe alloy alloy Zn amount in the deposit 183 0 0 130 126 ([10.sup.5] g) Ni amount in the deposit 0 56.6 0 18.3 16.5 ([10.sup.-5] g) Fe amount in the deposit 0 0 129 0 2.4 ([10.sup.5] g) Total mass of the 183 56.6 129 148.3 144.9 deposit ([10.sup.-5] g) Zn content (%) 100 0 0 87.8 86.9 Ni content (%) 0 100 0 12.2 11.3 Fe content (%) 0 0 100 0 1.7 Zn current efficiency 90.02 0 0 63.9 61.9 ([e.sub.zn]) (%) Ni current efficiency 0 31.02 0 9.9 9.0 ([e.sub.Ni]) (%) Fe current efficiency 0 0 74.3 0 1.38 ([e.sub.Fe]) (%) Zn-Ni deposit current 0 0 0 73.8 0 efficiency ([e.sub.[Zn-Ni]]) (%) Zn-Ni-Fe deposit current 0 0 0 0 72.4 efficiency ([e.sub.[Zn-Ni-Fe]]) (%) Thickness of the deposit 1.3 0.32 0.83 1.0 1.1 ([mu]m) [R.sub.p] (k[omega]) 0.131 2.24 0.117 0.127 0.194 [I.sub.corr] (A 2.88 0.08 0.87 1.48 1.27 [cm.sup.-2] x [10.sup.-5]) [E.sub.corr] (mV) 997 -169 -334 986 -608
Results and discussion
Figure 1 shows the cyclic voltammetry for the electro-deposition of Zn, Ni, and Fe alone, and the Zn-Ni and Zn-Ni-Fe alloys on steel rod in the bath solutions at 30[degrees]C. From the figure, the potential jumps were performed from 0.0 V ([E.sub.i]) to more negative potentials -1.2 V ([E.sub.f]); in the negative scan, the deposition of Zn alone starts at about -1110 mV and close to Zn-Ni and Zn-Ni-Fe codeposition potential (at about -1050 mV and -1038 mV, respectively). On the other hand, from the same figure, it is obvious that the deposition of Ni and Fe alone starts at about -900 and -950 mV, respectively, and the growth of deposited layer increases gradually when the potential was shifted to more negative values. Although, the polarization curve of Zn-Ni and Zn-Ni-Fe alloy deposition lies between the polarization curves of each deposition Zn and Ni and/or Fe, but Zn-Ni-Fe alloy deposition potential is nobler than Zn-Ni deposition potential; this may be due to codeposition of Fe into the alloy. This position suggested that the codeposition enables Zn to deposit at more positive potential (i.e., shifts the deposition potential of Zn to less negative values) due to the presence of [Ni.sup.2+] and [Fe.sup.2+], which facilitates Zn deposition. However, the codeposition of Ni and Fe shifted negatively in the presence of [Zn.sup.2+].
[FIGURE 1 OMITTED]
There is a cathodic cathodic
pertaining to or emanating from a cathode. peak started at about -577 mV and appeared in the presence and absence of Zn, Ni, and Fe ions in the plating bath (Fig. 2). This cathodic peak may be due to the codeposition of sulfur, which liberated lib·er·ate
tr.v. lib·er·at·ed, lib·er·at·ing, lib·er·ates
1. To set free, as from oppression, confinement, or foreign control.
2. Chemistry To release (a gas, for example) from combination. from the reduction of sulfate group at the cathode in the presence of [H.sub.2][SO.sub.4]. Figure 3 shows the voltammograms of all the constituents of the bath in absence of ions that form alloy. It could be seen from the figure that the cathodic peak appeared only in the presence of [H.sub.2][SO.sub.4], in spite of the presence of [Na.sub.2][SO.sub.4], which was considered as a source of [SO.sub.4.sup.-2] group in the plating bath. Moreover, the cathodic peak appeared only in the reduction of sulfuric acid sulfuric acid, chemical compound, H2SO4, colorless, odorless, extremely corrosive, oily liquid. It is sometimes called oil of vitriol. Concentrated Sulfuric Acid
alone and reduction of other constituents with sulfuric acid. These results confirm that the cathodic peak attributed to the codeposition of sulfur from the reduction of the sulfate group occurs only in the presence of [H.sub.2][SO.sub.4], which is the source of [H.sup.+] that reduces the sulfate groups. Taking into consideration that this process is composed of several consecutive steps, the overall reaction in the plating bath is as follows:
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
[SO.sub.4.sup.2-] + 8[H.sup.+] 6[e.sup.-] [right arrow] S + 4[H.sub.2]O.
These results were in agreement with the results obtained by using XRD and EDX analysis. Figure 4 shows the EDX pattern of the deposit containing Zn-Ni-Fe alloy. It can be seen from the peaks in this figure that there is another peak that corresponds to the presence of sulfur. In addition, Fig. 5 shows the XRD pattern of the deposit in the absence of Zn, Ni, and Fe, and the obtained peaks correspond to the presence of sulfur only, which is in contradiction with Abou-Krisha's research. (32) He explains the appearance of this peak due to hydrogen evolution. Nevertheless, it was concluded here that the hydrogen evolution started after the deposition of sulfur (Fig. 3) and appeared as wobbly wob·bly
adj. wob·bli·er, wob·bli·est
Tending to wobble; unsteady.
wobbli·ness n. in the cyclic voltammograms, which is due to the reduction of [H.sub.2][SO.sub.4] and [H.sub.2][SO.sub.4] + [H.sub.3][BO.sub.3]. Both the hydrogen evolution and the deposition of sulfur decrease in the presence of [Zn.sup.2+] and/or [Ni.sup.2+] and/or [Fe.sup.2+] due to surface effect that occurs with the addition of these cations. This may be ascribed to the start of competitive adsorption between [Zn.sup.2+] and/or [Ni.sup.2+] and/or [Fe.sup.2+] (or its monovalent intermediate), and S, and [H.sup.+]. On the other hand, the addition of these cations could decrease the adsorption of S and [H.sup.+] and consequently their deposition and evolution, respectively. The anodic current peak (Fig. 3), which attributed to the dissolution of the deposited sulfur, appears at -225 mV and its height decreases with the addition of other constituents to sulfuric acid in the bath. Fortunately, the codeposition of sulfur leads to more improvement of the crystallinity Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. In a gas, the relative positions of the atoms or molecules are completely random. of the deposits. (33)
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
From the positive scan of the cyclic voltammogram (Fig. 1), there is only one anodic peak at about -1110 mV, which corresponds to the anodic dissolution of Zn deposited alone in the absence of Ni and Fe. In addition, there are two anodic peaks at -527 and -101 mV, which correspond to the dissolution of separately deposited pure Fe and Ni, respectively. For Zn-Ni voltammogram, there are three peaks that correspond to the dissolution of the constituents of two phases, [delta]-phase ([Ni.sub.3][Zn.sub.22]) and [gamma]-phase ([Ni.sub.5][Zn.sub.21]). The first and second anodic peaks correspond to the dissolution (dealloying) of Zn from [delta]- and [gamma]-phases, respectively. The third peak corresponds to the dissolution of Ni from its phases as reported earlier by Abou-Krisha. (32) However, for the Zn-Ni-Fe curve, there are four anodic current peaks. The first dissolution anodic peak at -1038 mV is attributed to the dissolution of zinc from pure Zn phase, while the second anodic peak at about -704 mV corresponds to dissolution of zinc from ([gamma]-[Ni.sub.2][Zn.sub.11]) phase. The third and fourth anodic peaks at -633 and -318 mV correspond to the dissolution of iron from ([Fe.sub.3][Ni.sub.2]) phase and nickel from the two phases, respectively, which was confirmed by XRD (Fig. 6).
[FIGURE 6 OMITTED]
The height of any peak is considered as an indication of the quantity of its phase in the deposit. Therefore, from Fig. 1 the increase in height of the second Zn-Ni-Fe peak and its shift to more noble direction, in comparison with the content of the same phase for Zn-Ni alloy deposition, reflects the high content of ([gamma]-[Ni.sub.2][Zn.sub.11]) phase in the deposit for Zn-Ni-Fe alloy, and consequently means that the corrosion resistance increases. In addition, the height of the third peak, which corresponds to the dissolution of iron from its phase in the Zn-Ni-Fe alloy, is too low in comparison with the height of the peak that corresponds to the dissolution of Fe alone. This may be ascribed to the presence of Zn and/or Ni in the plating bath that inhibits the codeposition of Fe.
The ternary Zn-Ni-Fe deposits exhibit higher corrosion resistance in comparison to Zn-Ni deposits. The data showed a significant change in the preferred crystal orientation for Zn-Ni-Fe deposits compared to Zn-Ni deposits; this may be explained by the adsorption inhibition theory Inhibition theory is based on the basic assumption that, during the performance of any mental task, which requires a minimum of mental effort, the subject actually goes through a series of alternating states of distraction (non-work) and attention (work). . (34) Some iron atoms adsorb adsorb /ad·sorb/ (ad-sorb´) to attract and retain other material on the surface; to conduct the process of adsorption.
To take up by adsorption. on the active planes or sites, which have relative high energy, and inhibit crystal growth at that location. Through this mechanism, the growth direction of crystals changes due to this inhibition and remaining plane develops preferred orientation.
Changes in the structure can be observed by SEM analysis that is shown in Figs. 7a and 7b. Figure 7a shows the surface morphology for Zn-Ni deposits which had coarse grain coarse grain - granularity size. The ternary Zn-Ni-Fe deposits show bright, smooth, and more homogenous homogenous - homogeneous form of crystallites in which the grain size is finer in contrast to that of Zn-Ni deposits, as shown in Fig. 7b. Moreover, it was found that the grain size decreased with increasing iron content in the ternary Zn-Ni-Fe deposits, even though the nickel content in these deposits is lower than that of binary Zn-Ni alloy. (12)
[FIGURE 7 OMITTED]
Figure 8 shows the potential-time dependence for the deposition of Zn, Ni, and Fe alone, and Zn-Ni and Zn-Ni-Fe alloys on steel at 5 mA [cm.sup.-2] for 10 min. It is clear that the deposition of pure Ni and Fe needs low overpotential to create the initial nucleus and the deposit grows at low potentials. However, the deposition of pure Zn takes place with higher nucleation nu·cle·a·tion
1. The beginning of chemical or physical changes at discrete points in a system, such as the formation of crystals in a liquid.
2. The formation of cell nuclei. overpotential and grows at high potential. The Zn-Ni and Zn-Ni-Fe alloys are codeposited at moderate overpotential values lying between Zn overpotential and Ni and Fe overpotentials. This is because the deposition of Ni or Fe is strongly inhibited by the presence of [Zn.sup.2+]. while the deposition of Zn is induced by the presence of [Ni.sup.2+] and/or [Fe.sup.2+] On the other hand, Zn-Ni-Fe alloy is codeposited at more noble overpotential than Zn-Ni alloy that deposited at relatively more cathodic overpotential.
[FIGURE 8 OMITTED]
Figure 9 shows the anodic linear sweep voltammograms obtained during the dissolution of the deposits produced galvanostatically by Zn, Ni, and Fe alone, and Zn-Ni and Zn-Ni-Fe alloys. The phase structure was investigated in [Na.sub.2][SO.sub.4] solution containing complex-forming ions, in which a Zn-Ni-Fe alloy completely dissolves. It is well known that pure Zn dissolves but zinc alloys do not dissolve in [Na.sub.2] [SO.sub.4] solution, while in the presence of a small amount of a complex-forming agent (EDTA), both Zn and its alloys dissolve. (35) It is clear from the figure that each of pure Zn, pure Ni, and pure Fe have only single anodic dissolution peaks (-588, -98, and -291 mV, respectively). In addition, the dissolution peaks of Zn and Fe are high but Ni dissolution peak is low, giving rise to more pure Zn deposition and less Ni, which may be due to surface effect. Also from the same figure, it is clear that pure iron is deposited with high content when deposited alone but with low content when alloyed with other metal. There are three anodic dissolution peaks for the Zn-Ni alloy. However, for the Zn-Ni-Fe alloy, there are also three anodic dissolution peaks, but they attribute to dissolution of zinc from pure Zn phase, which is characterized by the first dissolution anodic peak at -987 mV. The second anodic peak represents the dissolution of zinc from ([gamma]-[[Ni.sub.2][Zn.sub.11]) phase, which overlaps with the dissolution of iron from ([Fe.sub.3][Ni.sub.2]) phase. The third anodic peak at more noble potential characterizes the dissolution of nickel from its phases. There is a clear shift for second and third peaks toward the noble direction comparable with the Zn-Ni alloy peaks, giving rise to an increase in corrosion resistance of the ternary Zn-Ni-Fe deposits.
[FIGURE 9 OMITTED]
The corrosion resistance of the electrodeposited Zn-Ni-Fe and Zn-Ni in 0.05 M HCl using galvanostatic technique was investigated (Fig. 10). It is obvious from the obtained data (Table 2) of corrosion behavior that the corrosion potential of these deposits depended on the alloy composition. However, the deposits with iron codeposition have nobler [E.sub.corr] in contrast to these deposits without iron content. It is clear that the corrosion resistance of Zn-Ni-Fe alloy deposits is higher than those of Zn-Ni deposits, when both types of deposits contain approximately the same nickel content as shown from the polarization resistance curve.
[FIGURE 10 OMITTED]
According to the previous work, (12) anomalous code-position behavior is attributed to the formation of zinc hydroxide Zinc hydroxide (Zn(OH)2) is an inorganic chemical compound.
It is unusual in that, like zinc oxide, it is amphoteric. Thus it will dissolve readily in a dilute solution of a strong acid, such as HCl, and also in a solution of sodium hydroxide. film on the cathode surface due to hydrogen reduction, which suppresses the discharge of nickel and iron ions in the deposition of Zn-Ni and Zn-Fe alloys. It was (36) concluded previously that the anomalous code-position occurred even at low current densities, where hydrogen formation was unable to cause large alkalinization effects. In the present work, anomalous code-position may be attributed to the Ni and Fe ions (or its monovalent intermediate) adsorbed first; followed by adsorption of [Zn.sup.2+] (or its monovalent intermediate) onto the freshly adsorbed and deposited nickel and iron. The adsorption of zinc ions inhibits subsequent deposition of nickel and iron [i.e., the competitive adsorption between [Zn.sup.2+] and [Ni.sup.2+] and/or [Fe.sup.2+] (or its monovalent intermediate) to occupy active sites leads to the preferential deposition of Zn], although it does not block it completely. In absence of [Fe.sup.2+], as shown in Table 2, the nickel and zinc content was 12.2% and 87.8%. respectively; but after addition of [Fe.sup.2+] to the bath, nickel and zinc contents in the deposit generally decreases, and reaches 11.3% and 86.9%, respectively. This decrease in zinc and nickel contents was replaced by iron in the deposit, which leads to: first, decrease in the alloy current efficiency from 73.8% (i.e., for Zn-Ni alloy) to 72.4% (i.e.,for Zn-Ni-Fe alloy); second, increase in the thickness of the deposit from 1.0 to 1.1 [micro]m: third, a decrease in the corrosion potential and corrosion current with the codeposition of Fe: and finally, the polarization resistance increases from 0.127 to 0.194 k[OMEGA 1. (programming) Omega - A prototype-based object-oriented language from Austria.
["Type-Safe Object-Oriented Programming with Prototypes - The Concept of Omega", G. Blaschek, Structured Programming 12:217-225, 1991].
2. ]. According to these results the ternary Zn-Ni-Fe deposits showed higher corrosion resistance in comparison with Zn-Ni deposits.
This work represents the electrodeposition and corrosion of Zn, Ni, and Fe alone, and Zn-Ni and Zn-Ni-Fe alloy at ordinary conditions.
The results revealed that
1. The electrodeposition of Zn-Ni-Fe exhibited the phenomenon of anomalous type codeposition.
2. Bright and smooth Zn-Ni-Fe alloy surfaces were produced from baths containing approximately equimolar e·qui·mo·lar
Having an equal number of moles. ratio of [[Ni.sup.+2]/[Fe.sup.+2]/[Zn.sup.+2]], even without organic brighteners.
3. The ternary Zn-Ni-Fe deposits showed higher corrosion resistance in comparison with Zn-Ni deposits.
4.The increase in corrosion resistance of Zn-Ni-Fe deposits is not only due to the formation of a high nickel ([gamma]-[[Ni.sub.2][Zn.sub.11]]) alloy phase but also due to codeposition of iron and formation of ([Fe.sub.3][Ni.sub.2]) phase, which causes a clear change in crystal orientation and produces a liner grain size.
5. Zn-Ni-Fe alloys formed a mixture of three phases: ([gamma]-[Ni.sub.2][Zn.sub.11]), ([[Fe.sub.3][Ni.sub.2]). and pure Zn.
6. Sulfur was codeposited during the electroplating of the alloys, which results from the reduction of sulfate group in the presence of [H.sub.2][SO.sub.4].
(1.) Muller Mul·ler , Hermann Joseph 1890-1967.
American geneticist. He won a 1946 Nobel Prize for the study of the hereditary effect of x-rays on genes.
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Any of a class of thermosetting polymers, polyethers built up from monomers with an ether group that takes the form of a three-membered epoxide ring. The familiar two-part epoxy adhesives consist of a resin with epoxide rings at the ends of its molecules and a curing Coatings Electrodeposited on Galvanized gal·va·nize
tr.v. gal·va·nized, gal·va·niz·ing, gal·va·niz·es
1. To stimulate or shock with an electric current.
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New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of (1963)
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(18.) Lana, CJ, Liua, WY, Kea kea, in zoology
kea: see parrot.
Large, stocky parrot (Nestor notabilis, subfamily Nestorinae) of New Zealand. It lives in mountain habitats and is known for its curious and playful character. , ST, Chin, TS, "Potassium potassium (pətăs`ēəm), a metallic chemical element; symbol K [Lat. kalium=alkali]; at. no. 19; at. wt. 39.0983; m.p. 63.25°C;; b.p. 760°C;; sp. gr. .862 at 20°C;; valence +1. Salt Based Alkaline Bath for Deposition of Zn-Fe Alloys." Surf. Coat. Technol., 201 (6) 3103-3108 (2006)
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A salt or ester of tartaric acid.
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(34.) Dawei, WEI, Toshiya, TADA, Takeo, OKI, "Characteristics of Titanium titanium (tītā`nēəm, tĭ–) [from Titan], metallic chemical element; symbol Ti; at. no. 22; at. wt. 47.88; m.p. 1,675°C;; b.p. 3,260°C;; sp. gr. 4.54 at 20°C;; valence +2, +3, or +4. Electrodeposited by Potential Pulse Method in Molten Salts Molten salt may refer to:
(35.) Bajat, JB, Maksimovic, MD, Radovic, GR, "Electrochemical Deposition and Characterization of Zinc-Nickel Alloys Deposited by Direct and Pulse Current," J. Serb. Client. Soc. 67 (8-9) 625-634 (2002)
(36.) Soaresa, ME, Souzab, CAC See Consumer Advisory Council. , Kuric, SE, "Corrosion Resistance of a Zn-Ni Electrodeposited Alloy Obtained with a Controlled Electrolyte Flow and Gelatin gelatin or animal jelly, foodstuff obtained from connective tissue (found in hoofs, bones, tendons, ligaments, and cartilage) of vertebrate animals by the action of boiling water or dilute acid. Additive additive
In foods, any of various chemical substances added to produce desirable effects. Additives include such substances as artificial or natural colourings and flavourings; stabilizers, emulsifiers, and thickeners; preservatives and humectants (moisture-retainers); and ." Surf. Coat. Technol., 201 (6) 2953-2959 (2006)
M. M. Abou-Krisha ([??]), F. H. Assaf, S. A. El-Naby
Faculty of Science, Chemistry Department,
South Valley University, Qena 83523, Egypt