Pulsed electrodeposition of Zn in the presence of surfactants

Article abstract of DOI:10.1016/j.electacta.2005.06.023

The preparation of Zn deposits has been performed by galvanostatic pulsed electrolysis, from acidic zinc sulphate solutions, on a stainless steel substrate. The influence of the surfactants (cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and octylphenolpoly(ethyleneglycolether) _n, n = 10, Triton X-100) on the voltammetric behaviour, structural and morphological characteristics of the deposits have been investigated. The characterization of the samples was made by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS). The experimental data shows that the presence of surfactants affects the zinc deposition process. The electrodeposits are mainly composed by Zn with different texture, crystal shape and size (grain size ranging from 40 to 20 nm). The obtained results led us to conclude that the Zn deposits prepared in the absence of surfactants and in the presence of SDS are more crystalline and with a higher grain size than the ones obtained in the presence of CTAB and Triton X-100. These facts may be justified by the increase on the overpotential deposition as the electrochemical studies confirm. The XRD results show that the deposits prepared, in the absence of surfactant and in the presence of SDS, contain ZnSO₄ and Zn₄SO₄(OH)₆ as oxidation products. ZnO is also detected on the deposits obtained in the presence of CTAB and Triton X-100.

Full text of DOI:10.1016/j.electacta.2005.06.023

Electrochimica Acta 51 (2006) 1342–1350
Pulsed electrodeposition of Zn in the presence of surfactants
∗
,1
A. Gomes, M.I. da Silva Pereira
C.C.M.M., Departamento de Qu ´ı mica e Bioqu ´ı mica da Faculdade de Ci eˆ ncias da Universidade de Lisboa,
Campo Grande, 1749-016 Lisboa, Portugal
Received 26 April 2005; received in revised form 16 June 2005; accepted 23 June 2005
Available online 27 July 2005
Abstract
The preparation of Zn deposits has been performed by galvanostatic pulsed electrolysis, from acidic zinc sulphate solutions, on a stain-
less steel substrate. The influence of the surfactants (cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and
octylphenolpoly(ethyleneglycolether) , n = 10, Triton X-100) on the voltammetric behaviour, structural and morphological characteristics
n
of the deposits have been investigated. The characterization of the samples was made by X-ray diffraction (XRD) and scanning electron
microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS). The experimental data shows that the presence of surfactants
affects the zinc deposition process. The electrodeposits are mainly composed by Zn with different texture, crystal shape and size (grain size
ranging from 40 to 20 nm). The obtained results led us to conclude that the Zn deposits prepared in the absence of surfactants and in the
presence of SDS are more crystalline and with a higher grain size than the ones obtained in the presence of CTAB and Triton X-100. These
facts may be justified by the increase on the overpotential deposition as the electrochemical studies confirm.
The XRD results show that the deposits prepared, in the absence of surfactant and in the presence of SDS, contain ZnSO
as oxidation products. ZnO is also detected on the deposits obtained in the presence of CTAB and Triton X-100.
4 4 4 6
and Zn SO (OH)
©
2005 Elsevier Ltd. All rights reserved.
Keywords: Zn deposition; Pulsed electrodeposition; Surfactants; Steel substrate; Crystal structure
1
. Introduction
additives are changes in the preferred deposit orientation,
morphology and an increase in the deposition overpotential.
The specific activity of the surfactants are generally under-
stood in terms of adsorption at the cathode surface during
deposition and depends on the concentration of the surfactant
molecules. When the concentration approaches the critical
micelle concentration (cmc) the formation of bilayers or mul-
tilayers at the electrode interface occurs [7].
The adsorption of surfactants aggregates onto electrodes
can have large effects on the kinetics of the electron transfer
and consequently on the electrodeposition process. The effect
on the electron transfer rates includes blocking of the active
sites by the surfactants, and electrostatic interactions between
electroactive species and adsorbed surfactants [8]. Due to
those effects it is possible to modify the growth mode of
the crystals and tailor the morphology and structure of the
electrodeposits.
The electrodeposits of zinc on different metals, namely
steel, have special relevance due to their anticorrosive prop-
erties by the formation of passive layers in contact with air,
and in aqueous solution.
In practice, it is well known that the introduction of small
amounts of adequate organic additives in the electrodeposi-
tion bath results in beneficial quality changes on the deposits,
namely the homogeneity. Organic additives, such as surfac-
tants are commonly used in zinc electrodeposition to control
the metallic crystal shape and size, in order to produce smooth
and bright deposits [1–4]. Other additives such as polyacry-
lamine[5], thiourea[5]andbenzylideneacetone[6]havebeen
also used for zinc deposition. Common effects of the organic
∗
Corresponding author. Tel.: +351 217500109; fax: +351 217500088.
On the other hand the electrolysis conditions also have a
profound effect on the properties of zinc deposits, such as
E-mail address: misp@fc.ul.pt (M.I. da Silva Pereira).
ISE member.
1
0
013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2005.06.023

A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
1343
Table 1
Physico-chemical properties of the used surfactants
Surfactant
Chemical formula
Type
cmc (mM)
Aggregation number
References
CTAB
SDS
Triton X-100
C19H42BrN
C12H25NaO4S
C34H62O11
Cationic
Anionic
Non-ionic
0.85
8.10
0.24
78
87
100
[10]
[10]
[11]
grain size, surface morphology and preferred orientation. It
is known that pulse plating improves the morphology and
properties of the deposits due to its positive effects on mass
transport, electrode kinetics and the nucleation of growth cen-
tres [9–11]. Youssef et al. [5] report modifications on the
grain size and crystal orientation by changing the pulse elec-
trodeposition parameters, for zinc deposition from chloride
electrolytes in the presence of additives.
In a previous work we have studied the influence of the
cationic surfactant, CTAB, on the characteristics of Zn–TiO2
composite prepared by pulsed electrodeposition. It was con-
clude that the use of the surfactant leads to a decrease in the
grain size of the zinc matrix, but little effect is observed on
the dispersion of the semiconductor particles [12].
In this work we present a study on the effect of differ-
ent type of surfactants on the electrochemical deposition of
zinc, and the resulting changes on the morphology and struc-
tural characteristics of the electrodeposits. Cationic, anionic
and non-ionic surfactants have been used to investigate the
effect of the charge of headgroups on the electrodeposition
process. X-ray diffraction, scanning electron microscopy and
X-ray dispersive analysis were used to characterize the struc-
ture, morphology and composition of the electrodeposits,
respectively. Correlation between electrochemical data and
structure and morphology were attempted.
properties [13,14]. For all the solutions the pH value was 4.
Table 2 shows the chemical composition of solutions stud-
ied. It is noteworthy that the surfactants concentrations were
above their critical micelle concentration values.
All the experiments were carried out at room temperature
and the deposition was performed under magnetic stirring.
N2 was bubbled through the solution for 15 min before each
experiment and during the deposition, a weak flux of N2 was
maintained.
Zinc electrodeposits were prepared applying a galvano-
static square wave during 60 min with a pulse peak current
of 100 mA and a current-on time and a current-off time of 4
and 40 ms, respectively. This corresponds to an average cur-
−
2
rent density of −11.5 mA cm . This value was chosen on
the basis of the voltammetric curves. After the deposition the
samples were washed with Millipore Milli-Q ultra pure water
and dried under an N2 flux. The deposits prepared with Triton
X-100 were also washed with ethanol. The weight of the zinc
deposits, was calculated by weighing the samples before and
after deposition and was used to calculate the average film
thicknesses. Assuming that the deposits were composed only
by zinc, a value of 18.3 ± 0.9 ␮m was obtained.
Linear voltammetry experiments were carried in a three-
electrode glass cell with a stainless steel disc as the working
electrode, a platinum mesh as the counter electrode and a
commercial saturated calomel electrode (SCE) as the refer-
ence electrode. These electrochemical measurements were
carried out using a Voltalab 32 Radiometer apparatus con-
nected to an IMT 1 0 2 interface, controlled by a personal
computer through the VoltaMaster 2 software.
2
. Experimental
The electrodeposition was carried out in a two-
A JEOL scanning electron microscope (model JSM-
compartment glass cell using a stainless steel disc (AISI
16, diameter of 10 mm) as substrate, a platinum spiral as
6
301F) coupled with an energy-dispersive spectroscopic
3
(Noran/Voyager) were used to characterize the surface mor-
the counter electrode and a commercial saturated calomel
electrode (SCE) as the reference electrode. Before the exper-
iments, the stainless steel discs were mechanically polished
to a mirror finish using silica powder and ultrasonically
cleaned during 2 min with Millipore Milli-Q ultra pure water
phology and to analyse the elemental composition of the zinc
electrodeposits. The energy of the primary electrons beam
was 15 keV.
X-ray diffraction analysis was carried out using a Philips
X-ray diffractometer (model PW 1710) with Cu K␣ radiation
(
&
18 Mꢀ). The electrochemical cell was connected to an EG
G Princeton Applied Research potentiostat/galvanostat
model 263.
The electrolyte was prepared dissolving ZnSO4·7H2O
Merck) and (NH4)2SO4 (M & B) in Millipore Milli-Q ultra
pure water. Separately, cetyl trimethyl ammonium bromide
CTAB, Aldrich), sodium dodecyl sulphate (SDS, Sigma)
andoctylphenolpoly(ethyleneglycolether)n, n = 10(TritonX-
00, Fluka) were added to this base solution. All chemicals
Table 2
Chemical composition of the used solutions
Solution
Composition
(
− −3
3
1
2
0.6 mol dm ZnSO4 + 0.1 mol dm (NH4)2SO4
−
3
−3
−3
−3
0.6 mol dm ZnSO4 + 0.1 mol dm
(
(
NH4)2SO4 + 1 mM CTAB
−3
3
4
0.6 mol dm ZnSO4 + 0.1 mol dm
(NH4)2SO4 + 10 mM SDS
1
−
3
0.6 mol dm ZnSO4 + 0.1 mol dm
were analytical grade. The surfactants were used without fur-
ther purification and Table 1 presents their physico-chemical
(NH4)2SO4 + 0.3 mM Triton X-100

1
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A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
For the Zn(II) containing solutions, in the absence of
surfactant, and on the potential range between −870 and
1080 mV versus SCE a cathodic peak appears followed by
−
a sharp increase of current. Our results are in accordance with
those obtained by Casanova et al. [15] that found a peak in
the same potential region and assigned it to the hydrogen evo-
lution, and formation of an adsorbed zinc layer that occurs
before zinc crystallization.
According to the model proposed by Wiart et al. [16] for
the electrodeposition of zinc in acidic sulphate electrolytes,
the formation of ZnH, ZnO, ZnOH and hydrogen can occur in
the peak region. As a consequence zinc hydroxide may also
be formed, by hydrolysis, due to a local pH increase. This
assumption is in accordance with a model proposed by Yan
et al. for zinc electrodeposition via a zinc hydroxide layer
formation [17].
At more negative potential region, the reduction of the
Zn2+ ions to Zn can occur, as the calculated equilibrium
potential (−1040 mV versus SCE) indicates.
Fig. 1. Linear voltammetric curves obtained for a stainless steel electrode
−3
−3
from solutions containing 0.6 mol dm ZnSO4 + 0.1 mol dm (NH4)2SO4
a) and adding SDS (b), CTAB (c) and Triton X-100 (d). Sweep rate of
mV/s.
(
1
For this potential region the mechanism proposed by Wiart
et al. involves various reduction steps, including the forma-
tion of active sites for the Zn deposition.
(
λ = 0.15604 nm), working at 30 mA and 40 kV. The diffrac-
◦
In the presence of the surfactant molecules the shape of
the curves is similar to the ones obtained, in the absence of
the surfactants, in the peak region. As it was expected the
presence of the surfactant affects the peak size and causes a
negative shift on the peak potential value. The increase on
the current density should be attributed to an enhancement of
the zinc reduction in comparison with the hydrogen evolu-
tion. This conclusion is supported by the experimental results
obtained in the absence of Zn(II) in solution (Fig. 2). It is clear
that the current density under these conditions is very low and
no cathodic peak is observed.
For the potential region between −1080 and −1300 mV,
the shape of the curves are similar but a shift to more negative
potential and a decrease on the current density are observed,
depending on the presence and nature of the surfactant. This
behaviour is more evident in the presence of Triton X-100.
The comparison between the polarisation curves, shows that
the negative shift on the potential, increases in the following
order: SDS, CTAB and TritonX-100. Increases on the zinc
deposition overpotential have been observed in the presence
of commercial additives [18], polyethoxylated additives [4]
and gelatine [19]. This result is usually interpreted by a partial
coverage of the electrode surface by the additive which blocks
the active sites, decreasing the nucleation rate and affecting
the nucleation mechanism [17]. In addition, adsorption of the
surfactanct molecules on the growing zinc deposit can also
occur, blocking the electrocrystallization process. This inhi-
bition depends on the size of the organic molecules and the
specific interactions between the surfactant and the substrate
and the surfactant and the deposit.
tograms were obtained in the 2θ range of 20–90 using a
0
◦
.02 step and acquisition time of 2 s/step.
3
. Results and discussion
3
.1. Voltammetric study
Fig. 1 shows the i versus E curves obtained for the
Zn2+ solution in the presence and absence of the surfactant
molecules, at a sweep rate of 1 mV/s. For comparison lin-
ear voltammograms obtained in the same conditions without
Zn(II) in solution are presented in Fig. 2.
Considering the polarity of the CTAB and SDS surfac-
tants it is expected that they present mostly surface active
properties. The surface coverage of the referred surfactants
Fig. 2. Linear voltammetric curves obtained for a stainless steel electrode
from solutions containing 0.1 mol dm (NH4)2SO4, in the presence and
absence of surfactant molecules. Sweep rate of 1 mV/s.
−3
has be estimated by the equation θ = 1 − (i /i) where i and iS
S

A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
1345
are the current density without and with surfactants at a con-
stant potential value, respectively [20]. The coverage values
obtained for E = −1275 mV versus SCE were 0.19 and 0.36
for the SDS and CTAB, respectively.
In the case of Triton X-100, a non-ionic surfactant with
oxyethylene groups, it is possible that both adsorption and
complex formation occur. Taking into account that the sur-
factant concentration is above the cmc, complex forma-
tion with the adsorbed molecules could be promoted what
would explain the strong increase on the zinc deposition
overpotential. Stoychev et al. proposed a similar interpre-
tation for the electrodeposition of copper in the presence of
polyethyleneglicol [21].
The deposits obtained in the presence of Triton X-100
(Fig. 3d), are more irregular, with a distinct morphology, con-
stituted by cauliflower type agglomerates. Comparing with
the previous micrographs it can be concluded that this non-
ionic surfactant have a strong influence on the Zn deposition
process. Trejo et al. have reported a similar morphology [4]
for zinc electrodeposits obtained from acidic solution in the
presence of organic polyethoxylate (PEG) additives. Sulphur
is also detected on the coating surface.
For the deposits obtained with the surfactant-free solu-
tion, some protuberances were observed, due to the presence
of hydrogen bubbles adsorbed on the substrate surface and/or
on the zinc deposits (Fig. 4), during the deposition process.
The morphology found in this region is very peculiar. Flake
forms constituted by Zn, S and O, were identified using EDS.
Similar features were observed by Cachet et al. [23] for the
corrosion of zinc coatings in sulphate medium. This fact was
explained by the formation of a zinc-hydroxi-sulphate, due to
local pH changes. For the deposits obtained in the presence
of the organic molecules, this morphology due to the adsorp-
tion of hydrogen bubbles was not detected. It seems that the
surfactant molecules on the electrode interface inhibit this
phenomenon.
3
.2. SEM/EDS characterization
The electrochemical studies have shown that the addition
of small amounts of surfactant modifies the electrodeposi-
tion process. In order to determine whether these changes
were reflected in the deposit morphology and composition,
an SEM/EDS study was performed.
The data show that the surface morphology and the crys-
tal shape and size are markedly affected by the presence
and nature of the surfactants. The EDS spectra obtained in
different local points of the electrodeposits surface showed
that they were mainly composed by zinc. Sulphur and oxy-
gen were also detected and their presence may be associated
with the corrosion of the deposits or with occluded solu-
tion. Finally the detected carbon can be due to either some
surfactant incorporation on the deposit or atmospheric con-
tamination. A complementary analysis must be performed in
order to clarify this situation.
In the absence of organic molecules in the electrodepo-
sition bath (Fig. 3a), the deposit display the hexagonal zinc
plates aligned parallel to the substrate as usual for zinc elec-
trodeposits [11].
The deposits, prepared from solutions with SDS (Fig. 3b),
are very uniform with plate form crystals, perpendicularly
oriented to the substrate. When compared with the zinc
deposits from additive-free solution, the grains are relatively
smaller. Kelly et al. observed similar effects [22] for copper
deposition in the presence of sulphur containing compounds.
EDS analysis reveals the presence of Zn, O and S. Sulphur
could be due to the incorporation of the surfactant in the coat-
ing.
3.3. Structural characterization
Figs. 5–8 display the diffractograms for the hexagonal
Zn deposits obtained in different conditions. It is clear that
the presence of the surfactant, on the electrodeposition bath,
affects the crystallographic orientation and crystallinity of
the deposits.
In the absence of organic molecules in the deposition bath
(Fig. 5), the relative intensity of the lines indicates a strong
(0 0 2) orientation for the zinc electrodeposits [24]. This tex-
ture is in accordance with the hexagonal surface morphology
usually detected for these deposits. According to Li et al. [25],
the development of different textures is possible during the
growth of metal coatings. This is a consequence of surface
energy differences, which are responsible for the selective
growth of the grains that have the lowest surface free energy.
For the zinc crystal the lowest surface free energy is the basal
(0 0 2) plane, owing to its compactness [26]. Therefore, this
texture develops during the zinc growth in the absence of
surfactants, assuming that the adsorbed hydrogen does not
modify the metal surface energy.
In the presence of CTAB (Fig. 3c), the zinc grain size
is smaller, indicating a modification on the competition
between nucleation and crystal growth. It is also notewor-
thy to mention the porous nature of the coating due to the
needle shape grains. The morphology change can be associ-
ated to a strong blocking effect of the cationic surfactant,
which causes an enlargement of the nuclei renewal rates,
leading to an increase of nuclei number and needle growth.
On the coating surface, the presence of black points was
observed associated with an S line in the corresponding EDS
spectrum.
For the deposits obtained from solutions containing SDS
(Fig. 6), CTAB (Fig. 7) and Triton X-100 (Fig. 8), the
most intense diffraction lines are (1 0 1), (1 1 0), and (1 0 1)
respectively. In addition, a marked decrease on the basal
(0 0 2) plane intensity is found. The crystallographic orien-
tation changes because the metal’s surface energy is mod-
ified by the adsorption of the organic molecules [27]. The
variation on the crystallographic orientation by the pres-
ence of the surfactants should be due to their different
specific interactions with the different crystal planes, that
induces different growth mechanisms. The hindrance of the

1
346
A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
Fig. 3. Scanning electron micrographs and respective EDS spectra of the surface of the electrodeposits obtained in the absence of the surfactant (a) and in the
presence of SDS (b), CTAB (c) and Triton X-100 (d).

A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
1347
Fig. 4. Scanning electron micrographs of the surface of the electrodeposits obtained in the absence of the surfactant. EDS spectrum of the surface region where
the flakes forms are observed.
development of the basal (0 0 2) plane can be attributed to
an increase of the surface energy of this plane in these
conditions.
nated by the organic molecules presented in the solution,
which have an inhibiting effect on the electrocrystalization
process.
For the deposits prepared in presence of SDS, similar
results were obtained by Tripathy et al. [3] for the electrode-
position of zinc in sulphate solution.
Tripathy et al. [2] also investigated the zinc electrowin-
ning from acidic sulphate solutions in the presence of CTAB
and have found by XRD, that the strongest reflexion was the
Least-square refinements of the cell parameters (a and c)
of the hexagonal structure were performed, from the position
of the peaks indexed as Zn in the different diffractograms
[24]. The cell parameters and the cell volume were found to
depend weakly on the presence of the surfactant at the deposi-
tion bath (Table 3). The data show a small decrease on the cell
volume of the Zn structure for the samples prepared with the
presence of surfactants molecules. This fact is more evident
for the sample prepared with Triton X-100. This contraction
of the zinc structure may be associated to the other phases
present in the deposit.
(1 0 1). The different results are possible due either to the
concentration of the surfactant employed or to the electrode-
position technique used. To explain the preferential growth
in the (1 1 0) plane, Baik et al. [28] assumed that this is
associated to a low rate for the zinc ion discharge, origi-
Fig. 5. X-ray diffraction pattern of the electrodeposited film obtained in the absence of surfactant in the solution. The inset shows the expanded diffractogram
ꢁ: reflexions due to the steel substrate).
(

1
348
A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
Fig. 6. X-ray diffraction pattern of the electrodeposited film obtained in the presence of SDS in the solution. The inset shows the expanded diffractogram (ꢁ:
reflexions due to the steel substrate).
Fig. 7. X-ray diffraction pattern of the electrodeposited film obtained in the presence of CTAB in the solution. The inset shows the expanded diffractogram (ꢁ:
reflexions due to the steel substrate).
In Table 3, it is also presented the average grain size calcu-
lated from the line broadening of the most intense X-ray peak
Table 3
according to Scherrer’s formula. The average grain size of
zinc deposits decreases with the presence and type of surfac-
tant that confirms the results obtained by SEM. The smallest
value was obtained for the sample prepared with CTAB in
the solution. This result indicates once again that this cationic
surfactant inhibits drastically the growth process of zinc, at
the experimental conditions used.
Average grain size, cell parameters and unit cell volume for the zinc structure
of the different samples
Surfactant
Cell parameters
Unit cell volume
Grain size
(nm)
−3
3
(×10 nm )
a (nm)
c (nm)
None
SDS
CTAB
Triton X-100
0.26616
0.26602
0.26611
0.26608
0.49308
0.49308
0.49199
0.49182
30.25
30.22
30.17
30.16
50.4
40.3
20.4
29.0
In order to make possible the identification of the other
phases present on the deposits and whose existence was

A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
1349
Fig. 8. X-ray diffraction pattern of the electrodeposited film obtained in the presence of Triton X-100 in the solution. The inset shows the expanded diffractogram
ꢁ: reflexions due to the steel substrate).
(
pointed out by the EDS measurements, the X-ray patterns
were analysed in more detail (inset diffractograms), and the
obtained data is shown in Table 4. In what concerns the elec-
trodeposits prepared in absence of surfactant molecules, it
For the samples prepared in the presence of CTAB and
Triton X-100, ZnO was identified [31]. This result could be
justified by the modification on the zinc deposition mech-
anism as a consequence of the blocking effect due to the
surfactants molecules adsorbed on the metal surface. In the
reaction model proposed by Wiart [16] for the zinc deposi-
tion in acidic electrolytes, it was assumed that the species
ZnOHad and ZnOad are involved in the deposition process
when a low cathodic polarisation is applied. Our voltammet-
ric results for the zinc electrodeposition in the presence of
Triton X-100 show that the deposition potential is the most
negatively shifted. This result could be explained by the for-
mation and incomplete reduction of ZnO.
can be seen that ZnSO4 and Zn4SO4(OH) are present in
6
small amounts [29]. These products are normally obtained
as a result of the zinc oxidation in sulphate solutions, asso-
ciated to local pH changes, due to the hydrogen evolution at
the substrate [23,30]. Similar products were obtained for the
samples prepared in the presence of SDS. This result indi-
cates that the zinc dissolution during the electrodeposition
process is not totally inhibited by the presence of this anionic
surfactant at the interface.
Table 4
Identification of the others phases presented in the Zn electrodeposits
Surfactant presence
None
SDS
CTAB
Triton X-100
◦
◦
◦
◦
2
θ ( )
Irel (%)
Identified
phases
2θ ( )
Irel (%)
Identified
phases
2θ ( )
Irel (%)
Identified
phases
2θ ( )
Irel (%)
Identified
phases
2
1.385 0.1
ZnSO4
21.465 0.1
ZnSO4
35.270 0.1
ZnSO4 or
Zn4SO4(OH)6
ZnO
32.125 5.3
ZnO
3
3
2.900 0.4
4.940 0.5
Zn4SO4(OH)6
ZnSO4 +
Zn4SO4(OH)6
ZnSO4 +
33.090 0.1
35.315 0.2
Zn4SO4(OH)6
ZnSO4 +
Zn4SO4(OH)6
ZnSO4 +
48.025 0.1
56.860 0.1
34.775 4.5
41.695 0.8
ZnO
ZnO
ZnSO4 +
Zn4SO4(OH)6
ZnO
4
1.515 0.1
41.550 0.4
63.150 0.3
ZnO
ZnO
47.830 1.5
56.935 2.9
Zn4SO4(OH)6
Zn4SO4(OH)6
67.450 0.2
ZnO +
Zn4SO4(OH)6
ZnO
ZnO
ZnO
6
6
6
6
3.160 2.1
6.685 0.4
8.265 2.0
9.340 1.1
ZnO

1
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A. Gomes, M.I. da Silva Pereira / Electrochimica Acta 51 (2006) 1342–1350
[3] B.C. Tripathy, S.C. Das, G.T. Hefter, P. Singh, J. Appl. Electrochem.
4
. Final remarks
27 (1997) 673.
[
4] G. Trejo, H. Ruiz, R. Ortega Borges, Y. Meas, J. Appl. Electrochem.
The galvanostatic electrodeposition of Zn using a square
31 (2001) 685.
wave and in the presence of surfactants makes possible the
preparation of metallic deposits with different preferential
orientation, crystal shape and size.
When the electrodeposition process occurs in the absence
of organic molecules, the morphological and structural anal-
ysis show that the Zn deposition is accompanied by the
evolution and adsorption of hydrogen bubbles and in con-
sequence the surface is not uniform.
The electrodeposits prepared from solutions containing
SDS, exhibit a regular and uniform morphology where the
Zn presents a pyramidal orientation. The adsorption of the
anionic surfactant should occur at the metallic surface during
the on-time pulse and consequently a modification of the Zn
crystal shape takes place.
In the presence of CTAB, very porous Zn deposits with
needle shape and small size crystals were obtained. This
could be due to the formation of an adsorbed superficial film
of CTAB, on the metallic surface and consequently, Zn2+ ions
approach the surface with increasing difficulty, resulting in
an inhibition of the crystal growth.
[
5] Kh. M.S. Youssef, C.C. Koch, P.S. Fedkiw, J. Electrochem. Soc. 151
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1
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