Electrodeposition of lustrous nickel coatings from a sulfate electrolyte in the presence of organic substances

Article abstract of DOI:10.1134/S1070427211110073

Electrodeposition of nickel from a sulfate electrolyte containing 2,5-dimethyl-3-hexine-2,5-diol, formaldehyde, and benzaldehyde was studied.

Full text of DOI:10.1134/S1070427211110073

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 11, pp. 1878−1882. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © G.I. Medvedev, N.A. Makrushin, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 11, pp. 1792−1796.
APPLIED ELECTROCHEMISTRY
AND CORROSION PROTECTION OF METALS
Electrodeposition of Lustrous Nickel Coatings
from a Sulfate Electrolyte
in the Presence of Organic Substances
G. I. Medvedev and N. A. Makrushin
Novomoskovsk Institute, Mendeleev Russian University of Chemical Engineering,
Novomoskovsk, Tula oblast, Russia
Received September 24, 2010
Abstract—Electrodeposition of nickel from a sulfate electrolyte containing 2,5-dimethyl-3-hexine-2,5-diol,
formaldehyde, and benzaldehyde was studied.
DOI: 10.1134/S1070427211110073
Nickel coatings find use as protective-decorative
coatings and serve for improving the mechanical wear
resistance and for special purposes. These coatings have
a high corrosion resistance in the atmosphere, in alkali
solutions, and some organic acids, which is largely due
to the strongly pronounced ability of nickel to be passiv-
ated [1, 2]. Of particular industrial interest are lustrous
nickel coatings deposited from electrolytes in the pres-
ence of various organic substances.
thiocarbamide, alkyl-substituted nitriles, aldehydes, ke-
tones, dyes, and condensation products [1–3]. However,
only some of these organic substances are successfully
used in practice. The reason is that many of the suggest-
ed additives rapidly decompose in the course of electrol-
ysis and formation of decomposition products markedly
deteriorates the quality of lustrous deposits [1, 2].
To obtain lustrous nickel coatings, GOST (State
Standard) 9.305–84 “Metallic and nonmetallic inorgan-
ic coatings” recommends to introduce into sulfate elec-
trolytes 2-butine-1,4-diol together with other organic
additives. The working current densities in these elec-
The main advantages of lustrous coatings over matt
layers are the following: saving of nonferrous metals;
elimination of the labor-consuming, expensive, and
harmful polishing procedure and the associated excess
expenditure for materials and working power; and the
possibility of performing a continuous process in depo-
sition of nickel layers onto various metals. Therefore,
a study of the electrochemical nickel plating with or-
ganic substances is topical for development of modern
technologies.
–
2
trolytes do not exceed 8 A dm . In various companies
engaged in development of sulfate nickel-plating elec-
trolytes for deposition of lustrous coatings, the composi-
tion of luster-forming additive is classified commercial
information. However, the working current densities in
these electrolytes do not exceed 6 A dm–2. Therefore,
the main problem in nickel plating is in development of
high-performance electrolytes that would enable depo-
sition of lustrous coatings at high current densities.
Lustrous coatings are commonly obtained using
a rather large number of various organic substances:
sulfo compounds of the aromatic series, unsaturated al-
cohols and glycols with a double or triple bond (2-bu-
tine-1,4-diol, propargyl alcohol, and their derivatives),
lactones (coumarin and its derivatives), nitrogen-con-
taining compounds (quinoline etc.), amine-substituted
In this communication, we report results of a study of
how a homolog of 2-butine-1,4-diol (diatomic unsatu-
rated alcohol 2,5-dimethyl-3-hexine-2,5-diol (DHD),
formaldehyde (in the form of formalin, a 37% aque-
ous solution), and benzaldehyde affects the process
1
878

ELECTRODEPOSITION OF LUSTROUS NICKEL COATINGS
P = 2.3a/2πh log (H /H ),
1879
of nickel electrodeposition from a sulfate electrolyte.
av
0
fin
We could not find any evidence about use of DHD as
a luster-forming additive in nickel-plating electrolytes.
Formaldehyde and benzaldehyde are used together with
other organic additives in nickel- and tin-plating electro-
lytes to obtain lustrous coatings [1–4].
where a is the amplitude of the sinusoidal microprofile;
h , average coating thickness (10 μm); and H and H ,
initialandfinalamplitudesofthesinusoidalmicroprofile,
av
0
fin
respectively.
The pH of the near-electrode layer was measured by
the procedure described in [6].
EXPERIMENTAL
The results obtained in a study of how the DHD
concentration and current density affect the outward
appearance of the coatings are presented in Table 1. It
can be seen that matt and silvery coatings are obtained
The study was carried out in electrolytes of
composition (g l ): NiSO ·7H O 150–300, NaCl 10–15,
–
1
4
2
H BO 30–40, Na SO ·10 H O 50–80, at pH 2–5 and
3
3
2
4
2
–1
temperatures of 20–50°C. The electrodeposition was
performed in electrolytes without agitation and with
mechanical agitation. Nickel was deposited onto steel
samples to a thickness of 6–15 μm, with nickel anodes
used. Polarization curves were measured with a P-5828
potentiostat. The luster of the coatings was measured
by the photoelectric method with a FB-2 device. The
leveling power of the electrolytes, P, was determined
by the direct method of profilographic measurements of
the sample surface on a sinusoidal microprofiler. P was
calculated by the formula [5]:
at additive concentrations of 0.5–1 and 4.5–5.0 g l . At
the same time, at DHD concentrations of 1.5–4.0 g l–1
matt, silvery, and lustrous coatings are produced at ic =
–
2
2–5 Adm .
It was found that the quality of nickel coatings
deposited from electrolytes with DHD additive depends
on electrolyte agitation, temperature, and pH value.
For example, silvery coatings are obtained without
electrolyte agitation at working current densities in the
whole range under study, and semilustrous coatings are
deposited at T = 20–30°C. The highest quality coatings
Table 1. Effect of the DHD concentration and current density on the outward appearance of coatings. Electrolyte composition,
–
1
g l : NiSO ·7H O 200, NaCl 20, H BO 30, and Na SO ·10H O 50; pH 4.5, T = 40°C, mechanical agitation
4
2
3
3
2
4
2
DHD concentration, g l–1
Current density, A dm–2
1
Coating
Luster, %
0
.5–1.0
.5–2.0
Matte
Silvery
10
20–25
–
2
–4
5
Matte with burn-on
1
1
Matte
Lustrous
Silvery
10
2
–4
5
40–45
20–25
–
Silvery with burn-on
6
2
3
.5–3.0
.5–4.0
1
Silvery
Lustrous
Silvery with burn-on
20
2
2
–5
6
40–45
1
Silvery
Lustrous
Silvery
20
40–45
20
–4
5
Matte with burn-on
6
1
–
10
4
.5–5.0
Matte
Silvery
2
–4
5
20–25
–
Matte with burn-on
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 11 2011

1880
MEDVEDEV, MAKRUSHIN
CE, %
appearance of the coatings are listed in Table 2.
It can be seen that lustrous coatings are obtained at
–1
formaldehyde concentrations of 0.5 to 10 ml l and
–
2
current densities in the range 1–8 A dm . At the same
time, the widest range in which lustrous coatings are
obtained is observed at formaldehyde concentrations
–
1
of 8–10 ml l . It should also be noted that the luster
of the coatings substantially increases in this case. The
current efficiency by nickel in the presence of DHD and
formaldehyde is 65–78%.
ic, Adm–2
Additional introduction of benzaldehyde into an
electrolyte containing DHD and formaldehyde makes
substantially wide the range of current densities in
which lustrous coatings are obtained. Data on the
influence exerted by the benzaldehyde concentration
in the electrolyte and by the current density on the
outward appearance of nickel coatings are listed in
Table 3. At a benzaldehyde concentration of 0.5–1 g l–1
in the electrolyte, we observed two ranges of current
densities at which lustrous coatings are deposited. The
Fig. 1. Current efficiency by nickel, CE, vs. the cathode current
–1
density i . Electrolyte composition (g l ): NiSO ·7H O 200,
c
4
2
H BO 30, NaCl 15, Na SO ·10H O 50; pH 4.5, T = 50°C,
3
3
2
4
2
mechanical agitation; the same for Fig. 2. (1) Electrolyte and
–1
(
2–4) electrolyte + DHD (g l ): (2) 2, (3), and (4) 5.
are obtained at pH 4–5.
In electrolytes without organic additives and in those
with DHD, the current efficiency by nickel increases
with the cathode current density in the conditions under
study (Fig. 1). Presence of the DHD additive in a nickel-
plating electrolyte makes lower the current efficiency by
nickel. The strongest decrease in the current efficiency
–2
first and second ranges are at 2–5 and 10–16 A dm .
–1
At a higher benzaldehyde concentration (1.5–2 g l ),
–2
lustrous coatings are obtained in the range 2–7 A dm .
–
1
is observed at a concentration of 5 g l (Fig. 1, curves
–4).
Lustrous nickel coatings deposited from an
electrolyte with DHD have an insignificant luster (40–
0%). To raise the luster of the coatings, we studied the
The current efficiency by nickel in these nickel-plating
1
electrolytes varies within the range 65–95% at i =
c
–
2
2
–16 Adm .
In the electrolyte under study with organic additives,
5
we examined the influence exerted by the nickel sulfate
concentration, agitation, temperature, and pH value on
the outward appearance of the coatings and on the cur-
rent efficiency by nickel. It was found that variation of
effect of an additional introduction of formaldehyde
and benzaldehyde into the electrolyte. Data on how
the formaldehyde concentration affects the outward
Table 2. Effect of the formaldehyde concentration and current density on the outward appearance of coatings. Electrolyte
–
1
composition, g l : NiSO ·7H O 200, NaCl 20, H BO 30, and Na SO ·10H O 50; pH 4.5, T = 40°C, mechanical agitation
4
2
3
3
2
4
2
Formaldehyde concentration,
Current density, A dm–2
Coating
Luster, %
–
1
g l
1
2–4
5
Silvery
Lustrous
Silvery
20
60–65
25
0
.5–4.0
Matte with burn-on
6
–
5
8
–7
1–6
Lustrous
Silvery
60–65
7
–8
9
20–25
Matte with burn-on
Lustrous
–
–10
1–8
65–70
9
Silvery with burn-on
–
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 11 2011

ELECTRODEPOSITION OF LUSTROUS NICKEL COATINGS
1881
Table 3. Effect of the benzaldehyde concentration and current density on the outward appearance of coatings. Electrolyte
–
1
–1
composition, g l : NiSO ·7H O 200, NaCl 15, H BO 30, and Na SO ·10H O 50; DHD 8; formaldehyde 10 ml l ; pH 4.5, T =
4
2
3
3
2
4
2
4
0°C, mechanical agitation
Benzaldehyde concentration,
Current density, A dm–2
1
Coating
Luster, %
–
1
g l
0
.5–1
Silvery
Lustrous
Silvery
20
2
6
–5
–9
65–70
20–25
70–80
Lustrous
1
0–16
Lustrous with burn-on
1
7
–
1
.5–2
1
Silvery
20
Lustrous
2
8
–7
65–75
–
Lustrous with burn-on
–10
the nickel sulfate concentration from 150 to 250 g l–1
does not change the working range of current densities.
However, the quality of the coatings is sharply deterio-
rated at a nickel sulfate concentration of 300 g l (matt
coatings are produced. The current efficiency by nickel
grows with increasing nickel salt concentration. High-
quality coatings with high luster are obtained when the
electrolyte is agitated at a temperature of 40–50°C. Lack
of agitation and a temperature lowered to 20–30°C im-
pair the quality of the coatings.
in which DHD, formaldehyde, and benzaldehyde are
simultaneously present (Fig. 2, curves 1–4).
Electrolytes used to obtain lustrous nickel coatings
have a leveling power. It can be seen in Fig. 3 that the
–
1
maximum degree of leveling (P = 0.6) is observed at i =
c
–2
–2
4
A dm . At higher current densities (i = 5–8 A dm ),
c
it sharply falls to P = 0.15. Further increase in i leads to
c
a rise in the degree of leveling.
The leveling effect is related to the luster of electro-
lytic coatings because luster formation is also a process
in which the surface is leveled and coarse microscopic
irregularities with heights of 0.2 to 100 μm and more are
eliminated. In luster formation, very small submicrom-
eter irregularities (~1.5 μm and less) are smoothed [7].
We measured cathodic polarization curves in
nickel-plating electrolytes (Fig. 2). It was shown that
introduction of organic substances into the electrolyte
leads to enhancement of the cathodic polarization, with
the strongest polarization observed in the electrolyte
Thus, it was shown that introduction into a sulfate
nickel-plating electrolyte of a homolog of 2-butine-
ic, Adm–2
ic, Adm–2
–
Ec, V relative to s.h.e.
Fig. 3. Leveling power P of the nickel-plating electrolyte
–
1
Fig. 2. Current density i vs. the electrode potential –E in the
vs. the current density i . Electrolyte composition (g l ):
c
c
c
–1
nickel-plating electrolyte. (1) Electrolyte; (2) 1 + DHD, 3 g l ;
3) 2 + formaldehyde, 8 ml l ; and (4) 3 + benzaldehyde,
NiSO ·7H O 200, H BO 30, NaCl 15, Na SO ·10H O 50,
4
2
3
3
2
4
2
–1
–1
–1
(
1
DHD 3; formaldehyde 8 ml l and benzaldehyde 1 g l ; the
same for Fig. 4.
–
1
g l .
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 11 2011

1882
MEDVEDEV, MAKRUSHIN
–
1
(
g l ): NiSO ·7H O 150–250, NaCl 10–15, H BO 30–
4 2 3 3
4
0, Na SO ·10H O 50–80, DHD 2–3; formalin (37%
2 4 2
–
1
–1
solution) 8–10 ml l and benzaldehyde 0.5–1 ml l .
Deposition conditions: temperature 40–50°C, cathode
current densities i = 2–5 and 10–16 A dm , anode cur-
rent density 1–2 A dm , pH 4.5, NPAN nickel anodes,
agitation of the electrolyte mechanical or with com-
pressed air.
–
2
c
–
2
CONCLUSIONS
ic, Adm–2
(1) A study of the process of nickel electrodeposition
Fig. 4. pH value of the near-cathode layer vs. the current
from a sulfate electrolyte with addition of a diatomic
alcohol, 2,5-dimethyl-3-hexine-2,5-diol, formaldehyde,
and benzaldehyde demonstrated that, in the simultaneous
presence of these substances, lustrous nickel coatings
with leveled surface are obtained at current densities in
density i in the nickel-plating electrolyte.
c
1
3
,4-diol (unsaturated diatomic alcohol 2,5-dimethyl-
-hexine-2,5-diol), together with formaldehyde and
–
2
the ranges 2–7 and 10–16 A dm .
benzaldehyde, makes it possible to obtain lustrous
uniform coatings at current densities in the ranges 2–7
(2) A sulfate electrolyte from which lustrous uniform
coatings can be deposited at low and high current
densities was developed.
–2
and 10–16 A dm .
It is known that, for matte coatings to be formed,
it suffices that the additive is adsorbed on the cathode
surface and the electrocrystallization overvoltage
increases, whereas deposition of lustrous coatings
requires that an adsorption layer of certain composition
should be present on the cathode surface. Layers of
this kind can be formed from organic substances and
products of secondary reactions in the near-cathode
layer. In the case of simultaneous deposition of a metal
and evolution of hydrogen, the adsorption layer may be
composed of hydroxides and other basic compounds [1].
REFERENCES
1
. Blestyashchie elektroliticheskie pokrytiya (Lustrous
Electrolytic Coatings), Matulis, Yu.Yu., Ed., Vilnius:
MINTIS, 1969.
2
3
. Jelinek, T.W., Praktische Galvanotechik, Eugen Y. Leuze
Verlag, 2005.
. Vinogradov, S.S., Ekologicheski bezopasnoe gal’vaniche-
skoe proizvodstvo (Ecologically Safe Galvanic Shop),
Kudryavtsev, V.N., Ed., Moscow: Globus, 2002, 2nd ed.
rev. and suppl.
The assumption that nickel hydroxides are formed in
the near-cathode space was confirmed by measurements
of the pH of the near-cathode layer (pHs). It can be seen
4
. Medvedev, G.I. and Makrushin, N.A., Zh. Prikl. Khim.,
2
002, vol. 75, no. 11, pp. 1834–1838.
–
2
5. Bakhchisaraich’yan, N.G., Borisoglebskii, Yu.V., Bur-
kat, G.K., et al., Praktikum po prikladnoi elektrokhimii:
Uchebnoe posobie dlya vysshikh uchebnykh zavedenii
in Fig. 4 that pHs markedly increases at i = 1–4 A dm ;
c
at higher current densities, the pH of nickel salt hydrate
formation (7.2) is reached. The results we obtained
suggest the lustrous nickel coatings are deposited if an
adsorption layer composed of organic substances and
hydrolysis products of the nickel salt is formed on the
electrode surface.
(
Practical Works on Applied Electrochemistry: Textbook
for Higher School), Voropaev, V.N. and Kudryavtsev, V.N.,
Eds., Leningrad: Khimiya, 1990.
6
7
. Gershov, V.M., Purin, B.A., and Ozol'-Kalnin, S.A.,
Elektrokhimiya, 1972, vol. 8, no. 5, pp. 673–675.
Thus, we developed a sulfate nickel-plating electro-
lyte with new organic additives, which can be used to
obtain lustrous uniform coatings at low and high current
densities. The electrolyte has the following composition
. Kruglikov, S.S. and Kovarskii, N.D., Itogi nauki i tekh-
niki. Ser. “Elektrokhimiya” (Advances of Science and
Technology, Electrochemistry Series), Moscow: VINITI,
1975, vol. 10, pp. 106–188.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 11 2011