260
BALAKAI et al.
It is the surface tension forces at this boundary that create
a liquid-like surface of lustrous coatings.
(5) As the cathode current density increases, the
microhardness, internal stresses, porosity, and luster pass
through a maximum.
As the working current density increases, the pH
value in the near-cathode layers increases because of
the simultaneous, with nickel deposition, hydrogen
evolution. At a pH exceeding a certain value (depending
on temperature and composition and concentration of
REFERENCES
1
. Kudryavtseva, I.D., Kukoz, F.I., and Balakai, V.I., Itogi
nauki i tekhniki. Elektrokhimiya (Advances in Science and
Technology: Electrochemistry), Moscow: VINITI, 1990,
no. 33, pp. 50–81.
components in the electrolyte), the pH of nickel is
h
reached. This leads to formation of too coarse particles
of hydroxides and basic salts and to disintegration of
the phase surface of the more viscous layer (liquid 2) at
the electrode surface. This eliminates the second factor
favoring the formation of lustrous coatings [21]. The
hydrodynamic mode at the surface of a growing lustrous
coating is disturbed [22]. A specific hydrodynamic
mode is created by electrosurface phenomena in the
mobile system of pores at the cathode in the case of
a simultaneous reduction of finely dispersed particles of
compounds of a metal and its ions.
2
3
4
5
6
. Kudryavtseva, I.D., Selivanov, V.N., and Kukoz, F.I.,
Elektrokhimiya, 1984, vol. 20, no. 1, pp. 63–68.
. Balakai, V.I., Doctoral Sci. (Chem.) Dissertation, Novo-
cherkassk, 2004.
. Zhukov, I.I., Izbrannye trudy (Selected Works), Leningrad:
Akad. Nauk SSSR, 1952.
. Galus , Z., Fundamentals of Electrochemical Analysis,
Ellis Horwood, 1994.
. Zakharov, M.S., Bakanov, V.I., and Pnev, V.V., Khrono-
potentsiometriya (Chronopotentiometry), Moscow: Khi-
miya, 1978.
An X-ray structural analysis of coatings deposited
from a chloride electrolyte at pH 1.0, temperature of 20°C,
7
8
9
. Spravochnik po elektrokhimii (Handbook of Electro-
chemistry), Sukhotin, A.M., Ed., Leningrad: Khimiya,
1981.
−2
and current densities of 1 and 10Adm demonstrated that
the γ-NiOOH, Ni(OH) phase is present in the coatings
2
−2
[
3]; however, the number of reflections at 10 A dm
. Mairanovskii, S.G., Stradyn’, Ya.P., and Bezuglyi, V.D.,
Polyarografiya v organicheskoi khimii (Polarography in
Organic Chemistry), Leningrad: Khimiya, 1975.
is considerably lower. This also confirms that finely
dispersed nickel compounds start to be reduced at the
cathode as the reduction potential of nickel hydroxide
. Ovchinnikova, T.M., Taran, L.A., and Rotinyan,A.L., Zh.
Fiz. Khim., 1962, vol. 36, no. 9, pp. 1909–1913.
(−0.720 V) [7] is reached.
The adhesion of nickel coatings deposited from
a chloride electrolyte to steel, copper, and copper alloys
supports satisfies GOST (State Standard) 9.302–88.
1
0. Kublanovskii, V.S., Gorodyskii, A.V., Belinskii, V.N.,
and Glushchak, T.S., Kontsentratsionnye izmeneniya v
prielektrodnykh sloyakh v protsesse elektroliza (Variation
of Concentration in Near-Electrode Layers in the Course
of Electrolysis), Kiev: Naukova Dumka, 1978.
CONCLUSIONS
11. Balakai, V.I. and Kurnakova, N.Yu., in Zashchitnye
pokrytiya v mashinostroenii i priborostroenii: Sbornik
materialov II Vserossiiskoi nauchno-prakticheskoi
konferentsii (Protective Coatings in Machine-building and
Instrument-making: Proc. IIAll-Russia Sci.-Pract. Conf.),
Penza: PDZ, 2005, pp. 22–25.
(
1) The mass-transfer rate increases by a factor of 6.2
within the temperature range 20–50°C, and by a factor of
1.4 as temperature increases from 50 to 60°C.
2) The calculated temperature dependences have high
2
(
−1
values: approximately 4.8 % deg for the temperature
range 50–60°C and pH 1.0, and 5.6 % deg for pH 5.0.
1
2. Balakai, V.I. and Shevchenko, V.V., Izv. Vyssh. Uchebn.
Zaved., Sev.-Kavk. region, Tekhn. Nauki, 2002, no. 4,
pp. 110–111.
−1
(
3) Introduction of 1,4-butynediol into the chloride
nickel-plating electrolyte has no effect on the mass-
transfer rate.
13. Balakai, V.I., Izv. Vyssh. Uchebn. Zaved., Sev.-Kavk.
Region, Tekhn. Nauki, 2002, no. 3, pp. 35–36.
(
4) The pH of nickel is reached in the near-cathode
14. Balakai, V.I., Kirienko, L.V., and Shkumat, O.E., Izv.
Vyssh. Uchebn. Zaved., Sev.-Kavk. region, Tekhn. Nauki,
h
layer in the working range of current densities at both
0 and 60°C, and finely dispersed nickel compounds are
formed, which are involved in the acceleration of the
electrodeposition of nickel from a chloride electrolyte.
2
002, no. 1, pp. 103–104.
2
1
5. Gal’dikene, R.P., Shal’vene, Zh.P., and Petrauskas, A.V.,
Zashch. Met., 1994, vol. 30, no. 6, pp. 642–645.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 82 No. 2 2009