Influence of the composition of dilute nickel-plating electrolytes on the physicomechanical properties of electroplated coatings

Article abstract of DOI:10.1007/s11167-005-0342-8

The influence of the composition of dilute nickel-plating electrolyte containing luster-forming additives on the leveling, plasticity, and internal stresses of coatings being electroplated was studied. The possibility of combining nickel sulfate, sodium chloride, and boric acid as the main composition of a dilute nickel-plating electrolyte was analyzed.

Full text of DOI:10.1007/s11167-005-0342-8

Russian Journal of Applied Chemistry, Vol. 78, No. 4, 2005, pp. 565 567. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005,
pp. 572 574.
Original Russian Text Copyright
2005 by Binkauskene.
APPLIED ELECTROCHEMISTRY
AND CORROSION PROTECTION OF METALS
Influence of the Composition of Dilute Nickel-Plating Electrolytes
on the Physicomechanical Properties of Electroplated Coatings
E. Binkauskene
Institute of Chemistry, Vilnius, Lithuania
Received June 23, 2004
Abstract The influence of the composition of dilute nickel-plating electrolyte containing luster-forming
additives on the leveling, plasticity, and internal stresses of coatings being electroplated was studied. The
possibility of combining nickel sulfate, sodium chloride, and boric acid as the main composition of a dilute
nickel-plating electrolyte was analyzed.
Technological solutions that would make lower
the expenditure of nonferrous metals, such as nickel,
tin, copper, and their alloys, are sought for in order
to further develop the galvanic industries. Compo-
sitions of bright-nickel-plating electrolytes ensuring
30 NiCl2 6H2O, and 30 H3BO3; no. 2: 33 NiSO4
7H2O, 120 NiCl2 6H2O, and 30 H3BO3; no. 3:
150 NiSO4 7H2O, 50 NaCl, and 30 H3BO3. The elec-
trolytes prepared were subjected to selective purifica-
tion. Chemically and analytically pure reagents were
used in the experiments. OECAM was synthesized
and purified1 mp 87 C. 2-butyne-1,4-diol (YN) was
twice recrystallized from chloroform, mp 58 C;
2-butene-1,4-diol (EN) was purified chromatograph-
ically, mp 113 C at a pressure of 5 mm Hg. Sac-
charin was recrystallized from ethanol, mp 225
226 C. The temperature of the experiment was 50 C
and pH 4.0. The pH value of the electrolytes was
measured with an LPU-01 pH-meter and adjusted with
hydrochloric acid or sodium hydroxide.
1
a common plating rate of 0.8 1.2 m min at the
concentrations of salts of a metal being deposited
lowered by a factor of 2 2.5 (with a total nickel con-
1
centration of up to 30 35 g l ) have been suggested
[1 4]. The rate of nickel plating depends not only on
the anionic composition of an electrolyte [5], but also
on the luster-forming formulations used. The nature
and cathodic behavior of luster-forming additives may
lead to a redistribution of the rates of nickel deposi-
tion and hydrogen evolution in favor of the latter
process. In this case, formation of nickel hydroxide
compounds in a near-cathode layer and their inhibiting
effect on nickel electrodeposition become more likely,
and the microstructure of the resulting coatings is
changed. The considerable increase in the hydrogena-
tion of the deposits deteriorates the physicomechanical
properties of the coatings obtained [6 8]. To improve
the main characteristics of the bright-nickel-plating
process, acetylene compounds are used in combina-
tion with ethylene and organosulfur additives [9].
The microleveling power was determined by mea-
suring profilograms of a titanium substrate with tri-
angular grooves cut to a depth of about 4 m (angle
120 ). The microleveling factor B (%) was calcu-
lated from data on the average depth of the grooves
before and after the nickel plating with the use of
the formula:
h1
h2
(1)
100,
B =
h1
where h1 and h2 are the depths of the substrate grooves
( m) before and after the deposition of a coating, re-
spectively.
The aim of this study, was to assess the influence
exerted by the composition of a dilute nickel-plating
electrolyte containing luster-forming additives based
on -oxyethyl cinnamide (OECAM) on the physico-
mechanical properties of the coatings being deposited.
The plasticity of the coatings was evaluated by
their ultimate tensile elongation, measured with a spi-
ral elastometer.2 Plates with coatings (170 10 mm
in size and 1 mm thick) were placed on the elastomet-
er having the form of a spiral template with a step-
EXPERIMENTAL
1
At the Department of Organic Chemistry, Vilnius University.
The study was performed in nickel-plating elec-
trolytes containing (g l ): no. 1: 140 NiSO4 7H2O,
1
2
Designed at the Institute of Chemistry.
1070-4272/05/7804-0565 2005 Pleiades Publishing, Inc.

566
BINKAUSKENE
Limiting current density ic in a Hull cell for various nickel
plating electrolytes for bright nickel plating
a device that could measure the cathode curvature
after its being coated in a stirred electrolyte [10].
It is known that chloride nickel-plating electrolytes
ensure a higher rate of nickel deposition, compared
with sulfate electrolytes [5]. Introduction of sodium
salts as supporting additives, which are used to im-
prove the throwing power of nickel-plating electro-
lytes [6], makes lower the electrodeposition rate.
The table lists the electrolyte formulations and esti-
mates of the nickel-plating rates, found by the fast
method [5] with a Hull cell. The formulation sug-
gested is similar to the technological solution of
[9], which consists in that small concentrations of
YN are used in combination with an ethylene com-
pound, EN, with the key role played by the competi-
tion of acetylene and ethylene groups in hydrogena-
tion. -Oxyethyl cinnamide is described by the formu-
la C6H5CH=CH CONHCH2CH2OH and, unlike EN,
contains a phenyl radical and nitrogen. A comparative
study of the known bright-nickel-plating electrolyte
based on a mixture of YN and EN [9] in an untypical
formulation of a dilute electrolyte no. 2 demonstrated
that the rates of metal plating in a dilute chloride solu-
tion differ only slightly for the additives used.
Electro- Electro-
Luster-forming additive,
ic ,
A dm
1
2
lyte
lyte no.
g l
Sulfate
1
Saccharin, 1.5;
OECAM, 0.5; YN, 0.05
The same
1.9
Chloride
2
3
2
2.8
2.0
3.2
Saccharin, 1.5; YN, 0.08;
EN, 0.16
wise changing radius of curvature. The critical elonga-
tion, at which coatings cracked, was determined with
a special paste containing o-phenanthroline chloride
indicator, which could reveal an uncoated steel sub-
strate.
The elongation l (%) was calculated by the formula
l = [d/(2r + d)] 100,
(2)
where d is the thickness of a plate with a coating
(mm), and r, the radius of curvature at the critical
point of the spiral surface.
The coatings obtained in a chloride electrolyte have
a factor of 1.5 2.0 lower internal compression stresses
over the entire range of the current densities ic (Fig. 1a).
The internal stresses (IS) in the nickel coatings were
measured by the method of a flexible cathode with
Fig. 1. (a) Internal stresses IS, (b) plasticity l, (c) current efficiency
, and (d) microleveling factor B vs. the current density
Ni
i
in various nickel-plating electrolytes. Temperature 50 C and pH 4.0. (a, b, d) Digits at curves are the electrolyte numbers;
c
1
1
Additive to the electrolytes (g l ): saccharin 1.5, OECAM 0.5, and YN 0.05. (c) Electrolyte (g l ): (1) no. 2; (2) no. 2 + sac-
charin, 1.5; (3) NiCl 6H O, 27; Na SO , 70; H BO , 30; and (4) no. 1 + saccharin, 1.5.
2
2
2
4
3
3
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 4 2005

INFLUENCE OF THE COMPOSITION OF ELECTROLYTES ON THE PROPERTIES OF COATINGS 567
The plasticity of a lustrous nickel coating formed
under the same conditions reaches a value of 9%
(Fig. 1b), which is very high, compared with that
obtained previously (up to 6%) for the technological
solutions suggested in [9]. It should be noted that suf-
ficiently plastic deposits (6%) are also obtained from
dilute nickel-plating electrolyte nos. 1 and 3 (Fig. 1b).
Presumably, the possible reason for the smaller elon-
gation is the lower current efficiency by nickel in sul-
fate electrolytes, compared with chloride electrolytes.
A similar effect is produced by sodium ions (Fig. 1c).
In this case, a stronger alkalization of the near-cathode
space is observed and the amount of impurities in-
corporated into the nickel deposit is larger. The best
leveling power is observed for sulfate electrolyte
no. 1 (Fig. 1d). This may be due to different cata-
lytic activities of the renewed nickel surface in re-
actions of cathodic conversion of ethylene and acet-
ylene compounds. Therefore, the choice of the elec-
trolyte composition depends on whether a higher
plasticity or leveling is required for a particular
coating.
CONCLUSION
A study of the influence exerted by the composition
of a dilute nickel-plating electrolyte containing -oxy-
ethyl cinnamide as luster-forming additive on the phys-
icomechanical properties of the coatings deposited
demonstrated that nickel sulfate, sodium chloride, and
boric acid can be used in combination in the formula-
tion of a dilute nickel-plating electrolyte.
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el plating in dilute nickel-plating electrolytes, sulfate
electrolyte no. 1 and chloride electrolyte no. 3, are
nearly the same and the coatings obtained from these
electrolytes have the same internal stresses and plas-
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 4 2005