Electrodeposition of bismuth from acid lactate electrolyte

Article abstract of DOI:10.1134/S1070427206070317

Electrodeposition of bismuth from acid lactate electrolyte was studied.

Full text of DOI:10.1134/S1070427206070317

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 7, pp. 1200 1201. Pleiades Publishing, Inc., 2006.
Original Russian Text Yu.P. Perelygin, S.Yu. Kireev, A.Yu. Kireev, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 7, pp. 1210 1211.
BRIEF
COMMUNICATIONS
Electrodeposition of Bismuth from Acid Lactate Electrolyte
Yu. P. Perelygin, S. Yu. Kireev, and A. Yu. Kireev
Penza State University, Penza, Russia
Received February 2, 2006
Abstract Electrodeposition of bismuth from acid lactate electrolyte was studied.
DOI: 10.1134/S1070427206070317
Bismuth and its alloys are widely used in industry
CE, %
as antifriction and corrosion-resisting coatings, as elec-
trical contacts to semiconductors, including rectifying
and ohmic contacts formed by them on silicon and
germanium, and as coatings for soldering [1].
Presently, perchlorate, fluoroborate, phenolsulfon-
ic, fluosilicate, sulfate, EDTA, pyrophosphate, and
other electrolytes are used for the electrodeposition of
bismuth and bismuth-containing alloys [1].
c, M
Though ensuring deposition of high-quality coat-
2
ic, A dm
ings at high cathodic current efficiency and possessing
a high throwing power, the above electrolytes contain,
apart from bismuth ions, toxic anions, which makes
them more environmentally hazardous.
T, C
Fig. 1. Cathodic current efficiency (CE) by bismuth vs.
(1) concentration of lactic acid c in the electrolyte, (2) cath-
Much attention is given today to replacement of
toxic anions in electroplating solutions by less toxic
anions [2]. Lactic acid is abundant in nature and is
an intermediate product of metabolism in biological
tissues. The acid is readily biodegradable and, there-
fore, environmentally safe. In this respect, the devel-
opment of a lactate bismuth-plating electrolyte is of
certain theoretical and practical significance.
odic current density i and (3) solution temperature.
c
As the concentration of lactic acid in the electrolyte
1
is increased from 25 to 150 ml l , the cathodic cur-
rent efficiency by bismuth increases from 90.4 to
98.7%. In this case, light gray, good-quality coatings
are deposited. Raising the concentration of lactic acid
1
to 200 ml l leads to a decrease in the cathodic cur-
rent efficiency by bismuth to 55.1%, with the coating
quality deteriorated (Fig. 1, curve 1).
The effect of the electrolysis mode and electrolyte
composition was studied at 20 C and a cathodic cur-
2
The further study was carried out in the electrolyte
rent density of 0.3 A dm in the solution containing
1
containing lactic acid 150 ml l , bismuth nitrate (in
80% lactic acid [GOST (State Standard) 490 79]
1
1
1
1
terms of metal) 10 g l , sodium sulfate 20 g l ,
100 ml l , bismuth nitrate (in terms of metal) 10 g l ,
1
1
and 65% nitric acid (GOST 4461 77) 50 ml l .
sodium sulfate 20 g l , and 65% nitric acid (GOST
4461 77) 50 ml l .
1
Increasing the cathodic current density within 0.3
2
0.75 A dm leads to deterioration of the coating
With an increase in the concentration of bismuth
1
quality and a sharp decrease in the cathodic current ef-
ficiency by bismuth from 97 to 4.87%, which is due
to intensification of hydrogen evolution (Fig. 1,
curve 2).
ions in the electrolyte from 10 to 20 g l , the cathod-
ic current efficiency decreases from 97.5 to 91.7%,
with the coating quality improved. Raising the bis-
muth concentration further results in a drastic deteri-
oration of the coating quality and a decrease in the
cathodic current efficiency.
With an increase in temperature from 12 to 24 C,
the cathodic current efficiency by bismuth increases
1200

ELECTRODEPOSITION OF BISMUTH FROM ACID LACTATE ELECTROLYTE
log [Bi3+]
1201
2
ic, A dm
log ic
E, mV
Fig. 2. Cathodic potentiodynamic curves taken in the course of bismuth deposition at different concentrations of bismuth ions in
3+
1
3+
the solution. (E) Potential and (i ) current density. Bi concentration, g l : (1) 2.5, (2) 5, and (3) 10. Insert: logi vs. log[Bi
dependence at a cathode potential of 260 mV.
]
c
c
from 93 to 97%. At higher temperatures, the cathodic
current efficiency by bismuth decreases to 88%, which
may be accounted for by acceleration of chemical dis-
solution of the coating or by intensification of hydro-
gen evolution (Fig. 1, curve 3).
likely due to the fact that the electrochemical dissolu-
tion is accompanied by the chemical dissolution of
the anodes.
CONCLUSIONS
Stirring of the solution results in drastic deteriora-
tion of the coating quality and a decrease in the cath-
odic current efficiency by bismuth.
A process for the electrodeposition of high-quality
bismuth coatings was developed, and a less toxic elec-
trolyte containing 80% lactic acid (GOST 490 79)
The potentiodynamic curves taken at a potential
1
1
150 ml l , bismuth nitrate (in terms of metal) 10 g l ,
1
sweep rate of 4 mV s (Fig. 2) show that, with de-
1
sodium sulfate 20 g l , and 65% nitric acid (GOST
creasing bismuth concentration, the polarization
curves shift toward more negative potentials. For
1
4461 77) 50 ml l was suggested. At a cathodic
2
2
current density of 0.3 A dm and 20 25 C, the cath-
example, at the cathodic current density of 0.3 A dm
odic current efficiency is 95 98%. The deposition rate
of the bismuth coatings at these electrolysis conditions
the cathode potentials (relative to SHE) in the solution
1
containing 10, 5, and 2.5 g l bismuth ions are 262,
1
is 7.6 m h .
274, and 278 mV, respectively (Fig. 2).
The log log dependence of the cathodic current
density on the bismuth concentration in the electrolyte
is linear (Fig. 2, insert at the top). The slope of this
straight line is 1.3, which shows that the discharge
of bismuth ions occurs in steps [3].
REFERENCES
1. Azhogin, F.F., Belen’kii, M.A., Gal’, I.E., et al., Gal’-
vanotekhnika: Spravochnik (Electroplating: Reference
Book), Moscow: Metallurgiya, 1987.
The study of the processes occurring at the anode
showed that, as the anodic current density increases
2. Vinogradov, S.S., Ekologicheski bezopasnye gal’vani-
cheskie proizvodstva (Environmentally Safe Electro-
plating Plants), Moscow: Globus, 2002.
2
from 0.1 to 0.5 A dm , the anodic current efficiency
3+
by bismuth (in terms of Bi ) decreases from 141 to
3. Vetter, K.J., Elektrochemische Kinetik, Berlin: Springer,
102%. This high value of the current efficiency is
1961.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 7 2006