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.
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.
Bismuth and its alloys are widely used in industry
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 .
Presently, perchlorate, fluoroborate, phenolsulfon-
ic, fluosilicate, sulfate, EDTA, pyrophosphate, and
other electrolytes are used for the electrodeposition of
bismuth and bismuth-containing alloys .
Though ensuring deposition of high-quality coat-
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.
Much attention is given today to replacement of
toxic anions in electroplating solutions by less toxic
anions . 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.
The effect of the electrolysis mode and electrolyte
composition was studied at 20oC and a cathodic cur-
rent density of 0.3 A dm
in the solution containing
80% lactic acid [GOST (State Standard) 490379]
100 ml l
, bismuth nitrate (in terms of metal) 10 g l
sodium sulfate 20 g l
, and 65% nitric acid (GOST
4461377) 50 ml l
With an increase in the concentration of bismuth
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.
Fig. 1. Cathodic current efficiency (CE) by bismuth vs.
(1) concentration of lactic acid c in the electrolyte, (2) cath-
odic current density i
and (3) solution temperature.
As the concentration of lactic acid in the electrolyte
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
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 further study was carried out in the electrolyte
containing lactic acid 150 ml l
, bismuth nitrate (in
terms of metal) 10 g l
, sodium sulfate 20 g l
and 65% nitric acid (GOST 4461377) 50 ml l
Increasing the cathodic current density within 0.33
0.75 A dm
leads to deterioration of the coating
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,
With an increase in temperature from 12 to 24oC,
the cathodic current efficiency by bismuth increases