1070-4272/02/7511-1799$27.00C2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 11, 2002, pp. 1799!1803. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 11,
2002, pp. 1834!1838.
Original Russian Text Copyright + 2002 by Medvedev, Makrushin, Dubenkov.
AND CORROSION PROTECTION OF METALS
Organic Compounds for Preparing Lustrous Tin Coatings
G. I. Medvedev, N. A. Makrushin, and A. N. Dubenkov
Novomoskovsk Institute, Mendeleev Russian University of Chemical Engineering, Novomoskovsk,
Tula oblast, Russia
Received February 7, 2002
Abstract-Organic compounds for preparing lustrous tin coatings were selected taking into account their
ionization potential. The best electrolyte composition for plating these coatings was determined.
Various organic compounds are added to sulfate
electrolytes for tin-plating . To obtain dense finely
crystalline dull or lustrous coatings, these electrolytes
should contain colloid-forming compounds (glue, gela-
tin) and wetting agents (e.g., ethylene oxide condensa-
tion products) along with other organic compounds.
Unsaturated alcohols, ketones, aldehydes, and prod-
ucts of the electrochemical synthesis are used for
preparing lustrous tin coatings . It should be
noted that organic compounds for plating lustrous tin
coatings are selected empirically.
Nechaev et al. showed that the sorption on
the surface of tin and other metals is caused by not
only electrostatic interactions but also chemical bond-
ing. The chemisorption is maximal when the energy
of electronic levels of the metal is similar to that of
the molecular orbital of the organic compound, which
provides formation of donor3acceptor bonds between
the molecules of the additive and the metal surface.
Under these conditions the occupied molecular or-
bitals of the adsorbent and the adsorbate overlap to
form a common electronic system. The correlation
between the adsorption properties of organic com-
pounds and the energy of the highest occupied molec-
ular orbital (MO) can be quantitatively characterized
by the first ionization potential I.
According to , the range of I of organic com-
pounds optimal for their sorption on tin is 7.743
7.96 eV. The second maximum is observed at I =
9.6 eV. To explain this phenomenon, Nechaev and
Volgina suggested  that the tin surface consists of
pure and oxidized regions. However, the dependence
of the adsorption energy on I, measured on cathodical-
ly polarized tin whose surface is constantly renewed
(oxide formation is thermodynamically forbidden),
also has two maxima. It was suggested that not only
highest occupied MO characterized by the first I but
also other occupied orbitals are involved in the bond-
ing. Dull finely crystalline tin coatings were plated
from sulfate electrolyte containing organic compounds
with I = 7.838.0 eV [4, 5, 10]. Introductions of com-
pounds with I = 9.539.7 eV makes the coatings com-
pact, uniform, and semilustrous. Organic compounds
with I other than 7.838.0 and 9.539.7 eV do not in-
hibit tin-plating. No high-quality coating are formed
in their presence.
In this work, taking into account I of organic com-
pounds, we selected such compounds or their mixtures
that provide plating of lustrous tin coating from sul-
For this purpose we mainly used an electrolyte con-
taining 30 g l
and 100 g l
coatings were plated at 20322oC with or without stir-
ring of the electrolyte with a mechanical stirrer.
The tested organic compounds are presented in
Condensation products Syntanol DS-10 (I =
9.4 eV), OP-7, OP-10 (I = 9.3 eV), OS-20 (I =
9.2 eV), VA-20 smoothing agent (I = 9.5 eV), hide
glue, and gelatin (I = 7.5 eV) were also studied.
The ionization potentials of the tested organic
compounds ranged from 6.88 to 12.2 eV. The concen-
tration of these compounds was varied from 1 to
15 g l
. Saturated solutions of difficultly soluble
compounds were used. The ionization potentials of
organic compounds were taken from [6, 7] or calcu-
lated by the PM3 method .
The most precise experimental procedure for deter-
mining ionization potentials of atoms and molecules
is PES . In this work, the I values determined by
PES were correlated with those calculated quantum-
chemically. First, we examined how semiempirical