1802
MEDVEDEV et al.
their first ionization potential. Lustrous tin coating
C, F cm 2
were plated from the electrolyte containing an in-
hibitor, formaldehyde, and a luster-producing agent or
an inhibitor and a luster-producing agent.
(2) Products of ethylene oxide condensation (Syn-
tanol DS-10, OP-7, OP-10, and OS-20), VA-20
smoothing agent, as well as gelatin and glue in com-
binations with cresol, phenol, or naphthol can be used
as inhibitors.
(3) Diphenylamine (I = 7.25 eV), benzyl alcohol
(I = 8.95 eV), coumarin (I = 8.97 eV), 2-butene-1,4-
diol (I = 9.13 eV), acetic anhydride (I = 9.5 eV),
benzenesulfonic acid (I = 9.8 eV), 2-butyne-1,4-diol
(
I = 9.77 eV), p-phenolsulfonic acid (I = 9.8 eV),
propargyl alcohol (I = 10.41 eV), and butane-1,4-diol
I = 10.43 eV) can be used as luster-producing addi-
tives to tin-plating electrolyte.
(
Ec, V, vs. NHE
(4) The luster-producing additives allow plating of
Fig. 3. Capacitance of the electrical double layer C as
lustrous coatings from electrolyte containing or not
containing formaldehyde, depending on the particular
inhibitor. In the presence of gelatin, glue, and cresol,
formaldehyde exhibits luster-producing properties.
a function of the cathodic potential E : (1) electrolyte no. 1;
c
1
1
(
2) 1 + Syntanol, 2 g l + Formalin, 6 ml l + propargyl
1
1
alcohol, 10 ml l ; (3) 1 + Syntanol, 2 g l + Formalin,
1
1
6
ml l + benzyl alcohol, 6 ml l .
(
5) The proposed approach can be used to select
trolyte to obtain high-quality dull coatings [1, 2]. For-
maldehyde (I = 10.88 eV) present in the electrolyte is
a depolarizer of the process. Organic compounds with
I = 7.25 and 8.95 10.43 eV exhibit lister-producing
properties.
organic compounds that may provide formation of
lustrous tin coatings from electrolyte containing in-
hibitors.
REFERENCES
The fact that lustrous coating are formed only at a
definite combination of organic compounds and stir-
ring of the electrolyte suggests that sorption of or-
ganic compounds on the cathode surface is necessary
but insufficient for obtaining such coatings. In this
case, there are other factors affecting the luster of the
coatings. Among them are complex physicochemical
processes occurring in the catholyte layer [2] and
the conditions of diffusion hydrodynamic feeding
1
. Kudryavtsev, N.G., Elektroliticheskie pokrytiya metal-
lami (Metal Electroplating), Moscow: Khimiya, 1979.
2. Blestyashchie elektroliticheskie pokrytiya (Lustrous
Electrolytic Coatings), Matulis, Yu.Yu., Ed., Vilnius:
Mintis, 1969.
3. Medvedev, G.I., Influence of Surfactatns on Elec-
trolytic Tin Plating from Sulfuric Acid Electrolytes,
Cand. Sci. Dissertation, Moscow, 1992.
(or removal) of ions, which change the structure and
properties of the absorption layer on the cathode
surface [18].
4. Nechaev, E.A., Kudryavtsev, N.G., and Medve-
dev, G.I., Elektrokhimiya, 1971, vol. 7, no. 3,
pp. 383 386.
Thus, the proposed approach affords a criterion of
selection of organic compounds that, in combination
with inhibitors, may provide formation of lustrous tin
coatings. However, it does not warrant obtaining such
coatings with particular additives a priori. Electrolytes
for plating lustrous tin coatings are developed on the
basis of this principle [13 16, 19, 20].
5
. Kudryavtsev, N.G., Nechaev, E.A., and Medve-
dev, G.I., Elektrokhimiya, 1972, vol. 8, no. 4,
pp. 538 541.
6
. Nechaev, E.A., Khemosorbtsiya organicheskikh ve-
shchestv na oksidakh i metallakh (Chemisorption of
Organic Compounds on Oxides and Metals), Kharkov:
Vyshcha Shkola, 1989.
7
. Nechaev, E.A. and Kuprin, V.P., Itogi Nauki Tekh.,
Ser.: Elektrokhimiya, 1989, vol. 29, pp. 93 152.
CONCLUSIONS
(
1) Organic compounds promising for plating
8. Nechaev, E.A. and Volgina, V.A., Elektrokhimiya,
lustrous tin coatings were selected taking into account
1978, vol. 14, no. 3, pp. 417 421.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 11 2002