1070-4272/03/7601-0023$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 1, 2003, pp. 23!28. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 1,
2003, pp. 24!30.
Original Russian Text Copyright + 2003 by Gnedenkov, Khrisanfova, Zavidnaya, Sinebryukhov, Kon’shin, Bulanova, Gordienko.
AND INDUSTRIAL INORGANIC CHEMISTRY
Complex Formation in Electrolyte Solutions in the Course
of Plating Protective Coatings on Titanium
S. V. Gnedenkov, O. A. Khrisanfova, A. G. Zavidnaya, S. L. Sinebryukhov,
V. V. Kon’shin, S. B. Bulanova, and P. S. Gordienko
Institute of Chemistry, Far Eastern Division, Russian Academy of Sciences, Vladivostok, Russia
Received August 16, 2002
Abstract-Conditions for complex formation in aqueous electrolyte solutions containing salts of aluminum
and hydroxy carboxylic acids were studied by
F NMR spectroscopy. The formation of complex
anions in the electrolytes at various pH and their discharge on the anode under conditions of a microplasma
process allowed preparation of surface layers containing a-Al
on VT1-0 titanium. The interrelation
between the composition and properties of the coatings was studied.
It is known that the physicochemical and service
properties of coatings formed on metals and alloys
under microplasma anodizing conditions essentially
differ from the properties of common anodic films .
We have shown in  that certain factors should be
taken into account when selecting the electrolyte
composition and oxidation conditions for directed
synthesis of surface layers of required composition
on metals and alloys under the microarc oxidation
conditions. Among such factors are possible changes
in the forms of anionic complexes in solution depend-
ing on pH, both in the bulk of the electrolyte and
in a local area of the near-electrode space.
Electrolytes containing various anionic complexes
were used previously in the microarc oxidation of
aluminum , titanium , and some other metals
. The resulting coatings had various physicochemi-
cal properties determined by their phase and chemical
compositions. At the same time, the composition of
the complex anions at various pH of the electrolyte,
the interactions between various anions in solutions
before and during oxidation, and also the mechanism
of the complex formation are poorly understood.
To obtain on aluminum protective coatings exhibit-
ing high resistance to wear and heat owing to the
presence of a-Al
, an electrolyte containing alumi-
num tartrate complexes and also fluorides [6, 7] was
developed. In , aluminum alloys were selected as
model materials ensuring high concentration of alu-
minum ions in the near-anode space during oxidation.
Depending on pH, the complex formation can involve
various functional groups of tartaric acid: carboxy
(3COOH), hydroxo (3OH), or both . The presence
of such complexes in an electrolyte solution strongly
affects the composition and properties of the forming
surface structures .
Proceeding from model concepts developed for alu-
minum and its alloys [6, 9], we believe that develop-
ment of a process for obtaining solid layers on the
titanium surface by its oxidation in electrolytes con-
taining anions of hydroxy carboxylic acids should be
based on the following principles.
(1) Fluorine compounds do not form insoluble
compounds with titanium (in contrast to aluminum);
therefore, their presence in the electrolyte will result
in active etching of the substrate, thus hindering the
formation of a continuous uniform coating.
(2) To ensure formation of anionic complexes with
hydroxy acid ligands, aluminum(III)-containing com-
ponents should be added to the electrolyte.
(3) It is necessary to minimize formation of titani-
um(IV) complexes with hydroxy acid salts by select-
ing appropriate electrolyte composition and varying
its pH, as the existence of such complexes in solution
will result in the formation of coatings based on tita-
nium oxides and in decreased concentration of alumi-
num oxide in the film.
With the aim to obtain heat-resistant solid coatings
on titanium, we studied in this work the complex for-
mation in electrolytes containing aluminum salts
and certain hydroxy carboxylic acids, both aliphatic
(lactic, tartaric, and citric) and aromatic (salicylic).
For this purpose, we created conditions favoring