Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 5, pp. 857−861.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
I.P. Sizeneva, Yu.A. Shchurov, V.N. Strel’nikov, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 5, pp. 803−807.
AND CORROSION PROTECTION OF METALS
A Study of the Corrosion-Electrochemical Behavior of Mercury
in Alkaline Solutions of Sodium Hypochlorite
I. P. Sizeneva, Yu. A. Shchurov, and V. N. Strel’nikov
Institute of Technical Chemistry, Ural Division, Russian Academy of Sciences, Perm, Russia
Perm State University, Perm, Russia
Received June 18, 2008
Abstract—Oxidation rate of mercury in solutions of potassium chloride and sodium hydroxide and hypochlorite
was studied by measuring the polarization resistance.
Hypochlorites (HCs) are strong oxidizing agents
and find wide use in this respect, including that in
demercurization processes . It has been found that
particular effective for this purpose is sodium HC [sodium
oxochlorate(I)] [2, 3], which exhibits high oxidizing
capacity in alkaline media due to the reversible process:
+ 2NaOH ”! NaOCl + NaCl + H
O. The interaction of
mercury with alkaline solutions of HCs is a heterogeneous
process characterized by a certain potential discontinuity
at the metal–solution interface and by the formation of
difﬁ cultly soluble compounds on the mercury surface, of
which the most probable are mercury oxide and calomel.
The rate of this oxidation process can be estimated by the
known methods used to study the corrosion of metals.
The potentiostatic method for recording of polarization
curves is widely used to examine metals and alloys that
can pass to the passive state. In this study, the method
is employed to analyze the mercury oxidation rate in
solutions of potassium chloride and sodium hydroxide
A NaClO solution was prepared by passing chlorine
through a carbonate-free solution of sodium hydroxide
at temperatures of –5 to 0°C. Chlorine was obtained by
reacting chemically pure hydrochloric acid with potassium
permanganate . The hypochlorite concentration
was found iodometrically on the basis of the active
chlorine. The pH value of the alkaline solution of HC
remained nearly unchanged, irrespective of the duration
and temperature of experiments, because of the excess
amount of sodium hydroxide present in the HC solution.
Solutions of potassium chloride and sodium hydroxide
were prepared from reagents of chemically pure grade.
A preliminarily degreased mercury for electrodes was
subjected to additional puriﬁ cation by multiple passing
of a dispersed metal through a 5% solution of Hg
in 5% HNO
and the distillate.
The solution temperature was maintained with a UTU-
The polarization curves were measured with a PI-50
The electrochemical cell 1 (Fig. 1) had the cathode and
anode spaces separated by a porous glass partition
2. A saturated silver chloride reference electrode 3 was
placed in a side run-out, the end of whose capillary was
situated near the working electrode. The experimentally
found potential of the reference electrode was 0.203 V
(s.h.e.) at 20°C. A platinum wire was introduced as a cur-
rent lead into a tube with a diameter of 4 mm, sealed in
the cell bottom. Prior to measurements, mercury serving
as the working mercury electrode and having a 0.126-cm
surface area contacting with the solution was poured with
a pipette into tube 4. The auxiliary platinum electrode 5
was introduced into the separated cathode space. After
the measurements, the solution under study and mercury
were removed from the cell through a discharge pipe
equipped with a cock 6.