Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 9, pp. 1733−1737.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
V.S. Zotikov, 2009, published in Khimicheskaya Promyshlennost’, 2009, Vol. 86, No. 4, pp. 201−206.
Corrosion of Equipment and Its Protection at Producing
and Technical Application of Organoﬂ uorine Products
V. S. Zotikov
Russian Scientiﬁ c Center “Applied Chemistry,” St. Petersburg, Russia
Received May 18, 2009
Abstract—Extension of the nomenclature of fluorine-containing products, and modernization of the methods for
their synthesis (liquid-phase and gas-phase fluorination of the feedstock with hydrogen fluoride, electrochemical
fluorination in anhydrous hydrogen fluoride, direct fluorination with gaseous fluorine and with the use of metals
carrying fluorine, etc.) require extension of research on the corrosion safety of equipment at the implementation
of new technologies. Therefore, the Laboratory of Corrosion is systematically involved in the work on improving
the technology of producing basic fluorinating agents, elemental fluorine and hydrogen fluoride, that are highly
aggressive towards structural materials.
The speciﬁ c feature of working with ﬂ uorine is deﬁ ned
by the fact that among the chemical elements the ﬂ uorine
is the most active one and interacts with almost all other
elements with withdrawing electrons from their atoms,
that is, ﬂ uorine is always an oxidizer. With metals and
alloys, ﬂ uorine begins to react at room temperature and
atmospheric pressure with the formation of a ﬂ uoride
ﬁ lm, chemisorbed or as a separate phase which prevents
further exposure of the metal to ﬂ uorine. That is why
the most industrial alloys based on iron, aluminum,
copper and nickel have satisfactory corrosion resistance
in liquid and gaseous ﬂ uorine at moderate temperatures.
As the temperature increases the efﬁ ciency of protection
is reduced, and becomes possible ignition of metals in
contact with ﬂ uorine: steel at 600700°C, platinum at
400°C, titanium at 300°C. Therefore, for each metal
a temperature above which the metal should not be used,
was deﬁ ned.
The metals affording at the oxidation liquid or gaseous
ﬂ uorides without creation of the passive protective ﬁ lm
on the surface are the most prone to ignition. Many
refractory metals which are the main alloying elements
of high-melting alloys, such as chromium, molybdenum,
tungsten, niobium, silicon, tantalum, and titanium, and
noble metals, platinum, palladium, rhenium and osmium,
react with fluorine to form volatile or low melting
ﬂ uorides. To initiate the reaction of these metals with
ﬂ uorine typically required heating to 150200°C, and
then the reaction proceeds with self-acceleration due to
its own heat.
On the basis of studies carried out with the participation
of P.F. Drozhzhin, Z.A. Spelova, V.G. Nechaeva, and V.S.
Zotikov at temperatures ranging from –196 to 600°C
and at pressures up to 20 MPa acceptable conditions
for the use in work with ﬂ uorine of virtually all known
structural materials were established. In the Table 1 is
listed information on the corrosion resistance in ﬂ uorine
of the metallic materials the most widely used in chemical
Resistance of non-metallic materials in the atmosphere
of ﬂ uorine is determined by the temperature and pressure
of environment, the time of the impact of environment on
the material, condition and quality of surface preparation
of the material. Surface defects (burrs, extrusions,
foreign inclusions) may be the initiators of the ignition
of nonmetallic materials in ﬂ uorine.
The products from plastic, rubber, and ﬁ lms before
exposure to ﬂ uoride should be degreased with ethyl
alcohol and then dried in an incubator at 50°C at least
30 min or in air at least 2 h. Table 2 shows the limits of
the use of nonmetallic materials in ﬂ uoride.