THE QUESTION OF ATOMOSPHERIC CORROSION OF POWDERED COPPER

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82-00039R000200020005-3
• Release Decision: RIPPUB
• Original Classification: R
• Document Page Count: 10
• Document Creation Date: December 22, 2016
• Document Release Date: May 15, 2012
• Sequence Number: 5
• Publication Date: April 29, 1952
• Content Type: REPORT

t
ATMOSP~~~~TC CO1~:EZOSTON 0~' PO1J'DER~CD COPPER
OF
THE QUESTION O
A. V. Ponlosov and
A. T. Levin
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STAT
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T QUESTIOI'1 OF ATMd5P1iRIC CORRO aIOI~1 OF P)WDERED COPPER
i
In 'the literature of recent years, atmospheric corrosion is
treated as a special type of electrochemical corrosion, and it is
assumed that the corrosive processes take place beneath the.. film of
moisture on the borderline of the metal surface and the liquid
phase (1).
me, over 300 degrees centigrade far 94fle4 Tdride and over
One usually sets the temperature limits of atmospheric cor-
rosion within the bounds of existence of water in the liquid state
corrosive action of dry vapors and gases on metals (chemical
The
corrosion is considered possible at. temperatures much higher than
the boiling point of water -- over 200degrees Centigrade for chlor-
I, 3w~
But even in this case, when corrosion takes place in an atmosphere
of dry vapors and gases (of hydrogen sulfide for instance), one
generally assumes that here, too, the process takes place with the
participation of moisture forming through the interaction between
the attacking substance and the metal or the oxide fllmo
oQ degrees centigrade for stt` gas and hydrogen sulfide (2) a
Thus, the presence of moisture is considered indispensable to
atmospheric corrosion.
According to the film theory of Kistyakovskiy, atmospheric
corrosion is considered to be an intermediate stage between purely
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 habization of the metal particle surfaces (s)?
P
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chemical and electrochemical pxoceses. The process o? corrosion
consjStS of three phases;
between metal and moist oxygen with the forma
1. Interaction
tion of metal oxide films.
films coagulation, the formation of
2. Sol?da.fa.cata.on of
crystallites)
3. Adsarpt of gases, corlden$ation of liquids, and colloido-
~.on
elecrochema.cal processes (3)?
,
r-
The destruction of the original film (the appearance of a-e?as
l /1-, ,IL ;
.da.ficat be P. x4~aked by~ps,rticles suspended in air,
of sola.~.on} may b
r vidntl, in this theory too, the influence of
vapors and gages. E y
but the rocess of corrosion as a whole is not r-s=
water i.s decisive, , p
~va electrochemical reactions between
,ed~el~z~~ve:4~
the surface of the metal and the moisture f i1m
The study of corrosion of metals in powder form, where atmos-
pheric assumes a specific character and certain of its
~.c coz rosy.
be clearer than with compact metals, provides bet-
aspects appear to
ter insight into the mechanism of atmospheric corrosion.
~.
riments conducted on corrosion of copper powder in an
atmosphere of various aggressive gases have demonstrated moisture
antrolling factor in the corrosive process (L).
is the principal c
Starting from there we have evolved an original method of stabilizing
capper powders against corrosion; the method consists in the hydro-
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With the creation of chemiadsorbed hydrophobic films we pxe-
vent the adsorption of water vapors by the surfaces of the metal
particles, and consequently we wholly eliminate the possibility of
the formation of adsorption films of moisture.
The resistance to corrosion of a metal in powder form increases
considerably this way. For instance, in an atmosphere of carbon diw
oxide saturated with water vapor at L.O degrees Centigrade, the resis-
tance increases from ~O to 70 tunes. Such a high resistance against
atmospheric corrosion is understandable since the flow of electro-
chemical reactions is impossible in the rase of these stabilized nietal
powders.
In the present experiment we have endeavored to study and com-
pare qualitatively the corrosive behavior of hydrophobic and common
copper in powder form.
EXPERIMENTAL SECTION
The procedures followed in the corrosion experiments were
basically similar to those of previous tents (b). The corrosion tests
--i m
were conducted in ec cators with a capacity of 2 liters. To insure
complete uniformity in experimental conditions, two portions of
powder were placed in each .e,xsiccator, one hydrophobic, the other
common. The tests were conducted in an atoosphere of hydrogen sul-
fide9 cepi e_ Chide, a nia, and carbon dioxide. The gases were
;S 'v b
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(Technicians T. A. Tkachenko and K. V. Mityushina
took part in the experimental part of this work)
passed throug & c calcium chloride and sulfuric acid in order
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The results are given in Tables l and II.
Extent of Corrosion of Copper powder in Atmospheres
a Hydrogen Sulfide and Carbon Dioxidof
copper powder of factory make. The extent of COrraslOri was estab-
lished according to weight increase
and Identical procedure was followed. The tests were conduc~ea vil
gas Were always usea~
A
f 111in~ the e SiCCators the same amounts of
+.n ~ 'T them. DI certain !e$ soda lime were added. In
Temperature 40 ~ 1 degrees centigrade)
(Exposure 8 Hours Temp
powder Corrosive Atmosphere
Type of
Carbon Water
Hydrogen .
Sulfide 'p Dioxide Vapor
L.~ 6.6 0,0, o.oL
Hydrophobic
(Note: In Table x and following the amount of weight increase
.
1s expressed percentages of the original specimen weight.)
in perce ~,
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Table II
Degree of Corrosion of copper powder in
At pheres of Chlorine Hydride, and Ammonia
O
(Exposure, L hours, Temperate, 140 degrees Centigrade)
Type of Powder
corrosive Atmosphere
chlorine Hydride
pry saturated with
water vapor
common copper increases substantially, while in the case
phobic metal it either does not change (CO2 atmosphere),
l~.UO
Common 3 .U1 2.09
Hydrophobic 1,90 1.02 0.73
' the
(Note: The ammonia atmosphere was created by introducing into
exsiccator of a small amount of a 2 percent solution of ammonia.)
As follows from Tables I and II, hydrophobic powders are
always less subject to corrosion than the corrman powders. In moist
atmospheres of Hydrogen sulfide and carbon dioxide the corrosion of
results are presented in Table III.
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insignificantly (H2S atmosphere).
hydride we note an anomaly in the
corrosion of the metal appears to
of hydro-
or changes
In an atmosphere of chlori-fe
conduct of copper powder. Here the
be more intense an a dry gaseous
atmosphere than in the presence of water
anomaly later.
Ammonia
We will explain this
We then conducted experiments of powder corrosion in an atmos-
phere of hydrogen sulfide during a more prolonged period of time. The
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Table III
Corrosion of Copper powder in an Atmosphere of Hydrogen
and in relation to the length of exposure tame
Surf a.de
(Temperature + 16 ? 2 degrees centigrade)
Experiment Type of Powder Corrosion Exposure
(~ Hours)
Number Atmosphere 2L 148 261x.
1 Common
2 Hydrophobic
Common H25 saturated 18.8 18.1 20.0
3
l4 Hydrophobic
6 Hydrophobic
glasses containing water previously saturated with hydrogen sulfide
with water vapors
H2S saturated with
water vapors, and
water saturated
with H2S
12,2 l0m0 17.6
Apparently, the principal mass of non-hydrophobic copper is
corroded immediately, during the initial period. Later the process
of corrosion continues only in the depth of the specimen. Table III
also shows that hydrophobic copper is corroded considerably more
slowly than common copper. However, the extent of corrosion grows
in time. The concentration of gas in the reaction is very highly
important. For instance, in experiments 5 and 6 (Table II) small
were used, while in experiments 3 and I. common distilled water was
.
water and, as a consequence, it led to a reduction in the extent of
b. because of the partial absorption aE' theydrogen sulfide by the
usedo This led to a lower concentration of gas in experiments 3 and
corrosion.
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As we know, metal powders stabilized by means of soap are not
wetted by water. But still more interesting results were obtained
with regard to the wettability of portions previously used in corrow
sioh experiments. It developed that previously hydrophobized copper
powders retained the property, being unwettable by water even after
prolonged atmospheric corrosion.
It was noticed further that powder samples caked after corro--
lion tests. Common powders caked to a greater degree than the hydro-
phobic powders. Especially pronounced caking was observed in non-
hydrophobic powders in the presence of water vapor. However, when
corrosion took place in moist atmosphere, but under higher tempera-
tures (90 degrees Centigrade), the corroded samples of powder caked
considerably less compactly than under lower temperatures.
Moreover the difference in caking between common and hydro
phobic powders was not observed under these conditions. Consequently,
under normal temperatures, water has a substantial influence on the
caking process -- it facilitates, apparently, a closer contact and
relationship of the metal particles among themselves.
The corrosion tests of hydrophobic copper powder in atmos-
pheres of hydrogen sulfide, chlorine hydride, and ammonia doubtless
testify to the presence of atmospheric corrosion even in, the absence
of the moisture film on the surface of the highly dispersed particles
of metal. Apparently the corrosion process is the result of a direct
interaction between gases and vapors and the surface of the metal.
The relatively higher degree of corrosion in an atmosphere of
dry hydrogen sulfide of common copper in powder form as compared to
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 the hydrophobic powder, can be explained as follows; First, in the
case of unprotected powders, the complete surface of the particles
is accessible to the action of gases, whereas in the presence of
hydrophobic films over the metal surface, the gas must surmount a
certain resistance of the protective film in order to make direct
contact with the metal. Second, the water formed as a result of the
interaction between hydrogen sulfide and the metal will be adsorbed
by the common powder and will favor the appearance of an electrow
chemical corrosion in addition to the chemical one. It is self-
evident that in the case of hydrophobic powders this possibility is
excluded. A similar picture appears in even stronger light when the
reaction ahosphere is saturated with water vapor, in which case the
corrosion of a non.'hydrophobic metal increases considerably. Here
we have the formation of a moisture film not only as a consequence
of a chemical interaction between hydrogen sulfide and the metal, but
also as a result of adsorption and capillary condensation on the
highly-dispersed metal particles. It is quite understandable that in
addition to the chemical corrosion we have here a very intensive
electrochemical corrosion as well.
As follows from the experimental data, under similar conditions
the corrosion of copper powder either does not change at all in prac-
tice, or else changes very insignificantly. A certain intensification
of hydrophobic metal powder corrosion in the presence of water vapor
can be explained by the latter~s softening action on the film formed
by the products of reaction between the metal and hydrogen sulfide/
The lower degree of copper powder corrosion in an atmosphere of chlor-
ine hydride saturated with water vapor in comparison with the dry gas
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 is caused by the reduced concentration of the aggressive gas after
its partial absorption by the water.
1. With hydrophobic copper we show. the possibility of atmos~
pheric corrosion in the absence of a moist film on the corroded sur-
race. In connection with this we express an opinion about the faulti-
ness of indiscriminately assuming atmospheric corrosion to be a
special type of electrochemical corrosion.
2. In the temperature range corresponding to the liquid state
of water, a purely chemical _.. gaseous __ corrosion plays a role sub,
stantially paralleling that of electrochemical corrosion.
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