INFLUENCE OF AMMONIUM SALTS ON THE CORROSION OF COPPER IN POWDER FORM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82-00039R000200020009-9
• Release Decision: RIPPUB
• Original Classification: R
• Document Page Count: 6
• Document Creation Date: December 22, 2016
• Document Release Date: May 15, 2012
• Sequence Number: 9
• Publication Date: April 28, 1952
• Content Type: REPORT

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INFLUENCE OF AMMONIUM SALTS ON THE
As we know, copper in powder form is highly susceptible to the
action of various corroding agents. For instance, the storage of
powdered copper with ammonium salts and other chemicals will accele-
rate its corrosion.
t 3
We have previously expressed the the (l) that the corro-
sive activity of ammonium salts in atmospheric corrosion, in the
absence of direct contact with the corroded surface, must depend
4
nj ,?? ~A clj f. Z .f.. M , ?~^"~ N
'M
upon the volatility of the acid forming the salt a4 This theory was
formulated on the basis of a study of the corroding effect of only
two salts; ammonium chloride and ammonium carbonate. It seemed use-
ful, therefore, to check the correctness of the expressed point of
view on a wider number of subjects. In the present work we tested
t- r;,a
the corroding action of chemically pure ammonium ha-lo-O s and also
of ammonium acetate, ammonium nitrate' ammonium carbonate, ammonium
a~, ~E;.I;'d~s
sulfate and ammonium -:phosphate.
We tested common copper powder of ;factory make, containing
ti
C .
+:~v
99.92 percent of copper and having a dry weight of 0.9,.
F
A
The corrosion tests were conducted as follows. Small porce-
lain r&&ups containing portions of copper powder, and other cis
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STAT
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containing M? separately MM armnonium salts and water, were placed
in glass jars of 2. litre capacity. The portions of copper powder
were all of. identical weight 205 grams each. The portions of
salts were prepared from the measured quantity of 1 gram of ammonium
(NHS). The jars were then tightly closed with paraffin-soaked cork
stoppers, sealed with paraffin, and placed in a thermostat, The cor-
rosion experiments were conducted in a temperature of L.0 ? Ong de-
grees for a period of twelve hours. The samples were then trans-
ferred to an exsiccator with calcium chloride as the drying agent,
cooled and weighed until the weights became constant. The speed of
corrosion was expressed in the ratio of milligrams to a gram of sample
mgs.
in 2L~ hours .~. ,.
g x 2L. hrs.
The effect of corf'osive action of ammonium salts was deter-
mined as being the relation of the weight increase of a specific por~
Lion to the original weight, expressed in percent.
Results of the experiments are shown in Table I. The data
shown are averages of four readings; the readings did not differ from
each other by more than 10 to 15 percent.
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Table I
Corrosive Action of Ammonium Salts on Copper in Powder Form
(12 Hour Exposure, Temperature LO ? 0.5 Degrees Centigrade)
rags action
(g) i (mgs) g_ x 2114 hrs. (%)
Copper Weight Corrosion Effect of
portion increase ' speed corrosive
chloride 2.5 53.2 L.2.56 2.12
bromide 2,5 L~.2,9 31..?03 1.71
iodide 205 L3.4 311..72 1.73
t fluoride 2. 214. 17.12 0.81.
ammonium acetate 245 90.0 72oOO 3,60
nitrate 2.5 11.1 8.88 O,l
carbonate 2.5 299.9 239.12. 12.00
sulfate 2.5 9,3 7.L 0.37
'i
diphosphate 2,5 J.6 11.68 0.58
Table I shows that the corrosive actions of different ammonium
salts are not identical and depend upon the nature of the acid form
ing the salt
So far as atmospheric corrosion is concerned here, its speed
will be determined by the thickness of the liquid adsorption layer on
the surface of the metal and the quantity of vapors and gases disw
solved in it (2). In this case the formation conditions of the liquid
adsorption film on any of the tested salts are absolutely identical;
consequently, the thicknesses of the various layers are also equal.
Thus, the observed differences in the corrosion speed depend solely
upon the quantity and quality of vapors and gases dissolved in the
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liquid adsorption layer. The latter is formed in the reaction atmosw
phere as the result of a partial, decomposition of ammonium salts in
connection with their thermal,.instabiity. Consequently, in general
the corrosive action of an ammonium salt is the highest when its
thermal stability is the lowest.
is determined by the properties of the acid forming the anion -- by
its volatility. Salts formed by non-volatile acids (H2SOL, H3PO)
liberate only ammonia upon decomposing, while ammonium salts of vola-
tile acids (HC1, H.C03) liberate acid vapors as well. Therefore the
corrosive action of ammonium salts from volatile acids is usually much
higher than that of salts formed from non-volatile compounds. This
fact is well coni1irmed by the data in Table II, in which the effect
of the corrosive action of various ammonium salts is related to the
boiling points of the acids forming these salts,
With ammonium salts of similar structural type, the thermal
The character of the thermal decomposition of aninionium salts
Table II
Relation of the Corrosive Action of Ammonium Salts
to the Volatility of the Acids Forming Them
Studied Phenomena
Corrosive Action (%)
NHl~C1
2.12
Salts
NH4Br (NH )2CO3 NHS O3 (NH)2S0
1.71 11.10 O41. 0.37
0.,8
Boiling Point of p85 -68.7 .65 8L. 338* 2O
V acid (Deg. C.)
(*Boiling Point of a 98.3% mixture)
stability augments the power of the acid from which they are formed.
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(Decomposition)
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I n the acid series HJ-'HBr-HCl' lL the thermal stability dthi n'
fishes from HJ to HF (3). On this basis one could expect the aggres-
ive influence of these salts to grow in the same order. In the case
s
unonium.fluoride, however, we observe a departure from the rule,
of an
apparently explainable through the lesser volatility of HF in compar-
the other haloid hydrides (the boiling point of HF is 1905
a.son with
degyeas centigrade, while that of 11C1 is 85 degrees centigrade.)
Thus the volatility of the acid forming the anion of ammonium
salt is the basic factor determining the extent of corrosive action
of ammonium salts on powdered coppero
The presence of water vapors furthers the decomposition of
ammonium salts. Apparently, the decomposing action of water intensi-
fies as the extent of hydrolysis of .a given salt widens. For instance,
when ammonium carbonate is 80 percent hydrolized, the corrosive
action is 11 or 10 percent. At the same time, when ammonium chloride
is 0.1.E percent hydrolized, the corrosive action is 2.12 percent.
It is evident that these factors -- volatility of the acid,
thermal stability of the salts and their hydrolytic splitting -- do
not exhaust the complexity and variety of the described phenomenon.
Doubtlessly, the hygroscopic qualities of salts and the solubility
of the acid vapors in the liquid adsorption film are also important
factors which must be taken into consideration.
CONCLUSIONS
It is shoran that the volatility of the acid forming an anion
of salt is the fundamental factor determining the corrosive activity
of the salt.
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