CORROSION INHIBITING COMPOSITION AND METHOD

PRODUIT ANTICORROSION, ET SA COMPOSITION

English Abstract

CORROSION INHIBITING COMPOSITION AND METHOD
(D#77,983 -F)
ABSTRACT
A composition which is noncorroding to metals in
contact therewith includes water, an alkylene glycol and/or a
polyoxyalkylene glycol, a polyoxyalkylene amine and substantially
no inorganic nitrite. The polyoxyalkylene amine replaces the
previously used inorganic nitrite to reduce the toxicity of the
noncorroding composition.

Claims

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THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An inorganic nitrite free composition which is
noncorroding to metals in contact therewith comprising water, an
effective amount of a glycol selected from the group consisting of
an alkylene glycol, a polyoxyalkylene glycol, and mixtures
thereof, and an effective amount of a polyoxyalkylene amine of the
formula:
<IMG>
wherein x is a number between about 18 and 19, and y is a number
between about 2 and 3.
2. The composition of claim 1 wherein said polyoxyalkylene
amine comprises from about 0.1 to about 15 percent by weight of
said composition.
3. The composition of claim 1 wherein said polyoxyalkylene
glycol comprises a mixture of oxyethylene and oxypropylene in the
ratio by weight of between about 50/50 and about 90/10.
4. The composition of claim 1 and further comprising at
least one additive selected from the group consisting of
pelargonic acid, an alkali hydroxide and tetra sodium EDTA.
5. The composition of claim 1 wherein said alkylene glycol
comprises from 1 to about 5 carbon atoms.

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6. The composition of claim 1 wherein said glycol comprises
ethylene glycol and a polyoxyalkylene glycol comprising a glycol
formed from oxyethylene and oxypropylene in a weight ratio
between about 50/50 and about 90/10.
7. The composition of claim 1 wherein said water comprises
from about 10 to about 25 percent by weight, said glycol comprises
from about 90 to about 5 percent by weight, and wherein said
polyoxyalkylene amine comprises from about 0.3 to about 10 percent
by weight.
8. A method of preventing the corrosion of metals in
contact with an aqueous composition and simultaneously eliminating
the inorganic nitrite content thereof comprising the step of
replacing the inorganic nitrite of said aqueous composition
comprising water, a glycol selected from the group consisting of
an alkylene glycol, a polyoxyalkylene glycol and mixtures thereof
with an effective quantity of polyoxyalkylene amine of the
formula:
<IMG>
wherein x is a number between about 18 and 19, and y is a number
between about 2 and 3.
9. The method of claim 8 wherein said polyoxyalkylene amine
comprises from about 0.1 to about 15 percent by weight of said
composition.

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10. The method of claim 8 wherein said polyoxyalkylene
glycol comprises a mixture of oxyethylene and oxypropylene in the
ratio by weight of between about 50/50 and about 90/10.
11. The method of claim 8 and further comprising at least
one additive selected from the group consisting of pelargonic
acid, an alkali hydroxide and tetrasodium EDTA.
12. The method of claim 8 wherein said alkylene glycol
comprises from 1 to about 5 carbon atoms.
13. The method of claim 8 wherein said water comprises about
10 to about 25 percent by weight of said composition, said glycol
comprises from about 90 to about 5 percent by weight of said
composition and wherein said polyoxyalkylene amine comprises from
about 0.3 to about 10 percent by weight of said composition.

Description

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CORROSION INHIBITING COMPOSITION AND METHOD
(D~77,983-F)
BACKGROUND OF THE INVENTION
This invention relates to a corrosion inhibiting
composition and method and more particularly, to the use of a
polyoxyalkylene amine for such inhibition.
Aqueous systems have been preferred for many applica-
tions which are subject to high heat or sparks. Such applica-
tions included hydraulic fluids for use in systems involving a
high risk of fire, and quenchants used to cool heated metals
during various metal working processes where the hot metals can
ignite hydrocarbon based quenchants. However aqueous systems are
corrosive towards metal particularly ferrous metals. One type of
aqueous system presently in use comprises water, an alkylene
and/or a polyoxyalkylene glycol and one ox more other additives
to impart corrosion inhi~ition to the system~ Such aqueous
systems can be used as quenching mediums for heat treating metal
and for hydraulic fluids.
In a previously used aqueous ~ystem, which is noncor-
roding to metals, an inorganic nitrite, such as sodium nitrita,
was used to impart improved corrosion inhibition to the aqueous
alkylene glycol system. However, nitrites are somewhat toxic and
in recent years there is a movement towards the removal of
nitrites and their replacement with other materials to impart
corrosion inhibition to the aqueous system.

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A further problem with the previously used aqueous
systems is their tendency to foam on the introduction of air or
other gases into the system and the lack of corrosion inhibition
in the air or gas space above the aqueous systems which is
subject to corrosion.
U.S. Patent No. 3,928,219 sets forth the use of
lubricating oil compositions containing tetrapoly(oxyethylene)
poly(oxypropylene) derivatives of ethylene diamine having
molecular weights in the range from about 1650 to 15,000. The
patent states that these lubricating oil compositions exhibit
improved rust inhibition properties as well as sludge elimina-
tion.
U.S. Patent No. 3,235,501 sets forth the inhibition of
foaming in oil compositions containing materials which normally
tend to promote foaming of the composition. The additives
comprise a small amount of a polyalkyl oxylated aliphatic amine.
In an article by E. Ludosan et al In Rev. Coroz. 1972,
2(1) t 39-44 (Rom), Chemical Abstracts 19315p (1973),
the use of poly(ethoxyamines) is set forth as inhibiting the
corrosion of steel in HCl or H2SO4 solutions.
I.A. Mamedov et al in Azerb. Khim. Zh. 1977, (6~, 49-50
(Russ), Chemicals Abstracts 89: 63203b (1978) sets forth the
corrosion inhibition of steel by polyoxyethyleneamines under
conditions encountered by steel equipment in crude oil
extractions. The use of thesP amines broadened the range of

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corrosion inhibitors for steel in the electrolyte-hydrocarbon
systems.
US Patent No. 3235501 sets forth the use of other
amines containing a hydrophobic group of at least six carbon
atoms.
SUMM~RY OF THE INVE:NTION
It has now been discovered that the inorganic nitrit~
previously used in a corrosion inhibited composition comprising
water and an alkylene glycol and/or polyoxyalkylene glycol can be
replaced with a class of polyoxyalkylene amines. Further, such
polyoxyalkylene amines not only impart corrosion inhibition to
the liquid in contact with the metal but also impart corrosion
inhibition to the metal in contact with the vapors of the aqueous
composition. Aqueous compositions containing the glycol and the
polyoxyalkylene amine also exhibit a low foaming tendency while
previous additives had to be added to many corrosion inhibited
compositions to reduce the foaming of such compositions which
foaming is generally detrimental to the functioning of the fluid.
Preferred Embodiments of the Invention
The corrosion inhibited composition of the present
invention preferably comprises an effective amount of an alkylene
glycol and/or a polyoxyalkylene glycol, water, and an effective
quantity of one or more of the preferred polyoxyalkylene amine
and substantially no inorganic nitrite. Such a composition is
noncorroding to metals, is generally nontoxic due to the absence

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of nitrites, is low foaming and can also inhibit the corrosion of
metals in contact with the vapors of the composition.
The composition preferably comprises at least about 5
percent by weight of the glycol, at least about 0.2 percent by
weight of the polyoxyalkylene amine with the remainder being
wat~r. Other minor quantities of additives can also be used to
achieve desired results for specific applications of the compo-
sition of the present invention.
The glycol and/or polyoxyalkylene glycol can comprise
from about 5 to about 90 percent by weight of the composition and
more preferably from about 40 to 70 percent by weight of the
composition. One preferred glycol comprises an alkylene glycol
wherein the alkylene group has from 1 to about 5 carbon atoms.
Examples of such glycols are ethylene, propylene, butylene and
pentylene glycols. Water soluble polyoxyalkylene glycols
suitable for the present invention are known compounds and are
viscous liquids of high molecular weight ranging from about 600
to well over 100,000 and of high viscosity, for example, 100,000
SUS at 100F. One preferred group of polyalkylene glycols are
polymers formed of oxyalkylenes such as oxyethylene and higher
oxyalkylene groups such as oxypropylene and oxybutylene. Such
polymers are liquids at ordinary room temperature and are
generally mixable with water at ordinary temperatures. The most
preferred polyalkylene glycols are polymers formed from
oxyethylene and oxypropylene having a ratio of about 50/50 ko

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about 90/10 by welght and having a molecular weight ranging from
about 2,000 to 20,000. These polyalkylene glycols may be made in
a known manner by reacting a mixture of oxyethylene and
oxypropylene or higher oxyalkylene in the weight ratio of from
about 50/50 to about 90/10 with a compound having at least 1
active hydrogen atom and up to as many as 6 such active hydrogen
atoms. Suitable compounds are water, monohyd.ric alcohol,
dihydric alcohols, trihydric alcohols, and polyhydric alcohols.
The polyoxyalkylene amines useful in the composition of
the present invention are comprised of 3 portions, an aliphatic
portion generally at one end of the molecule either branched or
straight chained having one or more carbon atoms but most
preferably less than 6 carbon atoms, a repeating unit of either
oxyethylene (ethylene oxide) and/or oxypropylene tpropylene
oxide) and an amine function generally at the end opposite from
the aliphatic function. Diamines generally have an amine
function ~t both ends of the molecule while in triamineæ and
higher the amine function is at various portions of the molecule.
Monoamines are presently preferredO Generally, the
polyoxyalkylene amine useful in the composition of the present
invention is formed by reacting an aliphatic alcohol either
straight chain or a polyhydric alcohol with oxyethylene and/or
oxypropylene to form the polymer. The oxyethylene and
oxypropylene are preferably in the weight ratio of between about
4:1 and about 25O1; most preferably between about 5:1 and about

1~:6~ 9
20:1~ The resulting polymers are then rsacted with ammonia and
hydrogen under catalytic conditions to produce the desired amine.
The properties of th~ amine depend upon the number of carbon
atoms in the alcohol used to form the amine and the number of
oxyethylene and/or oxypropylene units used.
The molecular weight of the polyoxyalkylene amine can
vary from about 200 or less to several thousand. The preferred
polyoxyalkalene amine can have a molecular weight between about
300 and about 3,000, most preferably between about 700 and about
1500. The amine can be primary, secondary or tertiary, if
polyhydric alcohols are used the resulting amine can have
multiple amine groups. The preferred primary polyoxyalkylene
amine has the following formula:
IH3
R-(OCH2CH2)x-(OCH2CH)y NH2
In the above formula, R comprises a methyl or an alkyl group.
The number of oxyethylene and oxypropylene repeating units in the
polymer is represented by x and y. In preferred amines x can be
between 1 and about 50 and y can be between 1 and about 5. In
the presently preferred polyoxyalkylene amines, R can comprise a
methyl group with x=10 and y=2 (molecular weight about 600), or
x=18-19 and y=2-3 (molecular weight about 1,000), or x=32 and y=2
(molecular weight about 1,500), or x=41 and y=3 (molecular weight
about 2,0003, R can also comprise a linear alkyl group of 4
carbon atoms with x=9 and y=2 (molecular weight about 600).
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It is to be understood that these are presently the
most preferred and other similar polyoxyalkylene amines o-f
simllar structure and of similar molecular weight are also within
the scope of the present invention.
The polyoxyalkylene amine can comprise from about 0.1
to about 15 percent by weight of the composition. Preferably,
the polyoxyalkylene amine comprises from about 0.3 to about 10
percent by weight of the composition with about 0.5 being
presently most preferred. Water, the other major component of
the composition r can comprise upwards of 60 percent by weight.
Water preferably comprises from about 10 to 35 or about 10 to 25
percent by weight of the composition.
The present invention not only includes the above
composition containing substantially I10 inorganic nitrites but
also includes a method of preventing the corrosion of metals in
contact with aqueous systems and simultaneously eliminatiny the
presence of toxic inorganic nitrites in such corrosion inhibited
aqueous systems. The method of the present invention comprises
reducing the nitrite content of an aqueous composition comprising
.water, alkylene glycol and/or polyalkylene glycol by the step of
replacing the inorganic nitrite with a polyoxyalkylene amine.
The.composition and method of the present invention
will be better understood from the following examples which are
merely illustrative and not meant to limit the .invention in any

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way. All percentages unless otherwise indicated, are percentages
by weight.
EXAMPLE I
A corrosion-inhibited composition which is useful as a
hydraulic safety fluid was formed by combining about 30 percent
by weight watex, about 42.5 weight percent ethylene glycol, about
27 percent by weight of an aqueous polyalkylene glycol which was
formed of 75 percent oxyethylene groups and 25 percent
oxypropylene groups by weight (which aqueous polyalkylene glycol
comprised about 67 percent by weight of the polymer and about 33
percent by weight water) and about 0.5 percent by weight of a
polyoxyalkylene amine having the following approximate formula:
1 3
3(0CH2CH2)x(OcH2cH2)yNH2
Wher~ x is a number between about 18 and 19, most preferably
about 18.6 and y is a number between about 2 and 3, most
preferably about 2.6. The values for x and y are not exact since
the amine is a mixture of compounds and the preferred average
value of x and y are set forth above. The composition also
comprised about 0.35 percent by weight of an alkali hydroxide
~ere potassium hydroxide, about 0.05 weight percent tetrasodium
EDTA and about 1 percent by weight pelargonic acid.

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The corrosion inhibiting properties of this composition
was compared to that of a commercially available hydraulic safety
fluid which had approximately the same concentration of
ingredients with the exception that the polyoxyalkylene was
replaced wlth sodium nitrite and a quaternary ammonlum inhibitor.
Both fluid compositions exhibited the same low corrosion
properties desir~d of these hydraulic fluids and they passed all
corrosion tests.
One of the corrosion tests passed by both the prior art
composition and the composition of the present invention wherein
the sodium nitrite was replaced with the polyoxyalkylene amine
was a Modified ASTM D665 Rust Test. In -this modified test a
cylinderical steel specimen was polished by successive grinding
with 150 and 240 grit aluminum oxide abrasive cloth. The steel
specimen was inserted in a rubber stopper equipped with a hole.
Sufficient quantity of the fluid composition to be tested was
charged to a flask such that when the specimen was in place in
the flask, approximately one-half of the specimen was immersed.
The flask, test solution and specimen were placed in an oil bath
maintained at a temperature of about 140F. (55.5C)~ The
portion of the steel specimen subjected to vapor and the portion
subjected to the liquid portion of the fluid were rated after the
first hour for evidence of rusting and again after completion of
the first 24 hour test period. The rating system used was
similar to that defined by MIL-L-24467. This rating system

1 2~45;39
defined no rust as being no rust visible on the specimen. Trace
rust as being 1-6 rust specks of no more than 1 millimeter in
diameter, light rust as being 7-12 rust specks, moderate rust was
an overall light rust, and heavy rust was an overall heavy rust
or heavy rust spots.
A Vapor Corrosion Reflux Test which was based on
MIL-L-24467 (ships) testing procedure for vapor corrosion was
conducted on both the composition of the present invention and on
the prior art composition. In this test two mild carbon steel
specimens were polished, one was then suspended above a flask
containing about 5~ milliliters of the composition as above and
one above a flask containing the prior art composition. The
compositions were then heated in an oil bath for 48 hours at
180F (82C). The specimens were then rated as per the previous
paragraph for rust. Again, the composition of the present
invention and the prior art composition exhibited the same low
corrosion and passed the test.
The composition of the present invention was tested for
foaming according to Test Method ASTM D 892 Sequences I, II and
III. In the Sequence I Test approximately 200 milliliters of
sample were decanted into a beaker and were heated to about 49C
and then allowed to cool to about 24C. The cooled sample was
then poured into a 1000 milliliter cylinder until the liquid
level was at the 190 milliliter mark. The cylinder was then
immersed to at least the 900 milliliter mark in a bath maintained
,
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3~
at about 24C. A diffuser stone and air inlet tube were then
inserted into the cylinder and into the sample. About 94
milliliters of air per minute were forced through the stone for
about 5 minutes. At the end of the period the air flow was shut
off and the total volume of foam was measured and then measured
again after ten minutes of waiting.
In the Sequence II Test, a second portion of sample was
poured into a 1000 milliliter cylinder until the liquid level was
at the 180 milliliter mark. The cylinder was immersed into a
bath maintained at a temperature of about 93.5C. A diffuser
stone was then immersed into the sample in the cylinder and the
test was carried out as in the Sequence I Test.
In the Sequence III Test, any foam remaining after the
Sequence II Test was collapsed, the sample was then allowed to
cool to a temperature below about 43.5C and then further cooled
to a temperature of about 24C. A gas diffusex stone was
inserted and the test was then carried out as in Sequence I and
II. The composition of the present invention produced low or no
foaming in all sequences. Low foaming is important for hydraulic
fluids as well as for many other compositions.
EXAMPLE II
A composition which was to be used as a quenchant was
made by combining about 22.6 percent by weight of water, about
76.85 percent by weight of the polyalkylene glycol of Example I
and about 0.5 percent by weight of the polyoxyalkylene amine of

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Example I~ This composition was compared with a commercially
sold quenchant having less than about 5 percent by weight of
sodium nitrite and no polyoxyalkylene amine. The prior art
composition is set forth in U. S. Patent No. 3,220,893.
Both the composition of the present invention and the
prior art composition passed the Modified D665 Rust Test, vapor
phase and liquid phase.
The above examples are for illustrative purposes and
not meant to limit the invention in any way. Variations and
modifications of the above are possible without going outside of
the scope of the present invention which is set forth in the
following claims.
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