Note: Descriptions are shown in the official language in which they were submitted.
Express Mail No. MB17988469~
October 11, 1989 2561B
~ILICA~E-FREE CODL~NT CO~POSITIO~
~AYING CORROSION IN~IBITOR ~EREIN
8ACKGROUND O~ T~E IffVEN~ION
1. Field of the Invention
The pre~ent invention pertain~ to the field of
coolant compositions. More apecifically, the present
invention pertains to coolant compositions which contain
corrosion inhibitors. Corro~ion inhibitors are u~ed in
liquids which contact metals, the corrosion inhibitors
reducing the rate of corrosion of the metal by the liquid.
Commonplace examples of such liquids are engine coolants
(such as anti-freeæe formulations) as well as hydraulic
fluids. More specifically, the pre ent invention relates to
the uje of phosphate esters of organic alkyl polyoxyQthylene
polymers and phosphate esters of polyoxyethylene/polyoxy-
propylene copolymers for imparting corrosion inhibition to
liquid compositions. Furthermore, the liqui~ compositions
of the present invention are aqueous composition~.
.. . . ... ~ .... .. . . ., ., .. ~ .... .. . . . . . .. . . .
J j; 1~
2. Description of the Prior Art
Several members of the groups of inhibitors
described herein have been ~ade and sold by BASF Corporation
for more than one year. However, each of these ~pecies was
designed and sold for i~s surfactant characteristic~, and
Applicants have no knowledge that any of these surfactants
ever have been utilized in coolant compositions.
The closest prior art of which ~pplicants are
aware i~ U.S. 3,931,029. This p~tent, which pertains to
corrosion inhibited anti-freeze compositions, discloses the
use of particular anti-foam agents, which anti-foam agents
m~ include silicone anti-foam agents, aliphatic alcohols of
10 carbon atoms or more, organic pho~phates and phthal~te~,
and convent~onal nonionic synthetic detergents. The '029
patent refers generally to silicDne antifoam agents, as well
as antifoam a~ents comprising alcohol~ of 10 carbon atoms or
more, organic phosphates and phthalates, and conventional
nonionic surfactants. Mor~ particularly the '029 patent
refers to alkoxylated nonionic synthetic detergents includ-
ing polyoxyalkylene adducts of hydrophobic bases. 5pecifi-
cally, mentioned are polyoxyethylen~ esters of higher fatty
acids, ethylene oxide adducts of higher aliphatic alcoh~ls~
conjugated polyoxya}kylene compounds, polyoxypropylene-
... , .. . , . . . . . . . _ . . .. . . . . . .
~tij,i,
polyoxyethylene block copolymers, and ethoxylated andpropoxylated adducts of ethylene diamine. The '029 patent
nowhere specifically mentions phosphates of these particular
organic compounds.
Although the '029 patent utilizes anti-f~amin~
agents related to the corrosion inhibition agents utilized
in the present invention, the '029 patent repeatedly states
that the ethylene oxide content of the anti-foam agent
should not exceed 20 percent by weight of the molecule. In
stark contrast, Applicants of the present invention have
found that when the ethylene oxide residue conQtitutes less
than 20 percent by weight of the total molecular weight of
the molecule, the molecule is rendered substantially
insoluble in the agueous coolant formulation. Rather, the
present invention requir~s a minimum of at least 20 percent
by weight of the total molecule of ethylene oxide residue,
this higher percentage rendering the molecule soluble so
that the corrosion inhibition ch~racteri~tics are pro-
duced. Furthermore, ~he present invention is directed at
phosphate esters of these polymers, and the '20~ patent
nowhere even mentions the inhibitors u~ed in the composition
of the present invention.
~t3
U.S. 4,686,058, entitled l'Thickened Water Based
Hydraulic Fluids", states that certain compounds act as
thickening agents when used in hydraulic fluids. The '058
patent states that the primary purpose of increasing the
viscosity of the hydraulic fluids is to reduce leakage of
the fluid in the mechanical equipment utilized. The '058
patent refers to thickeners of the polyglycol type. More
specifically, the '058 patent refers to polyoxyalkylene
polyols having a molecular weight of about ~,000 to 40,000,
prepared by reacting an alkylene oxide with linear or
branched chain polyhydric alcohol. Furthermore, the '058
patent states that the hydr~ulic fluid having the polyether
polyol thickeners will lose viscosity unless there i~ ~lso
present a viscosity loss reducing compound. ~he viscos~ty
loss reduc~ng compounds suggested in the '058 patent include
et~ylene glycol, propylene glycol, propylene glycol polymers
and ~opolymers containing at least 50 percent by weight
oxypropylene groups, a dimercaptothiadiazole, neodecanoic
acid, hindered phenol ~ntioxidants, and ~ixtures thereof.
The ~058 pa~ent also refer~ to propylene glycol polymers or
~opolymers having molecular weight~ of from 75 to 5000, the
copolymers being heteric or block c~polymers. ~he '05~
patent also re~ers tG phosphate esters of polyoxyethylated
alcohols, wherein the residual alcohol moieties consist of
linear or branched chain alkyl groups oP from 6 to 30 carbon
atoms.
The composition of the present invention ~iffers
from the '053 patent in that the composition of the present
invention pertains to coolant~, rather than hydraulic
fluids. Purthermore, the composition of the present
invention does not compri~e such thickeners as polyoxy-
~lkylene polyols having a molecular weight of about 2000 to
40,000. Since it is apparent that the '058 patent utilizes
viscosity loss reducing compounds for the purpose of
preeerYing the thickening characteri~tic of the polyoxy-
alkylene polyols, if such polyoxyalkylene polyols are not
present, as in the case of the present invention, there is
no need for the viscosity loss reducing agents sug~ested by
the '058 patent. The present invention pertains to
coolants, rather than to hydraulic fluids. There i~ no need
to increase the viscosity of a coolant. Rather, it would be
hi~hly undesirable to do so.
BRIEF SUMMARY OF T~E INVENTIO
The present invention pertains to a silicate-free
coolant composition which comprises at least one corr4sion
inhibitor. The coolant composition comprises at least one
member select~d from the group consi~tin~ of:
A. phosphate esters of ethylene diamine ini~iated polyoxy-
ethylene/polyoxypropylene copolymers. ~hese copolymers may
be block copolymers or heteric copolymer6. The~e copolymers
have the following general formula:
po4(EO)y ~(PO)X / ~P~ (EO)y _pO4 2
NC2H4N ~
PQ4-~EO)y ~~PO)x / (PO)X -~EO)y _pO4 2
Ir, ~his formula, "EO" represents an ethyle~e oxide residue,
while "PO" represents an propylene oxide residue. Y is
selected so that the total weight percent of ~O in the
copolymer is from greater than 20 to about 40, based on the
molecular weight of the copolymer. The molecular w~ight of
the PO in the copolymer is from ~bout 1500 to about 7000.
This copolymer is present in the coolant compo-
5ition at a concentration of from about 0.05 weight percent
to ~bout 2 weight percent, based on the weight of the neat
composition.
. . .
~,~ t,~ '~J ~ ;.J ~ ,J
(B) phosphate esters ofpolyoxypropylene/polyoxyethylene
copolymers, which copolymers may be block copolymers or
heteric copolymers. The copolymers are of the following
general formula:
2po4 (EO)y -(PO~ - (EO)y - po~
wherein "EO" represents an ethylene oxide residue, and
wherein "PO" represents a propylene oxide residue, and
wherein Y is selected so that the total weight percent ~f EO
in the copolymer is from greater than 20 to about 80, based
on the molecular weight of ~he copolymer. The ~olecular
weight of the PO in the copolymer is from about 950 to about
4000. The copolymer i5 present in the coolant composition
at a concentration of from about 0.05 weight percent to
about 2 weight percent, based on th~ weight of the neat
composition.
--7--
.. , -
f) ~ `J ~ 'iJ.'
(C) phosphate esters of a polyoxyethylene/polyoxypropylene
copolymers, which copolymers may be block copolymers or
heteric copolymers, these copolymers being of the following
general ~ormula:
-2po ~ ~PO)X ~ (EO)y ~ (PO)X 4
whereir. "EO" represents an ethylene oxide residue and
wherein "PO" represents a propylene oxide residue, and
wherein X is selected so that the total molecular weight of
the PO in the copolymer is from about 1000 to about 3100,
based on the molecular weight of the copolymer, an~ wherein
the weight percent of the EO in the copolymer i~ from
greater than 20 to about 80 percent by weight, based on the
molecular weight of the copolymer. ~he copolymer i~ present
in the composition at a concentration from about 0~05
percent ~y weight to about ~ percent by weight, based on the
wei~ht of the neat composition.
,. ~ . .. .. . . . . .. . . .. . . . .... . . ..
3 f J ~
(D) phosphate esters of alkyloxyethylate polymers of the
general formula:
R - O - ~EO)y _ po4 2
wherein R represents a linear or branched alkyl moiety
having from 6 to 18 carbon atoms, and wherein "EO" repre-
sents a residual ethylene oxide moiety, and wherein the
alkyloxyethylate polymer has an average molecular weight of
from about 200 to about 3000 and an 2thylene oxide residue
content of from greater than 20 to about 80 weight pPrcent,
based on the molecular weight of the polymer. The concen-
tration of the alkyloxyethylate polymer in the coolant
composition is from about 0.05 percent by weight to about 2
percent by weight, based on the weight of the neat compo-
sition.
(E) phosphate esters of alkylphenol oxyethylate polymer~ of
the following ~eneral formula:
~,' "JJ 3~,
~ - O - IEO)y - H
wherein R is a branched or linear alkyl moiety having from 4
tO 12 carbon atoms, and wherein EO represents a residual
ethylene oxide moiety, and wherein the polymer has an
ethylene oxide residue content of from about 40 to about 90
weight percent, based on the molecular weight of the
polymer. The conc~ntration of the alkylphenol oxyethylate
polymer in the coolant composition should be from about 0.05
weight percent to about 2 weight percent, based nn the
weight of the neat composition.
.
(F) phosphate esters of fatty alcohol heteric ethylene-
oxide/propyleneoxide copolymer of the following general
formula:
R - O - ~ ~PO) , (EO) l_ po~ 2
L F l-FJ
-10--
wherein R represents a branched or linear alkyl moiety
having from 6 to 18 carbon atoms, and wherein E0 represents
a residual ethylene oxide moiety, and wherein P0 represents
a re~idual propylene oxide moiety. F and n are ~elected so
th~t the copolymer has a resulting weight percent E0 of from
greater than 20 to about 95, based on the molecular weight
of the copolymer. In the heteric block, F has a value of
fronl about 0.1 to about 0.99. The concentration of the
copolynler present in the composition is from about 0.05
weight percent to about 2 weight percent, based on the
weight of the neat composition.
The specific member or members of the above group
Gf inhibitors, as well as the concentration of the inhibitor
(Gr inhibitors), is selected so that the resulting liquid
composition exhibits a passivation current o~ less than a
standard reference composition, as is described below.
Applicants have surprisingly found that the above
group of polymers produces advantageous corrosion inhibition
of for aluminum exposed to coolant compositions. 80th Table
I and Table II, below, indicate the advantageous effect~ of
usi.ng these polymers in coolant compositions. Furthçrmore,
Applicant~ have discovered that the above group of poly~er~,
when utilized in liquid co~positions used ~s coolants,
produce highly advantageous results with respect to the
corrosion inhibition of aluminum.
Prior art anti-freeze compositions ~ave tradition-
ally utilized silieates to provide a hi~h degree of ~orro-
sion inhibition, so that metal parts in contact with the
coolant are not subjected to a high ~egree of corrosion due
to contact with the coolant. ~owever, it is believed that
the presence of silicate in coolant Eormulations may result
in deposits of silica gel particulates which have a detri-
mental effect upon pump seals, etc. The organic polymeric
phosphate ester inhibitors of the present invention enable
the complete elimination of the silicates from the compo-
sition, so that the deposition of ~ilica g21 i5
eliminated. It has unexpectedly been found that coolants
employing the inhibitors of ~he present invention ~ay
achieve a correspondingly high degree of corrosion inhib-
ition of aluminum, without silicates.
DETAILED DESCRIPTION OF THE PR~FERRED E~BODI~ENTS
The coolant composition of the pre~nt ~nvention
employs one or more of a ~pecific group of pho~phate ~ster6
og polyoxyethylene/polyoxypropyl~ne copolymers ~nd phospha~e
-12-
'; ' ~ 1 ' " i,
esters of alkyl polyoxyethylene polymers, for the purpose ~f
reduci~g the ~otential f~r the coolant composition tv
corrode metals. It has been found that each of these groups
effectively produce corrosion inhibition when the agent is
present within a certain concentration range. Furthermore,
it has been unexpectedly found that these corrosion inhib-
ition agents effectively reduce the corrosive character of
the coolant when these agents are used in the absenoe of
silicates.
Certain phosphate esters of ethylene diamine
initiated polyoxyethylene/polyoxypropylene copolymer~ may be
used as corr~sion inhibitors. These copolymer6 ~ay be block
copolymers or heteric copolymer~. These polymer~ are well
known to those ~f skill in the art, and can be produced in
acoordance with methods described in 2,979,528, which is
here~y incorporated by r~ference. U.S 3,986,922 describes
how to produce the phosphate esters of the~e poly~er~, and
is accordingly also incorporated by reference. Generally,
the non-phosphated polymers are char~cterized in that they
comprise an ethylene oxide residue (-C~-C~-O-) of from
greater than 20 weight percent to about ~D weight percent,
based on the ~olecular weight of the polymer ~ole~ule.
~owever, it i~ preferable that the molecule compri~es rom
-13-
. . . .. . ,, . ... ....... ... .. .... . , .. . . _ ... ..... . . . . ~ . . . . . . .. . . . .
about 30 to about 40 weight percent ethylene oxide residue,
and it is most preferred that the polymer molecule comprise
~bout 3Q weight percent ethylene oxide residue~ In general,
the average molecular weight of the polyoxypropylene in the
copolymer molecule averages from about 1500 to about 7500,
Hnwever, it is preferred that the polyoxypropylene in the
~op~lymer have a molecular weight on the average of from
about 4~00 to about 7000, and it is most preferred that the
average molecular weight of the polyoxypropylene in the
copolymer is about 6000. In general, the coolant compo-
sition should comprise copolymer in an amount from about
0.05 weight percent to about 2 weight percent, based on the
weight of the neat composition.
The coolant composition of the present invention ~i
may comprise phosphate ester~ of polyoxypropylene~polyoxy-
ethylene copolymers, which copolymer~ may be block copoly-
mer~ or heteric copolymers. These polymers are also well
known to those of skill in the art, and can be produced in
accordance with methods described in U.SO 2,674,619, which
i6 hereby incorporated by referenceO Again, U.S. 3,9R6,Q22
teaches methods for phosphorylation oP these polymer , and
i~ accordingly incorporated by reference. In general, these
copolymers have an ethylene oxide residue content of from
.. . . , . . .. .. ........ . _._ .. . . .. . . . . . ... . ... . .
greater than 20 weight percent to about Bn weight percent,
based on the molecular weight of the cop~lymer mol~cule.
~owever, i~ is preferred that the ethylene oxide residue
content is from greater than 20 weight percent to about 40
weight percent, and it is most preferred that the ethylene
oxide residùe content is about 30 weight percent~ based on
the molecular weight of the copolymer molecule. In general,
the molecular weight of the polypropylene oxide residue in
the copolymer is from about 950 to about 4000. More
preferably, ~he molecular weight of the propylene oxide
residue is from about 1100 to about 2000, and mo~t prefer-
ably the molecular weight of the propylene oxide residue is
around 1620. In general, the concentration of the polyoxy-
propylene/polyoxyethylene copolymer in the coolant compo-
sition is from about 0.0~ weight per~nt to about 2 weight
percent, based on the weight of the neat coolant compo-
~ition. Most preferably, the concentration of ~he copolymer
corrosion inhibitor in the coolant compo~tion is around 0.2
percent by weight, based on the weight of the neat coolant
composition.
The coolant composition of the present invention
may comprise phosphate ester polyoxyetbylene/polyoxy-
propylene copolymer G4rrOSiOn inhibitor5 which may b~ block
--15--
.. , . ,,, .. . . ~ . ,, .. ~ , . . . .. .. . ..
copolymers, or heteric copolymers. In general, these
copolymers have an e~hylene oxide residue content of from
~reater than 20 welght p~rcent to about 80 weight percent,
based on the molecular ~eight of the copolymer. More
preferably, these copolymers have an ethylene oxide residue
content of from greater than 20 to about 40 weight percent,
and most preferably these copolymers have an ethylene oxide
residue content of about 30 weight percent. In general, the
phosphate ester of the polyoxyethylene/polyoxypropylene
copolymer has a propylene oxide residue having a molecular
weight of from about 1000 to about 310D. More preferably
~he molecular weight of the propylene oxide residue i~ from
~bout 1500 to about 25Q0, and most preferably the molecular
w~ight is about 2000. The concentration ~f the polyoxy-
ethylene/polyoxypropylene copolymer in the coolant compo-
sition is, in general, from about 0~05 weight percent to
about 2 weight percent, based on the weight of th~ neat
coolant composition. Preferably the concentration of the
copolymer in the coolant is from about 0~1 wei~ht percent to
about 0.5 weight percent, neat basis. ~ost preferably the
copolymer is present at a level of about 0.2 weight percent,
ne2t basis.
-15-
3 $~ ~
The coolant composition of the presen~ invention
may comprise phosphate esters of alkoxyethylate polymers.
ln general, the alkoxyethylate polymers use~ul as corro~ion
inhibiting agents in the present invention comprise a linear
or branched alkyl moiety having from 6 to 18 carbon atoms,
inclusively. More preferably, the alkyl moiety has from 10
~o i3 carbon atoms, inclusively. These polymers are also
well known to those of skill in the artt and can be produced
in accordance with methods described in U.S. 4,210l764,
which is here~y incorporated by reference. The phosphate
es~ers of these polymers may be produced by the general
method described in U.S. 3r986,922 which has been herein
incorporated by reference. The alkoxyethylate polymers
further generally comprise residual ethylene oxide in a~
amount from greater th~n 20 weight percent to about 80
weight percent, based on the molecular weight of the
polymer. Preferably the ethylene oxide residue content i~
from greater than 20 weight percent to about 70 weight
percent, and most preferably the ethylene oxide residue
content is around 62 percent. Generally, the alko~yethylate
poly~er is pre~ent in the coola~t composition in an ~mount
of from about 0.05 weight percent to about 2 wei~h~ percent,
based on the weight ~f nea~ coolane ~ompositionu Prefer-
.. ~ . . . . ., . . . . . , . ., . , . . . _ . . .. .. . . . . . . . .
ably, the alkoxyethylate polymer is present in the coolantcomposition in an amount of from about D.l weight percent to
about 0.5 weight percent, neat basis. Most preferably, the
concentration of the alkoxyethylate polymer in the coolant
composition is about 0.2 weight percent, neat ba~is.
In general, the phosphate e~ters of alkylphenol
oxyethylate polymers present as corrosion inhibitors in the
coolan~ composition of the present invention comprise at
least one branched or linear alkyl Moiety having fro~ 4 to
12 carbon atoms, inclusively. More preera~1y, the branched
~r lineax alkyl moieties have from 8 to 10 carbon atoms,
inclusively, and most preferably the branched or linear
alkyl moieties have 10 carbon atoms therein. The phosphate
esters of alkylphenol oxyethylate polymers have either a
~ran~hed or a linear alkyl moiety thereon. ~hese polymers
ar~ also well known to those of skill in the art, and can be
produced in accordance with methods described in:
M.J. Bchick, "Nonionic Surfactants", pp 57, 58, and
92, ~arcel Dekker, Inc., ~.Y., ~1967)
This portion of this publicati~n is h~reby incorporated by
reference. The phosphate esters of these polymers may be
produced by the general method described in U.~ 3,9~6,922
lB-
which has been herein incorporated by reference. Generally,
t~e phosphate esters of alkylphenol oxyethylate polymers
hdve an ethylene oxide residue content of from about 40 to
about 90 weight percent, based on the molecular weight ~f
the polymer. Prefera~ly, the phosphate esters of alkyl-
phenol oxyethylate polymers have an ethylene oxide re~idue
content of from about 54 weight percent to about ~1 weight
percent, and most preferably the ethylene oxide residue
content is about ~ weight percent. The phosphate esters of
alkylphenol oxyethylate polymers are generally pres~nt in
the coolant composition at a concentration of from about
0.05 weight percen~ to about 2 weight percent, ~a~ed on the
weight of the neat coolant composition. M~st preferably,
the concentration of the phosphate e~ters of the alkylphenol
oxyethylate polymers is about 0.~ weight percent, baqed on
the w~ight of the entixe coolant composition.
In general, the phosphate esters of fatty alcohol
heteric ethyleneoxide/propyleneoxide copolymers effective a~
corrosion inhibitors in the coolant composition of the
present invention comprise a branched or linear alkyl ~oiety
having from 6 to lB carbon atom~, inclusively. ~ore
preferably, the branc~ed or linear alkyl moiety has between
lD and 16 carbon atoms. The3e polymer~ are al~o well known
--}~--
,, . , . , . . ~ , .
to those of skill in the art; and can be produced in
acco~dance with methods described in U.S. 3,986,922, which
is hereby incorporated by reference. The phosphate esters
of these polymers may be produced by the general method
described in U.S. 3,986,922, which ha~ been herein i~corpor-
ated by reference. Most preferably, the branched or linear
alkyl moieties present on the fatty alcohol oxyethylate
copolymers comprise a blend of alkyl moieties, the moieties
having from 12 to 15 carbon atoms, inclusively. F repre-
sents the EO fraction in the copolymer~ and F may range from
a~out 0.1 to about 0.99. Prefera~ly, ~ i~ from about 0.5 to
about 0.9 f and most preferably F is about 0.~5. "n"
repr~sents one size of the heteric block unit. ~enerally, F
and n are together selected so that the copolymer has an EO
content of from greater than 20 to about 95 weight percent,
nea~ basis. More preferably, F and n are together ~elected
to yield an EO content of about 25 to about 80 weight
percent, neat basis. Most preferably, ~ and n are together
selected to yield an EO content of about 75 weight percent
neat basis. In general, the copoly~er is prese~t in the
coolant compo~ition at a concentration o~ ~rom about 0.1
weight per~ent to about 2 weight percent~ ba~ed on the
w~ight of the neat coolant co~positionO Preferably the
, , ., . .. , . . . .. ,.. ,, _. ~.. . . . . ........ . .
.
concentration of th~ c~polymer is from about 0 2 weight
percent ~o 0.4 weight percent, neat basis. Most preferably,
the fatty alcohol oxyethylate polymer phosphate ester
concentration is about 0.2 weight percent, based on the
weight of the neat c~olant composition
The coolant composition of the present invention
comprises at least one water-soluble li~uid alcohol as a
freezing point depressant, in addition to the corrosion
inhibitors described above. Furthermore, the coolant
composition of the present invention may further comprise
~ny additional compatible additives known to produce .
advantages in anti-freeze formulations.
The above-described corrosion-inhibiting agents
may be utilized by themselves ~r in combination with other
corrosion-inhibiting agents which are compatible there-
with. Each of the corrosion-inhibiting ~gents described
above is compatible with the remainder of the corrosion-
inhibiting additives described above. ~owever r it i5
~urther contemplated that any cne or ~ore of the above~
described corrosion-inhibiting agents ~ay be utilized n
combina~ion with still further corrosion-inhibiting ~gents
which are compatible with the above-described corroæion-
inhibiting agents. As used herein, the term "compatibility'~
-21-
refers to the preservation of the corrosion-inhibiting
result, as well as the preservation of all of the desired
~hemical species present in the coolant composition.
In general, the corrosion inhibiting agents
utilized in ~he composition o~ the present invention should
be present at a concentration of from about 0.05 weight
percent to about 2 weight percent, based on t~e weight of
the "neat" (i.e. substantially wa~er-free) compos;tion.
More preferably, the concentration of the agents is between
0.05 weight percent and 0.5 weight percent lon a neat
basis), ~nd most preferably the concentration of the agents
is between 0.2 weight percent and 0.4 weight percent, on a
neat basis. Of course, for diff~rent agents, the optimal
concentration is different. The th~oretically opti~al
cGncentration is that concentration at which the critical
micelle concentration is only slightly exceeded, since it
has been found that significant concentration increa es over
the critical micelle concentration have a detrimental ~ffect
upon corrosion inhibition.
In general, the composition of the pre~ent
invention should have a p~ of from about 7 to about 12.
~ost preferably the pH of the composition is ~bout 8.5.
Also, the composition should contain a minimal ~mount of
-22-
, :
. . .
s ~;
~ ,J~
excess phosphate, ~s excess phosphate has been found to be
very agressive (corrosively) against aluminum. As used
herein, the phrase "excess phosphate" refers to phosphate
which is in excess of that phosphate which is part of the
polymeric inhibitor molecule.
As used herein, all of the weight percent figures
(~or the EO content, the corro~ion inhibitor concentration,
th~ PO content, etc.) are based ~olely on the polymer
portion of the molecule, i.e. without consideration for the
phosphate portion of the molecule. In other words, the
added weight of the phosphate group should not be considered
when interpreting the f.igures herein regarding the weight
percent EO, wei~ht percent PO, overall molecular weight r and
concentration of the inhibitor.
~ he phrase "on a neat basis", as used herein,
pertains to the coolant composi~ion with ~ maximum o~ about
5 weight percent water. This small ~mount of water ~prefer-
ably only 2 to 3 weight perc~nt) is n~cessary in order to
S~olubilize inorganic components in the coolant compo-
~ition. Of cour~e, the cool~nt co~position in actual use
optimally comprises about 50 weight percent w~ter.
~ h~ coolant composition of the present invention
is an agueou~-phase composition. Since the preferred
-23-
. . .. . . . . . . . . . .
freezing point depressant is a water-~oluble liquid alcohol,
(i.e. ethylene glycol), the mo~t preferred concentration of
water in the coolant composition is around 50 percent, based
on the weight of the total composition.
As has been described in ~he above recitation of
the corrosion inhibitors to be utilized in the composition
of the present invention, it is both unnecessary and
undesireable to utilize a silicate in combination with the
corrosion inhibitor. Thus, in contrast to compositions
which do not comprise one or more of the above-listed
inhibitors, it has been found that 6ilicate should be
eliminated as a result of the presence of the corrosion
inhibitors described herein. In general, for each of the
above-listed corrosion inhibitors, the optimal concentration
is from about 0.05 weight percent to about 2 weight percent,
based on the weight of the neat composition.
A first preferred coolant composition comprises a
corrosion inhibitor which is a phosphate ester of an
ethylene diamine initiated polyo~yethylene~polyo~ypropylene
copolymer, the copolymer being at least one member ~elected
from the group consisting of block copolymer~ and heteric
copolymers t the copolymer having the following g~neral
formula:
-24-
, .. ... . . , . . ~
~J ~ f, ,J ~
P04 - (EO)y ~ (P)X / (PO)x ~ (EO)y _ po4 2
~ NC2H4N ~
P04 - lEQ)y ~ (P~)x (P~)x (EO)y _ pO4 2
~herein Y is selected so that the total weight percent of EO
is about ~0, based on the molecular weight of the copolymer,
and wherein X is selected ~o that the molecular weight of
the PO in the copolymer is about 4833, and wherein the
ooncentration of the copolymer is from about 0.05 weight
percent to about 0.3 weight percent based on the weight of
the neat composition.
A second preferred coolant composition is
identical to the f irst pre~erred coolant composition
described immediately above, except that Y is ~elected so
that ~:he total weight percent EO in the ~opol3mer i~ abou~
30, based on the molecular weight of the copolymer, ~nd X is
selected ~o that the molecular weight o~ the PO in the
copolymer i~ about 5900.
A third preferred coolant oo~pvsition i8 identical
to ~be firs~ preferred coolant composition de~cribed above,
except that Y is ~elected BQ ~hat ~he ~o~l wei~ht percen~
-25-
. ~, .. , ,.. , . _ . . . ... , . , , . . . ~ , .
of EO in the copolymer is about 40, and X i~ selected ~o
that the molecular weight of the PO in the copolymer is
about 4830, and the concentration of the copolymer in the
composition is about O.S weight percent, based on the weight
of the neat composition.
A fourth preferred coolant composition is
identical to the first preferred composition described
above, except that Y is selected so that the total weight
percent of EO in the copolymer is about 40, and X is
selected so that the molecular weight of the P~ in the
copolymer is about 5910, and the concentration of the
copclymer in the composition is between about 0.1 and about
0.~ weight percent, based on the weight of the neat compo~
sition.
A fifth preferred coolant composition i~ identical
to the first preferred coolant ~omposition described above,
except that Y is selected ~o that the total weight percent
of EO in the copolymer is about 40, based on the molecular
weight of the copolymer and X i8 ~elec~ed 60 that the
molecular weight of ~he PO in the copolymer is ~bout 3750,
and the concentration of the copolymer in the composition is
about 0.5 weight percent, ba~ed on the weight of ~he nea~
co~posiion.
-2~-
._ . . .. . .......... . . ......... .... ........ .. ... . ... .
A sixth preferred coolant composition comprises a
phospha~e ester of a polyoxypropylene/polyoxyethylene
copolymer corrosion inhibitor, which copolymer i~ at least
one member selected from the group consisting of block
copolymers and heteric copolymers, the copolymer being of
the following general formula:
P4 ~ (~)y ~ (PO)X ~ (EO~y - PO4
wherein Y is selected 50 that the total weight percent of EO
in the copolymer is about 40, and wherein X is selected ~o
that the molecular weight of the PO in the ~opolymer i~
about 1970. ~urthermore, the concentration of the polyoxy
e~hylene/polyoxypropylene copolymer in the coolant compo-
sition is from about 0.05 weight percent to about 0.5 weight
percent, based on the weight of the neat composition.
A seventh preferred coolant compo~ition is
identical to the the ~ixth preferred coolant composition,
excep~ that X is ~elec~ed 50 that the total weight percent
EO in the copolymer is about 40 r and X is selected ~o that
the molecular weight of the PO in the copoly~er i~ a~out
-27
.. . , . . , . .; .. . . . . . . . . . . . .. .. . . ...
;J ~ i I J
1290, and wherein the concentration of the copolymer in the
composition is from about 0.05 weight percent to about 0.5
weight percent.
An eighth preferred coolant composition is
identical to the sixth preferred coolant composition~ except
that Y is selected so that the total weight percent E0 in
the copolymer is about 20 and X is selected ~o that the
molecular weight of P0 in the copolymer i~ about 1970, and
the concentration of the copolymer in the composition is
about 0.5 weight percent.
A ninth preferred coolant composition comprises a
corrosion inhibitor which is a phosphate ester polyoxy-
ethylene/polyoxypropylene copolymer, which copolymer
comprises at least one member ~elected from the group
consisting of block copolymers and heteric copolymers, the
copolymer being of the following general formula:
-20 P - ~P)X ~ (EO)y ~ (PO)x P4
-2~-
wherein X is selected BO that the total molecular weight of
the PO in the copolymer i5 about 2570, and wherein Y is
selected so that the weight percent EO in the cop~lymer is
about 20, based on the molecular weight of the copolymer.
The phosphate ester of the polyoxyethylene/polyoxypropylene
copolymer is present in the composition in an amount ~rom
about 0.05 weight percent to about O.S weight percent, based
on the weight of the neat composition.
A tenth preferred coolant composition comprises a
phosphate ester of a fatty alcohol heteric oxyalkylate
copolymer of the following general formul~:
R - O [(PO)F , (EO¦ ] - PO~ ~
wherein the weight percent EO in the copolymer i8 about 68,
and wherein the weight percent PO in the m~lecule is about
1~ weight percent, and wherein the mole~ule h~s a molecular
weight of ~bout 820. ~urther~ore, the ~opDlymer is present
in the composition in an amount from about 0.2 to about 0.4
wei~ht percent, base~ on the wei~ht of the neat co~po~ition.
--;29--
An eleventh preferred coolant composition, this
composition being identical to the tenth preferred compo-
sition, except that the phosphate ester of the fatty alcohol
heteric polyoxyethylene/polyoxypropylene copolymer has a
weight percent EO of about 25 based on the molecul~r weight
of the molecule, and a weight percent PO of about 50, based
on the molecular weight of the molecule, and wherein the
molecule has ~ molecular weight of about 820.
A twelfth preferred coolant composition which is
iden~ical to the tenth preferred coolant composition, except
that the heteric polyethylene oxide/polypropylene oxide
polymer has a weight percent EO of about 40, based on the
molecular weight of the molecule, and the copolymer has a
weight percent PO of about 27, based on the molecular weight
of the molecule, and wherein the molecular weight of the
molecule is about 625.
A thirteenth preferred coolant compo~ition i~
identical to the tenth preferred coolant compo~ition, except
that the fatty alcohol heteric polyethyleneoxide~poly
propyleneoxide polymer has a weight percent EO of about 47,
based on the molecular weight of the molecule, and the
copolymer has a wei~ht perce~t PO o~ about 31 ba~ed pn the
molecular weight of the molecule, and the molecular weight
of the molecul~ i~ about 930.
30-
A fourteenth pref~rred cn~lant composition
comprises an alkyethylate polymer of the following general
formula:
R - O - ~EO)y _ po4 2
wherein R - O - is a decylalcohol re~idue and wherein Y has
an average value of about 6, and wherein the concentration
of the polymer in the coolant is about 0.2 weight percent,
on a nea~ basis. ~urthermore, the concentration of the
polymer in the composition is from about 0.1 weight percent
to about 0.5 weight percent, based on the weight of the neat
composition.
A fifteenth preferred csolant composition is
identical to the fourteenth coolant composition, except that
Y has an average value of about 9.
A sixteenth preferred coolant compo~ition i~
identical to the ~o~rteenth pre~erred coolant compo~ition,
e~cept that ~ - O - is a tridecylalcohol residuet ~nd
wherein Y has an average value of about 8.
... . ..... . . ..
S~ 5 ~J~' '~ ~;/
A seventeenth preferred coolant composition
comprises a alkylphenol oxyethylate polymer of the following
general formula:
R - ~ - O - (EO~y - po4 2
wherein R is an alkyl group having eight carbon atoms
thereon, and wherein Y has an average value of about 10, and
wherein the concentration of the polymer in the coolant is
from about 0.05 weight percent to about 0~5 weight percent,
based on the weight of the neat composition,
Nethod for Determining Degree o~ Corrosion Inhibition
The above-identified corrosion ~nhibition agents
were evaluated to determine the degree to which they
affected corrosion inhlbition. A galvano~tairca~e polar-
ization method was utilized for this evaluation. ~alvano-
s~aircase polari2ation i~ described in the Pollowing,
publications:
-32-
1. S.~. ~irowawa, "Corrosion Moni~oring by
Galvanostaircase Polarization", p. 321 in ELECTRO-
CHEMICAL TECHNIQUES FOR COP~ROSION ENGINEE~ING,
edited R. Baboian, NACE, ~ouston (1986).
2. ASTM G100~89, "Standard ~est ~ethod for
Conducting Cyclic Galvanostaircase Polasization",
19 8 9 ANNUAL BOOK OF ASTM STANDARDS, ASTM,
Philadelphia, (1989)
-33
...... . .. .. ...... ..
The above references are herein incorporated by reference.
The galvanostaircase polarization apparatus consisted of a
recording device (recorder, printer or plotter), a p~lar-
ization cell and a potentiostat which was capable of
outpu~ing a current staircase signal. The polarization cell
consisted of saturated calomel reference electrode, a pair
of graphite counter electrod~s and a working electrode of
3003 wrought aluminum held in a flat specimen holder. One
square centimeter of the aluminum was exposed to the
solution. Upon carrying out the galvanostaircase p~lar-
ization, if the voltage rises immediately when the first
current step is applied, the media is effective in pass-
ivating the aluminum. However, if the media is non-pass-
ivating or slowly- or poorly- passivating, there is no
initial rise in the voltage relative to the corrosion
potential [ECorr)~ but the voltage may b~gin to rise at ~ome
higher current level. In very corrosive media, no ri~e in
volt~ge is observed up to B00 to 1,000 uA/cm2, which are
arbitrary limits of the experiment. The passivation current
iipaSS.n) is obtained by extrapolating the ~teepest part of
the curve to Ecorr
-34-
.. . . . . . ..
A base ooolant (s~lution A) was prepared having
the following composition:
Ethylene glycol, AF GRADE 95.44%
Water 2.00%
Borax 5 H~O 2.00%
HNO~ (70.5%) 0O263
NaN~2 0.10%
Na Tolyl triazole 550%) 0.20
NaOH as re~uired
The galvanostaircase polarization method was applied to the
above-base coolant (i.e. solution A). The aluminum ~howed
no sign of passivation in solution at 180F (82C) (and at a
~1 cf 8.5) as deduced from the observation that the pass-
ivation curren~ was greater than 800 uA/cm2 [See Figure
1). Figure 1 shows the effect of the ~ilicate level on the
passivation current of aluminum. A second bas~ coolant
(~lution B~ was made up according to the formulation o
solution A, e~cept that just enough silicate was added in
order to produce a pas~ivation current of 0 (5ee ~igure
everal potential corrosion inhibiting agents were
~creened in order to determine whether these age~ts have a
p~sitive corro~ion inhibition effect when utili~ed in the
pre~ence of ~ilica~e. A large batch of a Referenoe ~e~t
Solution w~s pr~pared by combining 65 parts of solution B
-3~-
... .
, ~ t,, ~,J, . ~ , "J
and 35 parts of solution A. The re6ulting mixture exhibited
a passivation current at around the mid-point (i.e. at 387
uA/cm2) of the highly silica-dependent portion of the curve
illustrated in Figure 1. The corrosion inhibitors were then
added to this reference test solution, and the change in
passivation current, if any, was de~ermined. If the
addition of the potential corrosion inhibitor lowered the
passivation current relative to the reference passivation
current ~i.e. if the passivation current of the solution
comprising the inhibitor was less than 387 uA~cm2), the
corrosion inhibiting additive was deemed to b~ "synergistio"
with silicate. It is prefer~ed to select a polymer which is
low foaming, high wetting, and which has a relatively high
water solubility, when making the co~positions of the
present invention. Furthermore, it is believ~d that a
higher passivation current corresponds with a lowering of
the corrosion inhibition. It is believed that a lower
passivation current corresponds with a greater degree of
corrosion inhibition. On the other hand, if the pa~ivation
current of the test solution containing the potential
corrosion inhibiting agent was found to be higher ~han the
refer~nce te~t solution value of 3B7 uA/cm2,.the agent was
deemed to be ~antisynergi~tic".
-36
., . .. . . ., . , ,, . ~ , . . .
Table I provides results which indicate the
various degrees to which various agent~ impart a lowering or
raising of the passivation current when added to the
reference test solution. As can be ~een in Table I, a
phosphate ester of a fatty acid heteric ethyleneoxide/-
propyleneoxide copolymer inhibition agent was tested to see
whether they were inhi~iting or non-inhibiting. As can
easily be seen in Table 1, most of the ~gents were found to
be significantly inhibiting only when present in the absence
of silica, but were found to be highly non-inhibiting when
utilized in the presence of silicates.
-37-
. .
--8E~--
,, ,` ., " .,
f'J ~ /; J ii ' J ~
V
~; 5: ~ g
~ ._,,,, CO ._
t) 3 V3 A
o
E-~ (1
Cl
:~ ~n ~ 0 ~0 0
t/~ ,C ~1 ~ O '- O
V~ V_l ~ C
~ 3 ~
Co ~ I .
O ~1
I O O O
N C:~ ~ I ~I t~l
oC
~ V
0 ~1 ~
~L O 3
t .
~1 o 1~
-O ¦ L
E-l x ~ ^
O Q~
Q C ~ ~ co $ a:~
Cl. 0 3
3 c~_
o
O
~ I~
.,, ~ _.
Ja ~ ~9
~: ~ I Ll~
C 03 000
.
I
1--
O
~L~ J
~, ~ o Q~
O_~ 9 ~ C e
o
~C C~ O ~ L C~ ~r
_ .
f~9 ~
The Pump Test
A standard test method was ca~ried out for testing
cavitation errosion-corrosion of an aluminum automotive
coolant pump. This method is describe~ in the following
publication:
~STM D 2809-83, "Standard Test ~ethod ~or
Cavitation ~rrosion-Corrosion Characteristic oF
Aluminum Pumps With Engine Coolants", 1988 ANNUAL
BOOK 0~ ASTM STANDARDS, ASTM, Philadelphia, (1988).
The above article is herein incorporated by reference for
the purpose of enabling the pump test. ~he cavitation
errosion-corrosion aluminum pump test was, in general,
carried out in a manner substantially equiv~lent t~ the
method described in the above ASTM publication. The
r~ference coolant solution utilized in the testing was the
same as Solution A, described above. Table II provides the
results of the pump test. As can be seen, the addition of
0~2 weight percent of a pho~phate ester of an ethylene
diamine initiated polyoxyethylene/polypropylene copolymer
~having about 30 weigh~ percent EO, and a PO molecular
weight of about ~900) produced signi~icantly les~ pump
cavitation corrDsion than a refer~nce coolant ~olution which
was identical except for its absence of ~hi~ org~nic
-39-
.. ~ . . . .. . .. . ... . .. ... . . . . . . .
~ ' t ~/J ~ 'J
inhibitor. In fact, the addition of the copolyme~ corrosion
inhibition agent permitted the pump to run three times as
long as the control and exhibit ~ubstantially less wear than
the control. Thus, the results of Table II indicate the
desirability of the coolant compo itions of the present
invention.
Table II
Pump Test Results
Weight PeroentNo ~rs. ASTM W¢ar
Coolant CompositionPolymeric Inhibitor Run . Ratin~ _
.
Solution A (described --- 100 6.8
supra) (CONTROL)
Solution A plus polymeric 0.4 600 8 D 8
inhibitor *
*The phosphate ester polyme~ic inhibitor was a pho~phate
~ster of a fatty acid heteric ethyleneoxide/pr~pyleneo~ide
copolymer of formula R-O- [(PO)~ , ~EO)l_~ ]-P~4~ whe~ei~
the weight percent of EO wa~ about 68, the weight percent ~O
was about 58, the weight percent PO was about 12, and ~he
weight percent ~f the R group was about 20.
--~0--
.. . . ... .... .. ... . . . ... . . . .
