Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1
CORROSION PROTECTION FORMULATION FOR PROTECTION AGAINST ZINC AND
CADMIUM CORROSION
Description
The present invention relates to a novel corrosion protection formulation and
a method of
protecting against zinc and cadmium corrosion by use of this corrosion
protection formulation.
Each year, corrosion damage on zinc-plated components occurs on winter service
vehicles
and airports as a result of the use of the globally used, strongly alkaline
runway deicing
compositions based on alkali metal acetates and alkali metal formates. The
snow plows,
spreading vehicles, aircraft deicing vehicles and blow sweeping equipment used
therefore
require frequent maintenance and repair and have only a limited life. Zinc-
plated and
cadmium-plated components and surfaces of the aircraft taking off and landing
are also
subjected to increased corrosion by the strongly alkaline runway deicing
compositions based
on alkali metal acetates and alkali metal formates.
Corrosion protection formulations for vapor space corrosion protection during
running in of
vehicle engines are known, for example from WO 2012/063164 Al (1) and WO
2013/160101
(2). Document (1) describes a thixotropic formulation composed of ethylene
oxide or propylene
oxide block copolymers as surfactants, castor oil ethoxylates, alkanolamines,
organic
carboxylic acids and triazoles as corrosion inhibitors, polyacrylate
thickeners and
monopropylene glycol. Document (2) describes a formulation composed of
alkylamine
ethoxylates as surfactants, castor oil ethoxylates, organic carboxylic acids
and triazoles as
corrosion inhibitors, polyacrylate thickeners and at least 75% by weight of
monopropylene
glycol. However, the abovementioned formulations from (1) and (2) do not
display efficient zinc
and cadmium corrosion protection.
Since there has hitherto not been an efficient corrosion protection for zinc
and cadmium, the
described corrosion damage on winter service vehicles at airports and for
aircraft has to be
accepted. Modified runway deicing compositions which cause less corrosion also
cannot be
used because of the strict environmental regulations for runway deicing
formulations.
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It is therefore an object of the invention to provide an efficient corrosion
protection formulation
which, in particular, alleviates the zinc and cadmium corrosion problems
experienced by winter
service vehicles at airports and for aircraft.
We have accordingly found a corrosion protection formulation which comprises
(A) from 0.01 to 5% by weight, preferably from 0.1 to 3% by weight,
especially from 0.5 to
1.5% by weight, of one or more alkylamine ethoxylates as surfactant component,
(B) from 0.01 to 10% by weight, preferably from 0.5 to 7% by weight,
especially from Ito 5%
by weight, of one or more corrosion inhibitors,
(C) from 0 to 0.3% by weight, preferably from 0.0001 to 0.15% by weight,
especially from
0.005 to 0.05% by weight, of one or more thickeners,
(D) from 5 to < 75% by weight, preferably from 10 to 70% by weight,
especially from 25 to
55% by weight, of one or more freezing point-lowering alcohols selected from
among alkanols,
glycols, polyalkylene glycols and glycerol,
(E) from 5 to 90% by weight, preferably from 15 to 80% by weight,
especially from 35 to 60%
by weight, of one or more vegetable and/or fatty oils,
(F) from 0 to 5% by weight, preferably from 0.1 to 4% by weight, especially
from 0.5 to 3% by
weight, of water and
(G) from 0 to 5% by weight, preferably from 0.1 to 4% by weight, especially
from 0.5 to 3% by
weight, of a conventional emulsifier,
where the sum of the components (A) to (G) in all cases is 100% by weight.
The components (A) to (G) are as a rule the important components of the
corrosion protection
formulation of the invention. In addition, relatively small amounts of further
components such as
further surface-active compounds which can aid the surfactant action of
component (A),
antifoams, dyes or fragrances can also be comprised, but these have no or no
significant
influence on the corrosion-inhibiting effect.
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A critical characteristic of the corrosion protection formulation of the
invention is its physical
consistency which is based, in particular, on the concomitant use of vegetable
and/or fatty oils
as component (E) and the physical interaction of the component (E) with the
thickener of the
component (C) and the surfactant of the component (A). The corrosion
protection formulation of
the invention is sufficiently fluid for it to be able to be applied without
problems by means of
conventional techniques, with uniform covering of the metal surfaces to be
protected being
achieved, but owing to its viscosity and its partially thixotropic properties
adheres well and for a
long time to the metal surfaces to be protected, thus ensuring lasting
protection.
The alkyl radical in the alkylamine ethoxylates of the component (A) can be
based on a
secondary or preferably primary monoamine which can be ethoxylated. Secondary
or preferably
primary aliphatic monoamines are normally used, but polyamines having at least
one secondary
and/or primary amino group which can be ethoxylated can also be used. The
alkyl radical on the
nitrogen atom usually comprises saturated linear or saturated branched alkyl
groups; however,
the term "alkali" can also refer to unsaturated linear, unsaturated branched
or saturated or
unsaturated cyclic hydrocarbon groups.
In a preferred embodiment, the corrosion protection formulation of the
invention comprises, as
component (A), at least one alkylamine ethoxylate which comprises at least one
linear or
branched C3-C20-alkyl radical, preferably a linear or branched C6-C13-alkyl
radical, in particular a
linear or branched C7-C12-alkyl radical, especially a linear or branched C8-
C11-alkyl radical. The
term "alkyl" in this context is preferably a saturated and acyclic hydrocarbon
group. The
alkylamine ethoxylates can also comprise mixtures of such alkyl radicals, for
example a mixture
of homologous alkyl radicals, depending on the specific industrial or natural
origin of the
alkylamines used.
Suitable examples of specific alkylamines which can be ethoxylated and then be
used in this
form as surfactant component (A) for the corrosion protection formulation of
the invention are n-
propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-
butylamine, n-
pentylamine, tert-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-
ethylhexylamine,
n-nonylamine, n-decylamine, 2-propylheptylamine, n-undecylamine, n-
dodecylamine, n-
tridecylamine, isotridecylamine, n-tetradecylamine, n-pentadecylamine, n-
hexadecylamine, n-
heptadecylamine, n-octadecylamine, n-nonadecylamine, n-eicosylamine, di(n-
hexyl)amine, di(n-
heptyl)amine, di(n-octyl)amine, di(2-ethylhexyl)amine, di(n-nonyl)amine, di(n-
decyl)amine, di(2-
propylheptyl)amine, di(n-undecyl)amine, di(n-dodecyl)amine, di(n-
tridecyl)amine,
di(isotridecyl)amine, di(n-tetradecyl)amine, di(n-pentadecyl)amine, di(n-
hexadecyl)amine, di(n-
heptadecyl)amine, di(n-octadecyl)amine, di(n-nonadecyl)amine, di(n-
eicosyl)amine, n-
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hexylmethylamine, n-heptylmethylamine, n-octylmethylamine, (2-
ethylhexyl)methylamine, n-
nonylmethylamine, n-decylmethylamine, (2-propylheptyl)methylamine, n-
undecylmethylamine,
n-dodecylmethylamine, n-tridecylmethylamine, isotridecylmethylamine, n-
tetradecylmethylamine, n-pentadecylmethylamine, n-hexadecylmethylamine, n-
heptadecylmethylamine, n-octadecylmethylamine, n-nonadecylmethylamine and n-
eicosylmethylamine.
The alkyl radicals in the alkylamine ethoxylates can originate entirely from
the production of the
corresponding intermediates by petrochemical processes, e.g. industrial Ca-Cis-
alkyl mixtures,
2-ethylhexyl or 2-propylheptyl, or can be based partially or completely on
renewable raw
materials, e.g. fatty amines such as stearylamine, oleylamine or tallow fatty
amine.
In a preferred embodiment, the corrosion protection formulation of the
invention comprises at
least one alkylamine ethoxylate comprising from 1 to 35 ethylene oxide units,
based on the
alkylamine molecule, as component (A). This degree of ethoxylation is even
more preferably
from 1.5 to 15, in particular from 1.8 to 9, especially from 2 to 6, ethylene
oxide units per
alkylamine molecule. This degree of ethoxylation is a statistical value, i.e.
the alkylamine
ethoxylates normally have to be regarded as mixtures of compounds (homologs)
having
different numbers of ethylene oxide units.
In a particularly preferred embodiment, the corrosion protection formulation
of the invention
comprises at least one alkylamine ethoxylate which contains at least one
linear C3-C20-alkyl
radical and from 1 to 35 ethylene oxide units, more preferably at least one
linear C6-C13-alkyl
radical and from 1.5 to 15 ethylene oxide units, in particular at least one
linear C7-C12-alkyl
radical and from 1.8 to 9 ethylene oxide units, especially at least one linear
C8-C11-alkyl radical
and from 2 to 6 ethylene oxide units, as component (A).
The alkylamine ethoxylates mentioned can be primary amines having an
oxyethylene chain and
the general formula alkyl-NH-(CH2CH20)m-H or primary amines having two
oxyethylene chains
and the general formula alkyl-NRCH2CH20)p-HI[(CH2CH20)q-H] or secondary amines
of the
general formula (alky1)2N-(CH2CH20),-H or mixtures of such primary amines
having an
oxyethylene chain with such primary amines having two oxyethylene chains or
mixtures of such
primary ethoxylated amines with such secondary ethoxylated amines, where m or
(p+q) denote
the total degrees of ethoxylation. Residual amounts of unethoxylated
alkylamines can be
present in relatively small amounts in the alkylamine ethoxylates, in
particular at low total
degrees of ethoxylation of less than 2.
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A typical alkylamine ethoxylate which can be used in the corrosion protection
formulation of the
invention is octylamine (caprylamine) having 2 ethylene oxide units, which is
commercially
available.
The alkylamine ethoxylates mentioned can be prepared by conventional methods,
for example
by reaction of the alkylamines with ethylene oxide in the presence of alkali
metal hydroxide
catalysis or double metal cyanide catalysis; both methods are known to those
skilled in the art.
If further surface-active compounds which aid the surfactant action of
component (A) are to be
concomitantly used in the corrosion protection formulation of the invention,
these can, for
example, be selected from the surface-active compounds listed in document (1).
Such
additional surface-active compounds can be anionic, cationic or nonionic
surfactants.
Particularly suitable additional nonionic surfactants are based on polyethers.
Apart from
unmixed polyalkylene oxides, preferably C2-C4-alkylene oxides and phenyl-
substituted C2-C4-
alkylene oxides, in particular polyethylene oxides, polypropylene oxides and
poly(phenylethylene oxides), block copolymers, in particular polymers having
polypropylene
oxide and polyethylene oxide blocks or poly(phenylethylene oxide) and
polyethylene oxide
blocks, and also random copolymers of these alkylene oxides are especially
suitable here.
These polyalkylene oxides can be prepared by polyaddition of the alkylene
oxides onto starter
molecules such as saturated or unsaturated aliphatic and aromatic alcohols,
saturated or
unsaturated aliphatic and aromatic amines, saturated or unsaturated aliphatic
carboxylic acids
and carboxamides. It is usual to use from 1 to 300 mol, preferably 3 to 150
mol, of alkylene
oxide per mole of starter molecule.
Suitable aliphatic alcohols generally comprise from 6 to 26 carbon atoms,
preferably from 8 to
18 carbon atoms, and can have an unbranched, branched or cyclic structure.
Examples which
may be mentioned are octanol, nonanol, decanol, isodecanol, undecanol,
dodecanol, 2-
butyloctanol, tridecanol, isotridecanol, tetradecanol, pentadecanol,
hexadecanol (cetyl alcohol),
2-hexyldecanol, heptadecanol, octadecanol (stearyl alcohol), 2-
heptylundecanol, 2-
octyldecanol, 2-nonyltridecanol, 2-decyltetradecanol, leyl alcohol and 9-
octadecenol and also
mixtures of these alcohols, e.g. C8/Cio-, C13/C15- and C16/C18-alcohol,
cyclopentanol and
cyclohexanol. The saturated and unsaturated fatty alcohols obtained by
cleavage and reduction
of fats from natural raw materials and the synthetic fatty alcohols from the
oxo synthesis are of
particular interest. The alkylene oxide adducts on these alcohols usually have
an average
molecular weight Mn of from 200 to 5000.
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As examples of the abovementioned aromatic alcohols, mention may be made not
only of
unsubstituted phenol and a- and 6-naphthol but also the alkyl-substituted
products which are in
particular, substituted by C1-C12-alkyl, preferably C4-C12- or Ci-C4-alkyl
e.g. hexylphenol,
heptylphenol, octylphenol, nonylphenol, isononylphenol, undecylphenol,
dodecylphenol, dibutyl
and tributylphenol and dinonylphenol, and also bisphenol A and its reaction
products with
styrene, especially bisphenol A substituted in the ortho positions relative to
the two OH groups
by a total of 4 phenyl-1-ethyl radicals.
Suitable aliphatic amines correspond to the abovementioned aliphatic alcohols.
Here too, the
saturated and unsaturated fatty amines, which preferably have from 14 to 20
carbon atoms, are
of particular importance. As aromatic amines, mention may be made by way of
example of
aniline and its derivatives.
Suitable aliphatic carboxylic acids are, in particular, saturated and
unsaturated fatty acids, which
preferably comprise from 14 to 20 carbon atoms, and hydrogenated, partially
hydrogenated and
unhydrogenated resin acids and also polybasic carboxylic acids, e.g.
dicarboxylic acids such as
maleic acid. Suitable carboxamides are derived from these carboxylic acids.
Apart from the alkylene oxide adducts onto the monofunctional amines and
alcohols, the
alkylene oxide adducts onto at least bifunctional amines and alcohols are of
very particular
interest.
As at least bifunctional amines, preference is given to bifunctional to
pentafunctional amines
which, in particular correspond to the formula H2N-(R1-NR2)n-H (R1= C2-C6-
alkylene;
R2 = hydrogen or C1-C6-alkyl; n = 1 to 5). Specific examples are:
ethylenediamine,
diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,3-
propylenediamine,
dipropylenetriamine, 3-amino-1-ethyleneaminopropane, hexamethylenediamine,
dihexa-
methylenetriamine, 1,6-bis(3-aminopropylamino)hexane and N-
methyldipropylenetriamine, with
hexamethylenediamine and diethylenetriamine being particularly preferred and
ethylenediamine
being very particularly preferred.
These amines are preferably reacted firstly with propylene oxide and
subsequently with
ethylene oxide. The content of ethylene oxide in the block copolymers is
usually from about 10
to 90% by weight.
The block copolymers based on polyfunctional amines generally have average
molecular
weights Mn of from 1000 to 40 000, preferably from 1500 to 30 000.
,
,
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As at least bifunctional alcohols, preference is given to bifunctional to
pentafunctional alcohols.
Examples which may be mentioned are C2-C6-alkylene glycols and the
corresponding dialkylene
glycols and polyalkylene glycols, e.g. ethylene glycol, 1,2- and 1,3-propylene
glycol, 1,2- and
1,4-butylene glycol, 1,6-hexylene glycol, dipropylene glycol and polyethylene
glycol, glycerol
and pentaerythritol, with ethylene glycol and polyethylene glycol being
particularly preferred and
propylene glycol and dipropylene glycol being very particularly preferred.
Particularly preferred alkylene oxide adducts onto at least bifunctional
alcohols have a central
polypropylene oxide block, i.e. start out from a propylene glycol or
polypropylene glycol which is
reacted firstly with further propylene oxide and then with ethylene oxide. The
content of ethylene
oxide in the block copolymers is usually from 10 to 90% by weight.
The block copolymers based on polyfunctional alcohols generally have average
molecular
weights Mn of from 1000 to 20 000, preferably from 1000 to 15 000.
Such alkylene oxide block copolymers are known and are commercially available,
for example
under the names Tetronic , Pluronic and Pluriol (BASF) and Atlas
(Uniquema).
Of course, it is also possible to use mixtures of a plurality of such
additional surfactants.
Particular preference is given to selecting surfactants which display very
little foaming. If
surfactants which foam to a great extent are used, it is possible to counter
this property by use
of antifoams.
Suitable corrosion inhibitors of the component (B) are all materials which can
potentially reduce
or completely prevent the corrosion of metallic surfaces or metallic
components which consist of
zinc and/or cadmium or comprise zinc and/or cadmium.
One class of suitable corrosion inhibitors comprises, for example, salts of
benzoic acids.
Preference is given to ammonium salts or salts of alkali metals or alkaline
earth metals.
Particular preference is given to sodium or ammoniums salts. The anions of
benzoic acid can be
unsubstituted or substituted benzoic acid. Examples of substituents on the
aromatic ring of the
benzoic acid are alkyl radicals, in particular methyl, ethyl, n-propyl,
isopropyl, n-butyl, tert-butyl,
isobutyl. These groups can optionally be further substituted. The benzoic acid
can be
monosubstituted or polysubstituted. Preference is given to unsubstituted
benzoic acid or
monosubstituted benzoic acids.
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Another class of suitable corrosion inhibitors comprises ammonium salts of
monocarboxylic or
dicarboxylic acids. Preference is given to ammonium salts of C1-012-
monocarboxylic or
-dicarboxylic acids. Particular preference is given to salts of C4-C12-
monocarboxylic or
-dicarboxylic acids. These monocarboxylic or dicarboxylic acids can comprise
one or more
substituents. In particular, they can have one or more OH groups.
A further class of suitable corrosion inhibitors comprises heterocyclic
compounds, in particular
nitrogen-heterocyclic compounds, which are preferably aromatic. Suitable
nitrogen-heterocyclic
compounds can bear one or more substituents. In a preferred variant, they are
fused with other
aromatic rings. Preferred nitrogen-heterocyclic compounds are, for example,
azoles. Particular
preference is given to triazoles or thiazoles. Examples of suitable azoles are
benzazoles or
toluazoles. Examples of suitable triazoles are benzotriazole or tolutriazole.
Examples of suitable
thiazoles are benzothiazole or 2-mercaptobenzothiazole.
Phosphates are also suitable as corrosion inhibitors. For the purposes of the
present invention,
these are first and foremost salts of phosphoric acid. Suitable phosphates are
formed, for
example, by adjusting the pH of an aqueous solution of phosphoric acid by
means of bases. All
bases which form soluble salts in the corrosion protection formulation of the
invention are in
principle suitable for adjusting the pH. Preferred bases are alkali metal
hydroxides such as
sodium hydroxide or potassium hydroxide.
Further suitable corrosion inhibitors are nitrites such as sodium or potassium
nitrite. Phosphates
are frequently combined with nitrates.
Water-soluble secondary or tertiary amines are likewise suitable as corrosion
inhibitor.
Examples of the class of these corrosion inhibitors are diethanolamine and
triethanolamine.
Further suitable corrosion inhibitors are esters of polyfunctional alcohols
and carboxylic acids.
Suitable polyfunctional alcohols are, for example, diols, trials or tetrols
which can optionally be
alkoxylated and can have been produced petrochemically or on the basis of
renewable raw
materials. Suitable esters generally have a molar mass of not more than 10 000
g/mol,
preferably less than 5000 g/mol and particularly preferably less than 2000
g/mol. In one
embodiment, suitable esters additionally bear unesterified alcohol or
carboxylic acid groups.
Further suitable corrosion inhibitors are polyethers of fatty alcohols. These
can have been
produced completely petrochemically or entirely or partially on the basis of
renewable raw
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materials. They are generally alkoxylates, preferably ethoxylates. Preference
is given to
polyethers of fatty alcohols which comprise from 2 to 200 mol of ethylene
oxide per mole.
Polyethers of fatty alcohols particularly preferably comprise from 4 to 100
mol of ethylene oxide
per mole or from 5 to 60 mol of ethylene oxide per mol. Polyethers of fatty
alcohols can also
have further alkylene oxides such as propylene oxide, butylene oxide or
styrene oxide in various
amounts in addition to ethylene oxide. Suitable polyethers of fatty alcohols
usually have
hydroxyl numbers in accordance with DIN 53240 of from 10 to 500, preferably
from 20 to 200. In
one embodiment, the hydroxyl number is from 30 to 100, in another embodiment
form 110 to
180.
A preferred corrosion inhibitor for the component (B) is alkoxylated castor
oil, preferably
ethoxylated castor oil. Particular preference is given to a castor oil
ethoxylate comprising from 2
to 200 mol of ethylene oxide per mol. In particular, the castor oil ethoxylate
comprises from 4 to
100 mol of ethylene oxide per mol or from 5 to 60 mol of ethylene oxide per
mol. Alkoxylated
castor oil can also have further alkaline oxides such as propylene oxide,
butylene oxide or
styrene oxide in various amounts in addition to ethylene oxide. The solubility
and the phase
inversion temperature can be influenced by the degree of alkoxylation of the
castor oil and
optionally the ratio of the various alkylene oxides.
The corrosion protection formulation of the invention frequently comprises
additives which
stabilize the pH and thus likewise contribute to the inhibition of corrosion.
An example of such
an additive is Borax.
The component (B) can consist of only one corrosion inhibitor but more
frequently comprises a
combination of various corrosion inhibitors. In a preferred embodiment, the
corrosion protection
formulation of the invention comprises, as component (B), at least one castor
oil ethoxylate or a
mixture of at least one castor oil ethoxylate and at least one further
corrosion inhibitor based on
organic carboxylic acids and/or heterocyclic compounds.
The organic carboxylic acids are in this case selected, in particular, from
the group consisting of
aliphatic C4-C12-monocarboxylic and ¨dicarboxylic acids, benzoic acid and
benzenedicarboxylic
acids and also the salts and anhydrides thereof. Examples of such organic
carboxylic acids are
isononanoic acid, succinic acid, adipic acid, sebacic acid, dodecanoic acid,
benzoic acid and the
alkali metal and ammonium salts thereof and also phthalic anhydride. The
conversion of the
organic carboxylic acids into their salts can also be carried out only in the
finished corrosion
protection formulation by addition of, for example, aqueous sodium hydroxide
or potassium
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hydroxide solution. The heterocyclic compounds are, in particular, the
abovementioned
nitrogen-heterocyclic compounds, especially tolutriazole and benzotriazole.
Thickeners of the component (C) are generally high molecular weight substances
which
increase the velocity of a liquid. In general, suitable thickeners have, as a
0.5% strength by
weight solution in water at 20 C, a viscosity of at least 50 mPas, preferably
at least 500 mPas,
particularly preferably at least 2000 mPas and in particular preferably at
least 5000 mPas
(determined as dynamic viscosity in accordance with ASTM D 4016-08). However,
the viscosity
of the aqueous 0.5% strength by weight solution is usually not more than 50
000 mPas.
The component (C) can comprise one or more natural thickeners or preferably
one or more
synthetic thickeners or mixtures thereof.
The choice of thickener depends on the use, the desired viscosity range, on
the use
temperature and on the solvent system which is to be thickened. The type of
thickener is not
critical for carrying out the invention, provided that the thickener system
does not enter into any
undesirable interaction with the corrosion inhibitor, the metallic surface to
be protected or the
other constituents which may be comprised.
Examples of suitable thickeners are given in Kittel, Lehrbuch der Lacke und
Beschichtungen,
volume 4, 2nd edition 2007, pp. 285 to 316.
Natural thickeners are thickeners which are natural products or can be
obtained by work-up, for
example purification operations, in particular extraction, of natural
products. Examples of
inorganic natural thickeners are sheet silicates such as bentonite. Examples
of organic natural
thickeners are preferably proteins such as casein or more preferably
polysaccharides.
Particularly preferred natural thickeners are selected from among agar agar,
carrageenan, gum
Arabic, alginates such as sodium alginate, potassium alginate, ammonium
alginate, calcium
alginate and propylene glycol alginate, pectins, polyoses, carob seed flour
and dextrins.
However, the use of synthetic thickeners is generally preferred. Examples of
suitable synthetic
thickeners are partially hydrolyzed polymers and copolymers of vinyl acetate.
These preferably
have a degree of hydrolysis of from 70 to 97%. Particular preference is given
to partially
hydrolyzed polyvinyl alcohols and polyvinyl alcohol itself.
Copolymers of vinyl acetate as thickeners are, in particular, fully hydrolyzed
or partially
hydrolyzed vinyl alcohol copolymers, in particular fully hydrolyzed copolymers
of alkylvinyl
esters and vinyl acetate having a proportion of alkylvinyl esters of
preferably from 5 to 20 mol%,
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very particularly preferably copolymers of alkylvinyl acetate and vinyl
acetate. Further possible
thickeners are homopolymers and copolymers of N-vinylpyrrolidone.
Further suitable thickeners are homopolymers and copolymers of acrylic acid
and methacrylic
acid and also salts thereof, esters of acrylic acid or methacrylic acid,
acrylamide,
vinylpyrrolidone, alkylene oxides such as polyethylene oxides, styrene-maleic
anhydride
copolymers and salts thereof.
In a preferred embodiment, the corrosion protection formulation of the
invention comprises, as
component (C) at least one polyacrylate as synthetic thickener, where, for the
purposes of the
present invention, the term polyacrylate refers to both homopolymers and
copolymers of acrylic
acid. Such polyacrylates can also comprise acrylamide and/or methacrylic acid
or derivatives
thereof in copolymerized form. In general, such polyacrylates are not
crosslinked or only weakly
crosslinked.
Very particularly preferred synthetic thickeners are selected from among
copolymers comprising
from 85 to 95% by weight of acrylic acid, from 4 to 14% by weight of
acrylamide and from 0.01
to 1% by weight of the (meth)acrylamide derivative of the formula
R4 H I R4
0 0
where the radicals R4 can be identical or different and can be methyl or
hydrogen.
Suitable synthetic thickeners generally have molecular weights Mw in the range
from 50 000 to
3 000 000 g/mol, preferably from 100 000 to 2 000 000 g/mol, particularly
preferably from
200 000 to 1 000 000 g/mol (determined by means of gel permeation
chromatography using
polystyrene as standard).
In general, thickeners suitable as component (C) are solid in neat form.
However, they can be
used as solution or as dispersion, for example in water.
It is desirable but not absolutely necessary for the thickeners used to
dissolve completely in the
other constituents of the corrosion protection formulation of the invention at
room temperature.
The corrosion protection formulation of the invention is also effective when
it has a plurality of
phases. However, it is advantageous for the thickeners used to be able to be
stirred readily into
the corrosion protection formulation of the invention. The stirring-in of the
thickeners frequently
occurs at a slightly acidic pH, for example at a pH of from 3 to 4.
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Furthermore, associative thickeners are suitable as thickeners. Associative
thickeners comprise
not only hydrophilic groups but also hydrophobic end groups or side groups in
the molecule.
Associative thickeners have a surfactant character and are generally capable
of forming
micelles.
Suitable associative thickeners are, for example, hydrophobically modified
polyacrylates,
hydrophobically modified cellulose ethers, hydrophobically modified
polyacrylamides,
hydrophobically modified polyethers or associative polyurethane thickeners
comprising
hydrophilic, relatively high molecular weight polyether segments which are
linked via urethane
groups and are capped by at least two terminal, hydrophobic molecule groups.
The thickener of the component (C), in particular the polyacrylate thickener,
and the alkylamine
ethoxylate surfactant of the component (A) and optionally further surface-
active substances
which aid the surfactant action of (A) should be considered to be an
interactive system which
can bring about non-Newtonian properties (thixotropic properties) in the
corrosion protection
formulation of the invention.
Freezing point-lowering alcohols of the component (D) are alkanols such as
ethanol, n-
propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol or n-
pentanol, glycols
such as monoethylene glycol or monopropylene glycol, polyalkylene glycols such
as diethylene
glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols,
dipropylene glycol,
tripropylene glycol, tetrapropylene glycol or polypropylene glycols, with such
polyalkylene
glycols being able to be etherified at one end, and glycerol and also mixtures
thereof.
In a preferred embodiment, the inventive corrosion protection formulation
comprises
monopropylene glycol or a mixture of monopropylene glycol and one or more
other freezing
point-lowering alcohols selected from among alkanols, glycols, polyalkylene
glycols and glycerol
as component (D).
The vegetable and fatty oils of the component (E) in the corrosion protection
formulation of the
invention serve mainly to produce the required physical consistency which is
necessary for
handlability and for an effective protective action. Vegetable oils (also
referred to as plant oils)
and fatty oils (also referred to as neutral fats) are oils obtained from oil
plants. Starting materials
for producing vegetable oils and fatty oils are oil seeds and oil fruits in
which the oil is generally
present in the form of lipids. Vegetable oils are predominantly esters of
glycerol with saturated
and/or unsaturated fatty acids, known as triglycerides. Examples of vegetable
oils are avocado
CA 02880265 2015-01-27
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oil, peanut oil, sunflower oil, palm kernel oil, rapeseed oil, olive oil,
poppy seed oil and soybean
oil.
Depending on the proportion of unsaturated fatty acids, a distinction is made
between nondrying
vegetable oils (e.g. olive oil), half-drying vegetable oils (e.g. soybean oil
and rapeseed oil) and
drying vegetable oils (e.g. linseed oil or poppy seed oil). Here, the term
"drying" does not refer to
evaporation but to the thickening ("resinification") of the oil caused by
oxidation by means of
oxygen and subsequent polymerization of the unsaturated fatty acids. Drying
oils thus have the
highest content of unsaturated fatty acids. For the purpose of the present
invention, such drying
vegetable oils and fatty oils, in particular those having a content of oleic
acid, linolic acid and
linolenic acid of together more than 50% by weight, especially more than 70%
by weight, based
on the total content of fatty acids in the oil, are preferred.
In a preferred embodiment, the corrosion protection formulation of the
invention comprises, as
component (E), linseed oil which owing to its high content of oleic acid (from
10 to 22% by
weight), linolic acid (from 12 to 18% by weight) and linolenic acid (from 56
to 71% by weight) (in
each case based on the total content of fatty acids in the linseed oil) cures
easily and thereby
ensures lasting adhesion of the corrosion protection formulation of the
invention to the metal
surfaces to be protected against zinc and cadmium corrosion.
Particular preference is given to refined linseed oil (also referred to as
boiled linseed oil), which
represents a particularly purified linseed oil. The mucilaginous materials
have been largely
removed by heating and addition of bleaching earth in the case of refined
linseed oil. This
improves the oxygen uptake and increases the drying capability.
Water is in principle not an essential constituent of the corrosion protection
formulation of the
invention and normally gets into the formulation, if at all, only inevitably
as a result of mixing-in
of other water-comprising components. If the corrosion protection formulation
of the invention
comprises water as component (F), the pH thereof can be neutral, acidic or
basic. The pH of the
formulation is frequently set to a slightly basic value at the end. A typical
corrosion protection
formulation according to the invention has a pH of from 7 to 10, preferably
from 7.5 to 9.5, in
particular from 8 to 9.
If necessary, the addition of a conventional emulsifier as component (G) is
advisable for
providing the corrosion protection formulation of the invention in the form of
a homogeneous
dispersion or microemulsion. This emulsifier can consist of a single substance
or of a mixture of
a plurality of substances having an emulsifying action. The precise structure
of the substances
CA 02880265 2015-01-27
14
having an emulsifying action is inconsequential for the mode of action of the
corrosion
protection formulation of the invention; it merely has to be ensured that the
emulsifier system
does not enter into any undesirable interaction with the other components of
the formulation and
the metallic surface to be protected. Suitable emulsifiers as component (G)
are commercially
available; the products of the Emulgan series from BASF SE are particularly
well suited.
The present invention also provides a method of protecting zinc or zinc-plated
components or
surfaces or cadmium or cadmium-plated metallic surfaces against corrosion,
wherein these
substrates are treated with the corrosion protection formulation of the
invention.
The corrosion protection formulation of the invention composed of the
components present in
the amounts indicated can be directly employed in this form for the use, i.e.
in principle does not
have to be diluted further. However, if desired, depending on the application
method and
application technology, it can be diluted further, for example with water. The
corrosion protection
is achieved by the formulation being applied mechanically in a fine spraying
process, analogous
to underfloor protection or hollow space protection in motor vehicles, to the
surfaces to be
protected. Application to the surfaces to be protected can be effected via a
pressure system, for
example a pressure spray gun.
Since the present invention is particularly suitable for protection of zinc
and cadmium
components and surfaces against corrosion in airport operation, the present
invention also
provides a method of protecting zinc or zinc-plated components or surfaces or
cadmium or
cadmium-plated metallic surfaces, especially on winter service vehicles at
airports or on aircraft,
against corrosion caused by runway deicing compositions used at airports, by
treatment with the
corrosion protection formulation of the invention.
The following examples relate to minimizing zinc corrosion caused by
reproduced runway
deicing compositions. They illustrate the present invention without limiting
it.
Examples: zinc corrosion test on hot galvanized steel sheets in a manner
analogous to
AMS 1435B
The corrosion protection formulation according to the teaching of the present
invention as
indicated below was tested for its corrosion protection action in respect of
the corrosion of zinc
on hot-galvanized steel sheets by in each case 50% strength by weight aqueous
potassium
acetate and potassium formate solutions in a manner analogous to the corrosion
tests from
AMS 1435B (3.2.5.2 Total Immersion Corrosion).
CA 02880265 2015-01-27
In AMS 1435B, only test specimens from aircraft construction (e.g. cadmium-
plated magnesium
or aluminum alloys) are usually used. In the following tests on corrosion of
zinc, the test
specimens described in the standard were replaced by hot-galvanized steel
sheets, but having
the identical geometric shapes.
Formulation according to the invention ("IF") used [composition in % by
weight]:
(A) commercially available octylamine ethoxylate having 2 ethylene oxide
units 0.90
(B) commercially
available castor oil ethoxylate (Leunapon ER 40) 0.30
(B) isononanoic acid 1.30
(B) dodecanedioic acid 0.50
(B) sodium benzoate 0.50
(B) phthalic anhydride 0.13
(B) tolutriazole 0.10
aqueous potassium hydroxide solution (48% strength by weight) 1.64
(C) polyacrylate
thickener (Lutexal GP ECO) 0.01
(D)
monopropylene glycol 41.17
(E) refined
linseed oil 49.00
(F) water 2.44
(G) commercial
emulsifier (EmuIan() ELH 60) 2.00
commercial antifoam 0.01
Total: 100.00
Experiment 1: Potassium formate solution and protected hot-galvanized steel
sheets
Metal: hot-galvanized steel sheets (50 x 20 x 2 mm)
Container: 100 ml glass flask made of Duran glass
Test medium: hot-galvanized steel sheet without surface protection (i.e.
bare) in
potassium formate solution (50% strength by weight, pH: 9-10)
Test: clean hot-galvanized steel sheets (test specimens) in
acetone, dry,
weigh (triplicate determination);
fully immersed in 100 ml of the potassium formate solution;
7 days at 40 C in a drying oven
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Evaluation: take test specimen from the test medium, rinse with water,
clean in
acetone, weigh (triplicate determination)
Mass before test [g] Mass after test [g] A
decrease in mass after test
[mg]
15.9543 15.8797 74.6
17.4241 17.3597 64.4
18.1169 18.0338 83.1
Experiment 2: Potassium acetate solution and unprotected hot-galvanized steel
sheets
Metal: hot-galvanized steel sheets (50 x 20 x 2 mm)
Container: 100 ml glass flask made of Duran glass
Test medium: hot-galvanized steel sheet without surface protection (i.e.
bare) in
potassium acetate solution (50% strength by weight, pH: 9-10)
Test: clean hot-galvanized steel sheets (test specimens) in
acetone, dry,
weigh (triplicate determination);
fully immersed in 100 ml of the potassium acetate solution;
7 days at 40 C in a drying oven
Evaluation: take test specimen from the test medium, rinse with water,
clean in
acetone, weigh (triplicate determination)
Mass before test [g] Mass after test [g] A
decrease in mass after test
[mg]
17.6523 17.6134 38.9
17.9249 17.8647 60.2
18.1410 18.0930 48.0
Experiment 3: Potassium formate solution and protected hot-galvanized steel
sheets
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Metal: hot-galvanized steel sheets (50 x 20 x 2 mm)
Container: 100 ml glass flask made of Duran glass
Test medium: hot-galvanized steel sheet with surface protection (IF) in
potassium
formate solution (50% strength by weight, pH: 9-10)
Test: clean hot-galvanized steel sheets (test specimens) in
acetone, dry,
weigh (triplicate determination);
dip test specimen into IF, allow to drip off (1 hour) and dry on a clock
glass (1 hour);
fully immersed in 100 ml of the potassium formate solution;
7 days at 40 C in a drying oven
Evaluation: take test specimen from the test medium, rinse with water,
clean in
acetone, weigh (triplicate determination)
Mass before test [g] Mass after test [g] A
decrease in mass after test
[mg]
17.5020 17.5005 1.5
17.8144 17.8087 5.7
17.9339 17.9297 4.2
Experiment 4: Potassium acetate solution and protected hot-galvanized steel
sheets
Metal: hot-galvanized steel sheets (50 x 20 x 2 mm)
Container: 100 ml glass flask made of Duran glass
Test medium: hot-galvanized steel sheet with surface protection (IF) in
potassium
acetate solution (50% strength by weight, pH: 9-10)
Test: clean hot-galvanized steel sheets (test specimens) in
acetone, dry,
weigh (triplicate determination);
dip test specimen into IF, allow to drip off (1 hour) and dry on a clock
glass (1 hour);
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fully immersed in 100 ml of the potassium acetate solution;
7 days at 40 C in a drying oven
Evaluation: take test specimen from the test medium, rinse with water,
clean in
acetone, weigh (triplicate determination)
Mass before test [g] Mass after test [g] A
decrease in mass after test
[mg]
17.7708 17.7688 2.0
17.6682 17.6652 2.0
17.2248 17.2223 2.5
It can be seen that the values for removal of material in the case of a 50%
strength by weight
potassium formate solution are somewhat higher than in the case of a 50%
strength by weight
potassium acetate solution.
The formulation according to the invention (IF) was able to reduce the degree
of corrosion on
zinc dramatically both in the case of 50% strength by weight aqueous potassium
acetate
solution and also in the case of 50% strength by weight aqueous potassium
formate solution
and, completely surprisingly, reduce it on average by a factor of 20.
