U.S. patent application number 10/138794 was filed with the patent office on 2002-12-26 for corrosion inhibitor composition applicable for aluminum and steel protection and procedure.
This patent application is currently assigned to Wayne Pigment Corporation. Invention is credited to Sinko, John.
Application Number | 20020197468 10/138794 |
Document ID | / |
Family ID | 23109115 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020197468 |
Kind Code |
A1 |
Sinko, John |
December 26, 2002 |
Corrosion inhibitor composition applicable for aluminum and steel
protection and procedure
Abstract
A corrosion-inhibiting composition for application to a metal
substrate, such as aluminum or steel, and in connection with a
paint, and the synthesis of the composition is disclosed. The base
of the inhibitor can be selected from the group consisting of
2,5-dimercapto-1,3,4 thiadiazole (DMTD),
2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole,
trithiocyanuric acid (TMT), and derivatives of DMTD and TMT,
including various N--,S-- and N,N--, S,S-- and N,S-- substituted
derivatives of DMTD, various S-substituted derivatives of
Trithiocyanuric acid, 5,5 dithio-bis (1,3,4
thiadiazole-2(3H)-thione or (DMTD).sub.2 or (DMTD).sub.n the
polymer of DMTD, dimer and polymers of TMT, Salts of DMTD of the
general formula: M(DMTD).sub.n where n=1,2 or 3, and M is a metal
cation and preferable M=Zn(II), Bi(III), Co(II), Ni(II), Cd(II),
Pb(II), Ag(I), Sb(III), or Cu(II) (examples: ZnDMTD,
Zn(DMTD).sub.2, Bi(DMTD).sub.3) , similar salts of TMT , as for
example, ZnTMT, in a ratio of 1:1, salts of (DMTD).sub.n of general
formula M[(DMTD).sub.n].sub.m, where n=2 or n>2, m=1,2, or 3 and
M is as above specified. Typical examples are: Zn[(DMTD).sub.2],
Zn[(DMTD).sub.2].sub.2, aryl or alkyl ammonium salts of DMTD or
(DMTD).sub.n, similar salts of TMT, quaternary ammonium salts of
DMTD or (DMTD).sub.n, and TMT, poly-ammonium salt of DMTD or
(DMTD).sub.n and TMT formed with polyamines; inherently conductive
polyaniline doped with DMTD or (DMTD).sub.2 and TMT ; inherently
conductive polypyrrol and/or polythiophen doped with DMTD,
(DMTD).sub.2 and/or TMT, micro or nano composites of poly DMTD/
polyaniline, poly DMTD/polypyrrol ,and poly DMTD/polythiophen,
similar micro or nano composites with TMT DMTD or salts of DMTD or
derivatives of DMTD and of TMT, as constituents of various pigment
grade inorganic matrixes or physical mixtures, DMTD or salts of
DMTD or derivatives of DMTD and TMT in encapsulated forms, such as:
inclusions in various polymer matrices, or as
cyclodextrin-inclusion compounds or microencapsulated form.
Inventors: |
Sinko, John; (Mequon,
WI) |
Correspondence
Address: |
RYAN KROMHOLZ & MANION, S.C.
Post Office Box 26618
MILWAUKEE
WI
53226
US
|
Assignee: |
Wayne Pigment Corporation
|
Family ID: |
23109115 |
Appl. No.: |
10/138794 |
Filed: |
May 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60288895 |
May 4, 2001 |
|
|
|
Current U.S.
Class: |
428/336 ;
428/458; 428/470 |
Current CPC
Class: |
C09D 5/086 20130101;
C23C 22/50 20130101; C23C 22/48 20130101; C23C 22/68 20130101; Y10T
428/265 20150115; C23F 11/161 20130101; Y10T 428/31681 20150401;
C23C 22/00 20130101; C23C 22/56 20130101 |
Class at
Publication: |
428/336 ;
428/470; 428/458 |
International
Class: |
B32B 015/08 |
Claims
What is claimed is:
1. A process for protecting an aluminum substrate against
atmospheric corrosion comprising: providing an aluminum surface to
be protected, applying a coating to said surface of a protective
material selected from a group consisting of di-mercapto and
poly-mercapto compounds and their derivatives, said coating
substance having a limited solubility in water of between about
0.01 and about 1000 mmoles/per liter of water.
2. A process for protecting an aluminum substrate against
atmospheric corrosion comprising: providing an aluminum surface to
be protected, applying a coating to said surface of less than
approximately 20 microns in thickness of a protective material
selected from a group consisting of di-mercapto and poly-mercapto
compounds and their derivatives, said coating substance having a
limited solubility in water of between about 0.01 and about 1000
mmoles/per liter of water.
3. A process according to claim 1 wherein said coating substance
has a limited solubility in water of between about 0.1 and about 10
mmoles/per liter of water.
4. A process according to claim 1 wherein said coating substance is
applied as a saturated solution and is subsequently dried whereby a
conversion coating is formed on said substrate, said conversion
coating being subsequently coated with a paint.
5. A process according to claim 1 wherein said coating substance is
incorporated into a silane-based gel coating.
6. A process according to claim 1 wherein saidsubstance is selected
from the group consisting of 2,5-dimercapto-1,3,4 thiadiazole
(DMTD), 2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole,
trithiocyanuric acid (TMT), derivatives of DMTD and derivatives of
TMT.
7. A process according to claim 1 wherein said substance is
selected from the group consisting of 2,5-dimercapto-1,2,4
thiadiazole; 2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole;
5,5 dithio-bis (1,3,4 thiadiazole-2(3H)-thione and (DMTD).sub.2;
(DMTD).sub.n; M(DMTD).sub.n where n=1,2 or 3, and M is a metal
cation selected from the group consisting of Zn, Bi, Co, Ni, Cd,
Pb, Ag, Sb, or Cu; aryl ammonium salts of DMTD; aryl ammonium salts
of (DMTD).sub.n; alkyl ammonium salts of (DMTD),; quaternary
ammonium salts of DMTD; quaternary ammonium salts of (DMTD).sub.n;
polyaniline, polythiophen, and polypyrrol doped with DMTD;
polyaniline, polythiophen, and polypyrrol doped with (DMTD).sub.2
and micro and nano composites of poly DMTD/polyaniline, DMTD
polythiophen and poly DMTD/polypyrrol.
8. A process according to claim 1 wherein said coating substance is
applied by incorporating the same in a curable polymeric coating
composition and applying said composition over said substrate.
9. A process according to claim 1 wherein said coating substance is
selected from the group consisting of: 2,5-dimercapto-1,3,4
thiadiazole (DMTD);
2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole; an organic
derivative of DMTD; N--, S-- and N, N--, S-- and N, S-substituted
derivatives of DMTD, 5,5 dithio-bis(1,3,4 thiadiazole-2(3H)-thione
or (DMTD).sub.2 or (DMTD).sub.n a polymer of DMTD; a salt of DMTD
of general formula, M(DMTD).sub.n, where n=1,2 or 3, and M is a
metal cation and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; a salt of
(DMTD).sub.n of general formula M[(DMTD).sub.n].sub.m, where n=2 or
n>2, m=1,2, or 3 and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu;
aryl and alkyl ammonium salts of DMTD and (DMTD).sub.n; quaternary
ammonium salts of DMTD and(DMTD).sub.n; polyammonium salts of DMTD
and (DMTD).sub.n formed with a polyamines; polyaniline, polypyrrol
and polythiophen doped with DMTD; polyaniline, polypyrrol and
polythiophen doped with (DMTD).sub.2; a micro and nano composites
of poly DMTD/polyaniline, poly DMTD/polypyrrol, and poly
DMTD/polythiophen; DMTD , salts of DMTD , and derivatives of DMTD,
as constituents of an inorganic matrix; DMTD , salts of DMTD ,and
derivatives of DMTD encapsulated form in a polymer matrix, or as a
cyclodextrin-inclusion compound; and a combination of said
forms.
10. A process according to claim 1 wherein said coating substance
is selected from the group consisting of: Trithiocyanuric acid
(TMT); S-substituted derivatives of TMT; a salt of TMT of general
formula, M(TMT).sub.n, where n=1,2 or 3, and M is a metal cation
and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; aryl and alkyl
ammonium salts of TMT; quaternary ammonium salts of TMT; polyamines
formed with TMT; polyaniline doped with TMT; polypyrroline and
polythiophen doped with TMT; micro and nano composites of poly
TMT/polyaniline, poly TMT/polypyrrolidone, and poly
TMT/polythiophen; TMT, salts of TMT, and derivatives of TMT, as
constituents of an inorganic matrix; salts of DMTD ,and derivatives
of TMT encapsulated form in a polymer matrix, or as a
cyclodextrin-inclusion compound; and a combination of said
forms.
11. The coating substance of claim 1 wherein the coating substance
is used in a paint.
12. The paint according to claim 9, whereby the paint is applied to
an aluminum surface.
13. A process for protecting a steel substrate against atmospheric
corrosion comprising: providing a steel surface to be protected,
applying a coating to said surface of less than approximately 20
microns in thickness of a protective material selected from TMT and
TMT derivatives.
14. A process according to claim 11 wherein said coating substance
is applied as a saturated solution and is subsequently dried
whereby a conversion coating is formed on said substrate, said
coating being subsequently coated with a paint.
15. A process according to claim 11 wherein said coating substance
is incorporated into a silane-based gel coating.
16. A process according to claim 11 wherein said coating substance
is selected from the group consisting of: Trithiocyanuric acid
(TMT); S-substituted derivatives of TMT; a salt of TMT of general
formula, M(TMT).sub.n, where n=1,2 or 3, and M is a metal cation
and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; aryl and alkyl
ammonium salts of TMT; quaternary ammonium salts of TMT; polyamines
formed with TMT; polyaniline doped with TMT; polypyrroline and
polythiophen doped with TMT; micro and nano composites of poly
TMT/polyaniline, poly TMT/polypyrrolidone, and poly
TMT/polythiophen; TMT, salts of TMT, and derivatives of TMT, as
constituents of an inorganic matrix; salts of DMTD ,and derivatives
of TMT encapsulated form in a polymer matrix, or as a
cyclodextrin-inclusion compound; and a combination of said
forms.
17. The steel substrate of claim 11, wherein said steel substrate
comprises a galvanized steel.
18. The coating substance of claim 11, wherein the coating
substance is used in a paint.
19. The paint according to claim 14, whereby the paint is applied
to a steel surface.
20. The paint according to claim 14, whereby said paint is applied
to a galvanized steel surface.
Description
RELATED APPLICATION
[0001] This application claims the benefit of provisional
application Serial No. 60/288,895 filed May 4 2001.
BACKGROUND OF THE INVENTION
[0002] Protection of aluminum against atmospheric tcorrosion
constitutes a challenge of significant economic importance. Several
distinct aluminum alloys are known, characterized by different
susceptibility to atmospheric corrosion. Among others, aluminum
alloys containing a small percentage of Cu are well known and
valued for their excellent mechanical properties, as, for example,
Al 2024 T-3, widely applied in aircraft manufacturing industry.
[0003] It is well known however, that due to copper rich
intermetallic species present in the aluminum matrix, Al 2024 T-3
is also more susceptible to atmospheric corrosion. There are two
distinct corrosion control technologies commonly applied to protect
aluminum alloys (such as Al 2024 T-3) against atmospheric
corrosion: conversion coatings and organic coatings.
[0004] As for conversion coatings, Alodine 1200 is one of the
well-known corrosion inhibitor techniques widely applied for Al
2024 T-3 protection. It is based on soluble chromates containing
CrO.sub.4.sup.-- as an inhibitor species and yields a robust
conversion coating on aluminum substrates. A measure of its
robustness, Alodine 1200 conversion coating on Al 2024 T-3 aluminum
panels is known to resist salt spray exposure in excess of 300
hours, without pitting. In addition, conversion coatings are
believed to enhance the adhesion of organic primers subsequently
applied on aluminum substrates, a requirement also satisfied by
Alodine 1200. Such procedures using chromates are thus considered
to be the standard of the industry with respect to obtainable
protection performance.
[0005] Aircraft primers and coil primers are the typical high
performance organic coatings that are applied for protection of
aluminum, especially in the aircraft manufacturing industry. A
thickness of less than 20 micron is characteristic of these
primers, which thus provide a negligible barrier function and,
consequently, mandate the use of effective corrosion inhibitor
pigments.
[0006] As is well known, pigment grade corrosion inhibitors used in
organic primers must contain anionic species with inhibitor
activity and must be characterized by limited, but effective,
solubility in water. For these reasons, it will be apparent that
Cro.sub.4.sup.-- is the corrosion inhibitor species preferred in
both corrosion control technologies applied on aluminum for
protection against atmospheric corrosion that is in conversion
coatings and high performance organic primers.
[0007] SrCrO.sub.4 is the corrosion inhibitor pigment of choice for
aircraft and coil primers, and is the standard in the industry. Due
to environmental concerns, finding a replacement for chromates in
conversion coatings and organic coatings constitutes the objective
of contemporary research in this field.
[0008] It is generally known, that the number of inorganic
corrosion inhibitor species available for chromate replacement is
limited essentially to a few, and specifically to MoO.sub.4.sup.--,
PO.sub.4.sup.---, BO.sub.2.sup.-, SiO.sub.4.sup.-- and NCN.sup.-.
As a consequence, all commercial non-chromate corrosion inhibitor
pigments are molybdates, phosphates, borates, silicates or
cyanamides, or combinations of these compounds.
[0009] In comparison to CrO.sub.4.sup.--, inherent limitations of
their corrosion preventing mechanism render these above-specified
species less effective inhibitors of corrosion, in general, and
specifically of atmospheric corrosion of aluminum. Consequently, it
appears that inorganic chemistry is unable to produce inhibitors of
atmospheric corrosion of aluminum, which would be comparably
effective, non-toxic alternative of CrO.sub.4.sup.--. In contrast,
a large arsenal of organic corrosion inhibitor is known and applied
in various corrosion control technologies. Excessive solubility in
water and/or volatility of most of the known organic inhibitors
appear to be the physical properties inconsistent with applications
in conversion coating technologies and in organic coatings. As of
up to date, no organic corrosion inhibitor is known to be an
effective replacement of chromates in conversion coatings or
organic coatings intended for aluminum protection.
SUMMARY OF THE INVENTION
[0010] It has been discovered pursuant to the present invention
that organic compounds possessing cyclic structural features of
aromatic character, carbocyclic and, specifically, heterocyclic
aromatic structures containing one or multiple hetero species, such
as, specifically, N, S, O atoms or combinations of the same, and
preferably multiple --SH (mercapto) and=S, or thiol-thion
functionalities attached, are effective inhibitors of corrosion of
aluminum and its alloys. This discovery was not anticipated,
considering that thiol-organic compounds (or/and H.sub.2S) do not
form essentially insoluble compounds (salts) with Al (III); as
known, forming essentially insoluble (in water) compounds with
ionic species of a specific metal is a general prerequisite for
corrosion inhibitor activity of organic compounds on the respective
metal substrate.
[0011] Specifically, the classification including di-mercapto and
poly-mercapto compounds and their derivatives have been established
as effective corrosion inhibiting compounds.
[0012] The following di- or poly-mercapto organic compounds are
applicable:
[0013] di-mercapto derivatives of thiophene, pyrrole, furane, and
of diazoles and thiadiazoles;
[0014] di- and tri-mercapto derivatives of pyridine, diazines,
triazines and of benzimidazole and benzthiazole;
[0015] The following compounds and related derivatives are
specifically identified
[0016] 2,5-dimercapto-1,3,4-thiadiazole and
2,4-dimercapto-s-triazolo-[4,3- -b]-1,3-4-thiadiazole
[0017] 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione, or trithiocyanuric
acid, and dithiocyanuric acid,
[0018] dimercaptopyridine, 2,4-dithiohydantoine, and
2,4-dimercapto-6-amino-5-triazine.
[0019] Applicable derivatives of the above-specified di- and
poly-mercapto organic compounds include:
[0020] salts formed with metal cationic species,
[0021] alkyl-, aryl-and quaternary-ammonium salts,
[0022] various N-- and S-substituted derivatives, and
[0023] various N,N--, S,S-- and N,S-substituted derivatives of the
above compounds;
[0024] dimer and polymer derivatives of the above, resulted form
oxidative dimerization or polymerization of di- and poly-mercapto
compounds.
[0025] More specifically, it has been discovered that
2,5-dimercapto-1,3,4 thiadiazole symbolized by HS--CN.sub.2SC--SH
or "DMTD" and its derivatives inhibit atmospheric corrosion of
aluminum, including Al 2024 T-3. It has been also proven that DMTD
and various of its derivatives in pigment grade form are applicable
as components of organic primers or in soluble or partially soluble
form as an inhibitor constituent of conversion coating compositions
intended for aluminum protection.
[0026] This discovery was not expected, considering that DMTD does
not form essentially insoluble compounds with Al(III), of which
this characteristic is generally a prerequisite for corrosion
inhibition activity of organic compounds on metal substrates.
[0027] Along with DMTD, it has also been discovered pursuant to the
present invention, that trithiocyanuric acid, or TMT, which can be
classified as a tri-mercapto derivative, and its derivatives are
also effective corrosion inhibitors of aluminum in a similar
fashion as DMTD, and it has also been discovered that TMT and its
derivatives are effective corrosion inhibitors when applied to
galvanized steel and similar substrates.
BRIEF DESCRIPTION OF THE DRAWING
[0028] FIGS. 1-8 are graphical prints representing IR spectra of
products produced pursuant to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The following description will describe in detail the
synthesis of selected derivatives of 2,5-dimercapto-1,3,4
thiadiazole symbolized by HS--CN.sub.2SC--SH or "DMTD", and of
selected derivatives of trythiocyanuric acid, or "TMT", preferably
used for application in a corrosion inhibitor in connection with a
paint. DMTD, which is a di-mercapto derivative, and TMT, which is a
tri-mercapto derivative, generally may be classified together.
While it is believed that the corrosion inhibitor is applicable to
a wide range of substrates, the following description reveals
examples of applications to aluminum and galvanized steel.
[0030] The following are examples of DMTD, TMT, and derivatives of
DMTD and TMT applicable to the practice of the invention:
[0031] 1. 2,5-dimercapto-1,3,4 thiadiazole (DMTD),
2,4-dimercapto-s-triazo- lo-[4,3-b]-1,3-4-thiadiazole, and
trithiocyanuric acid (TMT);
[0032] 2. Various N--,S-- and N,N--, S,S-- and N,S-- substituted
derivatives of DMTD ; various S-substituted derivatives of
trithiocyanuric acid;
[0033] 3. 5,5 dithio-bis (1,3,4 thiadiazole-2(3H)-thione or
(DMTD).sub.2 or (DMTD).sub.n the polymer of DMTD; dimer and
polymers of TMT
[0034] 4. Salts of DMTD of the general formula: M(DMTD).sub.n,
where n=1,2 or 3, and M is a metal cation and preferable M=Zn(II),
Bi(III), Co(II), Ni(II), Cd(II), Pb(II), Ag(I), Sb(III), or Cu(II)
(examples: ZnDMTD, Zn(DMTD).sub.2, Bi(DMTD).sub.3), similar salts
of TMT , as for example, ZnTMT, in a ratio of 1:1 ;
[0035] 5. Salts of (DMTD).sub.n of general formula
M[(DMTD).sub.n].sub.m, where n=2 or n>2, m=1,2, or 3 and M is as
above specified in 4. Typical examples are: Zn[(DMTD).sub.2],
Zn[(DMTD).sub.2].sub.2;
[0036] 6. Ammonium-, aryl-, or alkyl-ammonium salts of DMTD,
(DMTD).sub.n, or
2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole. Typical
examples: Cyclohexyl amine: DMTD, in ratios of 1:1 and 2:1;
Di-cyclohexyl amine: DMTD, in ratios of 1:1 and 2:1; Aniline: DMTD,
in ratios of 1:1 and 2:1; similar salts of TMT , as for example
Di-cyclohexyl amine: TMT, in a ratio of 1:1;
[0037] 7. Quaternary ammonium salts of DMTD or (DMTD).sub.n, and
TMT
[0038] 8. Poly-ammonium salt of DMTD or (DMTD).sub.n and TMT formed
with polyamines;
[0039] 9. Inherently conductive polyaniline doped with DMTD or
(DMTD).sub.2 and TMT ;
[0040] 10. Inherently conductive polypyrrol and/or polythiophen
doped with DMTD, (DMTD).sub.2 and/or TMT;
[0041] 11. Micro or nano composites of poly DMTD/polyaniline, poly
DMTD/polypyrrol, and poly DMTD/polythiophen; similar micro or nano
composites with TMT;
[0042] 12. DMTD or salts of DMTD or derivatives of DMTD and of TMT,
as constituents of various pigment grade inorganic matrixes or
physical mixtures;
[0043] 13. DMTD or salts of DMTD or derivatives of DMTD and TMT in
encapsulated forms, such as: inclusions in various polymer
matrices, or as cyclodextrin-inclusion compounds or
microencapsulated form;
[0044] 14. various combinations of all of the above.
[0045] Likewise, it is understood that the above list is not
conclusive, and similar compounds and derivatives will yield
similar results.
[0046] Pigment grade forms of DMTD include Zn(DMTD).sub.2 and
Zn-DMTD (among other salts of the former) and combinations of the
latter with inorganic products or corrosion inhibitor pigments,
such as, for example, ZnNCN, zinc phosphate, ZnO, and amorphous
SiO.sub.2 or combinations of the compounds.
[0047] In regard of the synthesis of the Zn salts of DMTD, it has
been discovered pursuant to the present invention, that the
spontaneous reaction of ZnO and DMTD yields exclusively
Zn(DMTD).sub.2, as follows:
ZnO+2HS--CN.sub.2SC--SH=Zn(--S--CN.sub.2SC--SH).sub.2+H.sub.2O
1
[0048] Reaction 1 implies that, apparently, Zn-DMTD cannot be
produced by simply adjusting the DMTD/ZnO stoichiometric ratio to
1:1.
[0049] Di-mercapto derivatives useful in the practice of the
invention are those having a limited solubility in water, from
about 0.01 and 1000 millimoles (mmole) per liter. The greatly
preferred range of solubilities is 0.1 to 10 mmole/1.
EXAMPLES
Example 1
[0050] This example is intended to disclose the synthesis of
Zn(DMTD).sub.2 according to the above presented Reaction 1.
[0051] As known, DMTD forms two distinct Zn(II) salts, that is
Zn-DMTD or the 1:1 salts, and Zn(DMTD).sub.2 or the 1:2 salts. Each
compound can be conveniently prepared by double decomposition in an
aqueous medium, using, in corresponding stoichiometrical ratio,
soluble Zn(II) salts and soluble salts of DMTD, such as
Na.sub.2-DMTD and Na-DMTD, respectively. Intuitively, both salts
are also expected to form by reacting ZnO and DMTD, in a 1:1 or 1:2
stoichiometrical ratio, respectively.
[0052] It has been discovered pursuant to the present invention,
however, that by reacting ZnO and DMTD, only Zn(DMTD).sub.2 forms.
It will be apparent, that Reaction 1 is convenient in that it does
not yield by-products. In practice, the synthesis according to
reaction 1 was carried out as follows:
[0053] 1 mol (81.4 g) of high grade ZnO, of 0.25 micron average
particle size, was re-slurried in 300 ml water by intense agitation
and by heating to 50-60.degree. C., after which the same conditions
were maintained for 1 (one) hour. Concurrently, an aqueous
suspension was prepared by stirring, at ambient temperature, 2
moles of DMTD (from R. T. Vanderbilt Company,Inc.) in 2000 ml
water.
[0054] Reaction 1 was realized by gradually transferring, in about
30 min., the aqueous suspension of DMTD into the intensively
stirred suspension of ZnO and by maintaining the same conditions,
at 50-60.degree. C., for 2 (two) hours. Subsequently, the solid
phase was isolated by filtration, dried at 100-105.degree. C. to
0.5-2% moisture content and pulverized. Notably, the process water
was integrally recyclable.
[0055] Relevant analytical data and IR spectrum are presented
below, in Table 1 and FIG. 1, respectively.
1 TABLE 1 Measured quality parameters Determined values appearance
Yellow powder specific gravity 2.2 solubility in water, at
24.degree. C. 0.4 g/l pH (saturated extract) 4.5-5.0 yield, g
355.0
Example 2
[0056] This example is intended to disclose one synthesis procedure
applicable for incorporating DMTD into a complex solid matrix
corresponding to the general composition of 45% Zn(DMTD).sub.2/32%
Zn.sub.3(PO.sub.4).sub.2 2H.sub.2O/23% ZnO.
[0057] In practice, the synthesis was carried out as follows:
[0058] 6.33 moles (515.0 g) of high grade ZnO (0.25 micron average
particle size), was re-slurried in 2000 ml water at 50-60.degree.
C. and intense agitation for 1 (one) hour. After that, 1.5 moles of
H.sub.3PO.sub.4, as 50% solution, were introduced gradually into
the ZnO slurry and the same conditions were continued for 30
minutes. Subsequently, an aqueous suspension of 2.5 moles of DMTD
in 1500 ml water was introduced in about 30 minutes. The
intensively stirred slurry was heated to 75-80.degree. C. and the
same conditions were maintained for 2 (two) hours. The solid phase
was isolated by filtration, dried at 100-105.degree. C. to 0.5-2%
moisture content and pulverized.
[0059] Relevant analytical data are presented below, in Table
2.
2 TABLE 2 Measured quality parameters Determined values appearance
Light yellow powder specific gravity 2.7 solubility, at 24.degree.
C. 0.3 g/l pH (saturated extract) 5-6 oil abortion, lbs/100 lbs 33
yield, g 992
Example 3
[0060] Application of a DMTD derivative as a corrosion inhibitor
pigment:
[0061] A pigment grade composite of 45% Zn(DMTD).sub.2/32%
Zn.sub.3(PO.sub.4).sub.2.multidot.2H.sub.2O/23% ZnO, synthesized
according to Example 2, was tested on aluminum, comparatively to a
double control: commercial strontium chromate (Control A), which is
the "gold" standard of the industry for corrosion inhibitor
pigments and a molybdate-based product (Control B) considered
representative of commercially available non-chromate corrosion
inhibitor pigments. The test was performed in a typical two
component aircraft primer formulation, specifically recommended for
aluminum protection.
[0062] The description of the different versions of this
formulation, the Test primer and of the Control A and Control B
primers, are presented below.
3TABLE 3 Trade Names & Parts by Weight Components of Suppliers
of Control Formulations Components Test A B Epoxy Base/Part A Epoxy
Resin Shell Epon 1001 163.0 163.0 163.0 CX75 (1) Solvents Glycol
ether PM 148.0 148.0 148.0 MIBK 36.7 36.7 36.7 Fillers RCL-535 TiO2
(2) 20.6 20.6 20.6 Min-U-Sil 15 (3) 26.0 26.0 26.0 12-50 Talc (4)
49.3 49.3 49.0 Corrosion Inhibitor Pigments Zn(DMTD).sub.2 in See
Example 2. 78.0 -- -- solid matrix composite (See Example 2)
Strontium SrCrO4-176 (5) -- 107.5 -- Chromate MoO.sub.4.sup.(2-)
based Commercial (6) -- -- 86.0 pigment. Total part A-weight 551.0
551.0 551.0 Volume, gallons 50.0 50.0 50.0 CATALYST/PART B Hardener
HY-815 67.1 67.1 67.1 Polyamide (7) Solvents Toluene 59.1 59.1 59.1
Isopropanol 218.5 218.5 21.5 Total Part B-weight 344.7 344.7 344.7
Volume, Gallon 50.0 50.0 50.0 Raw material suppliers: (1) Shell
Chemical (2) S.C.M. Chemicals. (3) Unimin Corporation (4) Pfizer.
(5) Wayne Pigment Corp. (6) The Sherwin-Williams Co. (7) Ciba-Geigy
Part A (epoxy base) and Part B (catalyst) were mixed in 1:1 ratio
by volume, and inducted for 30 min. before application.
Example 4
[0063] This example demonstrates the efficiency of DMTD derivatives
in organic coatings in a corrosion inhibitor pigment.
[0064] In order to comparatively assess the corrosion inhibitor
activity of DMTD derivatives, the Test primer of Example 3 as well
as Control A and Control B primer formulations were applied by
wire-wound rod, on several, Alodine 1200 (MIL-C-5541) treated bare
2024 T-3 aluminum panels (from The Q-Panel Co.), at 0.6-0.8 mils
dry film thickness, aged for 7 days at room temperature, scribed
and subsequently subjected to salt spray exposure (according to
ASTM B-117) for 2000 hours. Notably, the scribes were applied in
the typical cross form, at an approximate width of 2 mm, and, in
order to remove the Alodine 1200 conversion coating from the area,
at an appropriate depth.
[0065] By visual examination of their physical state at the end of
the test period, the coatings' corrosion inhibitor performance,
considered directly proportional to the tested pigment components'
corrosion inhibitive activity was qualified. The scribed area was
especially examined and the absence or presence of corrosion
products, respectively, was interpreted as display of, or absence
of, the respective corrosion inhibitor pigment's "throw power". It
will be apparent that the "throw power" is the discriminative
characteristic of effective corrosion inhibitor pigments. Test
results are summarized in Table 4.
4 TABLE 4 Qualification of Coating/inhibitor Performance "Throw
Pigment Tested Field Scribe Area Power" Obse Test primer/Zn Intact
Void of yes (DMTD).sub.2 in a solid corrosion matrix (See Example
2) products Control A/SrCrO.sub.4 Intact Void of yes corrosion
products Control B/MoO.sub.4.sup.(2-) Intact Filled with no based
pigment corrosion products
[0066] Both Control coatings and the Test coating were found intact
in the field at the end of the test 5 period and it was concluded
that 2000 hours of salt spray exposure was not sufficiently
discriminant. Similarly to Cro.sub.4.sup.--, DMTD displayed throw
power, however, by maintaining the scribe area void of corrosion
products, in a passive state for the duration of the salt spray
exposure test. In the same conditions, MoO.sub.4.sup.-- did not
show throw power. It was concluded that DMTD derivatives possess
effective corrosion inhibitor activity on aluminum and are
applicable in pigment grades in organic primers intended for
such.
Example 5
[0067] Applicability of DMTD in soluble forms in conversion
coatings for aluminum protection.
[0068] DMTD based conversion coating was applied on several 2024
T-3 aluminum (the Test and Control) panels according to the
following protocol: de-greasing, rinsing, deoxidizing (I), rinsing,
deoxidizing (II), rinsing, treatment with DMTD (only of the Test
panels), drying, post treatment with Zr(IV)/K.sub.2ZrF.sub.6
solution, rinsing and drying. In practice, rinsing (performed in
stirred water at ambient temperature for 1 minute) and all
operations were carried out by immersion as follows:
[0069] The Test and Control panels were de-greased in an alkaline
cleaner solution (containing 2% of each: Na.sub.2CO.sub.3 and
Na.sub.3PO.sub.4)at 50.degree. C. for 1 minute, followed by rinsing
at normal temperature for 1 minute. Deoxidizing was performed in
two phases. Phase (I) was carried out in 25% H.sub.2SO.sub.4
solution at 60.degree. C. for 1 minute, followed by rinsing, and
phase (II) was performed in 50% HNO.sub.3 solution at normal
temperature for 30 seconds, followed by subsequent rinsing. DMTD
based conversion coating was applied (only on the Test panels) by
immersion for 10 minutes in saturated DMTD solution at 60.degree.
C., under agitation and, without rinsing, by subsequent drying at
about 100-110.degree. C. for approximately 10 minutes. Both the
Test and the Control panels (the latter without DMTD coating) were
post-treated by immersion, for 10 minutes, in a solution containing
0.5% ZrNO.sub.3+0.5% K.sub.2ZrF.sub.6, at 60.degree. C. under
agitation. The treatment was finalized by rinsing and drying the
Test and Control panels at 110.degree. C. for 10 minutes.
Example 6
[0070] In order to assess the quality of DMTD-based conversion
coating on 2024 T-3 aluminum, the Test panels were tested for
corrosion resistance (according to ASTM B-117) and paint adhesion
(tape test), in comparison with the Control panels, as well as with
Alodine 1200 treated 2024 T-3 aluminum panels, the latter being the
standard of the industry. The test results are presented below.
5 TABLE 6 Corrosion resistance Rating* after 336 Paint adhesion
Tested panels hours salt spray: by tape test: Test 8, Pass some
pitting Control 0 Fail Standard 8, Pass some pitting *rating is
considered on the 0 (extensive corrosion) to 10 (no corrosion)
numeric scale.
[0071] As the presented data indicates, DMTD-based conversion
coating on 2024 T-3 Aluminum, applied according to the present
invention, possesses robust resistance to corrosion and good paint
adhesion, similar to chromate-based Alodine 1200 conversion
coatings.
[0072] It was concluded that the treated DMTD derivatives are
applicable as corrosion inhibitors in conversion coating
technologies intended for aluminum protection.
Example 7
[0073] Di-cyclohexyl mono-ammonium salt of trithiocyanuric acid was
synthesized according to the following procedure :
[0074] mole of di-cyclohexylamine (from Aldrich Chemical),
dissolved in 0.15 moles of H.sub.2SO.sub.4 solution of
approximately 20%, was subsequently reacted by agitation with 0.1
mole of Na-trithiocyanurate (from Aldrich Chemical) dissolved in
100 ml water. After the pH was adjusted to 6.5-7.0 , the resulted
slurry was filtered, washed to soluble salt free condition, dried
at approximately 100.degree. C. and the solid product subsequently
pulverized.
[0075] Yield: 34 g, 95% of theoretical.
[0076] The relevant IR spectrum is presented in FIG. 2.
Example 8
[0077] Di-cyclohexyl mono-ammonium salt of DMTD was synthesized as
follows :
[0078] 0.2 moles of DMTD (from R. T. Vanderbilt Company, Inc.),
previously dissolved in 150 ml aqueous solution containing 0.28
moles of NaOH, was reacted with 0.2 moles of di-cyclohexylamine
dissolved in 100 ml solution containing 0.14 moles of
H.sub.2SO.sub.4.
[0079] After the pH was adjusted to 6.5-7.0 , the resulted slurry
was filtered, washed to soluble salt free conditions, dried and
subsequently pulverized.
[0080] Yield: 66 g, approximately 90% of theoretical.
[0081] Relevant IR spectrum is presented in FIG. 3.
Example 9
[0082] Bi-DMTD (1:3)salt, or Bi(DMTD).sub.31 was synthesized as
follows :
[0083] Initially, (A) was prepared by dissolving 0.15 moles of
Bi(No.sub.3).multidot.5 H.sub.2O in 1000 ml aqueous solution
containing 0.5 moles of HNO.sub.3, and (B) was prepared by
dissolving 0.46 moles of DMTD in 1000 ml solution containing 0.92
moles of NaOH .
[0084] Bi(DMTD).sub.3 was subsequently obtained by introducing (A)
and (B) , at identical delivery rates and simultaneously , into 200
ml water under intense agitation. After the pH was adjusted to 3.0
, the obtained slurry was stirred for 1 hour, filtered, washed to
soluble salt free condition, dried at 110.degree. C. overnight and
pulverized.
[0085] Yield: 98 g, approx. 99% of theoretical.
[0086] Relevant IR spectrum is presented in FIG. 4.
Example 10
[0087] Poly-aniline/Trithiocyanuric acid (2:1) microcomposite was
prepared according to the following procedure:
[0088] Initially, an aqueous suspension of Trithiocyanuric acid was
prepared by reacting 0.05 moles of trisodium salt of
trithiocyanuric acid (or 2,4,6-Trimercapto-s-triazine trisodium
salt) dissolved in 200 ml water, with 0.16 moles of H.sub.2SO.sub.4
under intense agitation. Subsequently, a previously prepared
aqueous solution, containing 0.1 mole aniline and 0.22 moles of HCl
in 200 ml water, was added to the above-described suspension.
Finally, 23 g ammonium persulfate (as an aqueous solution) and 0.5
g of FeCl.sub.3 was introduced into the reaction system, which was
stirred overnight at room temperature. The resultant dark green
slurry was filtered, washed to soluble salt-free conditions, dried
at 70-100.degree. C. and pulverized.
[0089] Yield: 17 g Relevant IR spectrum is presented in FIG. 5.
Example 11
[0090] Zn(II) salt of trithiocyanuric acid, ZnTMT 1:1, was produced
according to the following procedure:
[0091] Solution (A), containing 0.1 mole of trisodium salt of
trithyocyanuric acid in 500 ml water, and solution (B), containing
0.1 mole of Zn(NO.sub.3).sub.2 and 0.1 mole of HNO.sub.3 in 500 ml
water, were introduced simultaneously and at identical delivery
rates, into 200 ml of intensively stirred water at about 50.degree.
C. The pH of the obtained slurry was adjusted to about 5 and after
1 (one) hour, during which the reaction conditions were maintained
the same, the solid phase was separated by filtration, washed to
soluble salt-free conditions, dried at 110.degree. C. overnight and
subsequently pulverized.
[0092] Yield: 22 g, 89% of theoretical.
[0093] Pertinent IR spectrum is presented in FIG. 6.
[0094] While the invention may be used in connection with a paint,
it may also be used in connection with other protective coatings.
For example, sol-gel protective coatings, which are generally known
in the art, are silane-based, applicable for aluminum protection,
and are considered as replacement of chromate-based conversion
coatings such as Alodine 1200. The following example shows a
practical procedure for applying the current invention in
connection with a typical sol-gel process.
Example 12
[0095] Several Al 2024 T-3 Aluminum panels were degreased, and also
de-oxidized in identical fashion as described in Example 5, and
subsequently air-dried.
[0096] Solution (A) was prepared by dissolving 0.02 moles of
diethylenetriamine and 0.01 moles of DMTD, in 100 ml water.
[0097] Solution (B) was prepared by the addition of 0.02 moles of
tetramethoxysilane and 0.06 moles of
glycidoxypropyltrimethoxysilane into 200 ml water and by adjusting
the pH of the solution to about 4-4.5 with acetic acid, under
continuous stirring at normal temperature.
[0098] After approximately 1 (one) hour, during which the
hydrolysis process of the silane precursors proceeded in Solution
(B), solution (A) was introduced into it under continuous
agitation.
[0099] Test panels were prepared by the application, after about 10
minutes of stirring, of the resulted emulsion of silane condensate
onto above specified aluminum panels at a spread rate of
approximately 0.2-0.3 ml per 100 cm.sup.2 and air-dried.
[0100] Control panels were prepared in similar fashion, except that
Solution (A) was void of DMTD.
Example 13
[0101] Pigment grade Sr-doped amorphous silica of
SrSiO.sub.3.multidot.11S- iO.sub.2.multidot.5.multidot.7H.sub.2O
composition, containing approximately 9.5% Sr species, was
synthesized according to the following procedure:
[0102] Initially, solution A was prepared by reacting 0.51 mole of
SrCO.sub.3 and 3.5 moles of HNO.sub.3 and dissolving the
composition in 1300 ml of water. Solution B was prepared by
dissolving 1.9 moles of sodium silicate of
Na.sub.2O(SiO.sub.2).sub.3.22 composition (from Hydrite Chemical
Co., WI.), in 900 ml of water.
[0103] Solutions A and B were delivered simultaneously and with
identical rates for approximately 1 (one) hour into 500 ml of
intensively stirred water at 70-85.degree. C. At the end, the pH
was adjusted to 8-8.5 and the same conditions were maintained for
an additional 2 (two) hours, after which the resultant solid phase
was separated by filtration, washed to soluble salt-free
conditions, dried at approximately 105.degree. C. overnight, and
pulverized.
[0104] Relevant analytical data and IR spectrum results are
presented below in Table 13 and FIG. 7, respectively.
6 TABLE 13 Measured Parameters Determined Values appearance White
powder specific gravity 1.8-1.9 pH (saturated extract) 9.0-9.3 oil
absorbtion, lbs/100 lbs 52-60 Sr, % (calculated) 9.5 H.sub.2O, %
(by ignition at 600.degree. C.) 16.5 yield, g 471
Example 14
[0105] A pigment grade mixture of trithiocyanuric acid+Sr-doped
Amorphous Silica of
SrSiO.sub.3.multidot.11SiO.sub.2.multidot.5H.sub.2O+1TMT
(approximate composition) , containing about 8% Sr (calculated) and
17% TMT (calculated) , was produced as follows:
[0106] 100 g of trithiocyanuric acid, in powder form, was blended
into 460 g of Sr-doped amorphous silica in dry granular form. The
Sr-doped amorphous silica was synthesized and processed as shown in
Example 13. The obtained mixture was subsequently pulverized to a
fineness of about 6 on the Hegman scale.
[0107] Trithiocyanuric acid was obtained from an aqueous solution
of tri-sodium-trithiocyanurate, by adjusting the solutions pH to
about 3, filtering, washing, and drying the resultant solid
phase.
[0108] Relevant analytical data and IR spectrum results are
presented below in Table 14 and in FIG. 7, respectively.
7 TABLE 14 Measured Parameters Determined Values appearance Light
yellow powder specific gravity 1.7 pH (saturated extract) 6.9 oil
absorbtion, lbs/100 lbs 75-85 Sr, % (calculated) 7.9 TMT %
(calculated) 17 yield, g 560
Example 15
[0109] This example is intended to demonstrate the application of
trithiocyanuric acid ("TMT") as a corrosion inhibitor constituent
of an amorphous silica+TMT pigment grade mixture in a typical coil
coating formulation.
[0110] The pigment grade mixture of
SrSiO.sub.3.multidot.11SiO.sub.2.multi- dot.5H.sub.2O+1TMT
composition was synthesized according to the process in Example 14,
and was tested (See Test formulation, Table 15) on galvanized steel
(from L. T. V. Steel Co.), in comparison with commercial strontium
chromate (Control A formulation, Table 15), the "gold" standard of
the industry for corrosion inhibitor pigments, and respectively,
Sr-doped amorphous silica synthesized according to Example 13
(Control B formulation, Table 15).
[0111] The typical solvent-borne polyester coil primer formulation
is specifically recommended for galvanized steel protection.
Description of the test formulation, and control formulations A and
B are presented below in Table 15.
8 TABLE 15 Parts by Weight Trade Names & Control Components of
Suppliers of Test Formulation Formulations Components Formulation A
B Polyester Resin EPS 3302 (1) 536.0 536.0 536.0 Solvents Aromatic
150 118.0 118.0 118.0 Diacetone 73.5 73.5 73.5 Alcohol Fillers
RCL-535 TiO.sub.2 (2) 46.0 46.0 46.0 Aerosil R972 (3) 2.1 2.1 2.1
Catalyst Cycat 4040 (4) 7.6 7.6 7.6 Hardener Cymel 303 (4) 73.6
73.6 73.6 Corrosion Inhibitor Pigments Strontium SrCrO.sub.4-176
(5) -- 143.5 -- Chromate Sr-doped As shown in -- -- 120.0 amorphous
Example 13 silica Sr-doped silica + As shown in 150.0 -- -- TMT
pigment Example 14 grade mixture Total Weight 1006.8 1000.3 976.8
Raw Material Suppliers: (1) Engineering Polymer Solutions (2)
Millennium Inorganic Materials (3) DeGussa Corporation (4) Cytec.
(5) Wayne Pigment Corporation The formulation was ground to a
fineness of 6.5-7.0 Hegman before application.
Example 16
[0112] This example demonstrates the applicability of di-mercapto
and tri-thio derivatives according to the present invention, as
corrosion inhibitor additives in paint formulations. Specifically,
the application of trithiocyanuric acid-di-cycloamine, in a salt of
a 1:1 ratio, as an additive in a typical coil primer formulation,
is disclosed.
[0113] The coil primer formulation prepared was identical to the
test formulation described in Example 15 (See Table 15), except
that the corrosion inhibitor constituent consisted of 120 parts by
weight Sr-doped Amorphous Silica, prepared according to example 13,
and 30 parts by weight of trithiocyanuric acid-di-cyclohexylamine,
in a salt of a 1:1 ratio. This was introduced into the formulation
to end up with 1006.8 parts by weight of paint and ground to
6.5-7.0 fineness on the Hegman. The trithiocyanuric
acid-di-cyclohexylamine 1:1 salt was synthesized according to
Example 7 of the present invention.
[0114] Consequently, the corrosion inhibitor constituent of the
test formulation according to Example 16 consists of an ordinary
physical mixture of the above two components. The results are shown
in Table 17 (See Example 17).
Example 17
[0115] This Example demonstrates the efficiency of di-mercapto
derivatives, in general, and of trithiocyanuric acid and its
derivatives, in particular, as corrosion inhibitor pigments or
additives in coil primer formulations and on typical coil
substrates, such as galvanized steel. It will be, however, apparent
to one skilled in the art that the concept of the present invention
applies for primers intended for steel protection in general.
[0116] In order to comparatively assess the corrosion inhibitor
activity of trithiocyanuric acid and its derivatives, the test
primers of Examples 15 & 16, along with control formulations A
& B from Example 15, were applied by wire-wound rod, on several
galvanized steel panels (from L. T. V. Steel Co.), at 0.6-0.7 mil
dry film thickness, aged for at least 2 (two) days at room
temperature, scribed and subsequently subjected to salt spray
exposure (according to ASTM B-117).
[0117] The scribes were applied in the typical cross form, and, in
order to cut through the protective galvanic zinc coating from the
area of the scribes, at appropriate depth. During salt spray
exposure, the coatings' physical state was assessed periodically by
visual examination. Scribe areas were observed for the absence or
presence of corrosion products (white rust), and "field" areas were
observed for the physical integrity of coatings and the presence of
white rust.
[0118] Notably, the protective performance of the tested coatings
was qualified by the service life of coatings, defined as the total
hours of salt spray exposure that result in extensive corrosion
along the scribes and considerable corrosion in the "field" areas.
Service life of a coating is considered directly proportional to
the related pigments' or additives' corrosion inhibitor
performance, which is conveniently qualified by E.sub.i, the
Inhibitor Efficiency Index, defined as:
E.sub.i=100[(service life).sub.TEST-(service
life).sub.CONROL]/(service life).sub.CONTROL.
[0119] It is important to note, that the service life of control
formulation A from Example 15, containing SrCrO.sub.4 as a
corrosion inhibitor pigment, was considered as the test control, or
(service life).sub.CONTROL. It will be apparent, that values of
E.sub.i>0 indicate comparatively better corrosion inhibitor
performance than the control's (SrCrO.sub.4's) performance, whereas
values of E.sub.i<0 indicate a poorer corrosion inhibitor
performance than that of the control. The test results are
summarized below in table 17.
9TABLE 17 Inhibitor Pigment or Service life of Test
additive/coating Coating (hours) E.sub.i % 1. Trithiocyanuric
acid-di- 3000 87 cyclohexykamine, 1:1 salt and Sr-doped amorphous
silica mixture, as described by the test primer in table 16 (Ex.
16). 2. Trithiocyanuric acid + Sr- 2000 25 doped amorphous silica
pigment grade mixture, as described by the test primer in table 15
(Ex. 15). 3. SrCrO.sub.4, as described by 1600 0 control A in table
15 (Ex. 15) 4. Sr-doped amorphous silica, 1000 -37 as described by
control A in table 15 (Ex. 15).
[0120] The disclosed E.sub.i values indicate that, in comparison
with Sr-doped amorphous silica, trithiocyanuric acid and
trithiocyanuric acid-di-cyclohexylamine, 1:1 salt significantly
extend the service life of the coatings. Trithiocyanuric acid
extends the service life of coil coatings on galvanized steel by
100% over Sr-doped amorphous silica, and tithiocyanuric
acid-di-cyclohexylamine, 1:1 salt, extends the service life by 200%
over Sr-doped amorphous silica. Likewise, both compounds display
considerably better corrosion inhibitor performance than
SrCrO.sub.4, and more specifically trithiocyanuric
acid-di-cyclohexylamine, 1:1 salt displayed the best corrosion
inhibiting performance. Also, Sr-doped amorphous silica, as
expected, displayed significantly poorer inhibitor performance than
SrCrO.sub.4.
* * * * *