U.S. patent application number 10/220715 was filed with the patent office on 2003-08-14 for method for providing metal surfaces with protection against corrosion.
Invention is credited to Quellhorst, Heike, Schenzie, Bernd, Wichelhaus, Winfried.
Application Number | 20030150524 10/220715 |
Document ID | / |
Family ID | 7633615 |
Filed Date | 2003-08-14 |
United States Patent
Application |
20030150524 |
Kind Code |
A1 |
Wichelhaus, Winfried ; et
al. |
August 14, 2003 |
Method for providing metal surfaces with protection against
corrosion
Abstract
A process for the anti-corrosive treatment of vehicle bodies or
domestic appliances which have, at least in part, a metal surface
and wherein this metal surface consists of at least 90%, based on
the metal surface, zinc, aluminum and/or magnesium and/or alloys of
these metals with one another or with other alloying elements,
wherein the vehicle bodies or domestic appliances are cleaned,
passivated and painted, characterised in that, for the purpose of
passivation, the vehicle bodies or domestic appliances are
contacted with an aqueous solution having a pH of 1 to 12 and
containing complex fluorides of Ti, Zr, Hf, Si and/or B in a
quantity such that the content of Ti, Zr, Hf, Si and/or B is 20 to
500 mg/l, and 50 to 2000 mg/l organic polymers, the composition of
the aqueous solution being selected such that no crystalline
zinc-containing phosphate layer is formed on the metal surface.
Inventors: |
Wichelhaus, Winfried;
(Wuelfrath, DE) ; Schenzie, Bernd; (Kopfelweg,
DE) ; Quellhorst, Heike; (Duesseldorf, DE) |
Correspondence
Address: |
HENKEL CORPORATION
2500 RENAISSANCE BLVD
STE 200
GULPH MILLS
PA
19406
US
|
Family ID: |
7633615 |
Appl. No.: |
10/220715 |
Filed: |
December 23, 2002 |
PCT Filed: |
February 23, 2001 |
PCT NO: |
PCT/EP01/02073 |
Current U.S.
Class: |
148/252 |
Current CPC
Class: |
C23C 22/364 20130101;
C23C 22/34 20130101 |
Class at
Publication: |
148/252 |
International
Class: |
C23C 022/05 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2000 |
DE |
100-10-758.3 |
Claims
1. A process for the anti-corrosive treatment of vehicle bodies or
domestic appliances which have, at least in part, a metal surface
and wherein this metal surface consists of at least 90%, based on
the metal surface, zinc, aluminum and/or magnesium and/or alloys of
these metals with one another or with other alloying elements,
wherein the vehicle bodies or domestic appliances are cleaned,
passivated and painted, characterised in that, for the purpose of
passivation, the vehicle bodies or domestic appliances are
contacted with an aqueous solution having a pH of 1 to 12 and
containing complex fluorides of Ti, Zr, Hf, Si and/or B in a
quantity such that the content of Ti, Zr, Hf, Si and/or B is 20 to
500 mg/l, and 50 to 2000 mg/l organic polymers, the composition of
the aqueous solution being selected such that no crystalline
zinc-containing phosphate layer is formed on the metal surface.
2. A process as claimed in claim 1 wherein the aqueous solution
contains complex fluorides of Ti, Zr, Hf, Si and/or B in a quantity
such that the content of Ti, Zr, Hf, Si and/or B is 50 to 400
mg/l.
3. A process as claimed in one of claims 1 or 2 wherein the aqueous
solution contains 100 to 1000 mg/l organic polymers.
4. A process as claimed in one or more of claims 1 to 3 wherein the
organic polymers are selected from epoxy resins, amino resins,
tannins, phenol-formaldehyde resins, polycarboxylic acids,
polymeric alcohols and/or the esterification products thereof with
polycarboxylic acids, poly-4-vinylphenol compounds, amino
group-containing homo- or co-polymer compounds and polymers or
copolymers of vinyl pyrrolidone.
5. A process as claimed in claim 4 wherein the organic polymers are
selected from poly-4-vinylphenol compounds corresponding to general
formula (I): 7wherein n represents a number between 5 and 100, x
independently represents hydrogen and/or CRR.sub.1OH groups wherein
R and R.sub.1 represent hydrogen, aliphatic and/or aromatic
radicals having 1 to 12 carbon atoms.
6. A process as claimed in claim 4 wherein the organic polymers are
selected from amino group-containing homo- or co-polymer compounds,
comprising at least one polymer selected from the group consisting
of (a), (b), (c) or (d), wherein: (a) comprises a polymer material
having at least one unit of the formula: 8wherein: R.sub.1 to
R.sub.3, independently for each of the units, are selected from the
group consisting of hydrogen, an alkyl group having 1 to 5 carbon
atoms or an aryl group having 6 to 18 carbon atoms; Y.sub.1 to
Y.sub.4, independently for each of the units, are selected from the
group consisting of hydrogen, --CR.sub.11R.sub.5OR.sub.6,
--CH.sub.2Cl or an alkyl or aryl group having 1 to 18 carbon atoms
or Z: 9 but at least a fraction of the Y.sub.1, Y.sub.2, Y.sub.3 or
Y.sub.4 of the homo- or co-polymer compound or material must be Z;
R.sub.5 to R.sub.12, independently for each of the units, are
selected from the group consisting of hydrogen, an alkyl, aryl,
hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl group;
R.sub.12 may also be --O.sup.(-1) or --OH; W.sub.1, independently
for each of the units, is selected from the group consisting of
hydrogen, an acyl, an acetyl, a benzoyl group;
3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxypropyl;
3-butoxy-2-hydroxypropyl; 3-alkyloxy-2-hydroxypropyl;
2-hydroxyoctyl; 2-hydroxyalkyl; 2-hydroxy-2-phenylethyl;
2-hydroxy-2-alkylphenylethyl; benzyl; methyl; ethyl; propyl; alkyl;
allyl; alkylbenzyl; haloalkyl; haloalkenyl; 2-chloropropenyl;
sodium; potassium; tetraarylammonium; tetraalkylammonium;
tetraalkylphosphonium; tetraarylphosphonium or a condensation
product of ethylene oxide, propylene oxide or a mixture or a
copolymer thereof; (b) comprises: a polymer material with at least
one unit of the formula: 10wherein: R.sub.1 to R.sub.2,
independently for each of the units, are selected from the group
consisting of hydrogen, an alkyl group having 1 to 5 carbon atoms
or an aryl group having 6 to 18 carbon atoms; Y.sub.1 to Y.sub.3,
independently for each of the units, are selected from the group
consisting of hydrogen, --CR.sub.4R.sub.5OR.sub.6, --CH.sub.2Cl or
an alkyl or aryl group having 1 to 18 carbon atoms or Z: 11 but at
least a fraction of the Y.sub.1, Y.sub.2, or Y.sub.3 of the end
compound must be Z; R.sub.4 to R.sub.12, independently for each of
the units, are selected from the group consisting of hydrogen, an
alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or
phosphoalkyl group; R.sub.12 may also be --O.sup.(-1) or --OH;
W.sub.2, independently for each of the units, is selected from the
group consisting of hydrogen, an acyl, an acetyl, a benzoyl group;
3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxypropyl;
3-alkylbenzyloxy-2-hydroxypropyl; 3-phenoxy-2-hydroxypropyl;
3-alkylphenoxy-2-hydroxypropyl; 3-butoxy-2-hydroxypropyl;
3-alkyloxy-2-hydroxypropyl; 2-hydroxyoctyl; 2-hydroxyalkyl;
2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkylphenylethyl; benzyl;
methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl;
haloalkenyl; 2-chloropropenyl or a condensation product of ethylene
oxide, propylene oxide or a mixture thereof; (c) comprises: a
copolymer material, wherein at least part of the copolymer has the
structure 12 and at least a fraction of the above part is
polymerised with one or more monomers, which are selected,
independently for each unit, from the group consisting of
acrylonitrile, methacrylonitrile, methyl acrylate, methyl
methacrylate, vinyl acetate, vinyl methyl ketone, isopropenyl
methyl ketone, acrylic acid, methacrylic acid, acrylamide,
methacrylamide, n-amyl methacrylate, styrene, m-bromostyrene,
p-bromostyrene, pyridine, diallyldimethylammonium salts,
1,3-butadiene, n-butyl acrylate, t-butylaminoethyl methacrylate,
n-butyl methacrylate, t-butyl methacrylate, n-butyl vinyl ether,
t-butyl vinyl ether, m-chlorostyrene, o-chlorostyrene,
p-chlorostyrene, n-decyl methacrylate, N,N-diallyl melamine,
N,N-di-n-butylacrylamide, di-n-butyl itaconate, di-n-butyl maleate,
diethylaminoethyl methacrylate, diethylene glycol monovinyl ether,
diethyl fumarate, diethyl itaconate, diethyl vinyl phosphate,
vinylphosphonic acid, diisobutyl maleate, diisopropyl itaconate,
diisopropyl maleate, dimethyl fumarate, dimethyl itaconate,
dimethyl maleate, di-n-nonyl fumarate, di-n-nonyl maleate, dioctyl
fumarate, di-n-octyl itaconate, di-n-propyl itaconate, N-dodecyl
vinyl ether, acidic ethyl fumarate, acidic ethyl maleate, ethyl
acrylate, ethyl cinnamate, N-ethyl methacrylamide, ethyl
methacrylate, ethyl vinyl ether, 5-ethyl-2-vinylpyridine,
5-ethyl-2-vinylpyridine-1-oxide, glycidyl acrylate, glycidyl
methacrylate, n-hexyl methacrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl methacrylate, isobutyl methacrylate, isobutyl vinyl
ether, isoprene, isopropyl methacrylate, isopropyl vinyl ether,
itaconic acid, lauryl methacrylate, methacrylamide, methacrylic
acid, methacrylonitrile, N-methylolacrylamide,
N-methylolmethacrylamide, N-isobutoxymethylacrylamide,
N-isobutoxymethylmethacrylamide, N-alkyloxymethyl acrylamide,
N-alkyloxymethylmethacrylamide, N-vinyl caprolactam, methyl
acrylate, N-methylmethacrylamide, .alpha.-methyl styrene, m-methyl
styrene, o-methyl styrene, p-methyl styrene,
2-methyl-5-vinylpyridine, n-propyl methacrylate, sodium-p-styrene
sulfonate, stearyl methacrylate, styrene, p-styrenesulfonic acid,
p-styrenesulfonamide, vinyl bromide, 9-vinylcarbazole, vinyl
chloride, vinylidene chloride, 1-vinylnaphthalene,
2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridene,
2-vinylpyridine-N-oxide, 4-vinylpyrimidine, N-vinyl pyrrolidone;
and W.sub.1, Y.sub.1-Y.sub.4 and R.sub.1-R.sub.3 are as defined
under (a); (d) comprises a condensation polymer of the polymeric
materials (a), (b) or (c), wherein a condensable form of (a), (b),
(c) or a mixture thereof is condensed with a second compound which
is selected from the group consisting of phenols, tannins, novolak
resins, lignin compounds, together with aldehydes, ketones or
mixtures thereof, to produce a condensation resin product wherein
the condensation resin product, by adding "Z" to at least a part
thereof, then reacts further by reaction of the resin product with
(1) an aldehyde or ketone (2) a secondary amine to form a final
adduct which may react with an acid.
7. A process as claimed in claim 6 wherein at least a fraction of
the groups Z of the organic polymer has a polyhydroxyalkylamine
functionality, which results from the condensation of an amine or
ammonia with a ketose or aldose having 3 to 8 carbon atoms.
8. A process as claimed in claim 6 wherein the organic polymer
represents a condensation product of a polyvinylphenol having a
molecular weight in the range of 1000 to 10,000 with formaldehyde
or paraformaldehyde and with a secondary organic amine.
9. A process as claimed in one or more of claims 1 to 8 wherein the
aqueous solution additionally contains 0.001 to 2 g/l in each case
of one or more of the metals Mn, Ce, Li, V, W, Mo, Mg, Zn, Co and
Ni.
10. A process as claimed in one or more of claims 1 to 9 wherein
the aqueous solution additionally contains 0.001 to 1.5 g/l each of
phosphoric acid, phosphorous acid, phosphonic acid and/or the
respective anions and/or the respective esters thereof.
11. A process as claimed in one or more of claims 1 to 10 wherein
the aqueous solution contains one or more phosphating accelerators
selected from: 0.05 to 2 g/l m-nitrobenzene sulfonate ions, 0.1 to
10 g/l hydroxylamine in free or bound form, 0.05 to 2 g/l
m-nitrobenzoate ions, 0.05 to 2 g/l p-nitrophenol, 1 to 70 mg/l
hydrogen peroxide in free or bound form, 0.05 to 10 g/l organic
N-oxides 0.1 to 3 g/l nitroguanidine 1 to 500 mg/l nitrite ions 0.5
to 5 g/l chlorate ions.
12. A process as claimed in one or more of claims 1 to 11 wherein
the aqueous solution is free from chromium.
13. A process as claimed in one or more of claims 1 to 12 wherein
the vehicle bodies or domestic appliances have surfaces of at least
two materials selected from zinc, aluminum, magnesium, alloys of
these metals with one another or with other alloying elements.
14. A process as claimed in one or more of claims 1 to 13 wherein,
after passivation, the vehicle bodies or domestic appliances are
coated with a dipping paint suitable for electrodeposition or with
a powder coating.
Description
[0001] This invention relates to the field of the anti-corrosive
treatment of vehicle bodies or domestic appliances, wherein an
anti-corrosive coating is produced on selected non-ferrous
surfaces. It is particularly suitable for metal components having
surfaces of two or more different non-ferrous metals. A particular
feature of the present invention is the fact that no toxic chromium
has to be used.
[0002] An extensive prior art exists for the deposition of
anti-corrosive coatings on bright metal surfaces to increase
corrosion protection. A few examples of documents relating
particularly to the chromium-free treatment of aluminum surfaces
are listed below. This type of treatment is generally also suitable
for zinc surfaces. The term "conversion treatment" used here means
that components of the treatment solution react chemically with the
metal surface resulting in an anti-corrosive coating in which both
components of the treatment solution and metal atoms from the metal
surface are incorporated.
[0003] The chromium-free conversion treatment of aluminum surfaces
with fluorides of boron, silicon, titanium or zirconium in
combination with organic polymers to achieve permanent corrosion
protection and to produce a base for subsequent painting is known
in principle:
[0004] U.S. Pat. No. 5,129,967 discloses treatment baths for a
no-rinse treatment (referred to there as "dried in place conversion
coating") of aluminum, containing:
[0005] (a) 10 to 16 g/l polyacrylic acid or homopolymers
thereof,
[0006] (b) 12 to 19 g/l hexafluorozirconic acid,
[0007] (c) 0.17 to 0.3 g/l hydrofluoric acid and
[0008] (d) up to 0.6 g/l hexafluorotitanic acid.
[0009] EP-B-8 942 discloses treatment solutions, preferably for
aluminum cans, containing:
[0010] (a) 0.5 to 10 g/l polyacrylic acid or an ester thereof
and
[0011] (b) 0.2 to 8 g/l of at least one of the compounds
H.sub.2ZrF.sub.6, H.sub.2TiF.sub.6 and H.sub.2SiF.sub.6, the pH of
the solution being less than 3.5,
[0012] and an aqueous concentrate for regenerating the treatment
solution, containing:
[0013] (a) 25 to 100 g/l polyacrylic acid or an ester thereof,
[0014] (b) 25 to 100 g/l of at least one of the compounds
H.sub.2ZrF.sub.6, H.sub.2TiF.sub.6 and H.sub.2SiF.sub.6, and
[0015] (c) a source of free fluoride ions providing 17 to 120 g/l
free fluoride.,
[0016] DE-C-24 33 704 describes treatment baths to increase paint
adhesion and permanent corrosion protection on aluminum, among
other materials, which may contain 0.1 to 5 g/l polyacrylic acid or
salts or esters thereof and 0.1 to 3.5 g/l ammonium
fluorozirconate, calculated as ZrO.sub.2. The pH of these baths may
vary over a broad range. The best results are generally obtained
when the pH is 6-8.
[0017] U.S. Pat. No. 4,992,116 describes treatment baths for the
conversion treatment of aluminum with a pH of between about 2.5 and
5, which contain at least three components:
[0018] (a) phosphate ions in a concentration range of between
1.1.times.10.sup.-5 and 5.3.times.10.sup.-3 mol/l corresponding to
1 to 500 mg/l,
[0019] (b) 1.1.times.10.sup.-5 to 1.3.times.10.sup.-3 mol/l of a
fluoro acid of an element selected from the group consisting of Zr,
Ti, Hf and Si (corresponding to 1.6 to 380 mg/l depending on the
element) and
[0020] (c) 0.26 to 20 g/l of a polyphenol compound, obtainable by
reacting poly(vinylphenol) with aldehydes and organic amines.
[0021] A molar ratio of about 2.5:1 to about 1:10 should be
maintained between the fluoro acid and the phosphate.
[0022] WO 92/07973 teaches a chromium-free treatment process for
aluminum which uses as its main components 0.01 to about 18 wt. %
H.sub.2ZrF.sub.6 and 0.01 to about 10 wt. % of a
3-(N-C.sub.1-C.sub.4
alkyl-N-2-hydroxyethylaminomethyl)-4-hydroxystyrene polymer in an
acidic aqueous solution. Optional components are 0.05 to 10 wt. %
dispersed SiO.sub.2, 0.06 to 0.6 wt. % of a solubility promoter for
the polymer and surfactant.
[0023] Vehicle bodies, such as car bodies, are currently assembled
from steel and/or other metallic materials, such as galvanised
steel or aluminum. After assembly, the bodies are cleaned and
subjected to a conversion treatment before painting, to achieve
adequate corrosion protection and adequate paint adhesion. The
bodies are then painted, generally these days by cathodic
electrodeposition coating. Domestic appliances containing metal
components, such as refrigerators, freezers, washing machines,
tumble driers, cookers, microwave ovens or even metal furniture,
may be subjected to a similar process. Owing to the lower corrosion
protection requirements for these items, they are generally coated
with a powder coating after the conversion treatment.
[0024] Phosphating is widespread as a conversion treatment for
domestic appliances. For vehicle bodies, conversion treatment takes
place exclusively as so-called "layer-forming" zinc phosphating.
For this purpose, the vehicle bodies are contacted with an aqueous
solution having a pH of about 2.5 to about 3.8, containing about
0.3 to 2 g/l zinc ions and about 10 to about 20 g/l phosphate ions.
These phosphating solutions often also contain about 0.3 to 2 g/l
manganese ions and often nickel or copper ions. With this
treatment, a layer of crystalline zinc iron phosphates is formed on
steel surfaces and a layer of crystalline zinc phosphates on zinc
or aluminum surfaces.
[0025] So that these crystalline, zinc-containing phosphate layers
develop an adequate effect for corrosion protection and paint
adhesion, the actual phosphating step is accompanied by additional
steps. For example, before phosphating, the metal surfaces are
first cleaned, generally in several steps, and then activated. For
the activation step, the metal surfaces are contacted with a
solution which mainly contains secondary alkali metal phosphates
and suspended colloidal titanium phosphates. This step must be very
carefully controlled in order to guarantee sufficient quality of
the subsequent phosphating. In particular, compared with
phosphating baths, the activating baths are consumed relatively
quickly, so that they have to be renewed at short intervals of a
few days to several weeks. The monitoring and care of the
activation baths therefore represents a considerable proportion of
the care and monitoring expenditure for a phosphating line.
[0026] The actual phosphating step is generally followed by
so-called post-passivation. As a result of this post-passivation,
any pores remaining in the crystalline phosphate layer are closed
and corrosion protection and paint adhesion are improved. To this
end, the phosphated metal surfaces are contacted with an aqueous
solution which may contain various components. At present,
post-passivation solutions based on hexavalent chromium, complex
fluorides of titanium and/or hafnium, reactive polymers of vinyl
phenol derivatives or copper ions are in practical use. These
post-passivation baths also have to be checked and adjusted
regularly.
[0027] A conversion treatment in the form of phosphating therefore
generally requires, in addition to cleaning, at least three
treatment baths for activation, phosphating and post-passivation,
all of which have to be regularly checked and, if necessary,
adjusted or renewed. These at least three baths that are required
and the additional rinsing baths between them mean that a large
space and high investments are required, thus increasing costs for
the manufacture of vehicle bodies and domestic appliances.
[0028] At present, car bodies generally contain surfaces of steel,
often in conjunction with surfaces of aluminum and/or galvanised or
alloy-galvanised steel. However, car bodies and domestic
appliances, apart from plastics parts, may be assembled in such a
way that the metal surfaces thereof represent exclusively
non-ferrous surfaces. Examples of these non-ferrous surfaces are
surfaces of zinc (by the use of galvanised steel), aluminum,
magnesium or alloys of these elements with one another or with
other metals. Even for the anti-corrosive treatment of items of
this type, the phosphating described above is used exclusively at
present.
[0029] An object of the present invention is to reduce the cost of
anti-corrosive treatment for car bodies or domestic appliances
compared with the prior art. The present invention is based on the
knowledge that the complex process sequence for phosphating may be
made shorter if the metal surfaces of the car bodies or domestic
appliances have virtually no iron surfaces.
[0030] The present invention relates to a process for the
anti-corrosive treatment of vehicle bodies or domestic appliances
which, at least in part, have a metal surface and wherein this
metal surface consists of at least 90%, based on the metal surface,
zinc, aluminum and/or magnesium and/or alloys of these metals with
one another or with other alloying elements, wherein the vehicle
bodies or domestic appliances are cleaned, passivated and painted,
characterised in that, for the purpose of passivation, the vehicle
bodies or domestic appliances are contacted with an aqueous
solution having a pH of 1 to 12 and containing complex fluorides of
Ti, Zr, Hf, Si and/or B in a quantity such that the content of Ti,
Zr, Hf, Si and/or B is 20 to 500 mg/l, and 50 to 2000 mg/l organic
polymers, the composition of the aqueous solution being selected
such that no crystalline zinc-containing phosphate layer is formed
on the metal surface.
[0031] The complex fluorides of the above elements may be
introduced into the aqueous solution in the form of the
corresponding fluoro acids or the alkali metal and/or ammonium
salts thereof. However, it is also possible to form the complex
fluorides in the aqueous solution itself by the reaction of
hydrofluoric acid or of fluorides with the ions of the above
metals. For example, complex fluorides of titanium or zirconium are
formed by the reaction of oxides or salts of these elements with
hydrofluoric acid.
[0032] In addition to the complex fluorides, the aqueous solution
may contain free fluoride, for example in the form of hydrofluoric
acid or alkali metal or ammonium fluorides. The content of free
fluoride may, for example, be from 0.001 to 1 g/l. This addition of
free fluoride increases the pickling action of the aqueous solution
and thus the rate of formation of the conversion coating,
particularly in the case of hot-dip galvanised steel or
aluminum.
[0033] The present process is preferably used for those car bodies
and domestic appliances which have no surfaces of uncoated steel.
In practice, however, it is not impossible for the steel surface to
be bare at cut edges, weld points or grinding points even when
coated steel, such as galvanised steel, pre-phosphated steel or
organically pre-coated steel, is used. In the context of the
present invention, however, a proportion of at least 90%,
preferably 95% and particularly preferably 99% of the metal surface
should consist of the above-mentioned metals, zinc surfaces
generally being surfaces of galvanised steel. Non-metallic
surfaces, such as plastics surfaces or surfaces of pre-phosphated
or organically pre-coated steel, are not included in this area
relation.
[0034] The present process has the great advantage that, compared
with conventional phosphating, the activation and post-passivation
steps may be omitted. This means that the pre-treatment line is
shorter and the time spent on caring for the baths and disposing of
them is reduced. This simplifies the process control, reduces the
costs and decreases the burden on the environment.
[0035] Aqueous treatment solutions that may be used for the present
process are known in principle in the prior art. Examples are
mentioned in the introduction. Up to the present, treatment baths
of this type have been used for treating less complex components,
such as metal strips, metal sheets or metal cans. For complex
components, such as car bodies or domestic appliances, these
treatment baths have not been used up to now as the sole conversion
treatment before painting. In particular, these treatment baths
have not been used up to now in processes in which complex metal
components were coated by electrodeposition or with a powder
coating immediately after the conversion treatment.
[0036] The aqueous solution used for passivation in the process
sequence according to the present invention preferably contains the
complex fluorides of Ti, Zr, Hf, Si and/or B in a quantity such
that the content of Ti, Zr, Hf, Si and/or B is 50 to 400 mg/l. The
aqueous solution preferably contains 100 to 1000 mg/l organic
polymers.
[0037] The organic polymers may, for example, be selected from
epoxy resins, amino resins, tannins, phenol-formaldehyde resins,
polycarboxylic acids, polymeric alcohols and/or the esterification
products thereof with polycarboxylic acids, poly-4-vinylphenol
compounds, amino group-containing homo- or co-polymer compounds and
polymers or copolymers of vinyl pyrrolidone. The use of these
polymers in the area of metal surface treatment is known.
[0038] The organic polymers may, for example, be selected from
poly-4-vinylphenol compounds corresponding to general formula (I):
1
[0039] wherein
[0040] n represents a number between 5 and 100,
[0041] x independently represents hydrogen and/or CRR.sub.1OH
groups wherein R and R.sub.1 represent hydrogen, aliphatic and/or
aromatic radicals having 1 to 12 carbon atoms.
[0042] In another embodiment, the organic polymers may be selected
from amino group-containing homo- or co-polymer compounds,
comprising at least one polymer selected from the group consisting
of (a), (b), (c) or (d), wherein:
[0043] (a) comprises a polymer material having at least one unit of
the formula: 2
[0044] wherein:
[0045] R.sub.1 to R.sub.3, independently for each of the units, are
selected from the group consisting of hydrogen, an alkyl group
having 1 to 5 carbon atoms or an aryl group having 6 to 18 carbon
atoms;
[0046] Y.sub.1 to Y.sub.4, independently for each of the units, are
selected from the group consisting of hydrogen,
--CR.sub.11R.sub.5OR.sub.- 6, --CH.sub.2Cl or an alkyl or aryl
group having 1 to 18 carbon atoms or Z: 3
[0047] but at least a fraction of the Y.sub.1, Y.sub.2, Y.sub.3 or
Y.sub.4 of the homo- or co-polymer compound or material must be Z;
R.sub.5 to R.sub.12, independently for each of the units, are
selected from the group consisting of hydrogen, an alkyl, aryl,
hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl group;
[0048] R.sub.12 may also be --O.sup.(-1) or --OH;
[0049] W.sub.1, independently for each of the units, is selected
from the group consisting of hydrogen, an acyl, an acetyl, a
benzoyl group; 3-allyloxy-2-hydroxypropyl;
3-benzyloxy-2-hydroxypropyl; 3-butoxy-2-hydroxypropyl;
3-alkyloxy-2-hydroxypropyl; 2-hydroxyoctyl; 2-hydroxyalkyl;
2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkylphenylethyl; benzyl;
methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl;
haloalkenyl; 2-chloropropenyl; sodium; potassium;
tetraarylammonium; tetraalkylammonium; tetraalkylphosphonium;
tetraarylphosphonium or a condensation product of ethylene oxide,
propylene oxide or a mixture or a copolymer thereof;
[0050] (b) comprises:
[0051] a polymer material having at least one unit of the formula:
4
[0052] wherein:
[0053] R.sub.1 to R.sub.2, independently for each of the units, are
selected from the group consisting of hydrogen, an alkyl group
having 1 to 5 carbon atoms or an aryl group having 6 to 18 carbon
atoms;
[0054] Y.sub.1 to Y.sub.3, independently for each of the units, are
selected from the group consisting of hydrogen,
--CR.sub.4R.sub.5OR.sub.6- , --CH.sub.2Cl or an alkyl or aryl group
having 1 to 18 carbon atoms or Z: 5
[0055] but at least a fraction of the Y.sub.1, Y.sub.2, or Y.sub.3
of the end compound must be Z; R.sub.4 to R.sub.12, independently
for each of the units, are selected from the group consisting of
hydrogen, an alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl
or phosphoalkyl group; R.sub.12 may also be --O.sup.(-1) or --OH;
W.sub.2, independently for each of the units, is selected from the
group consisting of hydrogen, an acyl, an acetyl, a benzoyl group;
3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxypropyl;
3-alkylbenzyloxy-2-hydroxypropyl; 3-phenoxy-2-hydroxypropyl;
3-alkylphenoxy-2-hydroxypropyl; 3-butoxy-2-hydroxypropyl;
3-alkyloxy-2-hydroxypropyl; 2-hydroxyoctyl; 2-hydroxyalkyl;
2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkylphenylethyl; benzyl;
methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl;
haloalkenyl; 2-chloropropenyl or a condensation product of ethylene
oxide, propylene oxide or a mixture thereof;
[0056] (c) comprises:
[0057] a copolymer material, wherein at least part of the copolymer
has the structure 6
[0058] and at least a fraction of the above part is polymerised
with one or more monomers which are selected, independently for
each unit, from the group consisting of acrylonitrile,
methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl
acetate, vinyl methyl ketone, isopropenyl methyl ketone, acrylic
acid, methacrylic acid, acrylamide, methacrylamide, n-amyl
methacrylate, styrene, m-bromostyrene, p-bromostyrene, pyridine,
diallyldimethylammonium salts, 1,3-butadiene, n-butyl acrylate,
t-butylaminoethyl methacrylate, n-butyl methacrylate, t-butyl
methacrylate, n-butyl vinyl ether, t-butyl vinyl ether,
m-chlorostyrene, o-chlorostyrene, p-chlorostyrene, n-decyl
methacrylate, N,N-diallyl melamine, N,N-di-n-butylacrylamide,
di-n-butyl itaconate, di-n-butyl maleate, diethylaminoethyl
methacrylate, diethylene glycol monovinyl ether, diethyl fumarate,
diethyl itaconate, diethyl vinyl phosphate, vinylphosphonic acid,
diisobutyl maleate, diisopropyl itaconate, diisopropyl maleate,
dimethyl fumarate, dimethyl itaconate, dimethyl maleate, di-n-nonyl
fumarate, di-n-nonyl maleate, dioctyl fumarate, di-n-octyl
itaconate, di-n-propyl itaconate, N-dodecyl vinyl ether, acidic
ethyl fumarate, acidic ethyl maleate, ethyl acrylate, ethyl
cinnamate, N-ethyl methacrylamide, ethyl methacrylate, ethyl vinyl
ether, 5-ethyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine-1-oxide,
glycidyl acrylate, glycidyl methacrylate, n-hexyl methacrylate,
2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, isobutyl
methacrylate, isobutyl vinyl ether, isoprene, isopropyl
methacrylate, isopropyl vinyl ether, itaconic acid, lauryl
methacrylate, methacrylamide, methacrylic acid, methacrylonitrile,
N-methylolacrylamide, N-methylolmethacrylamide,
N-isobutoxymethylacrylamide, N-isobutoxymethylmethacrylamide,
N-alkyloxymethylacrylamide, N-alkyloxymethylmethacrylamide, N-vinyl
caprolactam, methyl acrylate, N-methylmethacrylamide,
.alpha.-methyl styrene, m-methyl styrene, o-methyl styrene,
p-methyl styrene, 2-methyl-5-vinylpyridine, n-propyl methacrylate,
sodium-p-styrene sulfonate, stearyl methacrylate, styrene,
p-styrenesulfonic acid, p-styrenesulfonamide, vinyl bromide,
9-vinylcarbazole, vinyl chloride, vinylidene chloride,
1-vinylnaphthalene, 2-vinylnaphthalene, 2-vinylpyridine,
4-vinylpyridene, 2-vinylpyridine-N-oxide, 4-vinyl pyrimidine,
N-vinyl pyrrolidone; and W.sub.1, Y.sub.1-4 and R.sub.1-3 are as
described under (a);
[0059] (d) comprises a condensation polymer of the polymeric
materials (a), (b) or (c), wherein a condensable form of (a), (b),
(c) or a mixture thereof is condensed with a second compound which
is selected from the group consisting of phenols, tannins, novolak
resins, lignin compounds, together with aldehydes, ketones or
mixtures thereof, to produce a condensation resin product wherein
the condensation resin product, by adding "Z" to at least a part
thereof, then reacts further by reaction of the resin product with
(1) an aldehyde or ketone (2) a secondary amine to form a final
adduct which may react with an acid.
[0060] In a preferred embodiment, the polymer described above is
characterised in that at least a fraction of the groups Z of the
organic polymer has a polyhydroxyalkylamine functionality, which
results from the condensation of an amine or ammonia with a ketose
or aldose having 3 to 8 carbon atoms.
[0061] Furthermore, the organic polymer may represent a
condensation product of a polyvinylphenol having a molecular weight
of 1000 to 10000 with formaldehyde or paraformaldehyde and with a
secondary organic amine. This secondary organic amine is preferably
selected from methylethanolamine and n-methylglucamine.
[0062] If the organic polymer represents polycarboxylic acid or the
anions thereof, it is preferably selected from polymers or
copolymers of acrylic acid, methacrylic acid or the esterification
products thereof with lower alcohols, for example having 1 to 4
carbon atoms. The solutions or suspensions of these polycarboxylic
acids may additionally contain polymeric alcohols, such as
polyvinyl alcohol, and/or the esterification products thereof with
polymeric alcohol and the polycarboxylic acid may be present
together. When the coating is dried, they then cross-link with one
another by at least partial ester formation.
[0063] In another embodiment, the aqueous solution may contain
polymers or copolymers of vinyl pyrrolidone. Suitable as homo- or
co-polymers of vinyl pyrrolidone are, for example, the polymers
listed in Table 1 or polymers of the monomers listed there.
1TABLE 1 Examples of homo- co-polymers of vinyl pyrrolidone Trade
name and Description manufacturer Vinyl pyrrolidone, homopolymer
Luviskol .RTM., BASF/ISP Vinyl pyrrolidone/vinyl acetate Luviskol
.RTM., BASF/ISP Vinyl pyrrolidone/vinyl caprolactam Luvitec .RTM.,
BASF Vinyl pyrrolidone/vinylimidazole Luvitec .RTM., BASF Vinyl
pyrrolidone/vinylimidazolium methyl Luvitec, BASF sulfate Vinyl
pyrrolidone/Na methacrylate Luvitec .RTM., BASF Vinyl
pyrrolidone/olefin ISP .RTM., Antaron Vinyl
pyrrolidone/dimethylaminoethyl ISP .RTM. methacrylate Vinyl
pyrrolidone/ ISP .RTM., Styleze dimethylaminopropylmethacrylamide
Vinyl pyrrolidone/dimethylaminoethyl ISP .RTM., Gafquat
methacrylate ammonium salt Vinyl pyrrolidone/vinyl caprolactam/ ISP
.RTM. dimethylaminoethyl methacrylate Vinyl
pyrrolidone/methacrylamidopropyl ISP .RTM., Gafquat
trimethylammonium chloride Vinyl pyrrolidone/vinyl caprolactam/ ISP
.RTM., Advantage dimethylaminoethyl methacrylate Vinyl
pyrrolidone/styrene ISP .RTM., Antara
[0064] If polymers or copolymers of vinyl pyrrolidone are used in
the process sequence according to the present invention, the
application solution preferably has a pH of 1 to 6, narrower ranges
possibly being preferred depending on the substrate, the type of
application and the time of exposure. For the treatment of aluminum
surfaces, a pH of 2 to 4 is preferably selected and for the
treatment of zinc or galvanized steel, a pH of 3 to 5.
[0065] The process sequence according to the present invention may
also be applied to car bodies or domestic appliances which have
some surfaces of pre-phosphated or organically pre-coated steel or
correspondingly pre-coated galvanised steel or aluminum. In this
case, the pH of the aqueous solution is preferably adjusted to
about 3 to about 10. A pH of about 3.5 to about 5 may be preferred.
The anti-corrosive coating already present is not attacked by this
process and is even partly reinforced in its anti-corrosive
effect.
[0066] Depending on the substrate, the aqueous solution may
additionally contain 0.001 to 2, preferably 0.005 to 0.5, g/l in
each case, of ions of one or more of the metals Mn, Ce, Li, V, W,
Mo, Mg, Zn, Co and Ni. For environmental reasons, however, the use
of Co and Ni will be avoided if possible. These additional metal
ions may further improve the anti-corrosive effect and paint
adhesion.
[0067] Furthermore, the aqueous solution may additionally contain
0.001 to 1.5, preferably 0.1 to 1 g/l each of phosphoric acid,
phosphorous acid, phosphonic acid and/or the respective anions
and/or their respective esters thereof. The esters should be
selected such that they are water-soluble or water-dispersible.
These additives also improve the anti-corrosive effect and paint
adhesion. However, in accordance with the basic concept of the
present invention, it should be ensured that a combination of
additives leading to the formation of a crystalline,
zinc-containing phosphate layer is not selected, as this would lead
to a conventional zinc phosphate layer which is known in the prior
art and which only brings about an adequate anti-corrosive effect
if the activation and post-passivation steps mentioned above are
additionally carried out. This, however, is precisely what the
present invention is intended to avoid. This may be achieved, for
example, if the treatment solution does not simultaneously contain
zinc and/or manganese in concentrations of more than 0.3 g/l and
phosphoric acid or phosphate ions in concentrations of more than 3
g/l.
[0068] It is advantageous, however, if the aqueous solution also
contains one or more components which are known in the technical
field of phosphating as so-called phosphating accelerators. These
accelerators have the main task, during phosphating, of preventing
the formation of bubbles of elemental hydrogen on the metal
surface. This effect is also referred to as the depolarisation
effect. As with conventional phosphating, this also has the result
in the present process that the formation of the conversion coating
takes place more rapidly and that it is formed more uniformly.
Accordingly, it is preferred for the aqueous solution to contain
one or more phosphating accelerators selected from:
[0069] 0.05 to 2 g/l m-nitrobenzene sulfonate ions,
[0070] 0.1 to 10 g/l hydroxylamine in free or bound form,
[0071] 0.05 to 2 g/l m-nitrobenzoate ions,
[0072] 0.05 to 2 g/l p-nitrophenol,
[0073] 1 to 70 mg/l hydrogen peroxide in free or bound form,
[0074] 0.05 to 10 g/l organic N-oxides
[0075] 0.1 to 3 g/l nitroguanidine
[0076] 1 to 500 mg/l nitrite ions
[0077] 0.5 to 5 g/l chlorate ions.
[0078] Since a particular aim of the process sequence according to
the present invention is avoiding the use of toxic chromium
compounds, it is preferred that the aqueous solution is free from
chromium. Although additions of chromium compounds to the aqueous
solution could, in individual cases, have a positive effect on the
corrosion protection, the corrosion protection that may be achieved
using the present process is adequate even without the use of
chromium compounds in the area of application in question.
[0079] Car bodies are often made from different materials. For
example, steels galvanised in different ways may be combined with
one another or with components of aluminum and/or magnesium or the
respective alloys thereof. A particular strength of the present
process lies in the fact that, even in these cases, effective
corrosion protection is created on the different materials during
the passivation. Accordingly, a specialised embodiment of the
present invention is characterised in that the vehicle bodies or
domestic appliances have surfaces of at least two materials
selected from zinc, aluminum, magnesium, alloys of these metals
with one another or with other alloying elements.
[0080] The aqueous solution used in the passivation step of the
process sequence according to the present invention preferably has
a temperature between ambient temperature (about 15 to 20.degree.
C.) and about 70.degree. C. A temperature of 25 to 40.degree. C. is
preferred. The car bodies or domestic appliances may be contacted
with the aqueous solution by spraying with the aqueous solution or
by dipping in the aqueous solution. Spray processes are preferred.
In general, the aqueous solution is left in contact with the car
bodies or domestic appliances for a period of about 1 to about 5
minutes for the passivation step. A period of 1 to 3 minutes is
preferred in spray processes and a period of 2 to 5 minutes in dip
processes.
[0081] According to the present invention, the passivation step is
followed by painting the vehicle bodies or domestic appliances with
a dipping paint suitable for electrodeposition or with a powder
coating. For vehicle bodies, electrodeposition, particularly
cathodic electrodeposition, is preferred. Modern, lead-free or
low-lead electrodeposition paints capable of being deposited
cataphoretically are suitable for this purpose, i.e. dipping paints
containing less than 500 mg lead per kg dry solids in the paint
suspension. Domestic appliances may also be coated by
electrodeposition. However, powder coating is preferred for this
application for reasons of cost.
[0082] The process sequence according to the present invention is
therefore characterised by the essential steps of cleaning,
passivation and painting. Between these essential process steps,
one or more rinsing stages with process water, tap water or
deionised water may be provided. For the rinsing steps, spray or
dip methods may be employed. The examples show a typical process
sequence. These are laboratory tests, however, where a longer
period of time elapses between passivation and painting than in the
industrial manufacture of car bodies or domestic appliances. For
this reason, the test sheets were dried after passivation and
rinsing by blowing with compressed air and storing in a drying
cabinet. In industrial applications, this drying is necessary if
painting is to be carried out using a powder coating after
passivation. If painting is carried out using electrodeposition, it
is not necessary to dry the components after passivation and
rinsing before they are introduced into the paint dipping bath.
EXAMPLES
[0083] The following substrates were used for the tests:
[0084] hot-dip galvanised steel sheets (HDG),
[0085] electro-galvanised steel sheets (EG),
[0086] aluminum sheets, Al 6016 grade (AC 120).
[0087] The test sheets were subjected to the following process
operation, all steps being carried out by the dipping method:
[0088] 1. Cleaning using an alkaline cleaner: Ridoline.sup.R 1250i
(2%, 65.degree. C., 5 minutes),
[0089] 2. Rinsing using deionised water,
[0090] 3. Passivation by treatment using a test product according
to Table 1 (pH 4, 30.degree. C., 3 minutes),
[0091] 4. Rinsing using deionised water,
[0092] 5. Drying by blowing with compressed air and storage in a
drying cabinet at 55.degree. C.,
[0093] 6. Cathodic electrodeposition painting using the lead-free
electrodeposition paint Cathoguard.sup.R CG 310 from BASF.
[0094] The following corrosion tests were carried out on the sheets
pre-treated in this way, the results of which are compiled in Table
2:
[0095] Test under changing climatic conditions according to VDA
621-415, 10 cycles. The creepage at the scribe over half the scribe
width (U/2) is entered in Table 2 in mm.
[0096] Flying stones impact test according to VDA 621-427. The
paint adhesion is given as the K-value, 1 representing the best
value (no paint spalling) and 10 the worst (complete detachment of
paint).
[0097] Copper/acetic acid-accelerated salt-spray test according to
DIN 50021 (CASS, 10 days) or neutral salt-spray test according to
DIN 50021 (SS, 20 days). The creepage is given as in the test under
changing climatic conditions.
2TABLE 1 Test products Test product Composition Test product 1 75
mg/l Ti as TiF.sub.6.sup.2- 125 mg/l condensation product of a
polyvinylphenol having a molecular weight of 1000 to 10000 with
formaldehyde and n-methylglucamine Test product 2 75 mg/l Ti as
TiF.sub.6.sup.2- 250 mg/l vinyl pyrrolidone-vinyl caprolactam
copolymer Test product 3 400 mg/l Zr as ZrF.sub.6.sup.2- 750 mg/l
modified polyacrylic acid (Acumer.sup.R 1510, Rohm and Haas) Test
product 4 400 mg/l Zr as ZrF.sub.6.sup.2- 250 mg/l modified vinyl
pyrrolidone-vinyl caprolactum copolymer Test product 5 150 mg/l Ti
as TiF.sub.6.sup.2- 200 mg/l condensation product of a
polyvinylphenol having a molecular weight of 1000 to 10000 with
formaldehyde and n-methylglucamine 350 mg/l phosphate 200 mg/l
Mn
[0098]
3TABLE 2 Corrosion protection results a) Substrate: aluminum AC120
CASS (DIN 50021) Test product no. U/2 (mm) K-value 1 0.5 8 2 0.4 7
cleaned only 0.6 9 (comparison) b) Substrate: EG Test product SS
(DIN 50021) VDA 621-415 no. U/2 (mm) K-value U/2 (mm) K-value 1 5
9.5 2.5 7 2 5.1 7 1.7 7 3 6.2 9.5 4 5.1 7 5 2.8 7 cleaned only 2.8
10 (comparison) Outdoor weathering test (1 year) painted with full
system Test product U/2 K-value 5 0.2 1.5 c) Substrate: HDG Test
product SS (DIN 50021) VDA 621-415 no. U/2 (mm) K-value U/2 (mm)
K-value 1 4.2 7.5 2.8 8.5 2 3.5 7.5 3.2 8 3 4.8 9.5 4 3.2 7.5 5 1.5
8 cleaned only 4.8 10 (comparison) Outdoor weathering test (1 year)
painted with full system Test product U/2 K-value 5 0.2 2
[0099] Another test was performed to see how the pre-treatment
process behaves on grinding points on pre-phosphated galvanised
steel. In practice, these grinding points occur when defects on a
car body are repaired by grinding them off.
[0100] For the test, electro-galvanised, pre-phosphated steel,
ground and unground, was treated with test products 1 and 2. The
cathodic electrodeposition paint Cathoguard.RTM. 310 was then
applied. The corrosion test took the form of a test under changing
climatic conditions according to VDA 621-415 over 10 cycles,
combined with a flying stones impact test according to VDA 621-427.
The results are compiled in Table 3.
4TABLE 3 Investigations into grinding points. Substrate:
electro-galvanised, pre- phosphated steel EG.sub.prephos
EG.sub.prephos unground ground U/2 U/2 Test product [mm] K [mm] K 1
0.3 4 1.0 3.5 2 0.4 3.5 0.9 3
* * * * *