U.S. patent application number 11/070540 was filed with the patent office on 2005-11-17 for process for production of a metal substrate containing a protective coating.
Invention is credited to Labouche, Didier, Matton, Stephane, Spehar, Jean-Marc, Tarlowski, Marc.
Application Number | 20050252578 11/070540 |
Document ID | / |
Family ID | 34746566 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050252578 |
Kind Code |
A1 |
Tarlowski, Marc ; et
al. |
November 17, 2005 |
Process for production of a metal substrate containing a protective
coating
Abstract
The present invention relates to a process for the production of
metal substrates containing a protective coating, especially
substrates based on iron, like steel, galvanized steel, or
electrogalvanized steel, generally used in construction and in the
automotive industry.
Inventors: |
Tarlowski, Marc; (Preseau,
FR) ; Matton, Stephane; (Herin, FR) ; Spehar,
Jean-Marc; (Lambres Les Douai, FR) ; Labouche,
Didier; (Saint Amand Les Eaux, FR) |
Correspondence
Address: |
PPG Industries, Inc.
Intellectual Property Department
One PPG Place
Pittsburgh
PA
15272
US
|
Family ID: |
34746566 |
Appl. No.: |
11/070540 |
Filed: |
March 2, 2005 |
Current U.S.
Class: |
148/247 |
Current CPC
Class: |
B05D 3/10 20130101; B05D
3/067 20130101; B05D 7/16 20130101; C23C 22/83 20130101; B05D 3/068
20130101; C09D 5/08 20130101; C23C 22/361 20130101; B05D 7/546
20130101 |
Class at
Publication: |
148/247 |
International
Class: |
C23C 022/48 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2004 |
FR |
04 50437 |
Claims
1. A process for the production of a metal substrate, containing a
protective coating, said substrate being based on iron, like steel,
galvanized steel or electrogalvanized steel, or based on aluminum
or its alloys, said process comprising the following steps: (a)
degreasing of the substrate with an alkaline solution, this step
being optional when treatment is carried out directly on a
continuous galvanizing or electrogalvanizing line; (b) rinsing with
water, preferably demineralized; (c) activation of the metal
substrate with an activation composition based on at least one
metal fluoroacid; (d) drying of the metal substrate; (e)
application of an aqueous primer composition capable of being
polymerized by irradiation with UV radiation or by electron
bombardment, to form film of aqueous primer composition at least on
1 .mu.m thick, preferably 3 to 5 .mu.m thick, said primer
composition containing: a polymer binder, containing: 40 to 85 % by
weight, relative to the total weight of said primer composition, of
at least one unsaturated polymer resin, containing at least one
acrylate group and capable of being polymerized by irradiation with
UV radiation or by electron bombardment; 5 to 50 % by weight,
relative to the total weight of said primer composition, of at
least one saturated polymer resin not containing an acrylate group;
and in the case, where polymerization is performed by irradiation
with UV radiation, 1 to 10 % by weight, relative to the weight of
the said primer composition, of at least one photoinitiator; a
pigment paste, containing: a grinding resin; 1 to 20 % by weight,
relative to the total weight of said primer composition, of at
least one corrosion inhibitor pigment; and optionally, at least one
filler; and water, preferably demineralized, as dispersion medium
of said primer composition, (f) heat treatment to eliminate the
residual water of the film of aqueous primer composition, and (g)
crosslinking of the film of aqueous primer composition to obtain a
primer film, having a thickness of at least 1 .mu.m, and preferably
3 to 5 pm, after crosslinking.
2. The process according to claim 1, characterized by the fact that
degreasing step (a) of the substrate is carried out with an
alkaline solution with a pH equal to or greater than 12, preferably
about 13.
3. The process according to claim 1 or 2, characterized by the fact
that the alkaline solution used in degreasing step (a) of the
substrate is a solution based on potassium hydroxide or sodium
hydroxide.
4. The process according to any of the claims 1 to 3, characterized
by the fact that the degreasing step (a) of the substrate is
carried out by immersion in a bath of said alkaline solution, whose
temperature ranges from55 to 60.degree. C.
5. The process according to any of the preceding claims,
characterized by.the fact that the metal fluoroacid of the
activation composition of step (c) is chosen from fluorozirconic
acid, fluorotitanic acid and fluorosilicic acid.
6. The process according to claim 5, characterized by the fact that
the fluoroacid is fluorozirconic acid.
7. The process according to claim 6, characterized by the fact that
the fluorozirconic acid is present in an amount of 0.1 g/L to 20
g/L, relative to the weight of the activation composition.
8. The process according to claim 6 or 7, characterized by the fact
that the fluorozirconic acid is associated with a resin having an
epoxide structure, preferably a resin derived from polyepoxides,
especially bisphenol A.
9. The process according to any of the preceding claims,
characterized by the fact that the unsaturated polymer resin,
containing at least one acrylate group of the primer composition of
step e), is a resin, chosen from epoxy-acrylates,
urethane-acrylates, polyester-acrylates,
polyester-urethane-acrylates, ether acrylates, amine acrylates or
their mixtures.
10. The process according to claim 9, characterized by the fact
that the unsaturated polymer resin, containing at least one
acrylate group, is a urethane-acrylate resin.
11. The process according to one of the preceding claims,
characterized by the fact that the saturated polymer resin not
containing an acrylate group of the primer composition of step e)
is chosen among dispersions or emulsions of acrylic,
acrylic-styrene, acrylic-urethane and polyester resin.
12. The process according to any of the preceding claims,
characterized by the fact that the photoinitiator of the primer
composition of step e) is chosen among benzyl ketones,
dialkylacetylphenones, alpha-hydroxyalkylphenones, acylphosphine
oxides and benzophenone.
13. The process according to any of the preceding claims,
characterized by the fact that the grinding resin of the primer
composition of step e) consists of a saturated polymer resin not
containing an acrylate group of said primer composition.
14. The process according to any of the preceding claims,
characterized by the fact that the inhibitor pigment or pigments of
the pigment paste of the primer composition is (or are) chosen
among calcium chromates, phosphates, borate, molybdates and
silicates.
15. The process according to one of the preceding claims,
characterized by the fact that the primer composition has a pigment
concentration in CPV volume of inhibitor pigments ranging from 0.1
to 0.25, preferably 0.1 to 0.15.
16. The process according to one of the. preceding claims,
characterized by the fact that the inhibitor pigment or pigments of
the pigment paste of the primer composition is (or are) associated
with one or more corrosion inhibitor(s) in liquid form.
17. The process according to claim 16, characterized by the fact
that the corrosion inhibitor or inhibitors in liquid form is (or
are) chosen among aqueous solutions of
1-(benzo-thiazol-2-ylthio)succinic acid and aqueous solutions of
ethylene methacrylate phosphate.
18. The process according to any of the preceding claims,
characterized by the fact that the crosslinking of step g) is
carried out under a UV lamp under nitrogen with an oxygen level
lower than 200 ppm.
19. The process according to any of the preceding claims,
characterized by the fact that it comprises, after the crosslinking
step g) of the aqueous primer composition film, a finishing step
h), comprising: application of finishing composition on the primer
film, followed by crosslinking of said finishing composition to
obtain a finishing coat.
20. The process according to claim 19, characterized by the fact
that the finishing step h) is a finishing [process-translator],
comprising: application of a finishing composition based on
polyester melamine or polyester urethane or polyvinyl difluoride,
followed by crosslinking of said finishing composition by heating
in a drying cabinet with a temperature in the range from
240-250.degree. C., to obtain a crosslinked finishing coat.
21. The process according to claim 19, characterized by the fact
that finishing of step h) is cold finishing, comprising:
application of a finishing composition based on urethane-acrylate,
followed by crosslinking of said finishing composition by electron
bombardment, to obtain a finishing coat.
Description
[0001] Aqueous Primer Compositions
[0002] Ingredients:
[0003] Aliphatic urethane-acrylate resins dispersed in an aqueous
phase:
[0004] resin, marketed by UCB under the commercial name Ucecoat
DW7770.RTM., and
[0005] resin, marketed by Synthopol Chemie under the commercial
name Syntholuc DRB 1577.RTM..
[0006] Acrylic resins dispersed in the aqueous phase:
[0007] resin, marketed by UCB under the commercial name Duroxyn
Vax.RTM., and
[0008] resin, marketed by Clariant under the commercial name
Mowilith LDM 7170.RTM..
[0009] Photoinitiator:
[0010] alpha, alpha-dimethoxy-alpha-hydroxyacetophenone, marketed
by Ciba Geigy under the commercial name Darocur 1173.RTM..
[0011] Inhibitor pigments:
[0012] calcium silicate, marketed by the GRACE Division under the
commercial name Shieldex C303.RTM.,
[0013] aluminum triphosphate, marketed by Safic Alcan under the
commercial name Kwhite KTC 720.RTM.kk,
[0014] zinc salt of an organic acid, marketed by Cognis under the
commercial name Alcophor 827.RTM..
[0015] Fluorinated surfactant:
[0016] solution of polyether modified with polysiloxane, marketed
by Byk Chemie under the commercial name Byk 346.RTM..
[0017] Thickener:
[0018] polyurethane thickener, marketed by Schwegmann under the
commercial name Schwego pur 8050.RTM..
[0019] Anti-foaming agent:
[0020] mixture of polysiloxane and hydrophobic particles, marketed
by Byk Chemie under the commercial name BYK 028.RTM..
[0021] Finishing composition:
[0022] hydroxylated polyester resin (in organic solvents)
[0023] Composition of Primer 1
1 Chemical nature Amount (parts by weight) Ucecoat DW 7770 .RTM. 80
Duroxyn Vax .RTM. 20 Shieldex C303 .RTM. 10 Kwhite KTC720 .RTM. 5
Alcophor 827 .RTM. 0.5 Byk 346 .RTM. 0.2 Schwego pur 8050 .RTM. 0.3
Irgacure 500 .RTM. 1
[0024] Composition of Primer 2:
2 Chemical nature Amount (parts by weight) Ucecoat DW 7770 .RTM. 80
Duroxyn Vax .RTM. 20 Shieldex C303 .RTM. 10 Kwhite KTC720 .RTM. 5
Alcophor 827 .RTM. 0.5 Byk 346 .RTM. 0.2 Schwego pur 8050 .RTM. 0.3
Irgacure 500 .RTM. 1
[0025] 2. Measurement Methods
[0026] Salt Spray Test
[0027] The anticorrosion performances of the samples are determined
with the salt spray test. After deposition of the protective
coating, the coated steel sheets are subjected to the salt spray
test, carried out according to Standard NF X 41-002. This test
consists of spraying of a 5% by weight aqueous solution of NaCl,
kept at a temperature of 35.degree. C., in the form of a mist. The
sheets are regularly examined at different stages (at 24 hours, 72
hours, 144 hours and 150 hours) of exposure to the salt spray. The
presence of formed zinc salts is evaluated visually according to
the following scale:
[0028] -: no zinc salts
[0029] +: traces of zinc salts
[0030] ++: formation of zinc salts (non-negligible)+
[0031] +++: abundant formation of zinc salts
[0032] Solvent Resistance Test
[0033] After application of the primer, and after application of a
finishing coat, the resistance of the coated sheets to a solvent
like methyl ethyl ketone is evaluated.
[0034] For this purpose, the following procedure is used:
[0035] cotton is dipped in methyl ethyl ketone,
[0036] the impregnated cotton is then applied to the surface of the
sheet with a back-and-forth movement, and
[0037] the number of back-and-forth movements (or passes) carried
out on the appearance of softening and detachment of the protective
coating from the sheet is determined.
[0038] The higher the number of passes, the greater the degree of
protection of the substrate, due to the coating.
[0039] Adherence Test
[0040] The degree of adherence of the protective coating to the
surface of the metal substrate is determined as follows, according
to Standard ISO 2409:
[0041] incisions are made, forming a square grid pattern on the
surface of the protective coating (10.times.10 on a 1.5 cm.sup.2
surface), then
[0042] adhesive tape with a width at least equal to the ruled
surface, carrying the reference 595TR1966, furnished by the 3M
company, is attached to the incised surface,
[0043] during peeling of the adhesive tape, the adhesive surface is
observed visually to determine the presence or absence of coating
flakes.
[0044] ERICHSEN Test
[0045] This test consists of deformation to 90% break of the coated
substrate. This deformation is done on the back of the coated
substrate.
EXAMPLE 1
[0046] Three galvanized steel sheets are degreased by immersion for
5 to 10 seconds in a bath containing 3.75% by weight of Chemetall
Parco 305E.RTM., relative to the total weight of the bath. The pH
of the bath is 13 to 14 and the temperature 50.degree. C. to
60.degree. C.
[0047] The sheets are then rinsed with cold demineralized water,
then dried in a drying cabinet at 125.degree. C. for 4 minutes.
[0048] The degreased, rinsed and dried sheets are then subjected to
activation treatment by immersion in a bath of composition AFZ1 for
one minute. The plates are then dried in a drying cabinet for 5
minutes at 125.degree. C.
[0049] In the five minutes following drying, the primer composition
1 is then applied, thus forming a moist primer film on the surface
of the sheets about 10-12 .mu.m thick.
[0050] The sheets coated with moist primer film are subjected to
heat treatment ("flash off") for 2 minute at 125.degree. C., then
crosslinking via radiation with UV radiation. A crosslinked coating
with a thickness of about 5-6 .mu.m is obtained.
[0051] The salt spray test is conducted on the sheets, along with
the adherence test, the solvent resistance test and the "ERICHSEN"
test.
[0052] The coated sheets are then subjected to finishing treatment.
This consists of applying a finishing composition of the
polyester/melamine type, conventionally used in the paint industry.
This finishing composition is applied by means of a laboratory
rule, then crosslinked by firing at 240.degree. C. for 30 s.
[0053] After finishing treatment, the solvent resistance test,
adherence test and "ERICHSEN" test are performed again.
[0054] The results obtained in these different tests are summarized
in Table 1.
COMPARATIVE EXAMPLE C1
[0055] As a comparison relative to example 1, the same protective
coating as described in example 1 is applied to the galvanized
steel sheets, proceeding in the same manner as described in example
1, except for the immersion step in the bath of composition AFZ 1
based on fluorozirconic acid, which was omitted.
[0056] In the same manner as in example 1, the salt spray test is
carried out on the sheets so coated (only before application of the
finishing coat), along with the adherence test, the solvent
resistance test and the "ERICHSEN" test.
[0057] The results obtained in these different tests are also
summarized in Table 1.
3 TABLE 1 "ERICHSEN" test Solvent Adherence of deformation Salt
spray test resistance test test resistance Example 1 without No
oxidation 90 2 0 finishing with >100 0 0-1 finishing Comparative
without Oxidation 90 2 3 example 1 finishing with >100 5 1
finishing
[0058] Comparison of the results of the salt spray test of examples
1 and C1 shows the presence of incipient oxidation when the
specimen was not subjected to initial activation treatment (example
C1). This is illustrated by examples 1 to 3, in different stages of
exposure to the salt spray (at 24 hours, 72 hours and 144 hours,
respectively). These figures show that the sheets of comparative
example 1 have white longitudinal traces (called "bleeding") that
correspond to the formation of zinc chloride and zinc hydroxide
(white rust), whereas the sheets of example 1 do not show them. The
resistance to salt spray is therefore better when the sheets have
been subjected to activation treatment with fluorozirconic acid
prior to deposition of the primer composition.
[0059] In addition, the adherence and behavior in the "ERICHSEN"
deformation test are significantly better with initial activation
treatment. In this case (example 1), no delamination of the coating
is observed. This is illustrated in FIG. 4. The sheets of FIG. 4
each show a lower part and an upper part: the lower part contains
the primer film and the finishing coat, whereas the upper part
contains only the primer film. FIG. 4 shows that at the deformation
site, there is no longer any coating for the sheet of comparative
example 1, both for the upper part (with finishing coating), or for
the lower part of the sheet (without finishing coating). On the
other hand, in the case of example 1, the coating persists (for the
lower part and upper part with the finishing coat). As a result,
activation treatment with fluorozirconic acid improves the
adherence of the protective coating to the metal substrate.
EXAMPLE 2
[0060] Galvanized steel sheets are degreased by immersion for 5
seconds in a bath containing 3.25% by weight of Chemetall Parco
305E.RTM., relative to the total weight of the bath. The pH of the
bath is 13 to 14 and the temperature 50.degree. C.
[0061] The sheets are then rinsed with cold demineralized water,
then dried at 125.degree. C. for 4 minutes.
[0062] The degreased, rinsed and dried sheets are then subjected to
activation treatment by immersion in a bath of composition AFZ1 for
1 minute.
[0063] The plates are then dried in a drying cabinet for five
minutes at 125.degree. C.
[0064] In the five minutes following drying, primer composition 2
is then applied, thus forming a primer film on the surface of the
sheet, having a thickness of about 10-12 .mu.m.
[0065] The sheets so coated with primer film are then subjected to
heat treatment ("flash off") for 2 minutes at 125.degree. C., then
crosslinking by irradiation with UV radiation (one pass at 10 m/min
under two emitters of the RPC 80 W type under nitrogen).
[0066] The salt spray test, adherence test ("ruling"), the solvent
resistance test (A/R MEK) and the "ERICHSEN" of deformation
resistance are then carried out on the sheets so coated.
[0067] The coated sheets with the primer film are then finally
subjected to the same finishing treatment as in example 1.
[0068] A new solvent resistance test, adherence test and RXN
"ERICHSEN" test of deformation resistance are then carried out.
[0069] The results obtained in the different tests are shown in
Table 2.
COMPARATIVE EXAMPLE 2
[0070] As comparison relative to example 2, the same protective
coating as described in example 2 is applied to the galvanized
steel sheets, proceeding in the same manner as described in example
2, except for the immersion step in the bath of composition AFZ1
based on fluorozirconic acid, which was omitted.
[0071] The results of the different tests are also shown in Table
2, as for example 2.sup.1. .sup.1Translator's note: sic--perhaps
the French should have read "as for example 1" because the
reference is to the way results were shown in the prior table,
which showed the results of example 1.
4 TABLE 2 "ERICHSEN" test Solvent Adherence of deformation Salt
spray test resistance test test resistance Example 2 without No
corrosion 15 0 0 finishing with X >100 0 1-2 finishing
Comparative without Traces of 17 0 0 example C2 finishing white
rust with X 90 1 2 finishing
[0072] Comparison of the results of the salt spray tests of
examples 2 and C2 is illustrated by FIGS. 5 and 6. These figures
show that the sheets of comparative example 2 have white
longitudinal traces (called "bleeding") after 140 hours in a salt
spray, whereas the sheets of example 2 do not show them. The
resistance to salt spray is therefore better when the sheets have
been subjected to activation treatment with fluorozirconic acid
prior to deposition of the primer composition.
[0073] Moreover, adherence and behavior in the deformation test
("ERICHSEN" test) of the sheets coated with a finishing coat are
significantly better, when the substrate has been subjected to
activation treatment.
EXAMPLE 3
[0074] Galvanized steel sheets are degreased by immersion for 5
seconds in a bath containing 3.75% by weight of Chemetall Parco
305E.RTM., relative to the total weight of the bath. The pH of the
bath is 13 to 14 and the temperature 50.degree. C.
[0075] In the same manner as in examples 1, 2, C1 and C2, the
sheets are then rinsed with cold demineralized water, then dried at
125.degree. C. for 4 minutes.
[0076] The degreased, rinsed and dried sheets are then subjected to
activation treatment by immersion in a bath of composition AFZ3 for
2 minutes.
[0077] The sheets are then dried in a drying cabinet ("flash off")
for 2 minutes at 1 25.degree. C.
[0078] In the five minutes following drying, the primer composition
1 is then applied, thus forming on the surface of the sheet a wet
primer film, having a thickness of about 10-12 .mu.m. The sheets
coated with primer are then subjected to the same finishing
treatment as for example 1.
[0079] FIG. 7 shows the state of the coated sheets of example 3,
after having been subjected to the salt spray test for 150
hours.
COMPARATIVE EXAMPLE 3
[0080] As a comparison relative to example 3, the same protective
coating as described in example 3 is applied to the galvanized
steel sheets, proceeding in the same manner as described in example
3, except for the immersion step in the bath of composition AFZ3
based on fluorozirconic acid, nitric acid and cationic resin, which
was omitted.
[0081] FIG. 8 shows the state of the coated sheets of example 3,
after having been subjected to the salt spray test for 150
hours.
[0082] The comparison of FIGS. 7 and 9 shows that the sheets of
example 3 have significantly fewer white traces ("bleeding") than
those of comparative example 3, indicating that prior activation
treatment imparts better corrosion protection to the primer
film.
EXAMPLE 4
[0083] Electrogalvanized steel sheets are degreased by immersion
for 5 seconds in a bath containing 3.75% by weight of Chemetall
Parco 305E, relative to the total weight of the bath. As for the
preceding examples, the pH is 13 to 14, and the bath temperature
50.degree. C.
[0084] The electrogalvanized steel sheets, in the same manner as
desribed in the preceding examples, are rinsed with cold
demineralized water, then dried at 125.degree. C. for 4
minutes.
[0085] The degreased, rinsed and dried sheets are then subjected to
activation treatment by immersion in the bath at ambient
temperature of composition AFZ2 for one minute.
[0086] The sheets are then dried in a drying cabinet ("flash off")
for 2 minutes at 125.degree. C.
[0087] In the five minutes following drying, the primer composition
1 is then applied, thus a film forming on the surface of the sheet
with a wet thickness of about 10-12 .mu.m. The sheets coated with
primer are then subjected to the same finishing treatment as for
example 1.
COMPARATIVE EXAMPLE 4
[0088] As comparison, relative to example 4, the same protective
coating as in described in example 4 is applied to the
electrogalvanized steel sheets, proceeding in the same manner as
described in example 4, except for the immersion step in the bath
of composition AFZ2 based on fluorozirconic acid, which was
omitted. The comparison of the results of the salt spray test
(after exposure of 150 hours to salt spray) of examples 4 and C4 is
illustrated in FIG. 9. This figure shows that the corrosion
behavior is significantly better when prior activation treatment
occurs with a composition based on the metal fluoroacid.
EXAMPLE 5
[0089] Electrogalvanized steel sheets are degreased by immersion
for 5 seconds in a bath containing 3.75% by weight of Chemetall
Parco 305E.RTM., relative to the total weight of the bath. As for
the preceding examples, the pH is 13 to 14, and the temperature of
the bath is 50.degree. C.
[0090] The electrogalvanized steel sheets, in the same manner as
the preceding examples, are rinsed with cold demineralized water,
then dried at 125.degree. C. for 4 minutes.
[0091] The degreased, rinsed and dried sheets are then subjected to
activation treatment by application with a roll coater in a bath at
ambient temperature of composition AFZ2 for one minute.
[0092] The sheets are then dried in a drying cabinet ("flash off")
for 2 minutes at 125.degree. C.
[0093] In the 5 minutes following drying, the following primer
composition is then applied, thus forming a wet primer film on the
surface of the sheet, having a thickness of about 6 .mu.m:
5 Rom UV: SM1530/140B Duroxyne VZX6127 18 Water 4.3 Anti-foaming
agent byk 028 0.1 TEA 1 Schieldex C303 3.6 K wite ktc 720 1.6
Ucecoat DW7770 72 Byk 346 0.3 Irgacure 500 1 Schewgo pur 0.4
[0094] The sheets so coated then receive a film with 20 .mu.m dry
thickness of the anticorrosion primer W780-9735 from PPG by cathode
electrodeposition.
[0095] A corrosion test VDA 621-41, an alkaline degreasing test and
an Erichsen test are then carried out on the sheets.
COMPARATIVE EXAMPLE C5
[0096] For comparison, relative to example 5, the same protective
coating as described in example 5 is applied to the
electrogalvanized steel sheets, proceeding in the same manner as
described in example 5, except for the immersion step in the bath
of composition AFZ2 based on fluorozirconic acid, which was
omitted.
[0097] Corrosion Behavior VDA 621-415
6 Example C5 Example 5 Red rust 30% 0-1% White rust 60% 15%
Degreasing behavior Complete softening Good behavior Example 5
Example C5 Erichsen adherence 3-4 0.1
[0098] Comparison of the results shows that activation (example 5)
imparts significantly better corrosion behavior, alkaline
degreasing behavior and adherence to the substrate.
[0099] This can be observed in FIGS. 9 and 10.
* * * * *