Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a process for the treatment
of a metal surface and a process for the aftertreatment of metal
surface containing a chemical conversion coating.
In conventional processes ~or treating metal surfaces
` in order to improve the corrosion resistance and adhesion of
paints, there have been used acids and salts containing cations
such as chromium, iron, manganese, aluminum, zinc, nickel and
; anions such as phosphates, borates, nitrates, chromates, bi-
` chromates to precipitate the insoluble salts on the metal sur-
face. Coatings containing a titanium compound as an essential
component have not provided satisfactory properties both for
the corrosion resistance and for the adhesion with paints. In
addition, the use of treating solutions containing ions such as
chromium, zinc, manganese and the like have been restricted in
~' view of the undesirability of their control and environmental
pollution.
It has now been found that a coating having an
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-~ improved corrosion resistance and good paint adhesion can be
formed by applying an aqueous treating solution or emulsion
comprising a solution or emulsion of a water soluble ~r water
emulsifiable type resin, a water soluble titanium compound, and
-iw luding fluoride ion, onto a metal surface.
In another aspect of the invention there is provided
an aqueous composition which comprises the water soluble or
water emulsifiable resin and the dissolved titanium compound
:- together with fluoride.
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Metals capable of being treated according to this
invention include, for example, iron, zinc and aluminum. The
;`1 metal may be treated with a conversion coating by any suitable
~ 30 zinc-based phosphating process, iron-based phosphating process,
or chromating process such as those disclosed in the Metal
Finishing Guidebook.
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Solution or emulsion resins usable in this invention
, may be those having an activity as a binder, but should prefer-
ably also be those having high corrosion resistance and high
stability in the presence of a water soluble titanium compound.
Solution or emulsion of resins may be conventional resins which
include, for example, polymers or copolymers based on vinyl
such as vinyl acetate, vinylidene chloride and vinyl chloride,
~ acrylic such as acrylates, acrylic acid, and methacrylic acid,
; polyesters, polymers or copolymers based on monomers of amino-
alkyl, epoxy, urethane, or styrene, polyethylene polymer or
copolymers, natural or synthetic rubber, natural high mole-
cular weight resins and the like.
These solution and emulsion resins are used in a con-
; centration of 0.1 to 6C% by weight of solid resin, depending
on the type of resin, viscosity and application procedure.
Water-soluble titanium compounds usable in the
invention include K2TiF6, Na2TiF6, (~H4 ~iF6, TiF4, Ti(S04)2,
TiOS04, acid soluble titanium compounds, for example, TiO,
; `Ti203, TiO3, H2TiO3, H4TiO4 can also be employed. The concent-
ration of the water-soluble titanium compound depends on the
solubility, stability in the presence of the resin, type and
viscosity o~ the resin solution or emulsion and application
procedure. In general, the compound is used as a solution con-
taining 0.1 to l~/o by weight.
In order to improve the solubility of the titanium
compound, to adjust the pH of solution or to stabilize the resin
solution or emulsion, there may be used amines such as ethylamine,
dimethylamine, trimethylamine, hexylamine and the like, alkaline
bases such as ammonia, caustic soda, caustic potash and the
like, inorganic acids, for example, phosphoric acid, nitric !'
~; acid, sulfuric acid, hydrofluoric acid and the salts thereof,
and organic acids, for example, oxalic acid, citric acid, malic
acid, maleic acid, phthalic acid, acetic acid and the salt~
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`~ thereof. If desired, the solution or emulsion may contain a
pigment.
The composition in a preferred embodiment may contain
' a fluoride, in particular the fluoride being present as
fluoride ion in an amount sufficient to complex at least a
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; portion of the titanium present. The fluoride may conveniently
form part of the water-soluble titanium compound as indicated
above, however, it may be added independently as hydrofluoric
acid or a salt thereof, as indicated above.
.
In order to prepare the treating solution or emulsion -
comprising a solution or emulsion of a resin and a water-soluble
,
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titanium compound, the titanium compound may be dissolved in
water and then ~he resin added to form the solution or
emulsion, or the resin may be dissolved or dispersed into
water to form the isolution or emulsion and then the water-
soluble titanium compound added as solid product as such or
as the solution, or both the water-soluble titanium compound
and the resin may be added concurrently to form the solution
or emulsion. The proportion on the basis of weight of said
resin to water-soluble titanium compound may be 100:1 to 1:10,
preferably 20:1 to 1:1.
The treating solution or emulsion may be applied
onto metal surace to be treated by any conventional technique,
...
such as immersiny, pouring, brushing or spreading by means of
a roller and allowed to stand as such or dried to form a tough
coating haviny an improved corrosion resistance. The coating
or immersion procedure may be conducted at a temperature
ranging from room temperatures to 80C or higher. The
i drying operation may be carried out at a temperature suitable
for the resin employed and normally ranging from 80 to 250C
~20 for 0.2 to 10 minutes.
The coating formed according to this invention
` provides excellent corrosion resistance and adhesion with
paints.
This invention will now be illustrated by the
~25 following examples, in which all percentages are by weight.
~- EXAMPLE 1
Potassium titanium fluoride (K2TiF6, 1 yram) was
dissolved in water (500 ml). To the solution was added an
aqueous 46~ emulsion o~ acrylic resin ~50 grams, Primal
~30 E-269 prepared by Nippon Acryl CoO) and water to make 1 liter.
The resulting treating emulsion contained the acrylic solid
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resin in a concentration o~ 2~3~ and potassium titanium
fluoride in a concentxation of 0.1~. This treating emulsion
was applied to degreased and cleaned alu~inum plate of 2S
- type by the immersion procedure and the coated aluminum
; 5 plate was dried at 120C for 3 minutes. The treated plate
was subjected to a corrosion test based on the salt spray
test according to JIS Z-2371 (referred to hereinafter as the
salt spray test~. For comparison, identical panels were
treated with the same solution without titanium. Results
are given in Table 1.
- Table 1
Salt Spray Test
.~.
Test Period Resin Only Resin with Titanium
100 hrs. 60 - 80% white stain No Stain
~15
200 hrs. 100% white stain No Stain
Coating Weight 300 - 350 mg/m2 300 - 350 mg/m2
,: EXAMPLE 2
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Various amounts of ammonium titanium fluoride
1 (NH4)2TiF6, 1 ~ram, 3 grams and 5 grams ] were dissolved
in water (500 ml.) and to each solution was added an aqueous
40% emulsion of acrylate resin (50 grams, Tocryl N-142~
prepared by Toyo Ink Co.) and the compositions were made up
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to 1 liter with water. The pH of each resulting emulsion
was adjusted to a value from 1 to 2 by adding 75% phosphoric
acid (10 grams). Degreased and cleaned aluminum plates of
~ 2S-type were brushed separately with the treating emulsion
`~ and dried under the same conditions to those disclosed in
EXAMPLE 1. The coated Al plate was subjected to the corrosion
resistance test based on the salt spray test.
Additionally, degreased and cleaned aluminum plates
treated as above were coated with a conventional paint solution
for protecting cans by means of a barcoatex and dried at 180C
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for 6 minutes to prepare coat~cl specimens having a ~ilm
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~ thickness of 3 microns. The specimens were immersed in pure
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,jj water at 80C for 30 minutes to simulate can processing
conditions and the whitening of the ~ilm was compared. Table 2
shows the results of these tests.
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Table 2
Salt Spra~
(NH4)2TiF6 75~ H3POa
g/l g/l 168 hrs 500 hrs Whitening test
.... . _ .. _ .. .
.I0 0 0 100% stained - lO0~ whitened
0 lO lO0~ stained - 100~ whitened
1 lO No Stain 50% stained 100% whitened
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3 lO No Stain No Stain No Stain
, 5 lO No Stain No Stain No Stain
__
EXAMPLE 3
Iron of SPC-l was degreased, cleaned and treated
with a zinc-based phosphating solution (Bonderite 137 prepared
by Nihon Parkerizing Co.). The thus-treated plate was
-20 immersed into an aqueous emulsion containing ammonium titanium
fluoride [ (NH4)2TiF6] in a concentration of lO grams/liter
acrylate resin emulsion (Tocryl ~-2009 prepared by Toyo Ink
Co.) in a solid resin concentration of 3% and dried at 120C
for 3 minutes. The treated plate was subjected to the salt
i25 spray corrosion resistance test. Table 3 shows the reswlts
obtained.
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Table 3
Salt Spray Test
Specimen 0.5 hrs 1 hr 2 hrs
No A~tertreatment 100% red - -
stain
Aftertreatment by resin 10-30% red 80~ red 100~ red
emulsion alone stain stain stain
Atertreatment according
to the invention No stain No stain No stain
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` 10 EXAMPLE 4
.
Galvanized steel plate was degreased, cleaned and
- pretreated with zinc-based phosphating solution. The pretreated
film was then coated with an aqueous dispersion containing -
~ ammonium titanium fluoride [ (NH4)2TiF6 ] in a concentration
'15 of 10 grams/liter and polyvinylidene (derived from ~iophane
.~. .
- 290D prepared by Petroleum Chemical Badisch Co.) in a solid
resin content of 10~ by means of roller coating process,
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dried at 120~C for 3 minutes. The aftertreated plate was -~
subjected to the salt spray corrosion resistance test, a
20 second set of panels were treated in the same manner and
painted with an aminoalkyd paint to a thickness of 20 microns.
- These panels were scribed and the corrosion creepage fxom the
scribe was measured. Table 4 gives the results.
.! Table 4
~25 Painted Panel
Salt Spray Test Scribe Creepzge
Specimen 1 hr 2 hrs 120 hrs
No aftertreatment 50~ white 100% white
rust rust 10 - 20 mm
Aftertreatment with 3% white 80~ white
resin emulsion only rust rust 10 mm
Aftertreatment
according to the No rust 20% whiteless than
invention rust 3 mm `
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