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(11) | EP 0 385 806 B1 |
(12) | EUROPEAN PATENT SPECIFICATION |
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(54) |
Phosphate coatings for metal surfaces Phosphatbeschichtungen für Metalloberflächen Revêtements en phosphate pour surfaces métalliques |
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Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
Background of the invention
(i) from 0.01 to 0.5g/l, preferably 0.01 to 0.4g/l, of nitrite ion,
(ii) from 0.05 to 5g/l, preferably 0.1 to 4g/l, of m-nitrobenzene sulfonate, or
(iii) from 0.5 to 10g/l, preferably 1 to 8g/l of hydrogen peroxide (based on 100% H₂O₂)
When the content of phosphating accelerator is less than the defined amounts, it is unable to get a fully satisfiable phosphate film on an iron-based surface, often resulting yellow rusts, and when the content of phosphating accelerator exceeds over the upper limit, there is a tendency that uneven, blue-colored phosphate film be formed on an iron-based surface.Examples 1 to 4 and Comparative Examples 1 to 4
(1) metal to be subjected to treatment
(a) galvanealed steel plate
(b) Electro galvanized steel plate
(c) Electro zinc-alloy plated steel plate
(d) Cold rolled steel plate
(2) Acidic aqueous phosphate solution:
Eight phosphate solutions having the compositions shown in Table 1 were used.
(3) Treating process:
The surfaces of the above 4 kinds of metals were simultaneously treated in accordance
with the following processes.
Degreasing→water washing→surface conditioning→ phosphating (dip treatment)→water
washing→ pure water washing→drying→coating
(4) Treating condition:
(a) Degreasing:
Using an alkaline degreasing agent ("Surfcleaner SD200" made by Nippon Paint Co.,
2wt% concentration), dip treatment was carried out at 40°C for 2 minutes.
(b) Washing with water:
Using tap water, washing was carried out at room temperature for 15 seconds.
(c) Surface conditioning:
Using a surface conditioning agent ("Surfline 5N-5" made by Nippon Paint Co., 0.1wt%
concentration), dip treatment was made at room temperature for 15 seconds.
(d) Phosphating:
Using the above acidic aqueous phosphate solution, dip treatment was carried out at
52°C or 40°C for 120 seconds.
(e) Water washing:
Using tap water, washing was carried out at room temperature for 15 seconds.
(f) Pure water washing:
Using deionized water, dip treatment was effected at room temperature for 15 seconds.
(g) Drying was carried out with hot blown air at 100°C for 10 minutes. The appearance of each phosphated plate thus obtained and the weight of the phosphate film were determined.
(h) Coating:
A cationic electro-coating composition ("Power Top U-30 Grey" made by Nippon Paint
Co.) was coated to a film thickness of 20µ (voltage 180V, electricity applying time
3 minutes), and was baked at 180°C for 30 minutes. A part of thus electro-coated plate
was used for the hot brine dipping test.
The remaining non-tested electro-coated plates were then applied with an intermediate
coating composition ("Orga TO 4811 Grey", melamine-alkyd resin base composition, made
by Nippon Paint Co.) to a film thickness of 30µ by spraying means, baked at 140°C
for 20 minutes, applied with a top coating composition ("Oega TO 630 Dover White",
melamine-alkyd resin base composition, made by Nippon Paint Co.) to a film thickness
of 40µ by spraying means, and baked at 140°C for 20 minutes. Thus obtained coated
plates by 3-coatings and 3-baking means were then subjected to adhesion test and scab
resistance test.
Examples 5,6 and Comparative Example 5
(1) Metal to be subjected to treatment:
(a) Galvanealed steel plate
(b) Electro galvanized steel plate
(c) Electro zinc-alloy plated steel plate
(d) Cold rolled steel plate
(2) Acidic aqueous phosphate solution:
Those having the compositions shown in Table 1 were used.
(3) Treating process:
The surfaces of the above 4 kinds of metals were simultaneously treated in accordance
with the following processes:
Degreasing→water washing→phosphating (by spray treatment)→water washing→pure water
washing→drying→ coating
(4) Treating conditions:
(a) Degreasing:
Using an alkaline degreasing agent ("Surfcleaner S102" made by Nippon Paint Co., 2wt%
concentration), stray treatment was carried out at 50°C for 2 minutes.
(b) Washing with water:
Using tap water, washing was carried out at room temperature for 15 seconds.
(c) Phosphating:
Using the above acidic aqueous phosphate solution, spray treatment was carried out
at 55°C for 120 seconds. (pressure 0.7kg/cm²)
(d) Water washing:
Using tap water, washing was carried out at room temperature for 15 seconds.
(e) Pure water washing:
Using deionized water, dip treatment was effected at room temperature for 15 seconds.
(f) Drying was carried out with hot blown air at 100°C for minutes. The appearance of each phosphated plate thus obtained and the weight of the phosphate film thereof were determined.
(g) Coating:
A cationic electro-coating composition ("Power TOP U-80 Grey" made by Nippon Paint
Co.) was coated to a film thickness for 20µ (voltage 180V, electricity applying time
3 minutes), and was baked at 180°C for 30 minutes. A number of each of the resulting
electro-coated plates were used for hot brine dip test.
The remaining non-tested electro-coated plates were coated with an intermediate coating
composition ("Oega TO 4811 Grey" made by Nippon Paint Co.) to a film thickness of
30 by spraying means, baked at 140°C for 20 minutes, coated with a top coating composition
("Orga TO 630 Dover White" made by Nippon Paint Co.) to a film thickness of 40µ by
spraying means, baked at 140°C for 20 minutes to obtain coated plates having a total
of 3-coatings and 3-bakings, which were then used for the adhesion test and the scab
corrosion test.
Test results: The test results are shown in Table 2. The test methods used are as follows:
(A) hot brine dip test
Cross cuts were made on the electro-coated plate, and thus prepared plate was placed
in a 5% aqueous brine maintained at 55°C for 480 hours. To thus treated plate, an
adhesive tape was applied on the cuts and peeled off. The maximum width of the peel-off
coating was determined.
(B) Adhesion test:
The coated plate was dipped in deionized water at 40°C for 20 days, after which it
was provided with grids (100 squared each) made at 1mm intervals and at 2mm intervals
using a sharp cutter. To each surface of the thus treated plate, an adhesive tape
was applied, after which it was peeled off and the number of the remaining coated
squares on the coated plate was counted.
(C) Scab corrosion resistance test:
Cuts were made on the electro-coated plate using a sharp cutter, and thus prepared
plate was subjected to 10 test cycles, each cycle consisting of a 5% brine spray test
(JIS-Z-2371, 24 hours) a humidity test (temperature 40°C, relative humidity 85%, 120
hours) standing in a room temperature for 24 hours.
(This 10 cycles' test is herein referred to as scab corrosion test) After the test,
the average value (mm) of the maximum diameter of abnormal coating (e.g. rust and
blisters) was measured.
Example 7
Example 8
Comparative Example 6
Comparative Example 7
(a) from 0.1 to 2.0g/l of zinc ion;
(b) from 5 to 40g/l of phosphate ion;
(c) a phosphating accelerator containing:
(1) from 0.01 to 0.5g/l of nitrite ion,
(11) from 0.05 to 5g/l of m-nitrobenzene sulfonate ion, or
(iii) from 0.5 to 10g/l of hydrogen peroxide (base on 100% H₂O₂);
and(d) from 0.01 to 10g/l of colloidal particles having an isolectric point of 3 or less and an average particle diameter of 0.1 µm or less.
and subsequently rinsing the solution from the surface.(a) von 0,1 bis 2,0 g/l Zink-Ion;
(b) von 5 bis 40 g/l Phosphat-Ion;
(c) einen Phosphatierungsbeschleuniger, enthaltend:
(i) von 0,01 bis 0,5 g/l Nitrit-Ion,
(ii) von 0,05 bis 5 g/l m-Nitrobenzolsulfonat-Ion, oder
(iii) von 0,5 bis 10 g/l Wasserstoffperoxid (bezogen auf 100 % H₂O₂); sowie
(d) von 0,01 bis 10 g/l kolloidale Teilchen mit einem isoelektrischen Punkt von 3 oder weniger und einem mittleren Teilchendurchmesser von 0,1 Mikrometer oder weniger; und
nachfolgendem Abspülen der Lösen von der Oberfläche.(a) de 0,1 à 2,0 g/l d'ions de zinc;
(b) de 5 à 40 g/l d'ions phosphate;
(c) un accélérateur de phosphatation contenant:
(i) de 0,01 à 0,5 g/l d'ions nitrite,
(ii) de 0,05 à 5 g/l d'ions sulfonate de m-nitrobenzène, ou
(iii) de 0,5 à 10 g/l de peroxyde d'hydrogène (sur la base de H₂O₂ à 100%); et
(d) de 0,01 à 10 g/l de particules colloïdales ayant un point isoélectrique de 3 ou inférieur à 3 et un diamètre particulaire moyen de 0,1 µm ou inférieur à 0,1 µm;
et le rinçage subséquent de la solution de la surface.