JPH07265789A - Pearl tone decoratively coated steel plate - Google Patents

Abstract

PURPOSE:To manufacture inexpensively a pearl tone decoratively coated steel plate of superior resistance to corrosion by forming a chromate film on the surface of a zinc plated steel plate, over which a colored film containing a rust-proof pigment and a clear film containing mica oxide powder are formed successively. CONSTITUTION:A film of chrome adhesion amount of 60-100mg/m<2> is formed on the surface of a zinc plated steel plate. A colored film of film thickness of 10-20mum containing a rust-proof pigment and a clear film of film thickness of 10-20mum containing mica oxide powder of 0.3-3.0% are formed successively on the chromate film. A pearl tone design coated steel plate thus manufactured is provided with resistance to corrosion equivalent to a steel plate manufactured by the conventional three coating three baking method. Also the manufacturing cost can be reduced by two coating two baking method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a design-coated steel sheet having a pearly appearance using oxidized mica powder, which is inexpensive to produce.

[0002]

2. Description of the Related Art As an exterior plate or decorative plate for home electric appliances, a clear coating film in which scale-like oxidized mica powder is dispersed is formed on a colored coating film, and pearls are formed on the colored coating film surface by diffuse reflection of the oxidized mica powder. Design-coated steel sheets are used that give an appearance that is dispersed. This design-coated steel sheet is a galvanized steel sheet, an alloyed hot-dip galvanized steel sheet, a zinc-based galvanized steel sheet such as electrolytic zinc or zinc alloy-plated steel sheet.
A chromate film of 0 to 30 mg / m ² is formed, and a film thickness of 3 to 10 containing an anticorrosive pigment on the chromate film.
μm undercoating film, 10 to 20 μm thick colored coating film, and 10 to 2 film thickness containing 0.3 to 3.0% of oxidized mica powder.
A 0-μm clear-coating film was sequentially formed.

This design coated steel sheet has a coating film as an undercoat coating film,
Since it has a three-layer structure consisting of a colored coating film and a clear coating film, its coating is repeated 3 times.
You must use the Bake method. But with this,
The manufacturing cost is higher than that of the conventional pre-coated steel sheet by the two-coat, two-bake method in which the coating and drying of the undercoat coating film and the colored coating film need only be repeated twice. As a countermeasure against this, it may be possible to omit the undercoat coating film, but there was a problem that the corrosion resistance was lowered. Further, it is possible to disperse the oxidized mica powder in the colored coating film, but this causes a problem that the oxidized mica powder in the coating film does not diffusely reflect, so that a pallet-like appearance cannot be obtained.

[0004]

SUMMARY OF THE INVENTION In view of the above points, the present invention provides a pallet-designed steel sheet which can be manufactured by the two-coat two-bake method.

[0005]

According to the present invention, a chromium coating film having a chromium deposition amount of 60 to 100 mg / m ² is formed on the surface of a zinc-based plated steel sheet, and a rust preventive pigment is formed on the chromium coating film. A pearl characterized in that a colored coating film having a film thickness of 10 to 20 μm and a clear coating film having a film thickness of 10 to 20 μm containing 0.3 to 3.0% of oxidized mica powder are sequentially formed. It is a decorative coated steel sheet.

[0006]

According to the present invention, as a result of various studies to develop a design-painted steel sheet having a conventional pale appearance and capable of being manufactured by the two-coat, two-bake method, the chromium film It has been found that the undercoat film can be omitted by strengthening the corrosion resistance and adding a rust preventive pigment to the colored film.

In the present invention, the amount of chromium deposited on the chromate film is 60 to 100 mg / m ² , preferably 70 to 90 mg.
/ M ² If the amount of deposited chromium is less than 60 mg / m ^{2, the} amount of rust preventive pigment to be added to the colored coating film must be increased, so that the processability of the coating film is deteriorated, and coloring by the rust preventive pigment is also recognized. There may be a case where the color cannot be adjusted to an arbitrary color. On the other hand, if it exceeds 100 mg / m ² , chrome-
The coating film becomes powdery and the adhesion of the colored coating film is reduced. The formation of the chromate film may be carried out by a single treatment with a known reaction type chromate treatment liquid or a coating type chromate treatment liquid, or a combination treatment of both. In the case of combined treatment, it is preferable to carry out the reaction type chromate treatment solution first.

A rust preventive pigment is added to the colored coating film in an amount of 2 to 20%, preferably 3 to 10%. If the amount of rust preventive pigment is less than 2%, the amount of chromium deposited on the chromate film is 100 mg / m 2.
^{Even in the case of 2} , the corrosion resistance is inferior to that in the case where the undercoating film is present, and if it exceeds 20%, the adhesion of the coating film is deteriorated because a coloring pigment must be added. The rust preventive pigment may be a known one, and for example, chromate-based zinc chromate or strontium chromate may be used. The film thickness is set to 10 to 20 μm as in the conventional case. As the clear coating film formed on the colored coating film, oxide mica powder having a particle size of 5 to 50 μm was used, the content thereof was set to 0.3 to 3.0% as in the conventional case, and the film thickness was 10 ˜20 μm. As the resin for the colored coating film and the resin for the clear coating film, polyester-based resin, acrylic resin, etc. can be used, and it is preferable to use the same resin for both coating films in order to improve the adhesion.

[0009]

EXAMPLE An alloyed hot-dip galvanized steel sheet (sheet thickness 0.65 mm, width 784 mm) which had been subjected to reactive chrome treatment was passed through a continuous coating line, and again subjected to coating chrome treatment, After coating a polyester coloring paint containing a zinc chromate rust preventive pigment to a dry film thickness of 15 μm, it is baked and dried at a plate temperature of 220 ° C. to 8 to 70 μm.
(Average particle size: 20 μm) A polyester clear paint containing 2.5% of oxidized mica powder with respect to the nonvolatile content was applied so that the dry film thickness was 15 μm, and baked at a plate temperature of 220 ° C. to dry.

Chromic acid 50 g for reactive chromate treatment
/ L, cobalt nitrate 100 g / l, ammonium fluoride ammonium 2 g / l, and a coating solution containing chromic acid 100 g / l was used for the coating type chromate treatment.

A corrosion resistance test and a coating film adhesion test were performed on the design steel sheet obtained as described above and the design steel sheet manufactured by the conventional 3 coat 3 bake method to compare the performance. The results are shown in Table 1. For the corrosion resistance test, put a cut that reaches the steel base and carry out a salt spray test (JIS Z 2371) with 24
After 0 hours, taping peeling, peeling width 1.0m
m or less was evaluated as ○, 1.1 to 3.0 mm or less as Δ, and 3.1 mm or more as ×. In addition, in the coating film adhesion test, after performing a 0t adhesion bending process, the bending part is taped and peeled off, and the coating film residual ratio of 90 to 100% is ◯, 70 to 89%.
Was evaluated as Δ, and 69% or less was evaluated as x. In addition, the conventional design steel plate has a chromium coating amount of 30 mg / m ² , a chrome coating film (polyester resin) 5 μm, a colored coating film (polyester resin) 15 μm, and a clear coating film (polyester resin) 12 μm. Using.

[0012]

[Table 1] (Note 1) The amount of anticorrosive pigment added to the colored coating film is based on the nonvolatile content of the coating material. (Note 2) Comparative Example 4 is a conventional design steel plate.

[0013]

As described above, the design steel sheet of the present invention has the same corrosion resistance as that produced by the conventional 3-coat 3-bake method. Further, the design steel sheet of the present invention can be manufactured by the two-coat, two-bake method, so that the manufacturing cost becomes low.

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Claims (1)

[Claims] 1. A zinc-plated steel sheet is provided with a chromium coating film having a chromium adhesion amount of 60 to 100 mg / m ² , and a film thickness 1 having a rust preventive pigment on the chromium coating film.
0 ~ 20μm colored coating film and oxidized mica powder 0.3 ~ 3.0
%, A clear coating film having a film thickness of 10 to 20 μm is sequentially formed.