JP2001288587A - Precoated steel sheet excellent in corrosion resistance and weatherability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a precoated steel sheet excellent in corrosion resistance and weatherability and used for house appliances, building materials, automotives or the like. SOLUTION: In this precoated steel sheet excellent in corrosion resistance and weatherability, at least one side of a steel sheet is provided with an organic coated layer containing soluble glass powder with the average particle size of <=30 μm having a composition containing one or more kinds of P2O5 and B2O3 by 40 to 75 mol% in total and one or more kinds of SiO2 and Al2O3 by 5 to 20 mol% in total, and the balance oxides containing one or more selected from alkali metals, alkaline-earth metals and nonferrous heavy metals by 0.2 to 50 mass % to the mass of the coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoated steel sheet having excellent corrosion resistance and weather resistance used for home appliances, building materials, automobiles and the like.

[0002]

2. Description of the Related Art Corrosion resistance is the most important characteristic for sheet steel products. In a precoated steel sheet, its function is often ensured by the rust preventive pigment in the plating layer and the coating layer. However, since the pre-coated steel sheet requires post-processing, there is a limit in increasing the thickness of plating. Therefore, it is important to enhance the type and amount of the rust preventive pigment to improve the corrosion resistance of the precoated steel sheet.

[0003] In precoated steel sheets, strontium oxide / chromate hydrate (hereinafter referred to as strontium chromate) is generally used as a rust preventive pigment in many cases. Strontium chromate is known to exhibit an excellent rust-preventive effect against corrosion of a plating layer made of zinc or the like.

[0004]

However, when strontium chromate is added to an overcoat layer or an undercoat layer in which the hiding of the overcoat layer is small, the degree of freedom of coloring is reduced due to the strong yellow-green color of the pigment. There is. In addition, the weather resistance of the coating film is degraded, such as deactivation of the rust-preventive pigment due to exposure, and oxidative degradation of organic components due to light activity. There are problems such as occurrence.

An object of the present invention is to solve such problems and to provide a precoated steel sheet having excellent corrosion resistance and weather resistance.

[0006]

The precoated steel sheet of the present invention, which achieves the above object, contains a soluble glass powder in an organic coating. That is, at least one of P ₂ O ₅ and B ₂ O ₃ is coated on at least one side of
0～75Mol%, contains 5 to 20 mol% of one or more of SiO _2, Al ₂ O ₃ in total, the balance being an alkali metal,
Having an organic coating layer containing 0.2 to 50% by mass, based on the coating film mass, of a soluble glass powder having an average particle size of 30 μm or less made of an oxide containing at least one of alkaline earth metals and non-ferrous heavy metals. This is a pre-coated steel sheet with excellent corrosion resistance and weather resistance.

By using the precoated steel sheet of the present invention for panels for roof walls, outdoor advertisements, lighting reflections, interiors of tunnels, interior home appliances, automobile exteriors, partitions, elevator interiors, etc. A thin steel plate product having excellent weather resistance can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a precoated steel sheet of the present invention will be described in detail. The pre-coated steel sheet is composed of a steel sheet and an organic coating layer. As a steel sheet as a base material,
Cold rolled steel sheet, hot rolled steel sheet, galvanized steel sheet, galvannealed steel sheet, zinc-iron alloy coated steel sheet, zinc-aluminum alloy coated steel sheet, aluminum plated steel sheet, chrome plated steel sheet, nickel plated steel sheet, zinc-nickel alloy plated steel sheet , Tin-plated steel sheets, stainless steel sheets, aluminum-plated stainless steel sheets, lead-plated stainless steel sheets, galvanized stainless steel sheets, and the like.

[0009] Within the scope of the inventors' investigation, zinc contained 80%.
In a plated steel sheet of not less than mass%, the rust-preventing effect of the soluble glass powder is most effectively exhibited, and it can be said that it is preferable as a substrate. Note that the present inventors have clarified the following through preliminary experiments. If necessary, the steel sheet can be pre-treated. Examples of the pretreatment include washing with water, washing with hot water, pickling, alkali degreasing, grinding, polishing, chromate treatment, zinc phosphate treatment, composite oxide film treatment, pretreatment combining a water-soluble resin, and the like. Alternatively, the pre-coating treatment may be performed in combination. Conditions for each pretreatment may be appropriately selected.

Next, it is essential that at least one surface of the steel sheet is provided with an organic coating layer containing a soluble glass powder. Soluble glass powders, 40~75mol% in total of one or more _{P 2 O 5, B 2 O} 3, SiO 2, Al 2 O 3
Of a total of 5 to 20 mol%, with the balance being a single or composite oxide containing at least one of an alkali metal, an alkaline earth metal and a non-ferrous heavy metal.

The total amount of P ₂ O ₅ and B ₂ O ₃ is 75 m
If it is larger than 0 mol%, the dissolution rate of the powder is too high to be suitable for use. Conversely, if it is smaller than 40 mol%, the dissolution rate is low and the rust prevention function becomes insufficient. When the total amount of SiO ₂ and Al ₂ O ₃ is more than 20 mol%, the glass structure becomes too stable, the components do not elute and the rust-preventing effect is not exerted. Unable to obtain powder with structure.

The balance is alkali metals (Li, Na, K,
Rb), alkaline earth metals (Be, Mg, Ca, Sr,
Ba), non-ferrous heavy metal elements (Mn, Mo, Zn, Ni, C
u, Ag, Sn, Cr, Co, V, Ti, Zr). Note that an oxide containing one or more of the above elements includes a single oxide composed of the one kind of element, a composite oxide containing two or more kinds of the above elements, and two kinds of these single oxides and composite oxides. The mixture consisting of the above is a generic name.

The pH at which the oxide component elutes is not particularly defined. If the steel sheet is a non-plated steel sheet such as a cold-rolled steel sheet, p
It is preferred to be H10 or more. When the steel sheet is a zinc or aluminum-based plated steel sheet, the conditions vary depending on the type of plating, but it is generally said that a composition condition showing a weak alkaline dissolution pH is suitable for the rust prevention effect. The average particle size of the melting glass powder is preferably 30 μm or less. If it is larger than 30 μm, the powder will be poorly crushed when mixed with the paint, and the appearance of the paint will be damaged.

The shape of the powder is not particularly defined. Spherical, elongated, filler-type or needle-type powders may be used alone or as a mixture. It is essential that the added amount of the soluble glass powder is 0.2% by mass to 50% by mass based on the mass of the coating film. If it is less than 0.2% by mass, sufficient corrosion resistance cannot be obtained, and if it is more than 50% by mass, the coating structure of the organic coating layer becomes sparse, and the corrosion resistance is rather reduced.

Next, any paint may be used for the organic coating layer as long as it is generally used for precoated steel sheets. As an example, an epoxy resin, an acrylic resin, a polyester resin, a urethane resin, a vinyl resin, an amino resin, a silicone resin, a PVDF-based fluororesin, and the like can be given. Further, a crosslinking agent can be used in the organic coating layer as needed. As the crosslinking agent, an aminoplast resin, a polyisocyanate compound, or an epoxy resin can be used alone or in combination. It should be noted that the type, composition and compounding method of each cross-linking agent, and the presence or absence of a curing catalyst are not particularly limited, and may be performed under conditions as needed.

Further, color pigments such as titanium white pigment, titanium yellow and carbon black, extender pigments such as silica, amphoteric surfactants, leveling effect agents, antioxidants,
Additives used in general precoated steel sheets, such as ultraviolet absorbers and design-added pigments, may be used by appropriately mixing them in necessary amounts. In particular, in order to improve the weather resistance performance, the use of an additive having an absorption capacity at a specific wavelength is effective. As an example, by using a benzotriazole-based or oxalic anilide-based ultraviolet absorber in the coating, the weather resistance in an accelerated weather resistance test using a germicidal lamp or the like as a light source, which has a strong line in a wavelength region of 200 to 220 nm, is improved. Can be done.

Although the thickness of the organic coating layer is not particularly limited, it is preferable that the dry thickness be 100 μm or less from the viewpoint of workability and coating workability. The film thickness is 1
When the thickness is larger than 00 μm, the processing adhesion to the base material is inferior, and there is a possibility that peeling of the coating film of the processed portion is induced. In addition,
An undercoat layer may be formed between the steel sheet and the organic coating layer, if necessary. Regarding the provided undercoat layer, there are no restrictions on the use of paint systems and additive components generally used for pre-coated steel sheets.

Further, if necessary, an overcoat layer may be formed on the organic coating layer. Regarding the provided overcoat layer, there is no restriction on the use of paint systems and additive components generally used for precoated steel sheets. The thicknesses of the undercoat layer and the overcoat layer are not particularly limited, but the total thickness of the coating layer is desirably 100 μm or less.
When the film thickness exceeds 100 μm, there is a possibility that the coating film in the processed portion may peel off when the product is processed.

The number of undercoat layers and overcoat layers is not particularly limited. The number of each layer can be increased as needed. Further, the soluble glass powder of the present invention can be added to the undercoat layer and the overcoat layer. The composition and the amount of addition to these are the same as those described for the organic coating layer. The above-described precoated steel sheet of the present invention is applied to, for example, roof wall panels, outdoor advertising panels, lighting reflection panels, tunnel interior panels, indoor home appliances, automobile exterior panels, partition panels, elevator interior panels, and the like. By doing so, a thin steel plate product having more excellent corrosion resistance and weather resistance than before can be obtained.

[0020]

[Embodiment 1] An embodiment of the precoated steel sheet of the present invention will be described. On a steel plate subjected to alkali degreasing and chromate treatment, a coating material for an organic coating layer having a composition shown in Table 2 containing a soluble glass powder having a composition shown in Table 1 and a dry film thickness of 1
The composition was applied using a bar coater to a thickness of 5 μm, and then baked by a high-frequency induction heating method.

The obtained precoated steel sheet was evaluated for corrosion resistance and weather resistance under the following conditions. The weather resistance was evaluated by measuring the chromaticity difference (ΔE) before and after the test for 500 hours by using a sunshine weather meter (SWOM). Table 2 shows the results. Note that ΔE of 2.0 or less was judged to be good. Corrosion resistance was evaluated by salt spray test (SST) and 1000
The maximum corrosion width of the crosscut portion at the time was measured and evaluated.
Table 2 shows the results. In addition, when the maximum corrosion width was within 5 mm, it was judged to be good.

[0022]

[Table 1]

[0023]

[Table 2]

[Example 2] Alkaline degreasing, chromate treatment, and Nippon Paint Co., Ltd. Flexcoat 600EU primer as a subbing layer was coated on a steel plate coated with 5 μm of primer.
A coating material for an organic coating layer having a composition shown in Table 3 containing a soluble glass powder having a composition shown in Table 1 was applied using a bar coater so as to have a dry film thickness of 15 μm, and then baked by a high-frequency induction heating method.

The obtained precoated steel sheet was evaluated for corrosion resistance and weather resistance under the same conditions as in Example 1. Table 3 shows the results.

[0026]

[Table 3]

Example 3 On a steel plate subjected to alkali degreasing and chromate treatment, a coating material for an organic coating layer having a composition shown in Table 4 and containing a soluble glass powder having a composition shown in Table 1 was dried to a thickness of 15 μm. Apply using a bar coater so that
Thereafter, it was baked by a high frequency induction heating method. In addition, Nippon Paint Co., Ltd. Flexcoat 150 is used as an overcoat layer.
A 0HQ clear metallic color was applied and baked in the same manner as above by 15 μm.

The obtained precoated steel sheet was evaluated for corrosion resistance and weather resistance under the same conditions as in Example 1. Table 4 shows the results.

[0029]

[Table 4]

As is apparent from Tables 2 to 4, the precoated steel sheet according to the present invention shows excellent corrosion resistance and weather resistance when the melting glass powder having a proper composition is adjusted to a proper mixing ratio.

[0031]

According to the present invention, P_TwoO_Five, B_TwoO_ThreeOne or more of
Is 40 to 75 mol% in total, SiO _Two, Al_TwoO_Threeof
One or more kinds are contained in a total of 5 to 20 mol%,
Potassium metal, alkaline earth metal, non-ferrous heavy metal
Gas having an average particle size of 30 μm or less
Lath powder is contained in an amount of 0.2 to 50% by mass based on the coating film mass.
Pre-coated steel sheet that must have an organic coating layer
Thin steel plate with excellent corrosion resistance and weather resistance by using
Products can now be provided. Therefore, the present invention
It can be said that this is an extremely valuable invention.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // B05D 7/14 B05D 7/14 J F term (reference) 4D075 CA32 CA33 DB02 DC10 EC02 EC03 EC54 4F100 AA04B AA18B AA19B AA20B AA31B AB03A AG00B AK01B BA02 DE01B GB07 GB32 GB48 JB02 JB08B JL09 4J038 CD011 CD091 CG001 DA131 DB001 DD001 DG001 DL031 HA166 HA396 HA446 HA486 KA03 KA08 KA20 NA03 PB05 PB07 PB09 PC02 4K044 AA02 AB02 BA10 BA10 BA10

Claims (1)

[Claims] 1. A steel sheet comprising P ₂ O ₅ , B
_At least one of ₂ O ₃ is 40 to 75 mol% in total, SiO
₂ , an average particle size of an oxide containing one or more of Al ₂ O _{3 in} a total amount of 5 to 20 mol%, and the balance being an oxide containing one or more of an alkali metal, an alkaline earth metal, and a non-ferrous heavy metal;
m or less of a soluble glass powder,
A precoated steel sheet having excellent corrosion resistance and weather resistance, comprising an organic coating layer containing from 50 to 50% by mass.