JPH0938569A - Zinc-resin type surface treated steel sheet with excellent scratch resistance and corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet treated with zinc plating or zinc-based alloy plating with high cost efficiency and rust-proof performance. SOLUTION: On a galvanized or zinc-based alloy plated steel sheet directly or on a chromate film or a phosphate film formed thereon a rust-proof coating compsn. film is formed in which 10-300 pts.wt. in total of slug contg. alkali groups formed in a metallurgy process, or one or two powdery basic compd. with a pH of 8-13, and zinc powder are contained based on 100 pts.wt. of resin solid content of 100 pts.wt. or an epoxy resin with a mean MW of 300-3,000 and an epoxy equivalent of 180-2,200, and a curing agent. This steel sheet exhibits good coating film appearance and adhesiveness and excellent scratch resistance and corrosion resistance with no generation of white rust.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet on which a zinc-plated steel sheet which is resistant to flaws and has excellent corrosion resistance is used as a base.

[0002]

2. Description of the Related Art In recent years, the excellent corrosion resistance of zinc- or zinc-based alloy-plated steel sheets has come to the forefront with the demand for improved performance of durable consumer products such as automobiles, buildings, and home appliances. The demand is growing remarkably, especially in Japan. However, the standards for the requirements for better products have become more sophisticated year by year, and as surface-treated steel sheets are required to have even better corrosion resistance, coated steel sheets with plated steel surfaces further coated with resin are being used. It's coming. However, the plated zinc and zinc-based alloys are easily dissolved in water in the acidic region of pH 8 or less and the basic region of pH 13 or more, and the elution rate becomes fast, so the coating resin is also easily deteriorated and white rust is generated. There was a problem that was likely to occur.

Therefore, in the conventional galvanized or zinc-based alloy plated steel sheet, after forming a plating layer on the base steel sheet,
A chromate film or a phosphate film layer is formed, and an organic film layer is laminated to prevent the intrusion of water from the outside and suppress the occurrence of white rust, thus improving the corrosion resistance. . The chemical conversion coatings on zinc-plated or zinc-based alloy-plated steel sheets are mainly phosphate coatings and chromate coatings, which are intended to prevent white rust and improve the coating base. It was not enough as a countermeasure.

Therefore, in order to improve the corrosion resistance of the coated steel sheet, a means of incorporating zinc powder or zinc alloy powder in the resin film has been proposed (Japanese Patent Laid-Open No. 58-174582).
No. 62-234576, 63-270.
No. 131, etc.), the zinc powder and the zinc alloy powder contained in the resin film have a high elution rate in the organic film-plated steel sheet by these means, and there is no countermeasure for preventing the occurrence of white rust in the paint. In addition, the resin in the surface layer had a small hardness and was damaged by a small external force, and rust progressed from that portion.

The inventors of the present invention disclosed in Japanese Unexamined Patent Publication No. 7-53898 "A rust preventive coating composition prepared by mixing 10 to 300 parts by weight of slag containing an alkali group with 100 parts by weight of a resin solid content." It was found that it was applied to the surface of a soft iron plate and had excellent corrosion resistance. However, for applications such as automotive steel plates and outdoor steel structural materials such as bridges, which require stricter corrosion resistance, higher corrosion resistance and flaw resistance have been desired.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the occurrence of white rust, which is pointed out in a conventional coated steel sheet obtained by coating a resin on a galvanized or zinc alloy plated steel sheet, and to improve the corrosion resistance. Further, the strength of the resin is improved so that the resin is not easily scratched by an external force and partial rust is prevented from occurring.

[0007]

According to the present invention, the surface of a zinc-plated or zinc-based alloy-plated steel sheet is adjusted to pH 8 to 13 by applying a resin containing a slag containing an alkaline group or a powdery basic compound. It has been found that by controlling the rapid dissolution of zinc, which was a drawback of zinc, in acidic or strong alkaline regions, maintaining the sacrificial anticorrosion effect of zinc for a long period of time, preventing white rust and improving corrosion resistance. And completed it. The gist of the invention is that

(1) One or two kinds of slag containing an alkali group or powdery basic compound having a pH of 8 to 13 is added to 100 parts by weight of a resin solid content on the surface of a zinc or zinc alloy plated steel sheet. A zinc / resin-based surface-treated steel sheet excellent in flaw resistance and corrosion resistance, which is characterized by forming an anticorrosive coating composition film containing 10 to 300 parts by weight of (2) On the surface of a zinc or zinc-based alloy plated steel sheet, with respect to 100 parts by weight of the resin solid content, slag containing an alkali group or one or two kinds of powdery basic compounds having a pH of 8 to 13 and zinc powder are added in total. A zinc / resin-based surface-treated steel sheet excellent in flaw resistance and corrosion resistance, which is characterized by forming an anticorrosive coating composition film containing 10 to 300 parts by weight of

(3) Resin solids have an average molecular weight of 300 to 3
000 and an epoxy equivalent of 180 to 2200, and a curing agent, and a zinc / resin-based surface-treated steel sheet excellent in flaw resistance and corrosion resistance according to the above (1) or (2). (4) The total amount of one or two of the slag containing an alkali group and the powdery basic compound having a pH of 8 to 13 is 100 to 1.
0, zinc powder is contained in a proportion of 0 to 90 parts by weight, the zinc / resin-based surface-treated steel sheet having excellent flaw resistance and corrosion resistance according to the above (1) to (3). (5) A chromate film or a phosphoric acid film is formed on the surface of a zinc or zinc alloy plated steel sheet, and a rust preventive coating composition film is formed on the surface thereof (1)
It is a zinc / resin-based surface-treated steel sheet excellent in flaw resistance and corrosion resistance according to (4).

According to the present invention, a galvanized or zinc-based alloy-plated steel sheet is directly or after forming a chromate film or a phosphate film, and then has an average molecular weight of 300 to 3000 and an epoxy equivalent per 100 parts by weight of the resin solid content. 180-2200 total epoxy resin and curing agent 1
Anticorrosion by applying 10 parts by weight to 100 parts by weight of a slag containing an alkali group generated in the refining process or a powdery basic compound having a pH of 8 to 13 by coating. It improves performance.

In the present invention, slag containing an alkali group or a powdery basic compound having a pH of 8 to 13
The surface of zinc-plated or zinc-based alloy-plated steel sheet is kept alkaline to impart rust-preventing properties, thereby exhibiting the galvanic protection property of zinc. The blast furnace and converter slag have a pH range of 9 to 12.6. Zinc has a very slow corrosion rate and is stable in the pH range of 9 to 12.6. The surface of the zinc-plated or zinc-based alloy-plated steel sheet coated with this coating has a slow corrosion rate due to its alkaline atmosphere, and the amount of anticorrosion current is small, so zinc elution is small, and excessive elution of zinc is suppressed. It Therefore, when the anticorrosive coating composition of the present invention is coated on the surface of a galvanized or zinc-based alloy-plated steel sheet, the zinc consumption is small while exhibiting the anticorrosive function sufficiently, and is good for a long time. Rust prevention performance is maintained.

Further, the slag or the alkaline group of the powdery basic compound having a pH of 8 to 13 facilitates the formation of zinc hydroxide and keeps the film more alkaline. As a result, not only white rust does not occur, but also red rust on the steel sheet decreases, and good corrosion resistance can be obtained. Since the slag contains a large amount of Al ₂ O ₃ and SiO _{2, the} average hardness is Hv70.
It is about 0 to 900, which is an extremely high level. Therefore, a coating film containing slag has a strong protective power against external force, and has a property that the coating film is hardly damaged.

If the amount of the slag or the powdery basic compound having a pH of 8 to 13 is less than 10 parts by weight based on 100 parts by weight of the resin solid content, the alkali content is small and the iron surface cannot be kept alkaline, and the rust preventive effect is obtained. Does not exert. Also, 30
If the amount exceeds 0 parts by weight, the coating film becomes coarse and the water permeation increases, the alkaline component elutes rapidly, the effect does not last, and rust occurs, causing white rust or red rust. pH is less than 8 or 13
When it is larger, the dissolution rate of zinc increases rapidly, and the sacrificial anticorrosive action of zinc does not last long.

When zinc powder is added, 1 of slag containing an alkali group and a powdery basic compound having a pH of 8 to 13 is added.
The total amount of one or two kinds is less than 10, that is, zinc powder is 9
If it exceeds 0, the dissolution rate of zinc is increased, white rust is generated, and corrosion resistance is reduced. As the slag containing an alkali group, blast furnace slowly cooled slag, blast furnace granulated slag, converter slag, electric furnace slag, stainless slag, etc. are produced in the manufacturing process.

As the powdery basic compound having a pH of 8 to 13, magnesium hydroxide, basic magnesium carbonate, potassium carbonate, calcium oxide, calcium hydroxide, barium hydroxide, barium metaborate, borax, Portland cement, alumina cement , Blast furnace cement, etc., and the particle size of the powder is preferably 0.1 to 100 μm. If it is as small as less than 0.1, excessive agglomeration progresses in the paint, making it difficult to adjust the paint and apply it to the steel sheet. 10
If it is larger than 0 μm, the resin holding force of the particles will be weakened and the local coating film layer will be thin, resulting in deterioration of the corrosion resistance.

The pH of the alkaline group-containing slag and the powdery basic compound is 100 ml of the alkaline group-containing slag and the powdery basic compound in 900 ml of ion-exchanged water.
After adding 24 g, the mixture was stirred, and after 24 hours, measured at 20 ° C. with a glass electrode pH meter. The granulated blast furnace slag (Essent, Nippon Steel Chemical Co., Ltd.) showed 11.0, and barium metaborate (Busan 11M-1, Sakai Chemical Industry Co., Ltd.) showed 10.2.

As the resin component, epoxy resin, epoxy polyol resin, acrylic resin, phenol resin, epoxy ester resin, chlorinated rubber resin, chlorinated olefin resin, fluororesin, vinyl resin, vinyl butyral resin, petroleum resin, xylene resin, Alicyclic oligomer resins, alkyd resins, acrylated alkyd resins, phenol-modified alkyd resins, urethanized alkyd resins, polyester resins, fibrin-based resins, and the like.Epoxy resin curing agents include polyamide-based curing agents and fats. Examples thereof include aromatic or aromatic polyamine curing agents, ketimine curing agents, mercaptan curing agents, and the like.

Further, epoxy resin polyol, acrylic resin polyol, polyester resin polyol and the like can be mentioned, and the curing agent for these polyols is toluene diisocyanate, xylene diisocyanate, MD.
I, isocyanates such as isophorone diisocyanate. Epoxy resin has a molecular weight of 300-3
000 and an epoxy equivalent of 180 to 2200 are preferable. When the molecular weight is 300 or the epoxy equivalent is less than 180, the performance of the cured coating film such as mechanical strength, water resistance and corrosion resistance is insufficient, and the molecular weight is 300.
When 0 or the epoxy equivalent exceeds 2200, it becomes difficult to dissolve in a solvent, the solid content of the coating decreases, and it becomes difficult to apply a thick coating in heavy corrosion protection.

Bisphenol A glycidyl ether type epoxy resin is suitable as the epoxy resin, but various modified low molecular weight epoxy resins, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, aliphatic epoxy resin, glycidyl ester type resin, You may use it in mixture of 1 type, or 2 or more types in a novolak type epoxy resin. Further, a polyol of the above epoxy resin may be used. Also, one or more resins such as petroleum resin, xylene resin, alicyclic oligomer resin, coumarone resin, indene resin, polybutadiene resin, acrylic resin, alkyd resin and phenol resin are mixed with bisphenol A glycidyl ether type epoxy resin. You may use it.

As the curing agent, epoxy resin and polyamide resin having strong alkali resistance because slag is alkaline, curing agent such as polyamine resin, phenol resin, chlorinated rubber resin, acrylic resin, polybutadiene resin, vinyl resin, fluorine resin, Epoxy polyol resin, polybutadiene polyol resin and isocyanate type curing agent are preferable. Next, the anticorrosive coating composition of the present invention contains titanium dioxide, carbon black, graphite as a coloring pigment,
Inorganic pigments such as flaky iron oxide, iron oxide and chromium oxide, metal powders such as copper and stainless steel, and organic pigments such as phthalocyanine-based, azo-based and quinacridone-based pigments can be used.

In the anticorrosive coating composition of the present invention, extender pigments such as calcium carbonate, talc, kaolin, barium sulfate, precipitable barium sulfate, colloidal silica and mica can be used. Epoxidized soybean oil, chlorinated paraffin, phthalate ester-based and ether-based ones can be used as the plasticizer in the rust preventive coating composition of the present invention. Coating additives such as surface modifiers, dispersants, color separation inhibitors, precipitation inhibitors, anti-sagging agents, antifoaming agents and the like can be used in the anticorrosive coating composition of the present invention.

The rust preventive coating composition of the present invention includes toluene, xylene, a medium to high boiling point aromatic hydrocarbon solvent, an alcohol solvent, a ketone solvent, an ester solvent, a glycol ether solvent as an organic solvent. Can be used. The film thickness of the anticorrosion coating composition should be 10 to 100 μm. 1
If it is less than 0 μm, there is a problem in corrosion resistance. If it exceeds 100 μm, the coating film will be cracked or peeled off, which also causes a problem in corrosion resistance. Preferably, the thickness is 30 to 80 μm.

The coated steel sheet according to the present invention is basically a galvanized steel sheet or a zinc alloy plated steel sheet. Examples of the zinc plated steel sheet include a galvanized steel sheet and Zn-
Fe alloy plated steel sheet, Zn-Ni alloy plated steel sheet, Zn
-Mn alloy plated steel sheet, Zn-Al alloy plated steel sheet, Z
There is an n-Co alloy-plated steel sheet or the like, and further, a steel sheet plated with an alloy in which one or more kinds of Ni, Fe, Mn, Co, Al, Cr and the like are added to each of the plating components, and the above-mentioned plated layer A composite plated steel plate that is a composite of one or more types can also be raised. Of course, it is not limited to these, and a zinc-based plated steel sheet is appropriately selected according to the required corrosion resistance and the like.

Further, the coating amount is not particularly limited, and a coating amount of about ²⁰ to 400 g / m ² which is generally used for automobile steel sheets (per surface) is sufficient. Further, there is no particular limitation on the method of forming the plating layer, and any known plating method such as electroplating or hot dipping may be used. Further, the chromate film may be formed by any means of coating type, reaction type and electrolytic type. The chromate treatment liquid contains a water-soluble chromium compound as a main component, to which an appropriate amount of phosphate radicals, anions such as fluorine ions, metal ions such as Zn, Ni and Co, and organic substances such as starch and methanol are added as necessary. .

If the amount of the chromate coating layer deposited is less than 5 g / m ^{2 in} terms of the amount of metallic chromium, corrosion resistance cannot be obtained, and if it exceeds 400 g / m ² , peeling of the coating or deterioration of weldability is caused. 5 to 400 g /
A range of m ² is desirable. More preferably 20-300 g
It is better to adjust to the range of / m ² . Deposition amount of phosphate coating in the case of electro-galvanized steel sheet 2.5 g / m ² or less, it is desirable to the case of hot-dip galvanizing 2 g / m ² or less. If the coating layer becomes thick, peeling of the coating may occur and weldability may deteriorate.

[0026]

EXAMPLES Examples will be described below. The galvanized steel sheet sample was electroplated with zinc (per surface) at 20 g / m ² on a low carbon cold rolled steel sheet having a thickness of 0.7 mm. Chromate treatment is performed with a roll coater on the surface of 50 g / m ²
The maximum temperature reached is 130 ℃
I used the one that was baked in. Phosphoric acid treatment
Zinc oxide was dissolved in phosphoric acid, diluted with water, added with nitrite, and sprayed. The anticorrosion coating composition was produced as follows. In the examples, unless otherwise specified, parts are parts by weight. Epoxy equivalent: A 70% solution of an epoxy resin in xylene (Epicoat # 1001, manufactured by Yuka Shell Co., Ltd.) in an appropriate amount by weight of a combination of slag, a powdery basic compound, and zinc powder, and titanium dioxide 5 Parts by weight, 6 parts by weight of xylene, 4 parts of isobutanol
The resulting mixture was added to 100 parts by weight, and dispersed with a glass bead paint shaker for 60 minutes. To 100 parts by weight of this dispersion, 1 part of a polyamidoamine-based curing agent (Adeka Hardener EH-306, solid content 70%, manufactured by Asahi Denka Co., Ltd.)
0 parts by weight and 10 parts by weight of a dedicated thinning solution (weight ratio xylene / isobutanol / MIBK = 60/20/20) were added to the galvanized steel sheet with a brush and dried at 20 ° C. for 10 days to give a final dry film thickness of 70. It was set to ± 5 μm.
As the powdery basic compound, barium metaborate (View Sun 11M-1, manufactured by Sakai Chemical Industry Co., Ltd.) was used.

Test Items and Evaluation Method (1) Coating Film Condition The surface condition of the coating film was observed according to JIS K5400 7.1. It was visually inspected whether the appearance of the coating film was normal. Observation items include gloss, unevenness, wrinkles, dents, repelling, and crushing. When it is good, it is indicated by ◯, and when it is defective, it is indicated by Δ. (2) Adhesion test A test was conducted according to JIS K5400 8.5.2. The crosscut method was adopted. The gap between cuts is 2 mm and the number of squares is 25 mm.
A grid-like cut was made with a cutter knife specified in 4401, the adhesive tape was peeled off, and the adhesion of the coating film after peeling was visually observed.

(3) Scratch resistance JIS K5400
The pencil scratch value was calculated according to 8.4. The hardness of the coating film was examined by scratching the coating film with a pencil and represented by the density symbol of the pencil. (4) Salt Spray Test A test was conducted for 1500 hours under the conditions of JIS K5400 9.1. The test piece is JIS G44
The test was carried out by making a cross cut reaching the substrate with a cutter knife specified in No. 01. The salt spray test was evaluated as shown in Table 1. The evaluation results for each sample are shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

According to the present invention, the slag in the coating film or the powdery basic compound having a pH of 8 to 13 is gradually eluted to keep the surface of the galvanized or zinc-based alloy plated steel sheet alkaline and prevent rusting. It is possible to maintain stable rust prevention performance for a long period of time.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B05D 7/24 303 B05D 7/24 303B

Claims (5)

[Claims] 1. A total of one or two kinds of slag containing an alkali group or a powdery basic compound having a pH of 8 to 13 per 100 parts by weight of a resin solid content on the surface of a zinc or zinc alloy plated steel sheet. A zinc / resin-based surface-treated steel sheet excellent in flaw resistance and corrosion resistance, which is characterized by forming a rust preventive coating composition film containing 10 to 300 parts by weight. 2. One or two kinds of slag containing an alkali group or one or two kinds of powdery basic compounds having a pH of 8 to 13 and zinc powder per 100 parts by weight of a resin solid content on the surface of a zinc or zinc-based alloy plated steel sheet. A zinc / resin-based surface-treated steel sheet excellent in flaw resistance and corrosion resistance, which is characterized by forming a rust-preventive coating composition film containing 10 to 300 parts by weight in total. 3. The resin solid content has an average molecular weight of 300 to 300.
A zinc / resin-based surface-treated steel sheet excellent in flaw resistance and corrosion resistance according to claim 1 or 2, which is composed of an epoxy resin having an epoxy equivalent of 180 to 2200 and a curing agent. 4. A slag containing an alkali group and a pH of 8 to
The total amount of one or two of 13 powdery basic compounds is 1
The zinc / resin-based surface-treated steel sheet having excellent scratch resistance and corrosion resistance according to claims 1 to 3, wherein the zinc powder is contained in an amount of 0 to 10 and a zinc powder content of 0 to 90 parts by weight. 5. A chromate film or a phosphoric acid film is formed on the surface of a zinc- or zinc-based alloy-plated steel sheet, and a rust-preventive coating composition film is formed on the surface thereof. Zinc / resin-based surface-treated steel sheet with excellent scratch resistance and corrosion resistance as described.