JPS6147587B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing molten aluminized steel sheets that are colorful and have excellent heat resistance and corrosion resistance, and in particular, the method involves adding a specific surfactant to an inorganic paint and painting the molten aluminized steel sheets. It is characterized by: In recent years, various types of molten aluminized steel sheets, that is, steel sheets plated with aluminum alone or with aluminum containing silicon or iron as an auxiliary component, have been developed and widely used to improve the corrosion resistance and heat resistance of steel sheets. . For example, it is applied to automobile parts such as mufflers, converters, and shear heating plates, combustion equipment such as stoves, wind stoves, chimneys, and gas ranges, and various household appliances, and its range is gradually expanding. However, the surface of such an aluminized steel sheet has only a single color, and therefore is generally finished with various colors of organic paint. Although such coatings improve the weather resistance and anti-corrosion properties of molten aluminized steel sheets, the heat resistance of molten aluminized steel sheets is significantly reduced, and in the related technical field, efforts are still being made to color molten aluminized steel sheets. be. However, the present inventors investigated various methods of treating the molten aluminized steel sheet with inorganic materials, and found that it was not possible to directly coat the surface of the steel sheet with either a phosphate-based binder or a silicate-based binder. When applied, a chemical reaction occurred on the surface and hydrogen gas was generated, resulting in paint film defects such as pinholes and blisters, which was not a good treatment. Therefore, the present inventors happened to complete the present invention by adding a small amount of a specific surfactant to a silicate-based inorganic paint and painting with this. That is, the present invention provides the general formula M ₂ O・SiO ₂ (in the formula M
is an alkali metal, -N(ROH) ₄ or -NH ₄ ) is used as a binder, and a phosphorus compound is used as a hardening agent. This is a completed inorganic paint coating method characterized by adding approximately 0.01 to 2.0% by weight of an inorganic paint. The inorganic paint used in the present invention has the general formula M ₂ O.
It uses an alkali metal silicate or quaternary ammonium silicate represented by SiO ₂ as a binder and a phosphorus compound such as a phosphate or condensed phosphate as a hardening agent. The inorganic coating film is formed on the molten aluminized steel plate by baking and hardening at 150 to 250℃. However, since the steel plate that is the object to be painted is highly active, it is easy to cause chemical reactions when inorganic paint is applied, and even during baking, pinholes in the paint film can occur due to the relatively high temperature. , tends to cause problems such as blister, blistering, and dulling. Therefore, it is inherently difficult to form a hard and glossy inorganic coating film that adheres closely to the steel plate and has high adhesion. Therefore, the present inventors discovered that when considering various additives to make it difficult for the alkaline substances in the inorganic paint to come into direct contact with the surface of the steel sheet, the effect of using a specific surfactant would be very noticeable. I understood. That is, the above-mentioned surfactant is a nonionic or anionic surfactant, and the nonionic surfactant is selected from ethylene oxide type, diethanolamine type, anhydrosorbitol type, glucoside type, and glycerin type. The type surfactant is selected from carboxylic acid type, sulfuric acid ester type, sulfonic acid type, alkylaryl sulfonate type, etc. The amount of these surfactants added to inorganic paint is approximately 0.01 to 2.0
If it exceeds 2.0% by weight, there is a strong possibility that the inorganic paint film will be damaged. Of course, the inorganic paint can be colored freely by mixing various pigments, and by painting, a colored fused aluminized steel sheet with excellent color and gloss can be obtained. The colored hot-dipped aluminized steel sheet obtained by the method of the present invention is substantially made of inorganic material, is completely noncombustible, and has superior flame resistance and heat resistance compared to conventional ones. In addition to physical properties such as adhesion, bending resistance, impact resistance, and bending resistance, it also has various qualities normally required of colored steel sheets, as well as chemical resistance, stain resistance, normal water resistance, and weather resistance. is also excellent. What is noteworthy, and unexpected, is that the adhesion is greatly improved. This is probably due to the fact that the curing mechanism of the inorganic paint itself is caused by the function of specific additives to uniformly and strongly adhere to the molten aluminized steel sheet. Moreover, the anti-corrosion function of the molten aluminized layer,
The anti-corrosion function of the inorganic paint film shows a slightly different form, and these two types of anti-corrosion factors mutually enhance the effect, resulting in very good anti-corrosion properties. Needless to say, these improvements in quality dramatically improve the durability of colored hot-dipped aluminized steel sheets. Examples of the present invention will be described below. Example 1 The method of the present invention was carried out in accordance with the following procedure using a molten aluminized steel plate in which the plating layer was formed of 81% aluminum, 5% silicon, and 14% iron. First, after degreasing the above steel plate with alkaline and washing with water,
After drying for a minute, immediately mix the inorganic paint base and curing agent below thoroughly, then spray 200g/
Apply with a coating amount of m ² . (Formulation of inorganic paint) - Base - Sodium silicate No. 1 aqueous solution 1000 parts by weight Titanium oxide (rutile type) 100 parts by weight Inorganic pigment 100 parts by weight Polyethylene glycol lauryl ether
3 parts by weight Water 200 parts by weight - Hardening agent - Aluminum phosphate 400 parts by weight Water 800 parts After coating, the coating was baked and hardened in a far infrared heating furnace at 200° C. for 30 minutes to obtain a colored fused aluminized steel sheet. When the surface condition of this colored coating layer was carefully observed, it was observed that it was free from defects such as blisters, blisters, and pinholes, and formed a glossy and firm film. Further, this colored steel plate was used as a test plate and tested according to the following test method, and the results shown in Table 1 were obtained. (1) Chemical resistance test 1 Acid resistance Drop 35% Hcl/ml onto the test piece, wash with water after 24 hours, dry, and observe the state of the coating film. 2 Alkali resistance Drop 30% NaOH/ml onto the test piece, wash with water after 24 hours, dry, and observe the state of the coating film. (2) Erichsen test Cross-cut the test plate, perform the JIS Z 2247 test, and observe the state of the coating film. (3) Pencil hardness test According to the test method of JIS G 3312 8.8, the hardness of the pencil is measured just before scratches are observed on the coating film of the test plate. (4) Corrosion resistance test 1 Salt spray test The coating film on the test plate was cross-cut, and the JIS Z
2371 for 500 hours and observe the state of rust formation. 2 Salt water immersion test Cross-cut the coating film on the test plate and immerse it in salt water.
Soak for 30 days and observe the state of rust formation (5) Heat resistance test One cycle consists of leaving the test plate in an electric furnace set at 600℃ for 20 hours and at room temperature for 4 hours, and this is repeated for 10 cycles. After doing so, observe the condition of the paint film. (6) Flame resistance test The tip of the gas burner flame (approx.
1100℃) for 5 minutes, then observe the condition of the coating film. Example 2 A test was conducted in exactly the same manner as in Example 1, except that the additives in the paint were changed to the following method.
Obtained the results in the table. Method of adding additives: Add sodium dodecylbenzenesulfonate to 5 parts by weight. 【table】

Claims (1)

[Claims] 1 A molten aluminized steel plate is prepared using the general formula M ₂ O・
When applying an inorganic paint composed of an alkali silicate represented by SiO ₂ (wherein M is an alkali metal, -N(ROH) ₄ or -NH ₄ ) as a binder and a phosphorus compound as a curing agent, A method for applying an inorganic paint, characterized by adding about 0.01 to 2.0% by weight of a nonionic or anionic surfactant.