JPH0280595A - Method for coating metallic material - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of the weld zone, etc., of a metallic material by successively subjecting the material to degreasing, chemical treatment, washing and treatment with a specified % aq. soln. of water soluble resin having a specified surface tension to form a coat of a specified thickness on dry basis and by carrying out finish coating and baking. CONSTITUTION:A metallic material is degreased, chemically treated and washed. This washed material is directly treated with 1-10% ag. soln. of water soluble resin adjusted to <=40dyn/cm surface tension so as to form a coat of 0.05-3mum thickness on dry basis. The treated material is dried, finish-coated and baked. Primer coating may be carried out before the finish coating. The resin soln. is used as a soln. for cationic electrodeposition and the surface tension is adjusted with lower alcohol. The corrosion resistance of the weld zone, etc., can be improved.

Description

Detailed Description of the Invention Technical Field The present invention relates to a method for coating metal materials, and more specifically, the present invention relates to a method for coating metal materials, and more specifically, it can be applied directly to a top coat or baked after degreasing, chemical conversion treatment, washing, and drying. Even if the product is subjected to topcoating and baking treatment after treatment, it is possible to improve the corrosion resistance of the product to a level higher than that of simple chemical conversion treatment or a combination of chemical conversion treatment and primer treatment, without making major changes to conventional equipment. This invention relates to a novel coating method for metal materials such as metal structures and metal plates.

Prior Art Steel materials used for constructing sheds, fences, gates, etc.
Conventionally, products have been manufactured by degreasing, chemical conversion treatment, washing with water, draining and drying, followed by topcoating and baking, and in some cases, primers have not been applied to improve corrosion resistance and coating performance. In such coated steel plates, coating film defects are likely to occur, for example, at steel plate reinforcement seams, uneven areas, etc., and the corrosion resistance of these areas is a problem. Currently, steel plates are being changed from iron-based to zinc-based (including alloys, plating, etc.) for the purpose of improving corrosion resistance. Various other techniques are being considered, such as the adoption of electrodeposition coating and chrome cleaning after chemical formation, but these require the installation of new specialized equipment, which is uneconomical, and also poses pollution problems due to chromium-containing wastewater. However, it has not been adopted smoothly. Further, even if primer coating is attempted to be easily carried out using, for example, a conventional spray method, it is difficult for the paint to enter joints, uneven portions, etc., and a satisfactory improvement in corrosion resistance cannot necessarily be obtained.

Problems to be Solved by the Invention Therefore, metal materials, In particular, there is a demand for a significant improvement in the corrosion resistance of metal structures from the level of only f-heating treatment, and it is the main purpose of the present invention to meet this problem.

Furthermore, it is easy and easy to improve the corrosion resistance of steel sheets, galvanized steel sheets, galvanized steel sheets, alloyed galvanized steel sheets, etc., which are widely used in various fields, beyond the current level, regardless of the presence or absence of 1 limer. It is also an object of the invention to provide a simple method.

Means for Solving the Problems According to the present invention, the above object is to produce a water-based resin with a surface tension adjusted to 40 dynes/cm or less without drying the metal material after degreasing, chemical conversion treatment, and water washing. ~10%
This is achieved by a coating method characterized by treating with an aqueous solution to obtain a coating with a dry film thickness of 0.05 to 3 μm, drying, then applying a top coat, or a primer coat and a top coat, and subjecting it to a baking process. . That is, in the present invention, a metal structure or a metal material such as a metal plate that has been subjected to a chemical conversion treatment such as iron phosphate or zinc phosphate and washed with water after normal degreasing is still in a wet state. Corrosion resistance can be definitely improved by treating with a specific aqueous solution, then drying, and then applying a topcoat and baking, or by applying a conventional primer coating and then applying a topcoat and baking. be.

The present inventors have discovered that it is extremely effective to apply a resin film in small amounts for the purpose of improving the corrosion resistance of chemically treated metal structures, and that the conventional degreasing - chemical conversion treatment, washing with water, draining, drying, topcoating and baking. In a series of processes,
It is an effective method to use the resin in the form of an aqueous solution and apply it as a thin layer to the wet metal structure after washing with water, in terms of sag, uniformity, and penetration into the wet metal structures, etc. I learned from this that the surface tension of an aqueous resin solution is important, and that a resin coating with a thickness of 3μ or less, preferably about 105 to 1μ, can achieve a remarkable corrosion resistance improvement effect.
The invention has been completed.

In the present invention, as described above, a wet metal structure is treated with an aqueous solution of an aqueous resin. The treatment method in this case may be spraying or immersion, and in either case, it may be carried out during the final water washing step after chemical formation or immediately after, and drying using a conventional draining drying oven is possible. can. The resin liquid in this case is any aqueous liquid for paint, such as acrylic resin or epoxy resin.

It is desired that the resin solid content concentration is usually 1 to 10%,
If the concentration is too high, it may cause uneven processing, sagging, secondary sagging at seams, etc., and the appearance of the topcoat will be greatly affected.
Also, even if it is too diluted, the purpose of the invention will not be achieved sufficiently.
From the viewpoint of ease of controlling the concentration of the aqueous resin solution and workability, a resin solid content concentration of around 5% is particularly preferred.

If desired, a solvent and various additives can be added to this aqueous resin solution for the purpose of preventing foaming and forming a foam, but sufficient water solubility must be maintained. A particularly preferred aqueous resin solution is one based on a cationic electrodeposition solution.

However, the surface tension of the aqueous resin solution must be adjusted to 40 dynes/cm or less. In the present invention, the wet metal structure is treated with the aqueous resin solution, but the surface tension of the resin liquid must be adjusted to 40 dynes/cm or less. If it is larger, the resin liquid may not adhere uniformly to the metal surface due to poor wetting, and the object of the invention may not be fully achieved due to insufficient permeability to the seam. The surface tension of the aqueous resin solution can be easily controlled by using water containing a surface modifier as a diluent, but particularly preferred surface modifiers are lower alcohols,
Isopropyl alcohol is most suitable for cationic electrodeposition aqueous solutions, and surface conditioning agents that selectively dissolve resin components, such as Cellosolve, are not necessarily suitable for controlling the surface tension of resin aqueous solutions. .

It is important to spray an aqueous resin solution with controlled surface tension onto a wet metal structure to form a uniform coating. It has been confirmed that a sufficient corrosion resistance improvement effect can be obtained with a thickness of about 0.105 to 1 .mu.m, and that a maximum thickness of 3 .mu.m is acceptable in view of the effects on workability and the appearance of the topcoat film. The aqueous resin solution is thus sprayed onto the wet metal structure,
The spray liquid is collected and recycled. During this time, the resin liquid concentration,
In order to control the surface tension of the circulating fluid to 40 dynes/cm or less, the surface tension of the initial resin aqueous solution is adjusted to 30 dynes/cm.
It has also been found that it is particularly advantageous to keep it below a centimeter.

After the aqueous resin solution in the present invention is applied, it is dried, and the drying conditions may be selected from the range of appropriate baking conditions for the applied resin system. When commercialized as a product, the corrosion resistance is significantly improved compared to the conventional product that undergoes degreasing, chemical conversion treatment, washing with water, draining, drying, and topcoating and baking. The effect of improving the practical corrosion resistance of the parts and uneven parts is extremely large.

Furthermore, the method of the present invention exhibits a similar corrosion resistance improvement effect not only on metal structures but also on metal plates, and therefore can be applied to a wide range of metal materials including metal structures and metal plates. It is something. In the above, resin, chemical conversion treatment,
We have described in detail the products that are directly top-coated after washing and drying, but after applying an aqueous solution of water-based resin and drying, these metal materials are coated with a regular primer to further improve their corrosion resistance. A top coat and baking can then be applied, in which case the corrosion resistance will be even more improved than products with chemical conversion treatment and primer coating.

In the method of the present invention, the aqueous resin solution can be applied extremely easily and simply between the final water washing step and draining drying oven in conventional chemical conversion treatment without significantly changing the conventional treatment equipment and treatment process. Moreover, it is an industrially extremely important invention in that it can significantly improve the corrosion resistance of metal materials, especially in the case of metal structures.

The present invention will be explained below with reference to Examples. In addition, all "parts" in the examples mean "parts by weight."

A 4.9% aqueous solution of an aqueous resin is prepared according to the following formulation. The surface adjustment force at this time was 26 dynes/cm.

Epoxy cationic electrodeposition clear 100 parts Isopropyl alcohol 250 parts Tap water
In preparing 450 parts, first mix the solvent and tap water, and add the epoxy cationic electrodeposited clear to this while stirring.

In advance, the above aqueous solution is showered (sprayed) in a wet state on a structure of an alloyed galvanized steel sheet having reinforcing seams and uneven parts that have been subjected to normal alkali degreasing and zinc phosphate chemical conversion treatment. Then, by baking and drying at 190° C. for XIO minutes, a clear coating film of about 0.2 μm was obtained.

Acrylic resin paint (product name: "Super Lac F50 Beige Color" manufactured by Nippon Paint Co., Ltd.) is used as a top coat for this product.
Painted with air atomization electrostatic and spray method, 16
By baking and drying at 0° C. for 20 minutes, a coated plate with a total film thickness of about 25 μm (flat area) was prepared.

E1''L A comparative coated plate was prepared by repeating the same method as in Example 1, but without applying the aqueous resin solution.

Each coated plate of Example 1 and Comparative Example 1 was subjected to the Tsuruto Spray Test (J I 5-Z-2371') for 240 hours to examine changes in the values of each part of the coated plate. The test results are as shown in Table 1. there were. (Cross cuts are made on the flat surface.) (The following is a blank space.) [L] Prepare an aqueous solution of water-based paint with a non-volatile content of 5.2% according to the formulation below. The surface adjustment force at this time was 29 dynes/cm.

Epoxy cationic electrodeposition white 50 parts Epoxy cationic electrodeposition clear 150 parts Isopropyl alcohol 350 parts Butanol
50 parts tap water
900 parts Additive (antifoaming agent) 1.5 parts To make the adjustment, first mix the solvent (2 types) and tap water, then stir the water-based paint that has been mixed in advance with white/clear = 1/3. Add the defoamer at the end. In advance, a structure of an alloyed galvanized steel sheet with louvers (vents) that has been subjected to normal alkali degreasing and zinc phosphate chemical conversion treatment is immersed in the above aqueous solution, and baked and dried at 180°C for 8 minutes to obtain approximately A white coating film of 0.3μ was obtained.

Acrylic resin paint (product name: "Superlac F53 Green Color" manufactured by Nippon Paint Co., Ltd.) as a top coat for this product
A coated plate having a total film thickness (flat area) of approximately 30 μm was prepared by electrostatically coating #2 disk and baking and drying for 170×15 minutes.

A comparative coated plate was prepared by repeating the same method as Ltfi Main Example 2, but without applying a water-based paint.

The coated plates of Example 2 and Comparative Example 2 were subjected to a 360-hour Tsuruto spray test, and the results are shown in Table 2.

The same treated alloyed galvanized steel sheet as in Table 2-6 was applied to a film thickness of 3 μm or more, and the same top coat was applied. Table 3 also shows the physical properties and corrosion resistance test results for this comparative painted steel plate.

(Left below) Based on the same aqueous resin as in Example 1, using a solution of isopropyl alcohol/tap water = 1/2 as a diluent,
Aqueous solutions of 2.5%, 5%, 7.5%, and 10% were prepared.

Using an alloyed galvanized steel sheet that had been degreased and chemically treated in advance, it was treated with each aqueous solution in the same manner as in Example 1, and after being overcoated, physical properties and corrosion resistance tests were conducted, as shown in Table 3. I got good results.

Based on the same aqueous resin as in Examples 3 to 6, a 20% aqueous resin aqueous solution was prepared with a solution of isopropyl alcohol/tap water = 1/2, and Examples 3 to 7 and 4 Prepare a 4.9% aqueous solution of the same aqueous resin as in 1,
A 5PC-1 dull steel plate that had been degreased and chemically treated in advance was treated in the same manner as in Example 1, and after being overcoated, physical properties and corrosion resistance tests were conducted, and the results shown in Table 4 were obtained.

Comparative Example 4 is the result when no aqueous resin solution was used.

Table 4: Prepare a 4.8% aqueous solution of water-based paint according to the following formulation. The surface conditioning force at this time was 32 dynes/cm.

Epoxy cationic electrodeposition clear 100 parts Isopropyl alcohol 150 parts Tap water
550 parts An alloyed galvanized steel sheet that had been previously subjected to normal degreasing and chemical conversion treatment was immersed in the above solution in a wet state, baked at 200°C for 8 minutes, and then coated with acrylic resin paint (Nippon Paint A coated plate having a total film thickness of 25 μm was prepared by spray-coating the coated film with a commercial product (trade name: “Superlac F47 White Color”) and baking and drying at 160′ CX for 20 minutes.

Note that Comparative Example 5 is the same as above, except that no water-based paint was applied.

The corrosion resistance test results for both are shown in Table 5.

Table 5 patent application agent

Claims (2)

[Claims] (1) After the metal material has been degreased, chemically treated, and washed with water, it is coated with a 1 to 10% aqueous solution of an aqueous resin whose surface tension has been adjusted to 40 dynes/cm or less without drying to a dry film thickness of 0.
A method for coating metal materials, which comprises treating the metal material to obtain a coating of 0.05 to 3 μm, and after drying, applying a top coat, or a primer coat and a top coat, and subjecting it to a baking process. (2) The method according to claim 1, wherein the aqueous resin aqueous solution is a cationic electrodeposition liquid, and a lower alcohol is used to adjust the surface tension.