JPS5848677A - Pretreating agent for coating steel products and pretreatment for coating - Google Patents

Abstract

PURPOSE:To obtain uniform chemical films by adding a prescribed amount of oxalate to an acid composition soln. contg. phosphoric acid having a prescribed concn., a water soluble solvent and chelating agent and by carrying out pretreatment for coating with the resulting treating agent. CONSTITUTION:A treating agent is prepared by adding 50-10,000mg/l oxalate to an acid composition soln. contg. phosphoric acid having 1-30wt% concn., a water soluble solvent and a chelating agent. The surfaces of steel products are degreased and descaled with the treating agent. After washing and regulating the surfaces, chemical films are formed on the surfaces, washed and dried. Thus, uniform chemical films are obtd., and when the films as undercoats are coated, the resulting films have enhanced adhesive strength and corrosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pretreatment agent and a pretreatment method for coating the surface of steel materials, and in particular, a pretreatment agent suitable for painting steel surfaces that have been subjected to high-temperature treatments such as welding. and a pretreatment method.

Generally, when painting steel surfaces, the adhesion of the paint,
From the viewpoint of corrosion resistance, paint is not sprayed directly onto the surface of the steel material, but rather a chemical conversion film such as zinc phosphate is formed on the surface of the steel material by electrodeposition, and the paint is sprayed onto this film.

By the way, when steel materials are welded, rust preventive oil adheres to the welded portion and its vicinity, and furthermore, a film of strong oxide scale such as iron oxide is formed. A chemical conversion film is formed on the surface without removing these rust preventive oils or oxide scales, and when this film is painted, the appearance, adhesion, and
And a coating film with poor corrosion resistance etc. will be formed.

Therefore, conventional degreasing treatments include emulsion degreasing, alkaline degreasing, etc., and rust degreasing (descaling).
Physical treatments such as shot blasting, sandblasting or puffing, or inorganic acids such as hydrochloric acid, sulfuric acid or phosphoric acid? The chemical treatment used is carried out. This process is shown in Figure 1 in detail, starting with preliminary degreasing, then main degreasing, then pickling to remove scale with acid, surface treatment, and chemical conversion treatment to form a chemical conversion film such as zinc phosphate. It consists of 16 steps including drying and drying. For this reason, pre-treatment for painting takes time, equipment must be installed for each process, the area occupied in the factory is inevitably large, and quality is also subject to variation as it goes through many processes. There is a problem that occurs.

In addition, when using physical treatments such as shot blasting, there are disadvantages in that the surface roughness of the steel material surface becomes too rough and scale cannot be removed sufficiently in difficult-to-shot areas. In some cases, there are problems such as the need to carry out two neutralization treatments in order to prevent deterioration of the surface of the steel material due to hydrogen brittleness and generation of yellow spirit due to insufficient washing with water.

Various proposals have been made to solve the above-mentioned disadvantages. For example, a chemical that combines degreasing and greasy rust? Some methods are designed to reduce the number of treatment steps by using the method, and others are designed to form a phosphate film at the same time as degreasing and rust removal. This has the disadvantage that the parts to which it can be applied are limited, and it cannot be applied to products that require high quality, such as automobiles and motorcycles.

In view of the above-mentioned conventional technical problems, the present inventors have created the present invention to effectively solve the problems, and the purpose is to simultaneously degrease and remove grease and rust, The purpose of the present invention is to provide a pre-painting agent for steel materials that can form a chemical bottom film such as zinc phosphate that has excellent adhesion and stability.
In order to achieve such an object, @1 invention uses a coating pre-treatment agent for steel materials, a phosphoric acid concentration of 1 to 3 Qwt in an acid composition solution containing a water bath agent such as phosphoric acid and butyl cellosolve, and a chelating agent as a stabilizer. % and added oxalate 7al-50 to 1α000 my/ to the adjusted bath liquid.

Another objective is to provide a method for pre-painting steel materials that can reduce the number of processes and form a coating base film of zinc phosphate, etc., which is excellent in quality. The second invention is a treatment in which a solution containing a water-soluble solvent such as butyl cellosolve phosphate and a chelating agent and whose phosphoric acid concentration is adjusted to 1 to 80 wt% by adjustment such as dilution is prepared, and oxalate is added to this solution. After degreasing and descaling the surface of the steel material using a chemical agent, and performing further cleaning and surface conditioning (9), a chemical conversion film is formed on the surface of the steel material, and then washing and drying are performed.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings and experimental examples.

FIG. 2 is a simplified view of the apparatus used to carry out the painting pretreatment method of the second invention using the treatment agent of the first invention.

1 in the figure is a processing tank used in the cleaning process, and this processing tank 1
25-80w phosphoric acid, 9-50w water bathing solvent 1%
and a nonionic surfactant of 1 to 10 wt$ Y to form an acid composition with a phosphoric acid concentration of 1 to 80 wt% by diluting, etc., and to this composition, sulfuric acid salt with a concentration of 50 to lαo o o wt was added. Fill with treatment agent.

An example of a suitable sulfate salt is shown in Table I.

Table 1.

Next, a steel material made by welding mild steel or the like is put into the treatment tank 1 and degreased and descaled. Thereafter, the steel material is taken out from the treatment tank 1, and the treatment agent is removed from the surface of the steel material using the drain device 2, and then sent to the washing tank 3 for washing with water. Next, after draining water in a drain device 4, the steel material is sent to a surface conditioning device 5, and then passed through the drain device 6 and immersed in a chemical conversion coating treatment tank 7. Thereafter, the steel material is washed with water in a washing tank 8, and then sent to a surface conditioning device 5. At step 9, water is removed by air blowing, etc., and then transferred to a drying oven 10.
The steel material heated in this drying oven is sent to a cooling device 11. Furthermore, FIG. 3 shows the steps of the above pretreatment method in blocks similar to FIG. 1, and as is clear from these figures, the pretreatment method for painting using the pretreatment agent of the present invention is It can be seen that the number of pretreatment steps can be greatly reduced compared to the conventional method shown in FIG. 1, which requires 16 steps in total.

Figures 4 and 5 show the relationship between the phosphoric acid concentration of the acid composition, the oxalate concentration added to this acid composition, and the chemical conversion film properties using a 5-point method (3 points or more is considered good). This is shown by.

Of these, Figure 3 shows the relationship between the phosphoric acid concentration of the acid composition and the chemical conversion film properties when α95wt% of nickel oxalate is added.As is clear from the figure, the phosphoric acid concentration However, if the content is less than 1 wt%, the physical properties of the chemical conversion film formed on the surface of the steel material will deteriorate. Further, if the phosphoric acid concentration exceeds 3 Qwt%, the surface of the steel material will be etched and become rough, which is not preferable.

Therefore, the phosphoric acid concentration of the acid composition is between 1 wt% and 3 wt%.
It can be said that Q wt% is appropriate.

In addition, Figure 4 shows the phosphoric acid concentration of the acid composition = constant 10 wt%.
This figure shows the relationship between oxalate concentration and chemical conversion coating properties when the product is closed.As is clear from this figure, when the concentration of oxalate added is 50 mv'1 or less, the chemical conversion coating properties decrease. Furthermore, even if 1α000 my' or more is added, the chemical conversion film properties will not improve any further, so it can be said that the appropriate oxalate concentration is about 50 to 1α000 mg/l.

Next, specific experimental examples of the present invention will be given and compared with comparative examples to further clarify the effects of the present invention.

Experimental Example 1 Phosphoric acid 25 wtql, butyl cellosolve 5 Q wt%
Nonionic surfactant l Q wt%, chelating agent 5
wt%, and water lQwL% (hereinafter simply referred to as acid composition A) is prepared, and this acid composition A5wt
% and zinc oxalate α5wt%, and the liquid temperature was 55±5.
Fill the treatment tank in the cleaning process with a water bath solution at ℃.

Next, the rear fork, which is a workpiece welded using the steel iMIG method, is immersed in the above treatment tank and washed for about 5 minutes to remove press oil, rust preventive oil, and welding that adhered to the welded parts of the workpiece. Removes strong oxide scale formed on the surface of the treated material.

Next, the material to be treated is transferred to a water washing tank and washed with water for about 80 seconds.
After draining, transfer to the next chemical conversion coating treatment tank.

This chemical conversion coating treatment tank is filled with a zinc phosphate chemical conversion treatment agent (Granodine #C8100O) and a solution adjusted to 3wt% and at a temperature of 50±5°C, and the material to be treated is placed in this bath liquid. Soak for about 8 minutes and then take out.

Thereafter, the material to be treated is dried for about 10 minutes in a drain drying oven maintained at 120° C., and then taken out. A uniform chemical conversion film layer was formed on the surface of the treated material treated in this manner.

Next, a water-soluble acrylic topcoat paint (Aqua #7100: manufactured by NOF Corporation) is spray-coated to a thickness of 25 to 30 μm on the surface of the treated material on which the chemical conversion film layer has been formed, and the mixture is heated at approximately 170°C for 30 minutes. Baking is performed in a hot air oven, and then taken out from the oven and cooled to room temperature.

The painted appearance of the rear fork, which was the material to be treated as described above, and the physical properties of the coated film such as the adhesion and corrosion resistance of the coated film were extremely good.

Experimental Example 2 A treatment tank for the cleaning process was filled with a water bath solution containing 10 wt% of the acid composition AY, 1 wt% of nickel oxalate, and the remainder was water at a temperature of 55±5°C, and a steel material 7TIG system was placed in the treatment tank. The rear fork, which is a welded material to be treated, is immersed and washed for about 5 minutes to remove the rust preventive oil adhering to the material and the strong oxide scale formed on the surface of the material.

Next, the same chemical conversion coating treatment as above is performed. A uniform chemical conversion film layer was formed on the surface of the treated material thus treated.

And the same coating as above on the above treated material? give

As a result, a coating film having excellent appearance, adhesion, corrosion resistance, etc. similar to that described above was obtained.

Experimental Example 3 An acid composition (hereinafter simply referred to as acid composition B) consisting of 80 wt% phosphoric acid, 9 wt% butyl cellosolve, 2 wt% chelating agent, and 9 wt% water was prepared, and this acid composition B'&1
An aqueous solution containing 0 wt % and 11 wt % manganese oxalate and having a liquid temperature of 55±5° C. is filled in the processing tank for the cleaning step.

Next, steel material 7. - The rear fork, which is a material to be treated that has been welded using the MIG method, is immersed in the above treatment tank and washed for about 5 minutes to remove the rust preventive oil and oxidized scale from the surface of the material to be treated.

Next, this treated material was washed with water in the same manner as in Experimental Example 1, and then subjected to a chemical conversion coating treatment. Through this treatment, a uniform chemical conversion film was formed on the surface of the treated material.

Furthermore, the same coating treatment as in Experimental Example 1 was applied to the treated material on which the chemical conversion film had been formed. The thus obtained coating film on the surface of the treated material was excellent in physical properties such as appearance, adhesion, and corrosion resistance.

Experimental Example 4 Acid composition of Experimental Example 8 By5wt%, zinc oxalate 1
1wt% and the rest is water, stir well and bring the liquid temperature to ? 55±5
A treatment tank in the cleaning process is filled with a water bath solution at ℃, and steel such as mild steel is bathed in the bath using the 2yna method to produce a rear fork. The treated material was immersed and washed for about 5 minutes to remove rust preventive oil and oxidation scale from the surface of the material to be treated, and then treated with a chemical conversion coating in the same manner as in Experimental Example 1. Let's do it. A uniform chemical conversion film layer was formed on the surface of the treated material treated in this way.

Then, the same coating treatment as in Experimental Example 1 was applied to this treated material. As a result, a coating film with excellent appearance, adhesion, and corrosion resistance was formed on the surface of the treated material.

Next, a comparative example for comparison with the above experimental example is shown below.

Comparative Example 1 Acid composition A'Y of Experimental Example 1 10wt% qi
A treatment tank for the cleaning process is filled with an aqueous solution that has been well stirred as water and has a liquid temperature of 55 ± 5°C. Soak the fork, wash for about 5 minutes and remove.

The thus treated material is subjected to a chemical conversion coating treatment to form a zinc phosphate coating similar to that in Experimental Example 1. The obtained chemical conversion film contained a large amount of amorphous iron phosphate and was non-uniform. Child. The coating film on the surface of the treated material obtained in this way has better appearance,
The physical properties of the coating film, such as adhesion and corrosion resistance, were significantly inferior.

Comparative Example 2 A treatment tank for the cleaning process was filled with an aqueous solution containing 10 wt% of the acid composition B'a' of Experimental Example 8 and the remainder was water, and the temperature was adjusted to 55±5°C. - A rear fork, which is a material to be treated made of mild steel or other steel welded using the MIG method, is immersed, washed for about 5 minutes, and then taken out.

The thus treated material is subjected to a chemical conversion coating treatment to form a zinc phosphate coating similar to that in Experimental Example 1. There was a large amount of amorphous iron phosphate coating on the surface of this treated material, and the chemical conversion coating was non-uniform.
Apply the same paint treatment as above. The coating film on the surface of the treated material thus obtained has better appearance,
The physical properties of the coating film, such as adhesion and corrosion resistance, were significantly inferior.

The above experimental examples and comparative examples are summarized in Table 2. There is a noticeable difference in the quality of the chemical conversion coating that is the base for coating formed on the surface of the treated material, and there is also a large difference in the physical properties of the coating film formed on the surface of the chemical conversion coating.

Note that the oxalate salt added to the solution of the acid composition is not limited to a single one, and two or more types of oxalate salts may be added.

As is clear from the above description, according to the present invention, a predetermined amount of a steel coating pretreatment agent is added to a solution containing phosphoric acid, a water-soluble solvent, and a chelating agent, and with a phosphoric acid concentration of 1 to 30 wt%. By adding oxalate to the composition, and using such a treatment agent, degreasing and descaling are performed simultaneously in the pre-painting treatment process, which reduces the number of processes, thereby shortening treatment time and reducing the need for treatment equipment. Simplification can be achieved.

Furthermore, when 9 pre-treatments for painting are performed using the treatment agent 2 according to the present invention, a uniform chemical conversion film can be obtained. This chemical conversion coating has many advantages, such as improving the adhesion, corrosion resistance, appearance, etc. of the coating when it is applied as a base.

[Brief explanation of the drawing]

The drawings show a preferred embodiment of the present invention and a conventional example, and FIG. 1 is a block diagram showing a conventional painting pretreatment process, and FIG. 2 is a block diagram of a device for performing painting pretreatment according to the present invention. A simplified side view, FIG. 3 is a block diagram similar to FIG. 1 showing the pretreatment process of the present invention, and FIG. 4' shows the relationship between phosphoric acid concentration and chemical conversion film properties. FIG. 5 is a diagram showing the relationship between oxalate and chemical conversion film properties. In addition, in the drawing, 1 is a treatment tank, 2, 4, 6.9 are drain devices, 3, 8 are washing tanks, 5 is a surface conditioning device, 7 is a chemical conversion coating treatment tank, 10 is a drying oven, and 11 is a cooling device. be. Patent applicant: Honda Motor Co., Ltd. Agent Patent attorney: Yoichi Shimoda Patent attorney: Kunihiko Ohashi )

Claims (1)

[Scope of Claims] (It is made by adding 50 to 1α000 mg/l of oxalate to an acid composition solution containing 119 phosphoric acid, a water-soluble solvent, and a chelating agent and having a phosphoric acid concentration of 1 to 3 Qwt%. A pre-painting treatment agent for steel materials characterized by: (2) A sulfuric acid salt is added to an acid composition solution containing phosphoric acid, a water-soluble solvent, and a chelating agent, and with a phosphoric acid concentration of 1 to 3 Qwt%. A steel material characterized in that the surface of the steel material is degreased and descaled using a treatment agent, then cleaned and surface conditioned, a chemical conversion film is formed on the surface of the steel material, and further washed and dried. Pre-painting treatment method.