JPH0651172B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a coating method.

b. Conventional technology and its problems Conventionally, in the body painting of automobiles, in addition to conventional electrodeposition coating, so-called reverse coating, in which powder coating is applied to the outer peripheral surface of the body in advance and then electrodeposition coating is performed. The law has been adopted. According to this coating method, powder coating adheres to the outer peripheral surface of the body to increase electrical resistance,
The electrodeposition paint does not adhere to the outer peripheral surface of the body but adheres to the inside of a bag such as a side seal, thereby improving throwing power.

However, in the above reverse coating method, the film thickness becomes non-uniform at the boundary between the powder coating part and the electrodeposition coating part, and a thin film is formed, and the rust preventive power is lowered. For this reason, the boundary surface is covered by providing the powder coating material with conductivity or improving the flowability of the electrodeposition coating material, but both are inferior in appearance and coating film performance.

Further, since the coating film on the outer peripheral surface of the body is a hard powder coating film, the coating surface is poor and a good appearance cannot be obtained.
There was a problem in workability due to complicated water polishing work.

Further, draining in the pretreatment draining furnace must be completely performed, and a baking furnace for baking the powder coating film is required, which causes a problem that energy consumption increases and cost increases.

Therefore, there is a method in which after electrodeposition coating, the coating film is preheated and then dip coating is performed using a water-soluble coating material.

However, with this method, it is difficult to make the coating film thickness uniform, and the amount of paint taken out to the next step is large.
Further, since liquid pools are generated, it is necessary to mask the screw holes and the like, and there are drawbacks such that the coating hanger is extremely dirty.

The present invention has been made in view of such circumstances, and an object thereof is to provide a coating method capable of solving the above-mentioned problems.

c. Means for Solving Problems In order to solve the problems of the above-mentioned prior art, the present invention forms a coating film by adhering an electrodeposition paint to the surface of a pretreated object, and washing with water. And then apply hot water and / or
Alternatively, the present invention provides a coating method characterized by subjecting the coating film to a steam atmosphere treatment to fix the coating film, followed by dip coating with a water-soluble paint and washing with water.

As a method of fixing the electrodeposition coating film by the hot water and / or steam atmosphere treatment, a method of pre-curing the electrodeposition coating film by aging for 1 to 3 minutes with a hot water and / or steam atmosphere of 60 to 100 ° C. is there.

Further, the above water-soluble coating material is obtained by immersing an article to be coated in an aqueous solution of an aqueous resin as a coating film-forming substrate, whereby a chemical in the solution, such as phosphoric acid, reacts with the article to be coated, It is preferable that the aqueous resin coagulates on the surface of the article to be coated by the more eluted metal ions to form a coating film, or that the polymer compound contains a polymer compound that forms a chelate compound by coordinate bond with a metal. For example, an AP coat (trade name) manufactured by Nippon Paint Co., Ltd. The water-soluble paint also includes emulsion type paints.

d. Examples Hereinafter, the present invention will be described in detail based on illustrated examples.

Example First, as shown in FIG. 2, two cold-rolled steel plates 1, 2 were used.
With spacers 3 and 4 of thickness 200 μm sandwiched between them
A coating sample 9 was prepared by spot welding at points 7 and 8.

According to the flowchart shown in FIG. 1, the coating sample 9 was first subjected to chemical conversion treatment and pretreatment. Then, electrodeposition coating is carried out by a conventional method, and an electrodeposition coating material is attached to form a coating film.

After the above coating sample was washed with water, heat treatment (aging) was performed for 1 to 3 minutes with hot water at 60 to 100 ° C. to fix the coating film formed on the surface of the coating sample.

Next, water-soluble paint (AP coat manufactured by Nippon Paint Co., Ltd.)
Was immersed in a tank (30 ° C., 2 minutes) in which was dissolved to form a coating film.

The above coating sample was washed with water and then baked at 170 ° C. for 20 minutes to obtain a coating film.

The coating film of the obtained coating sample was subjected to evaluation of coating state and salt spray test. The results are shown in Table-1.

Comparative Example 1 The coating sample 9 was first subjected to chemical conversion treatment and pretreatment. Then, electrodeposition coating is carried out by a conventional method, and an electrodeposition coating material is attached to form a coating film.

The above coating sample is washed with water and then baked at 170 ° C. for 20 minutes to obtain a coating film.

The coating film of the obtained coating sample was subjected to evaluation of coating state and salt spray test. The results are shown in Table-1.

Comparative Example 2 Coating was carried out in the same manner as in Example 1 except that the coating film formed on the surface of the coating sample was not fixed by heat treatment (aging) for 1 to 3 minutes with hot water at 60 to 100 ° C. A coating film was formed on the sample, and the coating state was evaluated and a salt spray test was performed. The results are shown in Table-1.

e. Effect of the invention As described above, the coating method according to the present invention is a method of applying a coating film to the surface of an article to be pretreated to form a coating film, washing the surface with water, and then applying hot water to the article to be coated. And / or steam atmosphere treatment is applied to fix the coating film, and then water-soluble paint is used for dip coating, and then baking treatment is performed to form the coating film. It is possible to solve the drawbacks that the film thickness becomes non-uniform, and the film becomes a thin film and the anticorrosive power is lowered.

Further, in the coating method of the present invention, an ordinary pretreatment draining furnace and an electrodeposition baking furnace can be used, and a special furnace is not required unlike the powder coating method, so that the energy consumption is small and the cost is low. Is advantageous to.

Moreover, since the washing process is performed after immersion coating, there is no problem such as clogging of screw holes due to liquid pool, which was a problem in the conventional coating method that uses both electrodeposition coating and immersion coating. There is no need to mask the screw holes in advance, and the paint hanger does not get dirty. Furthermore, since it is possible to paint a portion that is difficult to energize, it is advantageous in terms of corrosion resistance.

[Brief description of drawings]

FIG. 1 is a flow chart showing a procedure of a coating method according to an embodiment of the present invention, and FIG. 2 is a view showing coating samples used in Examples and Comparative Examples. 1, 2 ... Cooled rolled steel plate, 3, 4 ... Spacer, 5, 6, 7, 8 ... Spot welding point, 9 ... Painting sample.

Claims (2)

[Claims] 1. A coating film is formed by depositing an electrodeposition paint on the surface of a pre-treated article to be coated, washed with water, and then subjected to hot water and / or steam atmosphere treatment on the article to be coated. Is fixed, and then dip-painted with a water-soluble paint and washed with water. 2. The water-soluble coating composition, wherein a water-based resin is coagulated on the surface of the coating object by a metal ion precipitated from the coating object by a chemical contained in the coating composition to form a coating film, or a combination with a metal. The coating method according to claim (1), characterized in that the coating method comprises a polymer compound which is bonded to form a chelate compound.