JP2003138400A - Method of preventing secondary sag of electrodeposition coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preventing secondary sags of an electrodeposition coating material which can effectively prevent the secondary sag of the electrodeposition coating material induced by the alkaline solution existing in the clearances of a material to be coated. SOLUTION: This method of preventing the secondary sag of the electrodeposition coating material includes a process step of providing the material to be coated which consists of a steel plate and has the clearances; a process step of subjecting the material to be coated to dip into a water bath to fill the clearance with water; a process step of subjecting the material to be coated to an alkaline degreasing treatment; a process step of forming the electrodeposition coating film by performing electrodeposition coating; and a process step of obtaining the hardened coating film by baking the electrodeposition coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing secondary sagging of electrodeposition paints, and more particularly to a method for preventing secondary sagging of electrodeposition paints caused by an alkaline liquid for degreasing.

[0002]

2. Description of the Related Art Electrodeposition coating can be applied to the inside of a narrow gap formed on the surface of an object to be coated and has a great anticorrosion effect, so that it is used as a base coating for automobile bodies. An automobile body is usually constructed by combining a plurality of steel plates, and a gap is formed at a joint between the steel plates.

On the other hand, the steel sheet is coated with rust preventive oil for storage, and it is necessary to degrease it before subjecting it to electrodeposition coating. When the object to be coated has a complicated shape such as an automobile body, degreasing is performed by immersing it in an alkaline bath. In that case, if there is a gap in the article to be coated, the alkaline liquid enters the gap.

The alkaline liquid that has penetrated into the gaps of the article to be coated is not easily removed in the subsequent water washing step, and the electrodeposition step is often performed as it is. Then, in this state the article to be coated is immersed in the electrodeposition tank, and when the electrodeposition coating material enters the gap of the coating object, the electrodeposition coating material is acidic and reacts with the alkaline liquid present in the gap to aggregate, Form a solid.

The solid matter formed in the gaps of the article to be coated is ejected from the gaps due to bumping of residual water during the subsequent baking step and adheres to the surface of the coating film as lumps or lumps. , The secondary sagging of the paint occurs. The secondary sagging to which such solid matter adheres causes a coating failure, and when polishing or repair coating for repairing the sagging of the coating film is performed, labor is required, the strength of the coating film is reduced, and the coating performance is also deteriorated.

Methods for preventing secondary sagging have been proposed so far. However, the conventional method is a technique for taking out the electrodeposition coating material once infiltrated into the gap as a liquid (sol), and in order to remove the coating material aggregated by the degreasing alkaline liquid from the gap of the object to be coated, It was insufficient.

Therefore, it is difficult to effectively prevent the secondary sagging of the electrodeposition coating material caused by the alkaline liquid for degreasing with such a conventional technique.

[0008]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems of the prior art, and its object is to prevent secondary sagging of the electrodeposition paint caused by the alkaline liquid present in the gaps of the article to be coated. It is an object of the present invention to provide a method for preventing secondary sagging of electrodeposition coatings, which can be effectively prevented.

[0009]

The present invention comprises a steel plate,
A step of providing an article to be coated having a gap; a step of immersing the article to be coated in a water bath to fill the gap with water; a step of performing an alkaline degreasing treatment; an electrodeposition coating to form an electrodeposition coating film And a step of baking the electrodeposition coating film to obtain a cured coating film, which is intended to achieve the above object.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In carrying out the method of the present invention, the object to be coated is not particularly limited as long as it is electrically conductive and has a gap. As the conductive material, for example, an iron plate,
Examples thereof include a steel plate, an aluminum plate, and a structure composed of a surface-treated product of these. The size of the gap is preferably such that water or the like once infiltrated does not easily come out during the electrodeposition process. For example, it is 100 to 500 μm, preferably 200 to 400 μm.

Particularly, in the case of a metal material coated with rust preventive oil and stored, a degreasing treatment is performed before the electrodeposition coating, so that the secondary sagging preventing effect is effectively exhibited. A preferred article to be coated is a structure made of steel sheet, especially an automobile body.

The article to be coated is first immersed in a water bath. The water to be put in the water bath need only be substantially free of non-volatile components, and the washing water usually used in the electrodeposition step, for example,
It may be deionized water. The time of immersion is sufficient to fill the gaps in the article to be coated with water.

In the case of carrying out on an industrial scale, a tank having an appropriate size corresponding to the object to be coated is installed, and the tank is filled with water. Then, as in the case of electrodeposition coating, the article to be coated may be moved in water by an appropriate time by the conveyor means.

After removing the article to be coated from the water bath, degreasing treatment is performed. This is for removing the rust preventive oil from the surface of the article to be coated. Degreasing is usually performed by immersing the article to be coated in an alkaline aqueous solution such as a degreasing solution or by spraying the alkaline aqueous solution onto the surface of the article to be coated. When the article to be coated has a complicated shape such as an automobile body, it is preferable to perform the degreasing by dipping it in an alkaline bath in order to sufficiently degrease the inside.

At this time, in the method of the present invention, since the gaps of the article to be coated are already filled with water, it becomes difficult for the alkaline aqueous solution to enter the gaps of the article to be coated.

After pulling the article to be coated from the alkaline bath, it is washed with water and electrodeposition coating is carried out. The electrodeposition coating may be performed by a usual method. Electrodeposition includes (i) a step of immersing an object to be coated in an electrodeposition coating material, and (ii) a step of applying a voltage between the object to be coated and a corresponding electrode to deposit a film, Composed of. At that time, in the method of the present invention, since the gap of the article to be coated is already filled with water, the electrodeposition paint cannot penetrate into the gap of the article to be coated.

The electrodeposition paint may be cationic or anionic. When the above voltage is applied, the bath temperature of the electrodeposition coating is usually preferably 10 to 45 ° C. Further, the time for applying the voltage varies depending on the electrodeposition conditions, but generally, it is 2
It can be ~ 4 minutes.

After the coated object is pulled out from the electrodeposition tank, the formed electrodeposition coating film is washed with water and hardened by baking to complete the coating. The baking conditions are generally 120
~ 260 ° C, preferably 160-220 ° C, 10-3
0 minutes.

During the baking step, in the method of the present invention, water is filled in the gaps of the article to be coated, and solid matter such as electrodeposition paint does not exist. Will never gush out. Therefore, solid matter does not adhere to the periphery of the gap, and no lumps or lumps are formed on the surface of the coating film. As a result, the occurrence of secondary sagging on which solid matter adheres is prevented, and the work for repairing the coating film becomes unnecessary.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[0021] Example dimensions longitudinal 150 mm, horizontal 70 mm, a combination of two pieces of flat steel plates of a thickness 0.8 mm, to prepare a structure having a gap 200 to 400, and the object to be coated.

A container having a capacity of 4 liters was filled with deionized water to form a water bath, and the article to be coated was immersed in the water bath for 20 seconds.
Then, a container having a capacity of 4 liters was filled with 2% degreasing liquid to make an alkaline bath, the article to be coated was taken out of the water bath and immersed in the alkaline bath for 20 seconds. The article to be coated was taken out of the alkaline bath and washed with deionized water.

Cationic electrodeposition paint "Power Top V system F-1" 500 manufactured by Nippon Paint Co., Ltd. in a container having a capacity of 4 liters.
g, "Powertop V-type F-2" 1500 g, and deionized water 2000 g were mixed, and after mixing them, the article to be coated was dipped to start electrodeposition coating. Electrodeposition condition is effective voltage 1
The film thickness was set to 0 to 250 V and the film thickness was set to 20 to 30 μm.

The coated article was taken out of the electrodeposition tank, washed with deionized water, and dried at room temperature for 10 minutes. Then, the coated article was placed in an oven and the coating film was baked at 160 ° C. for 10 minutes.

After the baking step, the coated article is cooled to room temperature,
The state of the coating film in the peripheral portion of the gap was observed. No lumps or lumps were formed around the gap, and no secondary sagging with solid matter was generated.

[0026]

According to the method of the present invention, it is possible to effectively prevent the secondary sagging of the electrodeposition coating material caused by the alkaline liquid existing in the gap of the article to be coated.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C25D 13/00 307 C25D 13/00 307D 13/12 13/12 A

Claims (2)

[Claims] 1. A step of providing an article to be coated, which is made of a steel plate and has a gap; a step of immersing the article to be coated in a water bath to fill the gap with water; a step of performing an alkaline degreasing treatment; an electrodeposition coating A method for preventing secondary sagging of an electrodeposition coating composition, comprising the steps of: forming an electrodeposition coating film; and baking the electrodeposition coating film to obtain a cured coating film. 2. The method according to claim 1, wherein the alkaline degreasing treatment is performed by immersing the article to be coated in an alkaline bath.