JPS60150870A - Electrodeposition painting method - Google Patents

Abstract

PURPOSE:To obtain a smooth interface by using the same resin and pigment in spray painting and in electrodeposition painting, and carrying out the electrodeposition painting before a spray-coated film is cured. CONSTITUTION:The paint contg. the same resin and pigment is used in spray coating 6 at the first step and in electrodeposition coating 7 at the second step. After the first-step coating 6, the paint is not completely cured, and only the solvent is volatilized to dryness. Then the second-step coating 7 is carried out, and both coatings are simultaneously cured. The fitness between both coatings can be enhanced in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to a closed cross section inside an automobile body,
The present invention relates to an electrodeposition coating method that yields good results.

[Prior art]

It goes without saying that the surface of an automobile body is painted, but there are some parts of the body that cannot be painted well. For example, the rear quarter section 2 of the automobile body 1 shown in FIG. 1 is formed by spot welding a quarter outer panel 5 and a quarter inner panel 4 together at the upper part as shown in FIG. When applying electrodeposition coating to the entire parts A and B, it is difficult to apply uniform coating because the total area is large. Therefore, a portion A' between the border line 5 and the upper end is spray-painted in advance.

This painting method, in which a part of the object to be coated is spray-painted in advance, baked and cured, and then electro-deposited is applied to the inner surface and closed cross-sections of the car body, is called reverse electro-deposition. Although this coating method has been practiced conventionally, poor adhesion may occur, for example, at the boundary line 5 between the coating film 6 formed by spray coating and the electrodeposited coating M7.

Figure 3 shows this, and shows the coating film 6 by spray painting.
There was a defect in that a poorly conforming area as shown by reference numeral 8 was generated between the electrodeposited coating film 7 and the electrodeposition coating film 7, which caused rust and corrosion.

[Purpose of the invention]

This invention eliminates these drawbacks of the prior art and
The object of the present invention is to provide an electrodeposition coating method that improves the adhesion of a coating film at the boundary between spray coating and fixed coating.

[Structure of the invention]

In order to achieve the above object, the present invention uses the above-described reverse electrodeposition coating method, in which the paint applied in the first step of spray painting and the paint used in the second step of electrodeposition are made of the same resin and pigment. After the first step of painting, the paint is dried to the extent that the solvent is volatilized without being completely cured, and then the paint is cured at the same time as the electrodeposition coating is cured. As a result, it is possible to obtain a smooth coated surface that eliminates the problem of paint smearing, which is a drawback of conventional reverse electrodeposition coating methods.

〔Example〕

The fixing paint used for painting mainly the inner panels and closed cross sections of the object to be painted (vehicle body 1) that has been subjected to phosphate treatment is applied to the outer panel surface by means such as air spraying, either as it is or with a solvent. After evaporating the amount by heating or the like, electromagnetic coating is applied to the unpainted parts of the inner panel, closed cross section, or outer panel surface, and is dried and hardened to obtain a uniform coated surface. According to the method of the present invention, the coating material mainly for the outer panel surface and the coating material mainly for the inner panel and closed section are the same resin, and the outer panel surface to be coated first after being broken is completely cured. Unlike the conventional method, as shown in FIG. , a flat painted surface was obtained.

[Actual example]

(1) Anionic electrodeposition paint made by Company A (Nileclone 7100
) using a replenishment paint, adjusted with a diluting solvent such as Ethicello to have a solid content of 40 cm and a viscosity of 25 seconds/2oC using a Ford cup A4, and then air spray to a dry film thickness of 2
0 to 25 degrees, set for 5 minutes, kept in a hot air oven at 120°C for 10 minutes to volatilize the solvent, and then coated with Nireclone 7100 (solids content: 14%, amine ratio: 1.0%). The coating was electrodeposited at a voltage of 200 V for 3 minutes in a paint (No. 75), then washed with water, drained, and kept in a hot air oven at 170° C. for 20 minutes to dry and harden the coating. The coating surface thus obtained, especially the boundary area, was smooth and free from poor compatibility between the coating resins.

(2) Cationic electrodeposition paint made by Company B (Pan-Top U-7
5) Replenishment paint (pigment part F1 and resin part F2 mixed in an appropriate ratio, typically 1:3) is added to Buticero/
Echicello mixed solution solid content 35% viscosity 22 seconds/20
℃ in an A4 Ford cup, then painted with air spray to a dry film thickness of 25 to 50 μm, set for 7 minutes, and kept in a hot air oven at 150℃ for 15 minutes. After volatilizing the solvent, electrodeposition was performed at a voltage of 150 V for 3 minutes in Power Top U-73 (solid content 204 ME028) paint, followed by washing with water, draining, and heating in a hot air oven at 170°C for 20 minutes. After holding, the coating was allowed to dry and cure. The resulting coated surface, especially the boundary area, was smooth without any misalignment between the paint resins.

〔Effect of the invention〕

Since this invention is a method as described above, it has the effect of smoothing the boundary surface in so-called reverse electrodeposition coating. Furthermore, since the outer panel surface is only dried to the extent that the solvent is evaporated, this method has an energy saving effect compared to conventional methods.

[Brief explanation of drawings]

Fig. 1 is a side view of an automobile body to which this invention is applied. Fig. 2 is an enlarged cross-sectional view taken along line 1-II in Fig. 1, Fig. 3 is a cross-sectional view showing a conventional painting state, and Fig. 4 is a cross-sectional view according to the present invention. This is a cross-sectional view showing the painted state. 600. Coating film 7... Electrodeposition coating patent applicant Toyota Auto Body Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1) In a painting method that uses spray painting and electrodeposition, the paint used in the first step of spray painting and the paint used in the second step of electrodeposition have the same resin and pigment, and After spray painting in the first step, the paint is dried to the extent that the solvent is volatilized without completely curing the paint, and then the first and second steps are performed to cure the paint film formed by electrodeposition in the second step. An electrodeposition coating method characterized by simultaneously curing and flowing the applied paint.