JPH0346184B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrodeposition coating method that can be applied to automobile bodies and the like to obtain good results.

[Prior art]

Electrodeposition coating is usually used as an undercoat for automobile bodies because it has excellent paint coverage inside the vehicle body, but there are some parts of the vehicle body that cannot be coated well. For example, a rear quarter section 2 in a car body 1 shown in FIG.
is the quarter outer panel 3 as shown in Figure 2.
and the quarter inner panel 4 are joined at the upper part by spot welding, but since the total painting area including the outer surface part A and the inner surface part B is large in this part, the electric current is applied to the inner part B. The coating has poor coverage. Therefore, the outer surface of the quarter outer panel 3 A' is spray-painted in advance from the boundary line 5 to the upper end.

In this way, a part of the object to be coated is spray-painted in advance, and after curing by baking, the unpainted part of the object is electrodeposited to improve the coverage of the electrodeposited paint on the inner surface and closed cross-section of the object. A coating method that improves the coating is called reverse electrodeposition coating and has been used for a long time.In this coating method, for example, the boundary line 5 between the coating film 6 formed by spray painting and the coating film 7 formed by electrodeposition coating is mixed. Defects may occur. Fig. 3 shows this, and there is a defective part as shown by reference numeral 8 between the coating film 6 formed by spray painting and the coating film 7 formed by electrodeposition, which causes rust and corrosion. It was hot.

In addition, in the drawing, only the outer surface side of the quarter outer panel 3 is shown as the coating film 7 by electrodeposition coating, and the other parts are omitted, but the coating film 7 by electrodeposition coating is applied to the inside and outside of the object to be coated except for the spray-painted area. Needless to say, it is formed all over the surface.

[Purpose of the invention]

It is an object of the present invention to provide an electrodeposition coating method that eliminates these drawbacks of the prior art and improves the conformability of the coating film at the boundary between spray coating and electrodeposition coating.

[Structure of the Invention] In order to achieve the above object, the present invention provides an electrodeposition coating method in which a part of the object to be coated is spray-coated in advance, and then an unpainted part of the object is electrodeposited. When spray painting a part, use the above-mentioned electrodeposition paint, spray paint a part of the object with the paint, and then leave the spray coating semi-hardened on the unpainted part of the object. This is an electrodeposition coating method characterized by applying electrodeposition, and then curing the electrodeposition coating and the spray coating simultaneously in a drying step. As a result, it is possible to obtain a smooth coated surface that eliminates the poor adhesion of the paint, which was a drawback of the conventional reverse electrodeposition coating method.

〔Example〕

Electrodeposition paint, which is used mainly for painting inner panels and closed cross-section parts, is applied to a part of the outer panel surface of the object to be coated (vehicle body 1) that has been subjected to phosphate treatment by means such as air spray painting, and then left as is. Alternatively, after the solvent is volatilized by heating or the like, electrocoating is applied to the unpainted portions of the inner plate, closed cross section, or outer plate surface, and the coating is dried and cured to obtain a uniform coated surface. According to the method of the present invention, the coating material for the outer panel surface by spray painting is the same as the coating material for the inner panel and closed cross section by electrodeposition coating, and the outer panel surface to be spray coated first. The coating material is heated and flowed in the drying process after the electrodeposition coating in the next process without being completely cured.
Unlike the conventional method, as shown in FIG. 4, a flat coated surface was obtained without any misalignment between the coating film 6 formed by spray coating and the coating film 7 formed by electrodeposition coating.

[Actual example]

(1) Anionic electrodeposition paint made by Company A (Electron
7100), adjusted with a diluent such as ethyl cellulose to have a solid content of 40% and a viscosity of 25 seconds/20°C using a food cup No. 4, and air spray to a dry film thickness of 20~20°C. After painting it so that it is 25mm and setting it for 5 minutes,
After keeping it in a hot air oven at 120℃ for 10 minutes to evaporate the solvent, it was electrodeposited in Elekron 7100 (a paint with a solid content of 14% and an amine ratio of 1.75) at a voltage of 200V3, followed by washing and draining. The coating film was dried and cured by holding it in a hot air oven at 170°C for 20 minutes.
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 (Power Top U
-73) replenishment paint (pigment content F1 and resin content F2)
(mixed in an appropriate ratio, typically 1:3) with a mixed diluent of butyl cellulose/ethyl cellulose with a solid content of 35% and a viscosity of 22 seconds/20°C.
The coating was adjusted using a food cup No. 4 to give a dry film thickness of 25 to 30 μm using air spray, and after setting for 7 minutes, it was kept in a hot air oven at 130℃ for 15 minutes to remove the solvent. After volatilizing the power top U-73 (solid content 20
%MEQ28) paint at a voltage of 150 V3, washed with water, drained, and held in a hot air oven at 170°C for 20 minutes to dry and harden the paint film. The resulting coated surface, especially the boundary area, was smooth with no occurrence of poor compatibility between the coating resins.

〔Effect of the invention〕

Since the present invention is a method as described above, it has the effect of smoothing the boundaries in so-called reverse electrodeposition coating. In addition, the unpainted parts of the object to be coated are electrocoated while the spray coating is semi-cured, and the electrocoating and spray coating are simultaneously cured in the drying process after electrocoating. Therefore, it has an energy saving effect compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a side view of an automobile body to which this invention is applied;
2 is an enlarged sectional view taken along the line - in FIG. 1, FIG. 3 is a sectional view showing a conventional coating state, and FIG. 4 is a sectional view showing a coating state according to the present invention. 6... Coating film by spray painting, 7... Coating film by electrodeposition coating.

Claims (1)

[Claims] 1 After spray painting a part of the object in advance,
In the electrodeposition coating method in which unpainted parts of the object are electrodeposited, when spray painting a part of the object, the above-mentioned electrodeposition paint is used, and the part of the object is coated with the paint. Spray painting, then electrocoating the unpainted parts of the object while the spray coating is semi-hardened, and then curing the electrodeposition coating and the spray coating simultaneously in the drying process. An electrodeposition coating method characterized by: