JPH07118893A - Formation of double layered coating film - Google Patents

Abstract

PURPOSE:To decrease the coating defects generating at the time of forming double layered coating films by providing the vertical hanging type coating film forming method with three coating stages consisting of respective stages for forming an electrodeposition coating film, forming an intermediate coating film and finish coating film and a baking stage after the respective stages for intermediate coating and finish coating. CONSTITUTION:1) The electrodeposition coating film is formed by electrodeposition coating in the vertical hanging state of directing the longest size direction of a material to be coated toward a vertical direction. 2) The electrodeposition coating film surface of the material to be coated is washed with water in the vertical hanging state. 3) Water draining is executed when moisture remains on the electrodeposition coating film surface of the material to be coated in the vertical hanging state (setting stage). 4) The intermediate coating film is formed on the material to be coated by plural stages in the vertical hanging state. 5) The electrodeposition coating film and the intermediate coating film are baked and dried in the vertical hanging state. 6) The finish coating film is formed on the material to be coated in the vertical hanging state. 7) The finish coating film is baked and dried in the vertical hanging state. This method includes the respective stages described above. The stages 1 to 7 are successively executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a multi-layer coating film, and more particularly to an improvement in a method for forming a vertically suspended coating film.

[0002]

2. Description of the Related Art In general, a surface of an automobile body, a home electric appliance, a building material, or the like is formed with a multilayer coating film in order to improve the corrosion resistance and the aesthetic appearance of the surface.

For example, an automobile body is first electrodeposited. Conventionally, the longest dimension of the car body was arranged along the transport direction, and the car body was hung on the hanger of an overhead conveyor (so-called "horizontal suspension") and immersed in the electro-deposition coating in a ship-shaped electro-deposition tank. . Then, the hanger and the electrode plate in the tank are energized to apply the paint to the vehicle body by electrodeposition coating.

In the case of electrodeposition coating, the pigment mixed in the electrodeposition coating material or foreign matter such as dust and lumps in the electrodeposition coating material tank settles on the horizontal surface to form a coating film. As a result of this, the horizontal surface tends to have a poorer coating quality than the vertical surface. However, when horizontally suspended, the horizontal plane is a portion such as a hood, a trunk lit, and a roof, which is important in the appearance of the automobile. Therefore, in order to improve the appearance, there is a problem that many steps are required to finish the above-mentioned portion. In addition, there is a problem that a large amount of electrodeposition paint is taken out of the electrodeposition tank due to the posture of the vehicle body.

Therefore, in recent years, in order to improve the above-mentioned problems, the body for automobiles has been subjected to electrodeposition coating from horizontal suspension to vertical suspension. For example, set the longest dimension of the vehicle body to the vertical direction (so-called "vertical suspension"),
Feltak (VERTAK) method (Takashi Heihachi, Painting Engineering, 196 (26): 200 (30), Vol.14,
No.5 (1979)).

[0006] Also, in "Electrodeposition coating method for automobile body" of Japanese Patent Laid-Open No. 3-68473, an electrodeposition coating method in which the vehicle body is immersed in the electrodeposition coating material in a posture in which the front-rear direction of the vehicle body is vertical. Is disclosed.

Further, US Pat. No. 3,705,817, "METHOD FORTREATING THE SURFA
"CES OF VEHICLE BODIES)" also discloses a method of electrodeposition painting of a vehicle body by a vertical suspension type.

Further, in Japanese Patent Application No. 3-42444, "Dip treatment apparatus for electrodeposition coating", two electrodes arranged on both sides of the vehicle body are used when electrodeposition coating is performed on the vehicle body by hanging vertically. An apparatus has been disclosed in which the ratio of the effective area of the plate is set to a specific ratio to obtain the required film thickness on the required portion of the coated object.

[0009] Further, although it is not the electric car electrodeposition coating of the vehicle body, the vertical suspension type electrodeposition coating is disclosed in Japanese Patent Publication No. 42925/1990, "Aluminum or aluminum alloy vertical suspension type surface treatment method". There is.

Therefore, in recent years, attention has been paid to the vertical suspension of the vehicle body in the electrodeposition coating.

Generally, after the electrodeposition coating, there is a step of baking the coating film formed by this electrodeposition coating, applying an intermediate coating and a top coating. In recent years, from the viewpoints of energy saving, resource saving, and labor saving, studies are being made on coating by a wet-on-wet (w / w) method that omits the baking step during electrodeposition coating.

[0012] For example, in JP-A-53-106740, "Novel coating method of solid color", an electrodeposition coating film is formed on an object to be coated, and then the electrodeposition coating film is formed on the electrodeposition coating film without baking. A coating method has been disclosed in which a color base coating composed of an aqueous coating is applied to form a color base coating, and a clear coating is formed on the color base coating without baking.

Further, in the "coating method" of JP-A-60-193568, a solvent-based paint containing a hydrophilic solvent in an uncured state (without baking) is applied by electrodeposition coating on an object to be coated. A coating method is described in which coating is performed and then baking is performed.

Further, in Japanese Patent Application Laid-Open No. 2-240295, "Electrodeposition coating method for automobiles", an object to be coated is subjected to electrodeposition coating, and after washing with water and removing water, the baking step is not performed. An electrodeposition coating method is disclosed in which a sealer / undercoat step and / or an intermediate coating step are performed.

Further, in JP-A-4-104862, "coating film forming method" and JP-A-4-110065, a hydrophilic solvent and A coating film forming method is disclosed in which a specific amount of a ketone solvent is applied to form a coating film.

Incidentally, in coating, the degree of adhesion of the coating film tends to be different between the vertical portion and the horizontal portion depending on the composition of the coating material. Therefore, in order to make the finish uniform, a method of forming a predetermined film thickness by setting the number of times of application of the vertical part to two or more stages with respect to the horizontal part 1 is disclosed in Japanese Patent Publication No. 4-74070. It is described in.

[0017]

However, even if a good and highly economical electrodeposition coating film is obtained by the above disclosed method of electrodeposition coating by vertical hanging, the subsequent baking step and medium If a baking process is performed between the coating process and the top coating process, energy saving that has been earnestly desired in recent years,
It goes against resource and labor saving.

Even if the above-mentioned wet-on-wet (w / w) intermediate coating and overcoating are applied after performing the above-mentioned electrodeposition coating method by vertical hanging, it is satisfactory in the intermediate coating process and the overcoating process. There is a problem that the final appearance is deteriorated unless a good coating film is obtained.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a method for forming a multilayer coating film which reduces coating defects occurring during coating of a multilayer coating film.

[0020]

In order to achieve the above object, the present invention according to claim 1 is (1) by electrodeposition coating in a vertically suspended state with the longest dimension of the object to be coated in the vertical direction. An electrodeposition coating film forming step of forming an electrodeposition coating film, and (2) a water washing step of washing the electrodeposition coating film surface of the coating object with water in a vertically suspended state,
(3) A setting step of draining water when the water remains on the electrodeposition coating film of the coating object in a vertically suspended state, and (4) an intermediate coating film is formed on the coating object by a plurality of stages in a vertically suspended state. An intermediate coating film forming step of: (5) a first baking drying step of baking and drying the electrodeposition coating film and the intermediate coating film in a vertically suspended state; and (6) a top coating on an object to be coated in a vertically suspended state. A topcoat coating film forming step of forming a film, and (7) a second baking and drying step of baking and drying the topcoat coating film in a vertically suspended state, including the above steps (1) to (7) Is characterized by.
That is, 3 coats including an electrodeposition coating film forming step, an intermediate coating film forming step and a top coating film forming step, and a baking step performed after the intermediate coating film forming step and the top coating film forming step, respectively. And a method for forming a multilayer coating film, which comprises baking.

Further, the invention according to claim 2 is (1) an electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating in a state where the longest dimension of the object to be coated is vertically hung. When,
(2) Water washing step of washing the electrodeposition coating film surface of the coating object in a vertically suspended state, and (3) Setting for draining water when water remains on the electrodeposition coating film surface of the coating object in a vertically suspended state. And (4) a first baking drying step of baking and drying the electrodeposition coating film in a vertically suspended state, and (5) an intermediate coating for forming an intermediate coating film on an object to be coated by a plurality of stages in a vertically suspended state. A coating film forming step, (6) a second baking drying step of baking and drying the intermediate coating film in a vertically suspended state, and (7) formation of an overcoat coating film to form an upper coating film on an object to be coated in a vertically suspended state. And a third baking and drying step of baking and drying the topcoat coating film in a vertically suspended state (8), and the above steps (1) to (8) are sequentially performed. That is, three coats consisting of an electrodeposition coating film forming step, an intermediate coating film forming step and a top coating film forming step, and an electrodeposition coating film forming step, an intermediate coating film forming step and a top coating film forming step respectively. It is a method for forming a multilayer coating film, which comprises 3 baking consisting of a baking process performed.

Further, the invention according to claim 3 is (1) an electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating in a state of being vertically suspended with the longest dimension of the object to be coated oriented vertically. When,
(2) Water washing step of washing the electrodeposition coating film surface of the coating object in a vertically suspended state, and (3) Setting for draining water when water remains on the electrodeposition coating film surface of the coating object in a vertically suspended state. And (4) an intermediate coating film forming step of forming an intermediate coating film on an object to be coated by a plurality of stages in a vertically suspended state, and (5) an overcoating forming an upper coating film on an object to be coated in a vertically suspended state. The method is characterized in that it includes a coating film forming step and (6) a baking and drying step of baking and drying the coating film in a vertically suspended state, and sequentially goes through the steps (1) to (6). That is, the electrodeposition coating film forming step,
It is a method for forming a multilayer coating film having three coats consisting of an intermediate coating film forming step and a top coating film forming step, and one bake consisting of a baking step performed after the top coating film forming step.

Further, the invention according to claim 4 is (1) an electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating in a state of being vertically suspended with the longest dimension of the object to be coated oriented vertically. When,
(2) Water washing step of washing the electrodeposition coating film surface of the coating object in a vertically suspended state, and (3) Setting for draining water when water remains on the electrodeposition coating film surface of the coating object in a vertically suspended state. And (4) a topcoat coating film forming step of forming a topcoat coating film on a substrate by a plurality of stages in a vertically suspended state, and (5) a baking drying step of baking and drying the coating film in a vertically suspended state. The above steps (1) to (5) are sequentially performed. That is, it is a method for forming a multilayer coating film having two coats consisting of an electrodeposition coating film forming step and a topcoat coating film forming step, and one bake consisting of a baking step performed after the topcoat coating film forming step. .

The invention according to claim 5 is characterized in that, in the step of forming a topcoat film according to any one of claims 1 to 3, the topcoat film is formed on the article by a plurality of stages. And

The invention according to claim 6 is characterized in that the washing water used in the washing step according to any one of claims 1 to 5 contains a surfactant.

The electrodeposition coating may be cation electrodeposition or anion electrodeposition. In addition, in the electrodeposition coating method, the vehicle body is hung vertically on an overhead conveyor, and the vehicle body is immersed by transporting it to the electrodeposition tank in which the electrodeposition paint is stored. The electrodeposition tank should be placed close to the top and bottom of the vehicle, respectively.
Two electrodes are provided, and by energizing them, the vehicle body is electrodeposited. In order to obtain a desired film thickness on the top and bottom surfaces of the vehicle body, the ratio of the effective area (SA) of the electrode on the bottom surface side of the vehicle body to the effective area (SB) of the electrode on the top surface side of the vehicle body is SA
It is preferable that / SB = 9/1 to 5/5. If the ratio is larger than 9/1, the film thickness on the top surface (roof) of the vehicle body is insufficient, resulting in poor coating. On the other hand, if the ratio is less than 5/5, the film thickness on the bottom surface of the vehicle body is insufficient, resulting in rust prevention. Is reduced. The transportation method may be a tact method or a conveyor method.

The voltage for electrodeposition coating is preferably 200 to 350 V, and the hot water temperature is preferably 26 to 30 ° C. The electrodeposition time is preferably 3 to 6 minutes.

The water washing step may be either spraying or dipping. In the washing step, if you add a surfactant,
Draining efficiency increases. Therefore, the setting process can be omitted. Although not particularly limited, in the case of anionic electrodeposition, a nonionic surfactant or anionic surfactant is preferable, and in the case of cationic electrodeposition, a nonionic surfactant or cationic surfactant is preferable. If a cationic surfactant is used for washing with water after anion electrodeposition, or if an anionic surfactant is used for washing with water after cationic electrodeposition, the stability of the paint may be impaired. The concentration of the surfactant used is preferably 0.005 to 0.5%. If the concentration used is less than 0.005%, the effect of promoting draining is not observed, and if the concentration used exceeds 0.5%, foaming occurs in the washing tank or the coating film is in poor condition (occurrence of blistering or cissing). ) It causes.

The setting step is a draining step, and is preferably performed after the water washing step when a high appearance is particularly required and the shape of the article to be coated is complicated.

The intermediate coating and top coating may be solvent-based, powder-based or water-based. In addition, the paint used for intermediate coating with the wet-on-wet method after electrodeposition coating and the paint used for top-coating with the wet-on-wet method after electrodeposition coating may be any commonly used paint. There is no particular limitation. For example, the above-mentioned JP-A-60-193.
A solvent-based paint containing a hydrophilic solvent described in JP-A-56810, or JP-A-4-104862 and JP-A-4-110.
You may use the hydrophilic solvent and ketone type solvent of 065 publication.

Here, when the intermediate coating and the top coating are performed on a plurality of stages, the time interval between the stages is 1 minute to 5 minutes.
It is preferable to wait for a minute. If the interval between each stage is less than 1 minute, paint dripping is likely to occur, while if the interval between each stage exceeds 5 minutes, the appearance of the coating becomes poor. The coating method is not particularly limited, but spraying is preferable.

The dry film thickness (DFT) of the electrodeposition coating film is
It is preferably 15 to 35 μm, the dry film thickness of the intermediate coating film is preferably 20 to 50 μm, and the dry film thickness of the top coating film is preferably 20 to 50 μm. In addition,
When the intermediate coating and the top coating are performed in a plurality of stages, the coating is performed in a plurality of stages so as to have the above thickness.

The baking temperature after electrodeposition coating is usually 1
60 ° C., 30 minutes are preferable, the baking temperature after the intermediate coating is usually 140 ° C., 30 minutes, and the baking temperature after the top coating is usually 140 ° C., 30 minutes.

Incidentally, pretreatment such as chemical conversion treatment before electrodeposition coating may be carried out by hanging vertically. Thereby, the drainage property is improved in a small space, and the processing time can be shortened as compared with the conventional case.

[0035]

According to the present invention, since a multilayer coating film is formed by hanging vertically, the finish appearance is improved, and dust and dirt are removed from the main part of the vehicle body.
No lumps settle and adhere. In addition, the space for the multi-layer coating film forming line can be saved. Furthermore, since the vehicle body is lifted in the vertical direction at the end of electrodeposition coating, the amount of paint taken out is reduced.

When the intermediate coating and / or the top coating is carried out by the wet-on-wet method after the electrodeposition coating, the multi-layer coating film forming step can be shortened. Further, since the baking process is omitted, energy is saved.

Further, by using a surfactant in the water washing step, the water draining step can be omitted.

Further, by performing intermediate coating or top coating in a plurality of stages, it is possible to reduce paint dripping and the like, and further improve the finished appearance of the coating film.

[0039]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

Examples 1 to 10 and Comparative Examples 1 to 5 In Examples and Comparative Examples, a multilayer coating film was formed under the following processing conditions, and the final coating appearance was evaluated by the following evaluation method.

Multilayer coating film forming treatment conditions (1) Paint and dry film thickness of coating film (DFT) Electrodeposition coating: Cationic electrodeposition coating "Power Top U-60"
0 "Gray (manufactured by Nippon Paint Co., Ltd.) Intermediate coating: Polyester resin coating" Oruger S-9 "
3 "Gray (manufactured by Nippon Paint Co., Ltd.) Top coat paint: Acrylic resin paint" Oruger G-75 "
White (manufactured by Nippon Paint Co., Ltd.) The production conditions for the intermediate water-based paint and the top water-based paint are shown below.

Dry film thickness (μm) Electrodeposition coating 25 Intermediate coating 30 Top coating 30 Water-based intermediate coating 30 Water-based top coating 30 In Examples 1 to 6, Examples 9 to 10 and Comparative Example, the above intermediate coating composition and top coating composition were used. In Examples 7 to 8, the above intermediate coating water-based coating material and top coating water-based coating material were used. Production of water-based intermediate coating: Water-based alkyd resin varnish (acid value 60, hydroxyl value 60, resin solid content 35%, molecular weight 1,50)
0, oil length 20, water content 56%, neutralization rate 70% with dimethylethanolamine, pH 7.0) 48 parts, rutile titanium dioxide 36 parts, and precipitating barium sulfate 15 parts by mixing and stirring to 5 μm or less. A pigment paste was prepared by dispersion.

Separately, a polyester resin (“Findick BP442”) manufactured by Dainippon Ink and Chemicals, Inc. 1
2.0 parts, Toto Kasei Co., Ltd. epoxy resin ("Epototo NT114") 10.4 parts, precipitated barium sulfate 1
1.2 parts of the resin was melt-mixed, cooled and ground to a particle size of 100 μm or less to prepare a resin fine powder. This resin fine powder 13
Parts, 16 parts of the water-based alkyd resin varnish was charged, and 10
After stirring for 1 minute, the mixture was heated to 70 ° C., further stirred for 10 minutes, and cooled to room temperature with stirring to prepare a powder paste having a particle size of 10 μm or less.

50 parts of the aqueous alkyd resin varnish, 99 parts of pigment paste, 29 parts of powder paste and 12 parts of melamine resin were mixed to prepare an aqueous intermediate coating composition.

Manufacture of water-based top coating: Polyester resin manufactured by Nippon Ester Co., Ltd. (“ESTER RESIN
ER-6610 ") 60 parts, a block isocyanate curing agent manufactured by Huls (" ADDUCT B 153 "
0 ") 10 parts and 30 parts of titanium dioxide pigment are melt mixed,
It was cooled and pulverized to 100 μm or less to produce a resin fine powder. A powder paste was prepared in the same manner from this fine powder and the aqueous alkyd resin varnish.

99 parts of the above-prepared pigment paste, 29 parts of the above-mentioned powder paste, 50 of the aqueous alkyd resin varnish.
Parts, 10 parts of melamine resin, and 3 parts of an aromatic sulfonic acid-based curing catalyst were mixed to prepare an aqueous top coating composition.

(2) Electrodeposition conditions Voltage: 200 V, hot water temperature: 28 ° C., electrodeposition time: 6 minutes (3) Water washing process Ten pieces at a 50 cm interval for each riser measurement from both sides centering on the object to be coated, length Pipe nozzle 2 liters / in 6m riser
Minutes, pressure 0.5 kg / cm ² is provided at 50 cm intervals at intervals of 50 cm, the entire interior and exterior of the coated object is spray-washed, spraying time is 10 minutes, and the washing liquid is industrial water and a surfactant of 0.0
A 2% solution stored in a 1t tank was used.

Surfactant: 0.02% of the nonionic surfactant "Neugen EA87" (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
An aqueous solution was used.

(4) Setting step After standing for 10 minutes, the process proceeded to the next step.

(5) Intermediate coating and top coating steps Single stage: coating film thickness 20 μm to 50 μm
m, batch spray coating (using air gun) For multiple stages: 1 stage coating film thickness 10μ
3 m (about 3 m) intervals, 2 minutes between stages, spray painting (using air gun) (6) Baking process

[Table 1] Final coating appearance evaluation method (1) Visual evaluation plate: A 50 cm x 50 cm SPC plate mounted on the hood and door of a sedan-type automobile having a length of 5 m, a width of 2 m and a height of 1.5 m, and subjected to a vertical suspension treatment. The finished appearance is evaluated on a 10-point scale. "8"
Was the passing level.

(2) Garbage / Bug Evaluation Board: Evaluation of a 50 cm × 50 cm SPC board mounted on a hood or door of a sedan-type automobile having a length of 5 m, a width of 2 m and a height of 1.5 m and subjected to a vertical suspension treatment It was evaluated by the rank of the number of dusts and lumps on the plate.

◎: 0 to 5 pieces ○: 6 to 20 pieces △: 21 to 20 pieces ×: 41 pieces or more (3) Secondary sag laminated plate: sedan type of length 5 m, width 2 m, height 1.5 m Two plates (50 cm in advance) inside the hood and door of the passenger car
(X50 cm) was attached so as to be partially overlapped with the upper and lower sides, and the evaluation was performed by observing the sag from the seam of the laminated plate.

⊚: No sagging ○: Slight sagging △ to ◯: Sagging on 1/4 surface Δ: Sagging on half surface ×: Sagging on entire surface The evaluation results are shown below. In addition, Examples 1 to 3 and Comparative Examples 4 to 6 are 3 coat-1 bake (3C-1B), and Examples 4 to 8 and Comparative Example 2 are 3 coat-2 bake (3C-Bake).
2B), Example 9 and Comparative Example 1 are 3 coat-3 bake (3C-3B) and Example 10 is 2 coat-1 bake (2C).
-1B).

[0054]

[Table 2] From these results, according to the multilayer coating forming method of the present invention, a coating film having a good final coating film appearance can be obtained.

The method for forming a multi-layer coating of the present invention is not limited to coating of automobiles, but is also useful for coating of home electric appliances, building materials and the like.

[0056]

As described above, according to the method for forming a multi-layer coating according to the present invention, since the multi-layer coating is formed by hanging vertically, the finished appearance is improved, and dust and lumps are not formed on the main part of the vehicle body. Since the sedimentation does not occur, the appearance of the final coating film is good. In addition, the space for the multi-layer coating film forming line can be saved. Furthermore,
Since the vehicle body is lifted in the vertical direction during the electrodeposition coating, the amount of paint taken out can be reduced.

When the intermediate coating and / or the top coating is carried out by the wet-on-wet method after the electrodeposition coating, the step of forming a multilayer coating film can be shortened. Moreover, since the baking process is omitted, energy is saved.

Further, by using a surfactant in the water washing step, the water draining step can be omitted.

Further, by performing the intermediate coating or the top coating in a plurality of stages, it is possible to reduce the liquid dripping and the like and further improve the finished appearance of the coating film.

That is, it is possible to perform coating with excellent economy and good quality.

Claims (6)

[Claims] (1) An electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating in a vertically suspended state in which the longest dimension of the object to be coated is in the vertical direction, and (2) vertically suspended state. (3) a washing step of washing the surface of the electrodeposition coating film of the coating object with water, and (3) a setting step of performing draining when water remains on the surface of the electrodeposition coating film of the coating object in a vertically suspended state, (4) ) An intermediate coating film forming step of forming an intermediate coating film on an object to be coated by a plurality of stages in a vertically suspended state, and (5) a first drying step in which the electrodeposition coating film and the intermediate coating film are baked and dried in a vertically suspended state. A baking drying step; (6) a topcoat coating film forming step of forming a topcoat coating film on an object in a vertically suspended state; and (7) a second baking drying step of baking and drying the topcoat coating film in a vertically suspended state. And a method for forming a multilayer coating film, which comprises sequentially performing the steps (1) to (7) above. 2. (1) An electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating in a vertically suspended state in which the longest dimension of the article to be coated is in the vertical direction, and (2) vertically suspended state. A washing step of washing the electrodeposition coating film surface of the coating object with water, (3) a setting step of draining water when water remains on the electrodeposition coating film surface of the coating object in a vertically suspended state, (4) A first baking / drying step of baking and drying the electrodeposition coating film in a vertically suspended state; (5) an intermediate coating film forming step of forming an intermediate coating film on an article by a plurality of stages in a vertically suspended state; (6) Second baking drying step of baking and drying the intermediate coating film in a vertically suspended state; (7) Topcoat coating film forming step of forming an overcoat coating film on an object to be coated in a vertically suspended state; (8) A third baking and drying step of baking and drying the topcoat coating film in a vertically suspended state, and the steps (1) to (8) above Multilayer coating film forming method comprising passing through. 3. (1) An electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating in a vertically suspended state in which the longest dimension of the object to be coated is in the vertical direction, and (2) vertically suspended state. A washing step of washing the electrodeposition coating film surface of the coating object with water, (3) a setting step of draining water when water remains on the electrodeposition coating film surface of the coating object in a vertically suspended state, (4) An intermediate coating film forming step of forming an intermediate coating film on a coating object by a plurality of stages in a vertically suspended state, and (5) an overcoat coating film forming step of forming an upper coating film on a coating object in a vertically suspended state, (6) A baking and drying step of baking and drying the coating film in a vertically suspended state, and a step of sequentially performing the steps (1) to (6) described above. 4. (1) An electrodeposition coating film forming step of forming an electrodeposition coating film by electrodeposition coating in a vertically suspended state in which the longest dimension of the article to be coated is in the vertical direction, and (2) vertically suspended state. A washing step of washing the electrodeposition coating film surface of the coating object with water, (3) a setting step of draining water when water remains on the electrodeposition coating film surface of the coating object in a vertically suspended state, (4) (5) a topcoat coating film forming step of forming a topcoat coating film on an object to be coated in a vertically suspended state by a plurality of stages, and (5) a baking drying step of baking and drying the coating film in a vertically suspended state. A method for forming a multilayer coating film, which comprises sequentially performing the step (5). 5. The method for forming a multi-layer coating film according to any one of claims 1 to 3, wherein the top coating film is formed on the article by a plurality of stages. . 6. The method for forming a multilayer coating film according to any one of claims 1 to 5, wherein the cleaning water used contains a surfactant.