JPH02182898A - Undercoating treatment in coating of automobile car body or the like - Google Patents

Abstract

PURPOSE:To easily perform undercoating treatment showing rustproof performance high in reliability at low cost by performing electrodeposition coating for one of parts and performing composite assembly of this part together with the other parts and thereafter performing electrodeposition coating and baking. CONSTITUTION:Prescribed pretreatment is performed for the inner panel 2 of the door of an automobile car body and thereafter this inner panel is immersed in cationic electrodeposition coating in an electrodeposition tank 5 and cationic electrodeposition coating is performed by allowing current to flow. Both the inner panel 2 with an electrodeposited film 7 formed thereon and an outer panel 1 are clinched and joined in the end part 1a and composite assembly is performed to form a door 3. This door 3 is fitted to the car main body 4 via a hinge and electrodeposition coating is performed in an electrodeposition tank 5. Then the car main body 4 is introduced into a baking oven 6 and baked and dried. Therein the electrodeposited film 7 is once fluidized and introduced into the clinching joint part and thereafter cured and rustproof performance is enhanced. In the ensuing stage, intermediate coating and top coating are performed on the car body 4 wherein undercoating treatment has been performed thereon and coating is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for treating an undercoat during a painting process for painting automobile bodies and the like.

(Prior Art) Generally, the painting of automobile bodies, etc. is carried out by baking painting, and the standard process is to finish with an undercoat, an intermediate coat, and a topcoat.

Conventionally, this undercoating process has been mainly carried out by the electrodeposition coating method described in Japanese Patent Publication No. 56-20073, and by applying rust-preventing sealer in the lamination process and rust-preventing wax in the painting process. Efforts are being made to improve rust prevention.

This painting method will be explained in detail with reference to FIG. 2, taking as an example the case where the painting process is applied to an automobile door.An anti-rust sealer S is applied to the joint between the outer panel 1 and the inner panel 2 of the automobile door, which is the object to be painted. coating, then this outer panel 1
Inner panel 2 and anti-rust sealer S, which were transported separately, are sandwiched and joined in the assembly process, and outer panel 1
The door 3 is manufactured by clinching and joining with the tsumagidori and is assembled to the vehicle body 4.

Next, the car body 4 to which the door 3 has been attached by the assembly process is transferred to an electrodeposition coating process, in which the car body 4 is immersed in a cationic electrodeposition paint liquid in an electrodeposition tank 5. Then, apply electricity to perform cationic electrodeposition coating. Subsequently, paint is removed on an overflow tank (not shown), and then cleaning is performed in a water washing step.

The car body body 4 has been subjected to cationic electrodeposition coating in this way.
Then, in the baking process, baking and drying is carried out in the baking drying furnace 6 at a predetermined ambient temperature for a predetermined period of time. Further, in this undercoating step, polishing is performed to improve the adhesion with the coating film applied on the electrodeposition coating film, and the undercoating step is completed. The painting process then proceeds in the following order: the intermediate coating process and the top coating process. Next, anti-rust wax W is applied to the bag-shaped interior formed by the outer panel 1 and inner panel 2 of the door 3 attached to the vehicle body 4, which has been topcoated, using the spray nozzle 8 of an anti-rust wax applicator (not shown). Apply.

(Problems to be Solved by the Invention) As mentioned above, in the conventional undercoating process, one of the members to be joined is coated with a rust-preventing sealer in advance, the other member is joined on the sealer, and the bag is sealed by clinching and joining. After forming a shaped part and applying electrodeposition coating, an intermediate coating and a top coating process are performed, and after the coating is completed, an antirust wax is sprayed and applied using an anticorrosion wax coating device to perform antirust treatment. For this reason, it is necessary to apply a rust-preventing sealer and a rust-preventing wax separately from the electrodeposition coating, making the work complicated and time-consuming, contributing to a rise in product prices, and requiring robot or human labor. Because it is carried out by

Therefore, an object of the present invention is to provide an automobile body that can obtain a rust prevention effect even if the application of rust prevention sealer and rust prevention wax is abolished, simplify the work, and provide a highly reliable and inexpensive product. An object of the present invention is to provide a method for treating undercoating in painting, etc.

(Means for Solving the Problems) In order to achieve the above object, the method for undercoating in painting of automobile bodies, etc. of the present invention includes applying an electrodeposition coating process to one of the parts to be joined. I! A young coating is formed, and then assembled together with the other parts using an assembly process, followed by an electrocoat coating applied to the assembly using an electrodeposition coating process, and then a baking process is used to apply the above It is characterized by finishing by baking the electrodeposition coating.

(Function) An electrodeposition coating film is formed on one of the parts to be joined by an electrodeposition coating process, the assembly is performed with the other part without baking, and the assembly is subjected to the electrodeposition coating process. The electrodeposited coating is formed by a baking process, and the electrodeposited coating is baked during the baking process. An electrodeposited coating film is also formed on the unpainted portions of the coating, which has the effect of improving rust prevention.

(Example) Hereinafter, an example of the undercoat treatment method for painting automobile bodies, etc. of the present invention will be described with reference to FIG. In addition, the first
In the figure, parts corresponding to those in FIG. 2 are given the same reference numerals for convenience of explanation. Taking as an example the case where this painting treatment method is applied to an automobile door and explaining it according to FIG. Then, the inner panel 2 is dipped in the cationic electrodeposition paint in the electrodeposition tank 5 and energized for a predetermined period of time to perform the cationic electrodeposition coating process to form the electrodeposition coating film 7 on the surface of the inner panel 2. Form.

Next, the inner panel 2 and the outer panel 1 are clinched together by the end portion 1a by an assembly process, and further spot welded as necessary to form a door 3 which is an assembly assembly of the outer panel 1 and the inner panel 2, It is attached to the vehicle body 4 via a hinge (not shown) provided on the inner panel 2. Note that the electrodeposited coating 8.7 of the inner panel 2, which has been electrocoated, has no tackiness unlike a top coat, and does not interfere with assembly work.

Next, the car body 4 is transferred to an electrodeposition coating process, in which the car body 4 is immersed in a cationic electrodeposition paint solution in an electrodeposition tank 5 and energized for a predetermined period of time to apply a cationic electrodeposition coating. The paint is removed on an overflow tank (not shown) and washed in a water washing process.

The vehicle body 4 that has been coated with cationic electrodeposition is then subjected to baking and drying in a baking drying oven 6 at a predetermined ambient temperature for a predetermined period of time in a baking process.

The electrodeposited coating 7 in the baking process softens during curing,
The electrodeposition coating film 7 is fluidized and adhered to the joint portion of the outer panel 1 and the inner panel 2, which are clinched together by the edge of the inner panel 2 which has been previously coated with the electrodeposition coating.

Subsequently, in this undercoating step, the surface of the electrodeposition coating is polished to improve adhesion to the coating film applied on the electrodeposition coating, as in the conventional example, and the undercoating step is completed.

After this, the painting process is completed through intermediate coating and top coating processes.

In the above description, an embodiment in which the present invention is applied to a door i4 attached to an automobile body has been described, but the present invention can be appropriately applied to parts to be joined by clinching, such as a front hood and a trunk lid.

(Effects) As detailed above, according to the undercoat treatment method for painting automobile bodies, etc. of the present invention, an electrodeposition coating film is formed in advance on one of the parts to be joined, and then the other part is joined. Assembling is performed, electrodeposition coating is applied, and then the electrodeposition coating is baked to finish the process. During the curing process of the coating film, the coating softens and flows, allowing the electrodeposition coating to be applied to the joint parts. A film adheres to the surface, improving rust prevention, eliminating the need to apply a rust preventive cooler or wax, simplifying work, and providing highly reliable rust prevention treatment at low cost. Furthermore, by applying electrodeposition coating to some parts in advance, the area to be coated with other electrodeposition coatings is narrowed, and the coverage of the electrodeposition paint to other parts of the bag structure is improved, making it easier to apply electrodeposition coatings to other parts. The overall rust prevention ability is improved, and since the coating film applied to the clinching joint functions as an adhesive, it contributes to reducing the number of spot welds and has the effect of improving strength.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing an embodiment of the undercoat treatment method for painting automobile bodies, etc. of the present invention, and FIG. 2 is an explanatory view showing an example of the conventional undercoat treatment method. 1...Outer panel, 2...Inner panel, 3
...door, 4.car body, 5.electrodeposition bath, 6.baking drying oven, 7.electrodeposition coating film. Baking process Figure 1 Figure 2

Claims (3)

[Claims] (1) Form an electrodeposition coating film on one of the parts to be joined by an electrodeposition coating process, then assemble it together with the other part by an assembly assembly process, and then electrodeposit it on the assembly assembly. 1. An undercoat treatment method for painting automobile bodies, etc., which comprises forming an electrodeposition coating film through a painting process, and then finishing the electrodeposition coating film by baking it through a baking process. 2. The method of claim 1, wherein the assembly is performed by clinching the two parts together. (3) The method according to claim 1 or 2, wherein the parts to be assembled are an inner panel and an outer panel for an automobile.