JPH01272794A - Electrodeposition coating method - Google Patents

Abstract

PURPOSE:To enable coating wherein an uncoated part is unexistent and rustproofing quality is improved by providing an electrode plate into a water tank in a water-washing method in which a material coated in an electrodepositing stage is immersed in the water tank and energizing the coated material to the takeout thereof from the water tank from the introduction thereinto. CONSTITUTION:A material W to be coated is immersed in the coating bath of an electrodeposition tank 1 in an electrodepositing stage, and voltage is impressed between it and an electrode 2 provided in the tank 1 and the coating component is deposited on the surface of the material W to be coated and coated thereon. Then in a water-washing stage, the material W coated in the electrodepositing stage is immersed in a water tank 3 and the bath coating stuck on the deposited film is washed down. In this case, an electrode plate 13 is provided into the water tank 3 and energizing is performed to the takeout of the coated material W from the introduction thereof. By this method, the uncoated part resulting from an air pocket which has been generated on the coated material after the takeout from the tank in the electrodepositing process is coated by the above-mentioned energizing when introducing the material into the water tank 3. Further since the washing water in the water tank 3 is difficult-to be bubbled in comparison with coating, the uncoated part resulting from the bubbles is coated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrodeposition coating method, and its purpose is to perform coating with improved rust prevention quality without uncoated areas.

<Prior Art> A conventional electrodeposition coating method consists of an electrodeposition process and a water washing process, as shown in FIG.

In the electrodeposition process, the object W to be coated is immersed in the paint bath of the electrodeposition tank 1,
A voltage is applied between the electrode 2 installed in the electrodeposition tank 1 and the coating film components are deposited on the surface of the object to be coated.

In the water washing step, the object W coated in the electrodeposition step is washed with water using ultrafilter filtrate washing and industrial water washing, and the coating material attached to the deposited coating film is washed away.

The ultra filter filtrate washing includes water washing with the spray 7 and dip washing in which the object W to be coated is immersed in the water tank 3,
From these washing water, the coating liquid in the electrodeposition tank 1 is taken out through a pipe line 6, and is separated into solids and moisture through an ultra filter 4.
The solid content is returned to the electrodeposition tank 1 through a pipe 5, and the water is supplied to the water tank 3 through a pipe 7 and is used for spraying 8. The water in the water tank 3 and the water in the spray 8 are collected in a recovery tank 9 and returned to the electrodeposition tank 1 for circulation use. It should be noted that the water from the ultrafilter filtrate rinse returned to the electrodeposition bath 1 contains the washed-off paint, and has a composition similar to that of a low-concentration paint. In addition, spray 10 can also be used for washing with industrial water.
The water washed with water is collected in a collection tank 11.

<Problems to be Solved by the Invention> As the electrodeposition coating described above, cationic electrodeposition coating is generally used. In this cationic electrodeposition coating, since the minimum electrodeposition current density is low, when a sudden current flows, problems such as "bumps" and pinholes due to abnormal deposition of paint are likely to occur. For this reason, as shown in Fig. 5, the electrode 2 is not installed in the bath entrance part 12 of the electrodeposition bath 1, and the current density is controlled so that the coating film is deposited after the object W is completely submerged. ing. Therefore, the object W to be coated is not coated at all when it enters the tank. Due to this, an uncoated portion is generated in a part of the object W to be coated due to air pockets. In addition, when the object to be coated is placed in the tank, air is drawn in, bubbles are generated on the surface of the paint, and the bubbles adhere to the surface of the object to be coated, resulting in unpainted areas with bubble marks.

As a countermeasure to this problem, measures have been taken to prevent air pockets by using a water jet toward the object to be coated or by shaking the object, and to prevent bubbles by applying a liquid stream to the surface of the bath paint, but these measures have not been sufficiently effective. I can't.

Means for Solving the Problems> The present invention was proposed to solve the above-mentioned conventional problems, and the feature of the method is that the object to be coated is immersed in the paint in the electrodeposition bath. , an electrodeposition step in which a voltage is applied between the electrodes installed in the electrodeposition bath to deposit coating film components on the surface of the object to be coated, and the object coated in this electrodeposition step is placed in a water tank. In the electrodeposition coating process, which consists of a washing process in which the bath paint adhered to the deposited coating film is washed away, an electrode plate is installed in the water tank of the washing process, and the process from the time when the object to be coated is placed in the tank until it is taken out of the tank is completed. It is energized.

Effect> By the above method, as described above, the rinsing liquid in the water tank contains the paint washed off from the object to be coated, and has a composition similar to that of a low concentration paint. Therefore, even in this water tank, the uncoated parts that were not coated in the electrodeposition tank are electrocoated by applying electricity from the entry of the object to the tank to the exit of the object.

Embodiment Examples of the present invention will be described below based on the drawings. FIG. 1 shows the electrodeposition process and water washing process of the electrodeposition coating method of the present invention, and the basic structure thereof is the same as the conventional one shown in FIG.

In the water tank 3 of ultra filtrate washing in the above-mentioned water washing process, that is, in the deep water washing process in which the object W to be coated is completely immersed in water, the electrode plate 3 is installed in the water tank 3, Electricity is applied from the time the product W enters the tank to the time it exits the tank.

By doing this, as shown in Fig. 2, uncoated areas caused by air pockets that occur on the object to be coated after exiting the electrodeposition process in the electrodeposition tank 1 can be removed in the water tank 3 during the dip washing process. When it enters the tank, it is painted by the above-mentioned energization. Further, since the washing water in the water tank 3 is less likely to generate bubbles than the paint, unpainted areas caused by bubbles are also painted. Note that the paint will not adhere to the surface that has already been painted because of the coating resistance.

FIG. 3 shows experimental data based on the method of the present invention, and as is clear from this data, there is a
As a result of applying a voltage of 5 to 75 V and immersing the object W to be coated for 30 seconds, it was demonstrated that a coating with a film thickness of 5 to 12 μl was obtained on the exposed portion of the steel plate.

<Effects of the Invention> As described above, according to the present invention, an electrode plate is installed in the dip washing tank in the washing process after the electrodeposition process, and electricity is applied from the time when the object to be coated enters the tank to when it exits the tank. , it is possible to paint the unpainted parts that were not painted in the electrodeposition process in the water washing process, without impairing the appearance quality (it has the effect of reducing the unpainted parts and improving the rust prevention quality).

[Brief explanation of the drawing]

Figure 1 is a process diagram of the method of the present invention, Figure 2 is an explanatory diagram of painting in the method of the present invention, Figure 3 is experimental data by the method of the present invention, Figure 4 is a process diagram of the conventional method, and Figure 5 is a cation electrolysis diagram. FIG. 2 is a configuration diagram of an electrodeposition tank in coating.

Claims (1)

[Claims] The object to be coated is immersed in a paint bath of an electrodeposition tank, and a voltage is applied between the electrodes installed in the electrodeposition tank to deposit coating film components on the surface of the object. In the electrodeposition coating process, which consists of an electrodeposition process in which the coated object is coated in this electrodeposition process, and a water washing process in which the object to be coated coated in this electrodeposition process is immersed in a water tank and the bath paint adhering to the deposited coating film is washed away, the water washing process is performed. An electrodeposition coating method characterized by installing an electrode plate in a water tank and applying electricity from the time the object to be coated enters the tank to the time it exits the tank.