JPS59173167A - Method for treating substrate of painting - Google Patents

Abstract

PURPOSE:To prevent rusting on an object to be treated stagnating near a zinc phosphate treating tank in the substrate treating stage of a phosphate film by specifying the amt. of the nitrite ion in the zinc phosphate treating liquid. CONSTITUTION:The amt. of the nitrite ion to be added in a zinc phosphate treating liquid is regulated to >=1.0X10<-3>M/l and <=2.5X10<-3>M/l in a method for substrate treating method of painting by which a phosphate film is formed on the surface of an object to be treated. Then the excess nitrite ion is discharged in the form of ammonia, nitrous acid, etc. to the outside of the system and the rusting on the material to be treated is prevented by the effect of neutralizing the atmosphere hear the zinc phosphate treating tank and the effect of forming a slightly non-conductive film on the surface of the object to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a phosphate film on the surface of a workpiece to treat the surface of the workpiece for painting, and in particular, to prevent rusting of the workpiece that stagnates during the basework treatment process and before and after the process. Regarding how to prevent this.

Traditionally, phosphate treatment has been used as a base treatment for painting vehicles, etc.
In particular, zinc phosphate treatment is widely used. For this phosphoric acid treatment process, a continuous VC treatment method using a conveyor or the like is usually applied. Shi rate.

Efforts are being made to improve safety. However, when carrying out continuous processing using a conveyor, etc., the treated material may stagnate near the zinc phosphate treatment layer due to circumstances before and after the zinc phosphate treatment, conveyor troubles, etc. be.

On the other hand, the composition of each component of the zinc phosphate treatment solution is determined from the viewpoint of chemical conversion, but usually phosphate ions, zinc ions,
It has strong acidic properties, mainly consisting of chlorate ions, nitrate ions, nitrite ions, etc., and the vicinity of the zinc phosphate treatment tank is a highly corrosive atmosphere, so as mentioned above, When the treated material stagnates near the zinc phosphate treatment tank, the stagnant treated material easily rusts in a short period of time, and the rusted treated material has to be discarded.

Conventionally, the following measures have been taken to prevent or alleviate such situations.

First, there was a method of normalizing the atmosphere by strengthening the air intake and exhaust in the vicinity of the zinc phosphate treatment tank and before and after the zinc phosphate treatment process. A second method is to perform a mist shower of an alkaline solution or a rust preventive solution on the workpieces stagnant in the vicinity of the zinc phosphate treatment tank to suppress rust formation.

However, the first method described above has the disadvantage that the object to be treated before the zinc phosphate treatment dries excessively, resulting in uneven treatment when the zinc phosphate treatment is performed. This method has the disadvantage that the alkaline liquid or rust preventive solution adhering to the object to be treated is carried into the zinc phosphate treatment solution, thereby contaminating the zinc phosphate treatment solution.

In order to overcome the above-mentioned drawbacks, in the conventional method described above, even if the intake and exhaust are strengthened or a mist shower of alkaline liquid or rust preventive solution is performed, the degree of influence must be relaxed. As a result, when the above conventional method is adopted, the time during which the condition of the workpiece can be maintained in good condition even if the workpiece is stagnant due to conveyor trouble, that is, the allowable stagnation time is lengthened. It is difficult to do so, and the allowable stagnation time is limited to approximately 10 minutes.

Therefore, when the above conventional method is used, since the permissible stagnation time is short, it is effective for troubleshooting conveyor problems that can be recovered in a short period of time, but on the other hand, the following disadvantages occur. Firstly, when the painting base treatment process is a series of continuous processes together with the preceding and succeeding machining/assembly processes and painting processes, the zinc phosphate treatment tank is The workpiece will be left in a nearby strongly acidic atmosphere for longer than the allowable stagnation time, which will inevitably lead to rusting and disposal of the workpiece, making it impossible to implement the series of continuous processes described above. It is. Second, if a conveyor problem occurs that cannot be resolved in a short time, the objects to be processed will stagnate in the above-mentioned strong acidic atmosphere for longer than the allowable stagnation time, and as a result will rust and have to be discarded. .

Therefore, the present inventors conducted intensive experimental studies to solve the above-mentioned problem, and found that the nitrite ion content in the conventionally used zinc phosphate treatment solution was 0.3x 10M/
l -0.8x 10M/1, while 1 containing nitrite ions was 1. OX 10M/l~2.5x 1
When nitrite ions are added in excess to 0'M/l, the excess nitrite ions are discharged from the system as nitrogen compounds such as ammonia and nitrous acid, and these nitrogen compounds are treated with zinc phosphate. It can be expected to have the effect of neutralizing the atmosphere around the tank and forming a light nonconducting film on the surface of the iron to be treated, and these effects will prevent the rusting of the to-be-treated materials stagnant near the zinc phosphate treatment tank. They discovered that it is possible to prevent this, and have come up with this invention.

In other words, the present invention prevents the zinc phosphate treatment object from rusting even if it stagnates near the zinc phosphate treatment tank, thereby increasing the time during which the object can stagnate and painting. Machining and machining before and after the surface treatment process
This makes it possible to perform a series of continuous processes together with the assembly process and painting process, thereby improving productivity and reducing production space, as well as reducing the number of discarded materials in the event of conveyor trouble, reducing production costs. In a painting base treatment method in which a workpiece is immersed in a zinc phosphate treatment solution to form a phosphorous salt film on the surface of the workpiece, the above-mentioned zinc phosphate treatment solution is used. The amount of nitrite ion added in the inside was 1. OX 10 M/β or more 2.5X lσ
The gist of the present invention is a method for treating a base for painting, which is characterized in that it is 3M/1 or less.

The method of the present invention will be explained in more detail below.

FIG. 1 shows a zinc phosphate treatment tank 1 storing a zinc phosphate treatment solution and its vicinity. As shown in the figure, a zinc phosphate treatment solution 2 is stored in this zinc phosphate treatment tank 1, and nitrite ions are added in excess to this zinc phosphate treatment solution 2.

As shown in the figure, the object to be treated 3 is immersed in the zinc phosphate treatment solution 2 in the zinc phosphate treatment tank 1, and a base treatment for painting is performed. Therefore, the zinc phosphate treatment solution 2 contains
As described above, since excess nitrite ions are contained, the excess nitrite ions are discharged into the atmosphere around the zinc phosphate treatment tank 1 as nitrogen compounds such as ammonia and nitric acid.

The discharged nitrogen compounds are then used in the zinc phosphate treatment tank 1.
The strongly acidic atmosphere near the front portion 4 and the rear portion 5 of is neutralized. At the same time, a light passive film is formed on the surface of the object to be treated 3 that remains near the front portion 4 or the rear portion 5 of the zinc sulfate treatment tank 1. As a result, the object to be treated 3 stagnant in the vicinity of the zinc phosphate treatment tank 1 is prevented from rusting.

In the above case, if nitrite ions are added to the zinc phosphate treatment solution 2 at a rate of 2.5x 10 M,/1 or more, harmful components will be discharged to the vicinity of the zinc phosphate treatment tank 1, resulting in safety concerns. Not sanitary. Also, the amount of nitrite ion added is 1. If it is less than OX 10 M/1, a neutralizing effect on the strong acid atmosphere near the zinc phosphate treatment tank 1 cannot be expected. Therefore, the amount of nitrite ions added to the curved lead phosphate treatment solution 2 is 1. Ox10M
/1 or more and 2.5×10M/1 or less. In addition, when adding nitrite ions in excess in this way, if chlorate ions are included as a component of the zinc phosphate treatment solution 2, chlorine is also discharged along with nitrogen compounds, and the rust prevention effect is significantly reduced. descend. Therefore, the zinc phosphate treatment solution components used in the method of the present invention do not contain chlorate ions. The other components may be the same as those in conventional zinc phosphate treatment solutions, and therefore usually include phosphate ions. Ox10M/1~5.5X
16M/1, nitric acid may be used.

Next, examples of the present invention will be described with reference to the table below. The zinc phosphate treatment solution used was Bt137B (trade name) manufactured by Nihon Bariki Rising Co., Ltd., and its basic components were phosphate ions at 1.2X i7 OM/1 and zinc ions at 3. Ox 10M/1, nitrate ion is 2.5x 10M/1, and the amount of nitrite ion added to this basic component is 0.3x1.
0M/f, 0.5X 10M/1.1. OX10
M/11, 2. Ox 10M/l, 3. Ox
It was changed in 5 steps to 10M/1. Further, the temperature of the zinc phosphate treatment solution was 50°C. Then, the time for which the object to be treated is stagnant in the atmosphere of the zinc phosphate treatment solution is set to 3 minutes.
The surface condition of the object to be treated was examined after changing the time to 30 minutes and 60 minutes. In addition, in the table, mark Q indicates that the surface condition of the object to be treated is good, mark Δ indicates that the surface of the object to be treated is slightly rusted,
An x mark indicates a case where rust is clearly generated on the surface of the object to be treated.

As shown in this table, the amount of nitrite ion is 1.0×
In the case of 10M/I1 or more, no rust was observed even if the object to be treated stagnated in the zinc phosphate treatment solution atmosphere for one hour.

Furthermore, as another example, the amount of nitrate ion added was changed to 1. sX 10 M/1, and using the apparatus shown in FIG. When the rusting conditions were actually tested when the objects were stagnated, no rust was observed in any of the objects 3 until 2 hours after the objects 3 had been stagnated.

As described above, according to the present invention, excessive nitrite ions are added to the zinc phosphate treatment solution for treating the base for painting, and the nitrogen compounds discharged from the zinc phosphate treatment solution cause damage to the vicinity of the zinc phosphate treatment tank. It neutralizes the atmosphere and at the same time forms a light passive film on the surface of the stagnant workpiece near the zinc phosphate treatment tank, preventing rusting of the stagnant workpiece for a long time. , the amount of time the material to be treated can stagnate near the zinc phosphate treatment tank is extremely long□
As a result, it becomes possible to perform the painting base treatment process as a series of continuous processes together with the machining/assembly process before and after it, and the painting process, making it possible to improve productivity and reduce production space. .

In addition, even if a conveyor problem occurs that does not recover for a long time, it is possible to prevent the objects to be processed from rusting for a long time, reducing the number of objects to be discarded and reducing production costs. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a zinc phosphate treatment tank used in carrying out the present invention. 1... Zinc phosphate treatment tank, 2... Zinc phosphate treatment liquid, 3... Treated object. Applicant Toyota Motor Corporation Agent Patent Attorney Yutaka 1) Hisashi Take (and 1 other person) Figure 1

Claims (1)

[Claims] In a painting base treatment method in which a treated object is immersed in a zinc phosphate treatment solution to form a phosphate film on the surface of the treated object,
The amount of nitrite ions added in the above zinc phosphate treatment solution was 1. O
A method for treating a base for painting, characterized in that the treatment is at least x10M/l and at most 2.5 x 10M/l.