JP2002266080A - Phosphate chemical conversion treatment solution, chemical conversion treatment method and chemical conversion treated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a phosphate chemical conversion treatment solution which can improves the corrosion resistance of furniture made of steel, to provide a phosphate chemical conversion treatment method and to produce a phosphate chemical convertion treated steel sheet for furniture made of steel. SOLUTION: The phosphate chemical conversion treatment solution of 2.5 to 3.5 pH containing phosphoric ions, chloric ions, nitric ions and bromic ions, and further containing zirconium hexafluoride ions of 200 to 800 ppm is prepared. The steel sheet is subjected to chemical conversion treatment by using the phosphate chemical conversion treatment solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphatization solution, a phosphatization method, and a steel plate for furniture made of phosphatization steel, and in particular, it can improve the corrosion resistance of steel furniture. It relates to a phosphate chemical conversion treatment solution and the like.

[0002]

2. Description of the Related Art Conventionally, for example, phosphate chemical treatment has been widely used as a coating base treatment for a metal surface such as iron.

[0003] The above-mentioned phosphate chemical conversion treatment can be exemplified by iron phosphate chemical conversion treatment and zinc phosphate chemical conversion treatment depending on the type of phosphate.

[0004] The former iron phosphate chemical conversion treatment is particularly awarded because it can improve the corrosion resistance of the treated metal surface and the adhesion of the paint applied to the metal to the metal surface. ing.

[0005] In the iron phosphate chemical conversion treatment, since the treatment liquid does not contain heavy metal ions, waste liquid treatment is easy.
Since the pH of the processing solution is relatively high, there is an advantage that it is not necessary to use stainless steel or the like as a material of the processing equipment.

[0006] For this reason, iron phosphate chemical conversion treatment is used as a base treatment for materials such as small parts and agricultural equipment parts that do not require special corrosion resistance.

As an improved technique of the iron phosphate chemical conversion treatment,
For example, Japanese Patent Application Laid-Open No. Hei 9-22806 previously proposed by the present applicant.
There is a method described in Japanese Patent Publication No.

[0008] In this iron phosphate chemical conversion treatment method, the treatment solution contains phosphate ions, chlorate ions, nitrate ions and bromate ions as main components, and further contains a polystyrene sulfonate of pH 4.5 to 5.5. The iron phosphate chemical conversion treatment liquid of No. 5 is used.

According to the iron phosphate chemical conversion treatment method described above, it is possible to suppress a decrease in the pH of the chemical conversion treatment solution during the chemical conversion treatment by containing the polystyrene sulfonate salt. It can be carried out.

However, these iron phosphate chemical conversion treatments cannot always provide sufficient corrosion resistance in specific applications.

For this reason, for example, in the case of home appliances such as automobile bodies and washing machines, the latter zinc phosphate chemical conversion treatment which can obtain higher corrosion resistance can be obtained in place of the former iron phosphate chemical conversion treatment. Is used.

In particular, a zinc phosphate chemical conversion treatment is suitably used as a base treatment for cationic electrodeposition coating of a body and the like of a car which has recently become mainstream.

Regarding the type of paint, a solvent type paint in which a resin as a coating film forming material such as an acrylic resin or a polyester resin is dissolved in a solvent such as a hydrocarbon causes the solvent to evaporate into the atmosphere and contaminate the environment. Due to the danger, a water-based paint has recently been used in place of the solvent-based paint.

[0014] For example, steel furniture such as a steel desk and a steel locker is often coated with a water-based paint containing a resin such as an alkyd resin.

[0015] Since these steel furniture are usually used indoors, they are not necessarily more sophisticated than those used outdoors under the environment exposed to the atmosphere, rainwater, etc., such as the above-mentioned automobile body. Does not require corrosion resistance.

[0016]

However, steel furniture coated with a water-based paint containing a resin such as an alkyd resin has a lower corrosion resistance than that coated with a solvent-type paint, and therefore, steel furniture according to JIS S1031-1033 is used. Furniture standards may not be met.

The present invention has been made in view of the above-mentioned problems, and particularly, it is possible to improve the corrosion resistance of steel furniture when the steel furniture coated with a water-based paint is used as a base treatment. It is an object of the present invention to provide a treatment liquid, a phosphate chemical treatment method, and a steel plate for furniture made of phosphate chemical treated steel.

[0018]

The phosphatizing solution according to the present invention comprises phosphate ions (PO ₄ ⁻ ), chlorate ions (ClO ₃ ⁻ ), nitrate ions (NO ₃ ⁻ ) and bromate ions. A phosphoric acid conversion treatment solution containing (BrO ₃ ⁻ ) having a pH of 2.5 to 3.5 and further containing 200 to 800 ppm of zirconium hexafluoride ion ((ZrF ₆ ) ²⁻ ).
It is characterized by containing.

As a result, zirconium is contained in the film, and for example, the corrosion resistance of the steel sheet subjected to the chemical conversion treatment can be improved.

Further, the phosphate conversion treatment method according to the present invention is characterized in that a steel sheet is subjected to a chemical conversion treatment using the above-mentioned phosphate conversion treatment solution. The steel furniture steel sheet is characterized by being subjected to a chemical conversion treatment by the above-mentioned phosphate chemical conversion treatment method.

Thus, a steel sheet having excellent corrosion resistance, particularly a steel furniture steel sheet can be obtained.

In the present invention, when a water-based paint is used as the paint to be applied after the chemical conversion treatment, a particularly large effect of improving corrosion resistance can be obtained.

[0023]

Embodiments of the present invention will be described below.

The phosphatizing solution of the present invention is a phosphating solution having a pH of 2.5 to 3.5 containing phosphate ions, chlorate ions, nitrate ions and bromate ions. 200 to 8 zirconium hexafluoride ions
Contains 00 ppm.

Here, the supply source of phosphate ions is as follows:
Phosphoric acid, monobasic sodium phosphate and the like. Also,
Examples of the supply source of chlorate ions include chloric acid, potassium chlorate, sodium chlorate, and ammonium chlorate. In addition, examples of the source of nitrate ions include nitric acid, potassium nitrate, sodium nitrate, and ammonium nitrate. Examples of the supply source of bromate ions include bromate, potassium bromate, sodium bromate, and ammonium bromate.

Of the above-mentioned ions, phosphate ion forms an insoluble metal salt with a metal and plays a role of forming a film on the surface of the object to be treated. On the other hand, chlorate ion, nitrate ion and bromate ion all play the role of the above-mentioned film formation accelerator.

The phosphatization solution of the present invention contains 4,000 to 10,000 ppm of phosphate ions. If the phosphate ion content is less than 4,000 ppm, the chemical conversion film is likely to be formed in an uneven state, while
Even if it exceeds pm, no improvement in chemical conversion can be expected, and only chemical consumption will increase.

The phosphatizing solution preferably contains chlorate ions in an amount of 100 to 500 ppm. When the chlorate ion content is less than 100 ppm, rust is liable to be generated.

Further, it is preferable that the phosphatization solution contains 1,000 to 5,000 ppm of nitrate ions.
If the nitrate ion content is less than 1,000 ppm, the film-forming reaction is delayed. On the other hand, if the content exceeds 5,000 ppm, improvement in the chemical conversion property cannot be expected.

It is preferable that the phosphatization solution contains 100 to 800 ppm of bromate ions. If the nitrate ion content is less than 100 ppm, it is difficult to form a chemical conversion film, while if it exceeds 800 ppm, improvement in chemical conversion properties cannot be expected.

The phosphate chemical conversion treatment solution of the present invention further comprises a zirconium hexafluoride ion of 200 to 80 as described above.
Contains 0 ppm.

Here, the source of zirconium hexafluoride ions is zirconium hexafluoride (H ₂ Zr
F _6), 6 zirconium fluoride ammonium ((N
H ₄ ) ₂ ZrF ₆ ).

When the content of zirconium hexafluoride in the phosphatization solution is less than 200 ppm, a sufficient effect of improving corrosion resistance cannot be obtained.
However, further improvement in corrosion resistance cannot be expected even if the temperature exceeds the limit, and the problem of cost increase due to an increase in drug consumption becomes apparent.

As described above, the pH of the phosphate conversion solution of the present invention is adjusted to a range of 2.5 to 3.5.

When the pH is less than 2.5, the etching becomes excessive, while when it exceeds 3.5, there is a fear of precipitation.

The above-described phosphate chemical conversion treatment liquid of the present invention can improve the corrosion resistance of the material subjected to the chemical conversion treatment.

Further, the phosphate chemical treatment method of the present invention comprises:
The steel sheet is subjected to a chemical conversion treatment using the above-mentioned phosphate chemical conversion treatment solution.

In general, when a steel sheet is coated, it is processed in the order of a degreasing step, a rinsing step, a chemical conversion step, a rinsing step, a pure water rinsing step, a drying step and a coating step. The chemical conversion treatment of the present invention is performed in the chemical conversion treatment step. In this case, the processing conditions of other steps than the chemical conversion step such as the degreasing step are not particularly limited.

The chemical conversion treatment may be performed by any of a spraying method and a dipping (dip) treatment, and the spraying treatment and the dipping treatment may be used in combination.

The phosphate conversion treatment of the present invention is preferably performed at a temperature of 30 to 45 ° C.

The processing time is preferably at least 10 s, more preferably from 30 to 180 s. If the treatment time is less than 10 s, it is not possible to form a film having a sufficient amount of film, which may cause poor paint adhesion and poor corrosion resistance after coating.

The phosphate conversion treatment method of the present invention described above can improve the corrosion resistance of the treated steel sheet.

The steel sheet for furniture made of phosphatized steel of the present invention has been subjected to a chemical conversion treatment by the above-mentioned phosphatization method.

Here, steel furniture refers to steel furniture used indoors, such as office desks, chairs, lockers, and the like.

As a material for steel furniture steel plates, for example,
A commonly used cold-rolled steel sheet is used. However, it is not limited to this.

The steel sheet subjected to the above-mentioned chemical conversion treatment is finished, for example, by one coat coating.

In this case, the paint used is a solvent type paint,
Although not particularly limited, such as an electrodeposition paint, a water-based paint, and a powder paint, when a water-based paint is used, a remarkable effect of improving corrosion resistance can be exerted. Minimal hygiene and environmental problems.

As the aqueous paint, a polyester resin paint is preferably used. The conditions for baking the water-based paint are, for example, 150 ° C. and 20 minutes.

The steel plate for furniture made of phosphate conversion-treated steel of the present invention described above can obtain high corrosion resistance.

[0050]

The present invention will be further described with reference to Examples and Comparative Examples. The present invention is not limited to the embodiments described below. (Object to be treated) The steel sheet as the object to be treated is a cold rolled steel sheet (JI
A 7 cm × 15 cm test piece of S SPCC SD3141) was used. (Surface treatment) Preliminary treatment such as degreasing for cleaning the steel sheet surface and the chemical conversion treatment of the present invention were performed using the above steel sheet according to the following procedure.

First, the degreasing treatment was performed using an alkaline degreasing agent manufactured by Nippon Paint Co., Ltd. (trade name: Surf Cleaner CS31)
0 ") was sprayed at a temperature of 50 ° C. for 2 minutes.

Next, in the water washing treatment, tap water is washed at room temperature for 30 seconds.
Performed by spraying.

Thereafter, phosphoric acid conversion treatment was performed under the following conditions.

The phosphatization solution had a phosphate ion content of 8,000 ppm and a chlorate ion content of 300 pp.
m, a liquid having a nitrate ion content of 3,000 ppm and a bromate ion content of 500 ppm was prepared, and zirconium hexafluoride was added to the liquid so that the zirconium hexafluoride ion content became a predetermined content shown in Table 1. An acid was added to prepare a phosphate conversion treatment solution having a zirconium hexafluoride ion content of seven levels including a blank (a case where zirconium hexafluoride was not added). The pH of each of the prepared phosphate chemical conversion treatment solutions is about 3.0.

[0055]

[Table 1] Each phosphatization solution was treated at a temperature of 40 ° C. for 2 m
in, sprayed on steel plate.

Further, as a water washing treatment, tap water of room temperature was added for 3 hours.
After spraying for 0 s, ion-exchanged water at normal temperature was sprayed for 15 s as a pure water washing treatment, and then dried at a temperature of 120 ° C. for 10 min as a drying treatment. (Painting) The steel sheet after the chemical conversion treatment was subjected to a coating treatment. As the paint, a water-based paint (trade name “Aude Recycle S-600” polyester resin paint) manufactured by Nippon Paint Co., Ltd. was applied to a thickness of 25 to 35 μm by a spray method. (Evaluation) The coated steel sheet obtained by the treatment under the above treatment conditions was subjected to a salt water immersion test to evaluate the corrosion resistance.

The salt water immersion test was conducted according to JIS S10
After applying a cut to the coating surface of the coated steel plate and immersing the steel plate in a 5% by mass NaCl aqueous solution maintained at 20 ° C. for 48 h, After the tape was adhered to the cut, the tape was peeled off, and the maximum peeling width (unit: mm on one side) of the tape peeled off from the steel sheet due to the adhesion of the coating film or the like to the tape.

Table 1 also shows the evaluation results.

According to Table 1, when the maximum peel width is allowed up to about 3 mm (accepted), favorable results were obtained when the zirconium hexafluoride ion content was 200 ppm or more. However, when the content of zirconium hexafluoride ion is excessive, the effect of further improving the corrosion resistance is not obtained. Therefore, considering the cost increase due to excessive use, the preferable upper limit of the content of zirconium hexafluoride ion is 80.
It is 0 ppm.

[0060]

According to the phosphate chemical conversion treatment solution of the present invention, a phosphate chemical conversion treatment solution having a pH of 2.5 to 3.5 containing phosphate ions, chlorate ions, nitrate ions and bromate ions can be used. In addition, since zirconium hexafluoride ions are further contained in an amount of 200 to 800 ppm, the corrosion resistance of the chemical conversion-treated object can be improved. Also,
ADVANTAGE OF THE INVENTION According to the phosphate chemical treatment method and the steel plate for furniture made of phosphate chemical treated steel according to the present invention, it is possible to obtain a steel plate excellent in corrosion resistance, particularly a steel furniture steel plate.

Continued on the front page (72) Inventor Satoshi Miyamoto 4-1-1-15 Minamishinagawa, Shinagawa-ku, Tokyo Japan Paint Co., Ltd. (72) Nobuo Nakatani 19-17 Ikedanakacho, Neyagawa-shi, Osaka Nippon Paint Co., Ltd. F term (reference) 4K026 AA02 AA22 BA03 BB08 CA13 CA18 CA26 CA28 CA32 CA34 DA02 DA06 DA11 EA08 EB08

Claims (3)

[Claims] 1. A phosphate chemical conversion treatment solution containing a phosphate ion, a chlorate ion, a nitrate ion, and a bromate ion and having a pH of 2.5 to 3.5, and further comprising a zirconium hexafluoride ion of 200 to 800.
A phosphoric acid conversion treatment solution characterized by containing ppm. 2. A phosphate chemical conversion treatment method, wherein a chemical conversion treatment of a steel sheet is performed using the phosphate chemical conversion treatment solution according to claim 1. 3. A steel sheet for furniture made of phosphatized steel, which is formed by a chemical conversion treatment according to the phosphatization method according to claim 2.