JP2002263564A - Coating method and coated steel plate for furniture made of steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method which can improve the corrosion resistance of a piece of furniture made of steel and a coated steel plate for the piece of furniture. SOLUTION: A steel plate is treated chemically with a phosphate solution of pH 3-4.5 containing phosphate ions and nitrate ions as main components and 100-300 ppm of zinc ions (chemical treatment process). Next, a water base coating is applied on the film of the steel plate which is formed by the chemical treatment (coating process).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and a steel coated steel sheet, and more particularly to a coating method for applying a water-based paint after a phosphating treatment and a steel coated steel sheet.

[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 carried out at pH 3 containing phosphate ions, carbonate ions and nitrate ions as main components.
An iron phosphate chemical conversion treatment liquid of ~ 6.5 is generally used. In addition to these ions, chlorate ions,
Some of them are used by adding bromate ion, hydroxyamine sulfate or the like.

[0005] The iron phosphate chemical conversion treatment can improve the corrosion resistance of the treated metal surface, and can improve the adhesion of the paint applied to the metal to the metal surface.
Especially awarded.

[0006] 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.

[0007] 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.

[0008] 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.

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

[0010] According to the iron phosphate chemical conversion treatment method described above, the decrease in pH of the chemical conversion treatment solution during the chemical conversion treatment can be suppressed by containing the polystyrene sulfonate, and as a result, a stable chemical conversion treatment can be performed. It can be carried out.

[0011] However, these iron phosphate chemical conversion treatments cannot always provide sufficient corrosion resistance in specific applications.

Therefore, for example, in the case of home electric appliances such as an automobile body and a washing machine, 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, zinc phosphate chemical conversion treatment is suitably used as a base treatment for cationic electrodeposition coating of the body of automobiles and the like, which has recently become mainstream.

In this case, the zinc phosphate chemical conversion treatment liquid mainly contains zinc as a main component metal and a metal such as nickel or manganese as an essential component.

Regarding the type of paint, a solvent-type paint obtained by dissolving a resin as a coating film forming material such as an acrylic resin or a polyester resin in a solvent such as a hydrocarbon is not always preferable in terms of work hygiene. There is a risk of volatilizing them and polluting the environment. Because of this,
There is a tendency to use water-based paints instead of solvent-based paints.

[0016] For example, a method of applying a water-based paint containing a resin such as an alkyd resin to steel furniture such as a steel desk and a steel locker is often used.

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.

[0018]

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.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has no problems in terms of work hygiene and environment, and a coating method and a steel furniture capable of improving the corrosion resistance of steel furniture. It is intended to provide a coated steel sheet for use.

[0020]

According to the present invention, there is provided a coating treatment method comprising a phosphate ion and a nitrate ion as main components, and further comprising 100 to 300 ppm of zinc ion and having a pH of 3.0 to 4.5. It is characterized by having a chemical conversion treatment step of subjecting a substance to be coated to a chemical conversion treatment with an acid conversion treatment liquid, and a coating step of applying a water-based paint on the film of the substance to be coated formed by the chemical conversion treatment.

The term "mainly phosphate ions and nitrate ions" as used herein means that other components contained in the conventional phosphatization solution, such as carbonate ion, chlorate ion, bromate ion, It means that it does not substantially contain hydroxyamine sulfate or the like.

Thus, a coating material having high corrosion resistance can be obtained by a coating method which is favorable in terms of work hygiene and environment.

Further, the coated steel sheet for furniture according to the present invention is characterized by being processed by the above-mentioned coating method.

As a result, a steel furniture steel sheet having excellent corrosion resistance can be obtained.

[0025]

Embodiments of the present invention will be described below.

The coating treatment method of the present invention comprises a phosphate ion and a nitrate ion as main components, and further comprises a zinc ion in an amount of 1%.
A chemical conversion treatment step of subjecting the article to be coated with a phosphate chemical conversion treatment solution having a pH of 3.0 to 4.5 and containing a water-based paint on the film of the article formed by the chemical conversion treatment. And a coating step of applying.

Here, when a coating film is formed on an object to be coated such as a steel plate, it is generally processed in the order of a degreasing step, a rinsing step, a chemical conversion step, a rinsing step, a pure rinsing step, a drying step, and a coating step. You. The chemical conversion treatment and the coating step of the present invention are also performed in this step in this series of steps. in this case,
The processing conditions in other steps such as the degreasing step are not particularly limited.

In the chemical conversion treatment step of the present invention, as described above, a phosphate ion and a nitrate ion as main components, and a pH containing 100 to 300 ppm of zinc ions.
A phosphoric acid conversion treatment solution (hereinafter, simply referred to as a chemical conversion treatment solution) of 3.0 to 4.5 is used.

Here, the supply source of phosphate ions is as follows:
Phosphoric acid, monobasic sodium phosphate and the like. Also,
Sources of nitrate ions include nitric acid, potassium nitrate, sodium nitrate, ammonium nitrate and the like.

Among 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 coated. On the other hand, nitrate ions play a role of a film formation accelerator.

The chemical conversion treatment solution of the present invention contains 9,000 to 13,000 ppm of phosphate ions. If the phosphate ion content is less than 9,000 ppm, the chemical conversion film is likely to be formed in an uneven state, whereas if it exceeds 13,000 ppm, no improvement in the chemical conversion property can be expected, and only the chemical consumption increases. It is.

Further, the chemical conversion treatment solution contains nitrate ions of 200
It is preferable to contain 含 む 800 ppm. When the nitrate ion content is less than 200 ppm, the film-forming reaction is delayed. On the other hand, even when the content exceeds 800 ppm, improvement in chemical conversion properties cannot be expected.

The chemical conversion treatment solution of the present invention further contains 100 to 300 ppm of zinc ions.

Here, as a source of zinc ions, zinc white, zinc nitrate, zinc carbonate and the like can be mentioned.

The content of zinc ions in the chemical conversion treatment liquid is 100
When the amount is less than ppm, a sufficient effect of improving corrosion resistance cannot be obtained. On the other hand, when the amount exceeds 300 ppm, further improvement in corrosion resistance cannot be expected, and the problem of cost increase accompanying an increase in drug consumption becomes apparent.

As described above, the pH of the chemical conversion treatment solution of the present invention is adjusted to a range of 3.0 to 4.5.

When the pH is less than 3.0, the etching becomes excessive, while when it exceeds 4.5, there is a problem that a precipitate such as a zinc compound is deposited.

The chemical conversion treatment of the present invention may use either a spray treatment or a dipping (dipping) treatment method, or a combination of the spray treatment and the dipping treatment.

The chemical conversion treatment is preferably performed at a temperature of 45 to 55 ° 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 film thickness, which causes poor paint adhesion after coating and does not improve corrosion resistance.

In the coating treatment step of the present invention, a water-based paint is applied on the film formed by the chemical conversion treatment using the above-mentioned chemical conversion treatment solution.

Here, the water-based paint is not particularly limited. For example, an alkyd resin, an acrylic resin, a polyester resin, a polyurethane resin, or the like can be appropriately mixed and used as a resin for forming a coating film. Also, as appropriate
A crosslinking agent, a coloring pigment and, if necessary, an extender are added.

In the coating treatment of the present invention, any coating method such as spray coating or roll coating may be used, or these coating methods may be used in combination.

The thickness of the coating film formed on the chemical conversion film is preferably 25 to 35 μm.

In the coating treatment, it is sufficient to form one layer of the above-mentioned coating film with one coat, but it is not limited to this.

According to the above-described coating treatment method of the present invention, a treatment method that is favorable in terms of work hygiene and
An article to be coated having high corrosion resistance can be obtained.

The coated steel sheet for furniture made of steel of the present invention has been treated by the above-mentioned coating treatment method.

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

[0049] Steel furniture steel sheets are, for example,
A commonly used cold-rolled steel sheet is used. However, it is not limited to this.

The phosphatized steel sheet for furniture of the present invention can provide high corrosion resistance.

[0051]

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. (Coating object) The steel sheet as the coating object is a cold rolled steel sheet (JIS
A 7 cm × 15 cm test piece of 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, the 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 11,000 ppm and a nitrate ion content of 200 p.
pm solution, and the zinc ion content in this solution is as shown in Table 1.
Add zinc nitrate so as to have the prescribed content shown in
Phosphate conversion treatment solutions having a zinc ion content of 6 levels including blanks were prepared. The pH of each of the prepared phosphate chemical conversion treatment solutions is about 4.0.

[0056]

[Table 1] Each phosphate conversion solution was treated at 50 ° C for 2m
in, sprayed on steel plate.

Further, as a water washing treatment, tap water of normal 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”, a main component polyester resin) 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 3% by mass NaCl aqueous solution kept at 20 ° C. for 100 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, it is found that the zinc ion content of 100 to 100 satisfies the standard value of the maximum peel width of 3 mm or less.
It is the case of 300 ppmm. These have significantly improved corrosion resistance as compared to the case where no zinc ion is added. Note that even if the zinc ion content exceeds 300 ppm, further improvement in corrosion resistance cannot be expected.

[0061]

According to the coating treatment method of the present invention, the pH of the coating solution containing phosphate ions and nitrate ions as main components and zinc ions of 100 to 300 ppm is further improved.
A chemical conversion treatment step of subjecting the article to be coated with a chemical conversion treatment solution of 0 to 4.5, and a coating step of applying a water-based paint on a film of the article formed by the chemical conversion treatment;
With a good treatment method for work hygiene and environment,
An article to be coated having high corrosion resistance can be obtained. Also,
According to the coated steel sheet for furniture of the steel according to the present invention, since the steel sheet is processed by the above-described coating treatment method, a steel sheet for steel furniture having excellent corrosion resistance can be obtained.

 ────────────────────────────────────────────────── ─── Continuing 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 Ikedananakacho, Neyagawa-shi, Osaka F-term (reference) in INT Co., Ltd. AA02 AB02 BA17 BA21 BB03 BC02 CA16 CA53

Claims (2)

[Claims] 1. A chemical conversion treatment in which a substance to be coated is subjected to a chemical conversion treatment with a phosphate chemical conversion treatment solution containing phosphate ions and nitrate ions as main components and further containing 100 to 300 ppm of zinc ions and having a pH of 3 to 4.5. A coating method, comprising: a step of applying a water-based paint on a film of the object formed by a chemical conversion treatment. 2. A coated steel sheet for furniture made of steel, which is processed by the coating method according to claim 1.