JPS63296870A - Method for forming high performance chromium-containing resin film to metal surface-treated steel plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention applies a thin film of a chromium component-containing resin to the surface of a metal surface-treated steel sheet by electrostatic atomization.
Regarding the method of forming a film with excellent uniformity and performance characteristics, the metal surface-treated steel sheets herein include zinc and zinc alloy plated steel sheets, lead and lead alloy plated steel sheets, aluminum and aluminum alloy plated steel sheets, etc. Specifically, galvanized and zinc alloy plated steel sheets include (a) galvanized steel sheets that contain elements that are unavoidably mixed in as impurities by electroplating or vacuum evaporation plating; and (b) galvanized steel sheets with Ae of 0.1 to 0.1. 0.3%, PI as other substances
), Ccl.

Hot-dip galvanized steel sheet containing one or more elements such as Fe, Sb, etc., and further containing unavoidable impurity elements (c) Fe
Fe-Z containing 5 to 90% and unavoidable impurity elements
n alloy plated steel sheet (d) Zn-Ni alloy plated steel sheet containing Wl of 5 to zo and inevitable impurity elements (e) Containing 3 to 60% of u, or Si, My
.

Mitsushi metal or Zn-A1 containing unavoidable impurities
Examples of lead-plated and lead alloy-plated steel sheets include (a) lead-plated steel sheets that contain unavoidable impurities during the N manufacturing process; and (b) lead-plated steel sheets that contain 30% or less of Sn. , in some cases sb
, : , , z blue or ゛P containing unavoidable impurity elements
Examples include b7sη alloy plated steel sheets, and furthermore,
As aluminum and aluminum alloy plated steel sheets, (a)
Aluminum-plated steel sheet that inevitably contains a small amount of Fe and other elements during plating (b) SL, Mg- or two or more types,
Examples include aluminum alloy plated steel sheets with sl of 12 or less, or Mg of 5 or less.

(,:,::1: Methods for forming a thin chromate film on the surface of a Q plate and improving its performance have been conventionally used: electrolytic chromate treatment technology, reactive chromate film generation technology, coating type chromate treatment. The technology is known.

The electrolytic chromate treatment technology for metal surface-treated steel sheets has already been developed in Japanese Patent Publication No. 47-44417 for galvanized steel sheets.
(cro3-H2so, method of cathodic electrolytic treatment using treatment solution), JP-A-60-110896 (CrO3-5
i02 Method of cathodic electrolytic treatment with treatment solution), zinc,
For aluminum, tin and their alloy plated steel plates:
Japanese Patent Application Publication No. 1973. No. 14+5 (Cr03-Various metal ions-Cathode electrolytic treatment method with fluorine or chlorine treatment solution)
All of these methods involve forming a chromate skin on the surface of a metal surface-treated steel sheet by cathodic electrolytic treatment. In general, these electrolytically treated coatings have excellent uniform elasticity and good coating performance, but c
It is said that the corrosion resistance is insufficient because it is formed of a film containing r,3+ as its main component.

Therefore, these cathode electrolytic coatings have a coating amount, i, □
AMtiFri□<t, bayoyo□.

Compensating for sex. However, the chromate film becomes colored when the amount of film formed increases, and the appearance of the treated material is impaired.
Furthermore, there is a drawback that the coating performance deteriorates, so the appearance,
It was difficult to form a film with excellent corrosion resistance and coating performance.

In addition, in the cathodic electrolysis method for galvanized steel sheets, there is a problem that when galvanized steel sheets are treated continuously, Zn2+ ions accumulate in the treatment solution, and a homogeneous romate film is not formed, resulting in a significant decrease in corrosion resistance. Also, from many patent publications so far, coating type, for example, CrO3-5i02
Chromate treatment methods using an aqueous treatment solution, a CrO3-water-soluble resin aqueous solution, etc. are known.

In addition, the reactive type has a process that has been known for a long time.
CrO3-5o42-based bath, Cr03-8○4”-PO
4”-F-based baths, and furthermore, T 1r Zr +
There is a chromate treatment method in which the surface of a galvanized steel plate or the like is reacted (etched) in a treatment bath to which metal ions such as Zn are added.

Although these methods have provided romate coatings with good corrosion resistance and coating performance, they also have the following drawbacks. In the coating type chromate treatment method, the chromate film mainly composed of Cr6+ is removed during the degreasing process.
Since a large amount of is eluted, there is a problem of deterioration of corrosion resistance.

On the other hand, in the reactive chromate treatment method, since a chromate film containing Cr3+ as a main component is formed, cracks occur in the film when processing begins, resulting in deterioration of corrosion resistance after processing.

Furthermore, these treatment methods have various problems in continuously ensuring the appearance performance after treatment, especially the uniformly stable treated appearance or the uniformity of the chromate film thickness over a long period of time industrially. Yes.

In other words, in these treatment methods, the amount or thickness of the chromate coating is controlled by using a roll wiping means, by a wiping means using high-pressure gas, or by applying a predetermined amount of treatment liquid using a roll coater or the like. method is implemented.

However, these chromate film control methods do not necessarily provide a good treated appearance or uniform coverage of the chromate film due to the following points, so it is desirable to develop a new method of depositing or controlling a chromate treatment bath. It is rare.

By the way, the method for controlling the amount of chromate film in the wiping means using high-pressure gas is to apply a large amount of treatment liquid to the material to be treated, and then wipe off the excess treatment liquid with high-pressure gas. It is operated by appropriately adjusting the flow rate and the distance between the material to be treated and the gas outlet nozzle.

Therefore, depending on the operation conditions for wiping off the excess solution, the liquid becomes a splash and adheres to the surface of the steel plate after film control, which may impair the appearance of the steel plate surface and significantly deteriorate its commercial value. This tendency is due to the amount of thin chromate coating (
On the other hand, in the case of a thick chromate coating, it is necessary to reduce the fluid wiping force (pressure, flow rate, etc.), which causes variations in the coating amount, resulting in poor performance. Characteristics (corrosion resistance, coating performance) also tend to vary.

In addition, in the control method using roll wiping means, fine scratches may occur (transfer) on the roll surface (flaws on the roll surface or defects on the plated steel plate surface such as roll scratches due to the passing edge), or the passing speed may vary. Due to mismatching of the rotational speed of the rolls, the amount of chromate film is formed unevenly in some parts, and the abnormally thick parts of the film exhibit a spotty or linear appearance of chromate film, which reduces the product value. This is not preferable because it causes damage to the chromate film and causes variations or deterioration in corrosion resistance and coating performance due to the coverage of the chromate film. Countermeasures have been taken to address these problems, such as frequently replacing the rolls and strictly adjusting the rotational speed and rolling reduction of the rolls, but none of these measures have been sufficient.

However, in this method, it was particularly difficult to adjust the coating amount by adjusting the rolling reduction amount of the roll.

As mentioned above, the conventional chromate treatment technology has various problems, and it is difficult to apply the chromate treatment solution to the material to be treated using a simple technique and improve the appearance characteristics of the steel sheet and the uniform coverage of the film. , development of a chromate treatment method with excellent corrosion resistance and coating performance is desired.

The present invention was made in response to these needs, and has hardly been applied to conventional chromate treatment techniques.

Applying and adhering the chromate treatment liquid to the treated material using the electrostatic atomization method. In other words, the chromate treatment bath is charged with a high voltage, and the negatively charged atomized particles are applied and adhered to the positively charged material. The present invention also provides a method for forming a high-performance romate coating that imparts excellent appearance, uniform coverage, and various performance characteristics by directly heat-treating the coated metal surface-treated steel sheet.

The electrostatic atomization method of applying the coating material to the surface of the treated material is
It is known as a method of applying oil or paint to a steel plate or a metal surface-treated steel plate.

In the case of oils and fats such as rust preventive oil and rolling oil, performance as a lubricating material can be obtained if particles atomized under high voltage are uniformly adhered to the surface of a steel plate or the like. That is, the fats and oils deposited in particulate form are easily smoothed by subsequent pressing means such as rolls and leveling, and have the property of easily covering the gaps between particles.

Therefore, the electrostatic atomization coating method is in practical use as a relatively superior method for coating oils and fats.

Furthermore, since the paint used in the electrostatic atomization method generally has a high particle size, a heat treatment is performed for a long time (usually 5 to 30 minutes) with the aim of smoothing and leveling the applied paint. Therefore, even if a highly viscous paint is deposited in a layered manner in the form of particles, there is an advantage that the gaps between the particles are covered by long-term heat treatment, resulting in a uniform coating film. Therefore, it is used in many practical applications as a coating method.

=9- However, when the electrostatic atomization method described above is applied to a method of forming a chromate film, the following problems arise. That is, (]) Even if an aqueous solution containing chromium is uniformly applied to a metal surface-treated steel sheet by electrostatic atomization, it is deposited in a layered state of particles, resulting in poor uniform coverage of the chromate film. That is, there is a problem in that many pinholes are formed in the chromate film, making it difficult to obtain excellent corrosion resistance, coating performance, etc.

(2) When the coating adhered to the layered state of the applied atomized particles is leveled and smoothed by a roll squeezing means, there will be no difference from oils and fats, roll squeezing unevenness, or roll scratches. Uneven spots and the like occur due to transfer, making it impossible to obtain good appearance and excellent uniform coverage.

Furthermore, in the chromate treatment, a chromate bath is applied and a heat treatment is performed for a short time (usually 1 to 30 seconds) after deposition, but it is difficult to coat the gaps in the particulate laminate.

(3) Depending on the composition or properties of the processing liquid, l
O- Industrially, it has been difficult to coat fine particles that are stably and uniformly atomized.

These problems made it difficult to put it into practical use.

(Problems to be Solved by the Invention) The present invention provides an industrially stable chromate treatment method that makes it possible to achieve both appearance performance, uniform coverage, corrosion resistance, and coating performance, which are the drawbacks of conventional chromate treatment methods. , and is intended to be formed on the surface of a metal surface-treated steel sheet. In particular, the chromate treatment method is aimed at, since it is possible to form a film with excellent appearance and uniform coverage regardless of the amount (thickness) of the chromate film.

(Means for solving the problem) Processing of metal narrow-surface treated steel sheets such as zinc or zinc alloy plated steel sheets, aluminum or aluminum alloy plated steel sheets, or lead or lead alloy plated steel sheets to improve appearance, uniformity of coating, and corrosion resistance. As a result of various studies on methods for forming a chromate film with excellent coating performance, the composition and properties of the chromate bath were adapted to the uniform formation of electrostatically atomized particles, and the chromate bath was applied statically to the surface of a metal surface-treated steel sheet. We have developed a method that enables the formation of a high-performance chromate film with excellent appearance, uniform coverage, and performance characteristics by coating by electro-atomization and heat treatment.

Therefore, the gist of the present invention is to apply a resin solution containing a chromium component to a metal surface-treated steel sheet using an electrostatic atomization method, and heat-treat it to form a resin coating containing a chromium component. The present invention provides a method for forming a high-performance chromium-containing resin coating on a metal surface-treated steel sheet. That is, a high voltage (usually -80KV to -
The solution was rotated at high speed (20,0 KV).
000~4' 5,000 rotations/1 minute) The atomized particles of the above-mentioned solution, which are negatively charged, are collided with the body and the atomized particles of the atomized solution are connected to the discharge port of the atomized solution and the metal surface-treated steel plate of the material to be treated, which is grounded. Through the electrostatic field formed between the metal and the metal, it is supplied and attached to the positively charged metal surface-treated steel plate. Therefore, by supplying a predetermined amount of Cr-containing resin solution corresponding to the desired coating amount to a metal surface-treated steel sheet and spraying negatively charged atomized particles from the discharge port, the atomized particles will repel each other. In particular, the supply amount of a Cr-containing resin solution that does not aggregate, flies out in a uniformly distributed state toward the positively charged ground (metallic surface treated steel sheet), and is uniformly attracted and coated on the metal surface treated steel sheet. By specifying the moving speed (threading speed) of the surface-treated steel sheet, the coating amount (coating thickness) can be adjusted arbitrarily.

At the same time, the chromate solution used in the present invention is
After the surface of the metal surface-treated steel sheet is sprayed and coated as described above, the resin in the solution wets and spreads over the surface of the metal surface-treated steel sheet, and the Cr-containing components and the resin are further heated through the coating treatment. Through the polymerization reaction with the polymer, it is possible to obtain an even coating effect of the film, and also an effect of improving various properties accompanying this.

That is, according to the method of the present invention, the coating amount (
Excellent uniform coverage regardless of coating thickness
Appearance performance, corrosion resistance performance, painting -] 3- It is possible to form a high performance, chromium-containing resin coating with excellent performance.

(effect) The present invention will be explained in detail below.

In the present invention, the surface of a metal surface-treated steel sheet such as a zinc or zinc alloy plated steel sheet, an aluminum or aluminum alloy plated steel sheet, or a lead or lead alloy plated steel sheet is subjected to activation treatment with an alkaline bath or the like immediately after plating. Then, using a resin solution containing a chromium component, a solution tank 2 and a supply pump 3 are used to store a coating solution 1, an example of which is shown in FIG.
Using an electrostatic atomization coating device consisting of a solution supply path communicating with the atomization device 4 and an atomization adjustment device consisting of a high-voltage transformer 9, an electric control panel 8, and a control operation panel 7, Atomized particles of a chromium-containing resin solution are sprayed onto the surface of a positively charged metal surface-treated steel plate to ensure uniform adhesion.

That is, the resin solution 1 containing the chromium component is supplied from the solution tank 2 to the desired amount by adjusting the supply pump 3 in accordance with the desired coating amount (coating thickness) and the passing speed of the metal surface-treated steel sheet 6 to be treated. Atomization device 4 that electrostatically atomizes a quantitative solution
The atomizing device 4 is connected to an air turbine 5, which rotates at high speed (20,
000-45. OOORPM) has capital A.

The solution 1 supplied to this electrostatic atomizer 4 is supplied from the solution supply pipe B to the rotating body part A rotating at high speed in the air turbine in FIG. 2, and the solution 1 hits the surface C of the rotating body part. It passes through a small diameter (usually 1 to 5 mm in diameter) D provided between the rotating bodies A and A', flows through the surface F of the tip end of the rotating body A, and reaches the tip end E.

In the process of flowing through this F plane, the solution 1 is atomized very uniformly by centrifugal force based on high-speed rotation, and flies out from the leading edge portion E in the form of very uniform particle sizes.

On the other hand, a high voltage (usually -80K) is applied to the entire electrostatic atomizer 4.
The solution supplied to the atomizer 4 is negatively charged, and the atomized particles G that have flown out of the atomizer are each equally negatively charged.

Therefore, these negatively charged atomized particles G do not repel each other and aggregate, but instead uniformly move toward the nearby ground, that is, the positively charged metal surface-treated steel plate 6. It jumps out and gets attached.

As a result, a predetermined amount of each particle is uniformly adhered to the surface of the metal surface-treated steel sheet.

In addition, the coating amount (coating thickness) of the material to be treated can be easily changed arbitrarily depending on the threading speed of the steel plate 6 to be processed by adjusting the solution supply pump 3, and when increasing the threading speed. This can be easily handled by arranging the electrostatic atomizers 4 in multiple stages.Of course, it is also easy to deal with wide-width materials by arranging them in multiple stages in the width direction of the board, corresponding to the width of the board. be.

Next, in this coating method, the atomized particles are uniformly supplied and adhered to the surface of the metal surface-treated steel sheet, and the coating form of the uniform atomized particles on the surface is such that extremely fine particles are uniformly layered. Therefore, even if the particles are extremely fine, they fill the gaps between these particles and the deposits spread evenly immediately after coating and during the heat treatment following the coating process, so it is important to have excellent uniform coating properties. be. For this purpose, the coating method of the present invention and the structure, properties, and heat treatment temperature of the chromate treatment bath for forming the coating are important.

Therefore, regardless of the coating amount (coating thickness), in order to obtain a coating with excellent uniform coverage, appearance performance, corrosion resistance performance, and coating performance, the composition and properties of the treatment bath should be adjusted as follows. Heat treatment temperature is regulated.

That is, a resin treatment bath containing a chromium component is used, the amount of the resin component is 50 to 400 f//l, the chromium component is contained at a ratio of 1150 to 1/l of the resin content, and the viscosity is 3 to 400 f//l. 50 centipoise (normal temperature), electrical conductivity 2-30 milliseconds/cm (ms/
It is necessary to use a chromium-containing resin solution consisting of lyn).

In the case of a chromium-containing resin solution in which the amount of resin component is less than 5 oy/and the content of chromium component is contained in a ratio of 1150 to 1/1 of the resin concentration, metal surface treated steel sheet after electrostatic atomization coating. The wetting and spreading properties of the treatment solution on the surface are poor, and even if heat treatment is performed, a sufficient uniform coating effect cannot be obtained, resulting in deterioration of uniform coverage, treated appearance, corrosion resistance, and coating performance.

However, in the case of chromium-containing resin solutions in which the resin concentration exceeds 400 y/l and the chromium content is contained in a ratio of 1150 to 1/1 of the resin concentration, the viscosity of these solutions becomes high, so electrostatic After atomization painting and in the heat treatment process, it takes time for the treatment bath to wet and spread on the surface of the metal surface treated steel sheet, which is disadvantageous in forming a chromium-containing resin film uniformly in high-speed treatment, and it is difficult to achieve uniform appearance. , the performance of the coating is poor.

Therefore, in the present invention, the resin component amount is 50 to 4.
o o f//l, preferably l 509/l~3
It is used in the range of 00Y/l.

The type of resin used in the present invention is not particularly specified, but for example, acrylic resin, epoxy resin, phenoxy resin, fluororesin-18= or phenol resin, etc. may be used alone or in combination of two or more types. used.

These resins can be used in an aqueous solution or in a solvent (xylene).

aromatic hydrocarbons such as, alcohols such as inglobil alcohol, esters such as butyl acetate, ethers such as ethyl cellosolve, or mixtures thereof).
Used as a solution containing 0-400 y/
Therefore, in the present invention, the solution containing the above-mentioned resin is used containing a chromium component, is safe to be used at high voltage, and has the following viscosity, electrical conductivity, etc. From the viewpoint of regulating the properties of the resin, it is preferable to use it as a water-soluble resin or emulsion as an aqueous solution using water as a solvent.

Furthermore, the Cr-containing resin solution used in the present invention needs to form a film at high speed and in a short time by thermal polymerization of the chromium component, especially Cr6+, and the resin in the heat treatment step performed after application. In order to accelerate this thermal polymerization, a curing accelerator (for example, phosphoric acid) may be added in advance to the bath.

Next, in the present invention, the chromium component is contained in a ratio of 1150 to 1/1 to these resins.

That is, the chromium component is i y/1 to 25 as the amount of Cr.
It is necessary to add it to the solution used in the present invention in the range of 0 f/t and at a ratio of 1150 to 1/l to the resin.

This chromium λ component is used with Cr6+ as its main component, and is important for ensuring the corrosion resistance and coating performance of the coating formed by heat treatment.

In the heat treatment process, the resin and this chromium polymerize to form a chromate film with excellent corrosion resistance and coating performance. However, if the chromium content is less than 1150% of the resin content, corrosion resistance due to the action and effect of chromium will decrease. It is difficult to form a film that is sufficient to ensure sufficient performance. That is, since a film mainly composed of a resin component is formed, it has the disadvantage that it is difficult to obtain the performance aimed at by the present invention.

On the other hand, when the chromium content is contained in a ratio exceeding 1/1 to the resin content, it is difficult to achieve sufficient uniform mixing of the treatment bath itself, and the wetting and spreading of the resin after electrostatic coating is caused by the oxidation effect. There are also disadvantages such as poor uniform coverage, and as a result, appearance performance, corrosion resistance, coating performance, etc. are poor.

Therefore, in the present invention, the resin concentration is 1150 to 1/
It is necessary that the treatment bath contain a chromium component in a ratio of 1/30 to 115, preferably 1/30 to 115.

In addition, this chromium component contains Cr'+ as a main component, and reacts with the resin in the heat treatment process to form a film mainly composed of Cr"+. Cr3+ may be mixed at a ratio of 40 or less to the total chromium.

Therefore, as an essential component of the treatment bath used in the present invention,
The chromium component contained with the resin is one or more of chromic acid, dichromate, and chromate. It is mixed in the form of chromic acid, chromate, etc. within the -21-' range specified above.

Note that when creating a chromate treatment bath containing this chromium component and a resin component, it is preferable to use a chromium component that corresponds to the stable pH range of the resin component used.

For example, when using acrylic resin that is stable in an acidic region, chromic acid is used as the main chromium component, and when using Gosenki resin, which is still stable in a neutral region, ammonium chromate is used as the chromium component. The method of using the main ingredient is adopted.

That is, from the viewpoint of stability over time of a chromate solution in which a resin component and a chromium component are mixed, it is preferable that the resin component and the chromium component are mixed and used in the range where both are stable.

Next, in order to obtain the desired effect of the present invention by using an electrostatic atomization coating method, the properties of the treatment solution mainly consisting of a chromium component and a resin component are defined as follows. First, the viscosity of the treatment bath used must be in the range of 3 to 50 centipoise at room temperature.

=22- That is, if the viscosity is less than 3 centibore, the processing bath spreads quickly on the metal surface-treated steel plate immediately after application, and the processing bath uniformly fills the gaps between particles in a short time. On the other hand, the baking of the film by heat treatment has the drawback that the deposits flow until the adhesion treatment, which impedes uniform coverage.

On the other hand, if the viscosity exceeds 50 centipoise,
A considerable holding time is required to uniformly cover the gaps between the electrostatically applied particles due to the wetting and spreading effect of the treatment bath. Therefore, in high-speed processing, it is disadvantageous in obtaining good appearance performance with excellent uniform coverage.

Therefore, in the present invention, the viscosity of the treatment bath is 3 to 3 at room temperature.
50 centipoise, with a good range of 4 to 30 centipoise.

Furthermore, in the present invention, it is necessary to apply the processing bath as negatively charged atomized particles of uniform particle size, and in order to generate these atomized particles in an electrostatic atomizer, it is necessary to Gender is an important factor.

That is, the electrical conductivity of the treatment bath used in the present invention is
2-30 mSequence/cTn (mS/cm) at room temperature
) The electrical conductivity of the treatment bath is regulated within the range of 2ms/c.
In the case of less than rn, that is, the resistance value of the treatment bath is large, so a very large high voltage is required to charge the treatment bath, which is important for safety during operation, and at the same time, it is necessary to obtain a uniform particle size with a negative charge. It becomes difficult to create atomized particles.

On the other hand, if the electrical conductivity of the treatment bath exceeds 30 mB/l'm, the current flowing through the solution will increase under the voltage range used in the present invention, making it extremely difficult to work safely.

Therefore, the electrical conductivity of the treatment bath used in the present invention is 2 to 30 ms/6n at room temperature, preferably 10 to 25 m5.
/C'm range.

As mentioned above, by using the composition and properties of a resin-based treatment bath containing chromium components, it is possible to uniformly apply the coating onto the metal surface-treated steel sheet, and it is possible to form a coating with excellent appearance and coating performance. In order to form
Heat treatment is performed in the range of 00℃, and the material to be treated and the coating are coated.
It is necessary to bond the deposits and at the same time form the deposits themselves into a stable film.

In this case, if the heating temperature is less than 50°C, a strong bonding effect between the deposit and the treated material cannot be obtained, and the hardening and polymerization reaction of the deposit itself and the chromium and resin components will not be sufficient, resulting in poor performance. It is difficult to form a good film.

On the other hand, if the heating temperature exceeds 350° C., there is a risk that the resin component used in the treatment bath of the present invention will be decomposed, and the corrosion resistance and coating performance of the formed film will deteriorate, which is not preferable.

Therefore, the heating temperature is 50 to 350"C1, preferably 1
Heat treatment is performed in the range of 00°C to 250' (:).

Further, the coating formed in this manner has excellent uniformity and good appearance, but from the viewpoint of corrosion resistance, it is necessary to ensure a sufficient amount of chromium in the coating.

That is, the amount of Cr deposited on one side in terms of the amount of metallic chromium is regulated within the range of 5 to 20 ohm97.1.

If the amount of Cr deposited is less than 5 mβ, it is difficult to secure performance characteristics such as corrosion resistance due to the action of Cr in the coating or corrosion resistance after painting, and if the amount of Cr deposited is less than 200 me/rr.
? If it exceeds this value, the effect of improving corrosion resistance becomes saturated, and cracks are more likely to be formed in the coating due to processing, which is not preferable because the corrosion resistance after processing deteriorates.

Therefore, in the present invention, the amount of Cr deposited is 5 to 20
0 m9/d, preferably within the range of 15-150 m97.

The treatment bath used in the present invention is composed of a chromium component and a resin component as main components, but to the extent that the properties of the treatment bath are not impaired, additives may be added to improve the reactivity with the material to be treated. Effective so4”, po4.”
Anions such as - or cations such as Co'' and Ni'' which are effective in improving the paint adhesion of the coating may be added singly or in combination.

m26- Alternatively, for the purpose of further improving the performance of the coating of the present invention, oxides such as silica sol, alumina sol, silicate, etc., as long as the composition and properties of the chromate bath used in the present invention are not impaired. Alternatively, a chromate treatment bath may be used in which a coloring pigment such as fine carbon black powder is added for the purpose of coloring the chromate film, and a conductive pigment such as phosphorous iron powder is added for the purpose of improving the weldability of the chromate film.

On the other hand, in order to make the appearance of the chromate film formed by the method of the present invention white and transparent, the chromate film of the present invention may be subjected to a method of reducing Cr6+ present in the chromate film.

That is, for example, a method in which a heat-treated chromate film is subjected to cathodic electrolysis treatment in an aqueous solution containing a conductive salt (ammonium chloride, ammonium carbonate, etc.), or an aqueous solution containing a reducing agent such as hydrazine hydrate or hydroquinone. Cr6+ in the coating is reduced to Cr"+, dissolved and removed by methods such as immersion in the coating, spray treatment, etc., and the coating becomes white and transparent, and further insolubilization of the coating is promoted. Ru.

Even if these methods are applied to the chromate coating of the method of the present invention, they do not have any adverse effect on the performance characteristics, but rather may improve the performance in some cases, and do not impair the present invention.

In order to clarify the effects of the present invention, several Examples and Comparative Examples will be given and specifically explained.

Example 1 An electrogalvanized steel plate with a coating amount of 2 of/rd per side was used as the material to be treated, and the plate width was 9 oomm.
Using the electrostatic coating device shown in Figure 1 at a plate passing speed of 90 m/min, we investigated the effects of the chromate bath composition and properties on the surface of the treated material and on its coating properties. In addition, some of these chromate baths were used to examine the covering properties of other chromate bath covering methods, and a comparative study was conducted with the method of the present invention.

In this evaluation test, (1) Composition of the treatment bath; average molecular weight of approximately 200,000;
In addition to using an emulsion type acrylic resin, Or"+, which is a part of CrO2 and Cr6+ reduced with starch as a chromium component, and a curing agent (CH3COO)3
(2) Electrostatic coating method: Using the electrostatic coating device shown in Figure 1, adjusting the speed and width of the plate to suit the plate threading speed, and applying a metering pump to achieve the desired adhesion. At the same time, the air turbine was rotated at 1.8 to 97 cm at 25,000 revolutions, the electrostatic coating device was loaded with a charge of lOOKV, and the electrostatic atomized particles were passed through at a constant speed. It was supplied and attached to electrogalvanized steel sheets.

(2) Heat treatment: Heat treatment was carried out for 0 seconds at a plate temperature of 150°C in a hot air oven.

Using the above method, we also investigated the film performance, focusing on the effects of the treatment bath and the amount of chromate film.

Table 1 shows the treatment conditions according to the method of the present invention, and Table 2 shows the evaluation results of the performance characteristics of the chromate film according to the method of the present invention.

The evaluation method and evaluation criteria were as follows, and the performance was compared and compared with those coated with chromate films with approximately the same amount of chromium deposited.

○Evaluation method and evaluation criteria ■Processing status and appearance After the treatment and after the chromate film was formed, internal observations were made, and evaluations were made based on the following evaluation criteria.

◎...The chromate bath is applied uniformly to both sides during the treatment, and the chromate film formed after the heat treatment is uniformly formed without color unevenness or spot patterns.○...The chromate bath is applied uniformly to both sides during the treatment. Although it adheres with partial unevenness, it becomes relatively uniform after heat treatment and forms a romate film △...During treatment, unevenness of adhesion occurs due to foaming of the processing bath or poor wetting, and Even after heat treatment, unevenness in the amount (thickness) of the chromate film deposited is clearly observed, but a chromate film is formed on the entire surface. If there are areas where no film formation is observed even after the chromate film is formed by heat treatment ■ For the 2 x 2M evaluation surface of the chromate film uniformity evaluation material, Cr characteristic X-rays with a beam diameter of 2μ are irradiated to lOOOXIOO0 squares, and the number of Cr X-ray counts (
CPS) was measured.

On the other hand, the chemical analysis value and the corresponding X-ray count number (cps) of the standard sample are measured, and the amount of Cr deposited in each square of the evaluation material is determined by comparing it with the above measured count number. The romate coverage was evaluated.

The evaluation criteria were based on the following method. That is, for the average chemical analysis value (Xm9/d) shown in Table 1, ◎・
If the Cr adhesion amount (within ±10 cm) occupies an area ratio of 80% or more of the Cr adhesion amount on the evaluation surface/entire surface, ○...(within ±10%) Cr adhesion amount occupies an area ratio of less than 80% to 60% or more of the Cr adhesion amount on the evaluation surface/full surface, the Cr adhesion amount of △... (also within ±10%) is the Cr adhesion amount on the evaluation surface/full surface. occupies an area ratio of 60 or more, but the amount of Cr deposited (±30% or more) is present at an area ratio of 20% or more ×...The area where the amount of Cr deposit is not detected is 2° on the evaluation surface. If it exists at an area ratio of 5 or more ■ Corrosion resistance salt spray test (JIS-Z-2371), ■
A flat plate! , Ma and ■ 0.8 tone plate thicknesses were processed into square tubes with a height of 30 mm from a blank size of 200 x 200 wn.Evaluation tests were conducted for a specified period of time, and evaluations were made using the following evaluation criteria. I did it.

■Corrosion resistance of flat plate◎・・・White rust occurrence rate less than 1%○・・・1% or more to less than 5%△・・・・・・
・ 5 inches or more ~ less than 20%×・・・・・・
20% or more■Corrosion resistance after processing◎・・・White rust occurrence rate less than 5%○・・・・・・5% or more to less than 15%△・・・
・・15% or more ~ less than 30 articles×・・・・
30% or more ■Paint adhesion After painting 25μ thick melamine-alkyd resin and baking,
Erichsen processing with a height of 7 mm was performed using the evaluation material with a thickness of 0.8 mm.

■-1 Evaluation method■ After Erichsen processing, apply sellotape to the surface and peel it off. Evaluate the peeling status of the paint using the following evaluation criteria ◎・・・・No beginning to peel off of the paint film○・・・・・・・
lfl1m diameter or less paint film peeling has decreased to 5 points or less...
・More than 5 cases of paint peeling of 1 scale diameter or less, or paint peeling of a fairly small area of 10% or less of the evaluated surface >0% of area paint peeling occurred ■-2 Evaluation method ■ The painted material was immersed in boiling water for 30 minutes, dried and left for 24 hours, then subjected to Erichsen processing and the same peeling test as above was conducted. , Evaluation based on the same criteria as above ■Corrosion resistance after painting 100X150. Melamine-
After painting and baking an alkyd paint with a thickness of 25 μm, scratches reaching the surface of the plating layer were made, and a salt spray test was performed for a predetermined period of time to evaluate the corrosion resistance performance after painting according to the following evaluation criteria.

◎・・・The maximum blistering width from the scratch area is less than 3 points, and the occurrence of blisters from the ground plane area is 3 points or less.

○...The maximum width of blisters from the scratch area is less than 6 feet, or the occurrence of blisters from the ground plane is 7 points or less.△...The maximum width of blisters from the scratch area is less than 10 feet, or, Occurrence of blisters from other flat surfaces: 10 points or less
34 = More than 11 points of blister generation from the ground plane.

−35= Example 2 A chromate film was formed by the method of the present invention on a zinc alloy plated steel sheet, a lead and lead alloy plated steel sheet, and an aluminum and aluminum alloy plated steel sheet under the conditions shown in Table 3, and the film performance was evaluated. We conducted an evaluation. The results are shown in Table 4.

As a comparative example, chromate coatings having the same amount of chromium deposited were formed by each method, and the performance was compared for each method.

Note that performance evaluation was performed using the method shown below, and a relative evaluation was performed according to the evaluation criteria.

■Processing status and appearance...The same evaluation was carried out as in Example 1-■, and the evaluation was made using the same standards. ■Uniform coverage of the chromate film...The same evaluation was carried out as in Example 1-■, and the evaluation was made using the same standards. Evaluation ■Corrosion resistance: The same evaluation as in Example 1-■ was carried out, and the evaluation was performed based on the incidence of white rust or red rust depending on the type of each evaluation material. The evaluation criteria for the incidence of each evaluation material were based on Example 1-■, and are indicated by white rust or red rust in Table 4.

■Paint adhesion...Performed the same evaluation as in Example 1-■ and evaluated using the same standards ■Corrosion resistance after painting...Performed the same evaluation as Example 1-■ and evaluated using the same standards Special opening aG3- 296870 (,11) (Effects of the Invention) That is, according to the method of the present invention, the coating amount (
Excellent uniform coverage regardless of coating thickness
It is capable of forming a high-performance, chromium-containing resin coating with excellent appearance, corrosion resistance, and coating performance.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of the electrostatic atomization coating device, and FIG. 2 shows a schematic diagram of the atomization device. 1... Coating solution 2... Solution tank 3...
・Supply pump 4...Atomization device 5...Air turbine 6...Surface treated steel plate 7...Operation panel
8...Electric control panel 9...High voltage transformer

Claims (1)

[Claims] The metal surface treated steel sheet contains a resin component of 50 to 400 g/l and a chromium component at a ratio of 1/50 to 1/1 of the resin component, has a viscosity of 3 to 50 centipoise at room temperature, and has an electrical conductivity of 50 to 400 g/l. 2 to 30 mm sequence/cm (m
C
A method for forming a high-performance chromium-containing resin coating on a metal surface-treated steel sheet, characterized by providing a resin coating containing a chromium component of 5 to 200 mg/m^2 per side in terms of r amount.