JPH09183186A - Organically after-treated metal sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organically after-treated metal sheet with excellent adhesiveness with a coating, especially excellent secondary adhesiveness and corrosion resistance. SOLUTION: A chem. treated film contg. an org. resin with a thickness of 0.3-5μm is formed on the surface of a galvanized sheet metal, an aluminum-based plated steel sheet, a zinc alloy sheet, an aluminum alloy sheet and a steel sheet and on the outermost surface of the treated film, the quantity of the surface C contg. C-O-O bonds detected by means of XPS is at least 25% of the quantity of the surface C consisting of C-C bonds. In addition, one or two or more metal compd. among Cr, Mo, W, Ti and Zr are incorporated in the chem. treated layer and the ratio of the quantity of the metal elements M detected on the outermost surface of the chem. treated film by means of XPS (when there exists at least two kinds of metals, the total amt. thereof is used) to the quantity of org. C is C/M>=70.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a zinc-based plated steel sheet, an aluminum-based plated steel sheet, a zinc alloy sheet, an aluminum alloy sheet, or a steel sheet as an undercoat, and has excellent paint adhesion, particularly long-term durability after painting, and The present invention relates to an organic post-treatment metal plate having corrosion resistance.

[0002]

2. Description of the Related Art Treatments for improving coating adhesion of zinc-based plated steel sheets, aluminum-based plated steel sheets, zinc alloy sheets, aluminum alloy sheets, or steel sheets include chromate treatment, phosphate treatment, treatment with silane coupling agent. ,
Anodizing treatment, treatment with an organic primer, or a combination of two or more of these is conventionally known. Among these, the chromate treatment and the phosphate treatment have the effect of imparting corrosion resistance as well as paint adhesion. Most of the conventional techniques relating to these metal surface treatments attempt to develop the performance by individually controlling the treatment conditions and the treatment bath composition, but the fact that paint adhesion is actually controlled is It is the surface structure of the treatment film formed as a result of these treatments. Therefore, it is this surface structure that should be controlled.

As a known technique for improving paint adhesion and corrosion resistance on a metal surface, for example, JP-A-60-8 is known.
There is a 6283 publication. That is, an aqueous solution containing chromic anhydride, a colloidal substance, a polymeric substance, etc. is applied to the metal surface, and after drying, a dilute aqueous chromic anhydride solution is further applied to cover the cracks generated in the treated film during drying. Therefore, it can be said that the application of a dilute aqueous solution of chromic anhydride is a kind of sealing treatment. The surface structure of the resulting treated film is such that the chromic acid compound is exposed on the surface in a considerable amount, centering on the defective portion of the film containing the resin of the first layer. The secondary adhesion of the paint deteriorates when it is subjected to conditions such that it can be eluted, for example, when it is immersed in boiling water.

On the other hand, in Japanese Patent Laid-Open No. 224175/1983, a metal plate is coated with a water-soluble acrylic resin, a chromate treatment liquid composed of reduced chromic acid and a mineral acid, and a sealing with an organic composite silicate resin is performed as a post-treatment step. A method of doing so is disclosed. Since the silicate contains a large amount of hydroxyl groups, which concentrate on the surface of the film, the primary adhesion of the paint is good, but since the surface hydroxyl groups have a strong affinity with water,
After all, the secondary adhesion of the paint after exposure to hot water or boiling water is poor.

Further, Japanese Patent Laid-Open No. 1-312082 discloses a method of surface-treating a steel sheet with a chromate treatment liquid containing a resin and a silane coupling agent. Here, since the acid value of the resin used is 250 or more, it can be expected that the carboxyl group effective for adhesion is concentrated to some extent on the film surface, but due to hydrolysis of the silane coupling agent used in combination, After all, excessive hydroxyl groups are generated on the surface of the film, and the corrosion resistance and the secondary adhesion of the paint are reduced.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic post-treatment metal plate excellent in secondary coating adhesion and corrosion resistance by controlling the surface structure of the post-treatment coating.

[0007]

The gist of the present invention is a zinc-based plated steel sheet, an aluminum-based plated steel sheet, a zinc alloy plate,
A film thickness of 0.3 ~ on aluminum alloy plate or steel plate
A chemical conversion treatment film having a thickness of 5 μm and containing an organic resin is formed, and the amount of the surface C containing a C—O—O bond detected by XPS on the outermost surface of the treatment film is C—C.
The organic post-treatment metal plate is characterized in that it is 25% or more of the amount of the surface C composed of bonds. In order to achieve both corrosion resistance and paint adhesion, Cr, Mo, W,
An amount of the metal element M containing one or more kinds of metal compounds of Ti and Zr and detected on the outermost surface of the treatment film by XPS (in the case of two or more kinds, a total value thereof); It is preferable that the ratio of the amount of organic matter to C is C / M ≧ 70.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. As a result of diligent studies on the relationship between the structure of the organic post-treatment film and coating adhesion and corrosion resistance, the inventors have found that in order to improve the secondary adhesion of the coating, a carboxyl group or / and an ester group is formed on the coating surface. It has been found that it is necessary to exist above a certain amount. Specifically, it is preferable that the amount of the surface C containing the C—O—O bond detected on the surface of the film by XPS is 25% or more of the amount of the surface C containing the C—C bond. It is necessary to develop adhesion.

Carboxyl group used in the present invention or /
The type of the resin containing an ester group includes, for example, an acrylic resin, an alkyd resin, a polyurethane resin, or a C—O—O bond by modification with these resins or carboxylation or esterification by another method. Introduced epoxy resin, styrene-maleic acid resin,
A phenol resin, a polyolefin resin, a mixture of two or more kinds of these, a copolymer with another resin, or the like can be used. The resin must be water soluble or water dispersible.

In order to develop corrosion resistance while maintaining good paint adhesion as described above, metal oxides such as chromic acid, molybdic acid, tungstic acid, titanic acid, zirconic acid, etc., which have antirust properties, The amount of the metal M detected on the outermost surface of the treated film by XPS, which forms a chemical conversion treated film composed of a hydroxide and an organic substance containing a carboxyl group and / or an ester group (in the case of two or more, they are Ratio of the total amount of) and the amount of C of organic matter is C / M
It is necessary that ≧ 70. When the value of C / M is less than 70, the metal oxide / hydroxide layer having rust preventive property is not sufficiently covered with the organic substance, and thus the coating adhesion is poor.

Examples of the metal oxides / hydroxides having rust preventive ability used in the present invention include chromic acid compounds, molybdic acid compounds, tungstic acid compounds, titanic acid compounds and zirconic acid compounds. As the chromic acid compound, chromic anhydride and reduced chromic acid partially reduced with starch or the like, or potassium dichromate, ammonium dichromate, sodium dichromate, potassium chromate, ammonium chromate, sodium chromate, etc. It is possible to use the dichromate or chromate. Of these, chromic anhydride or reduced chromic acid obtained by partially reducing chromic anhydride is preferably used from the viewpoints of bath stability, film-forming property, and economy.

As the molybdic acid compound, sodium molybdate, ammonium molybdate, zinc molybdate, zinc calcium molybdate, zinc potassium phosphomolybdate, etc. can be used. Similarly, various alkali metal salts and the like can be used for the tungstic acid compound, the titanic acid compound, and the zirconic acid compound. In addition to the above,
Inorganic sol such as silica, alumina, titania, phosphoric acid,
Inorganic acids such as polyphosphoric acid and boric acid, fluorides and the like can be contained in the chromate-treated film as required.

In order to control the surface structure of the organic post-treatment film as described above, the amount of functional groups in the resin, particularly the amount ratio of carboxyl group and / or ester group to hydroxyl group, resin, metal oxide / water, and the like. Appropriately adjusting the amount ratio with the oxide, and controlling the heating pattern in the drying after coating, and further, if necessary, appropriate post-treatment, for example, immersion treatment in hot water or a dilute organic solvent is required. In some cases.

By XPS, C--C bonds and C on the surface of the film
The procedure for measuring the amount of C containing a —O—O bond is as follows.
It is. First, the sample surface is covered with about 1% gold.
Vapor deposition. This compensates for charge up of the sample
Internal standard. Next, C and Au on the sample surface
Is measured by XPS. At this time, the Au4f3 / 5 peak
Position of the measured peak of C so that the peak position is 83.8 eV
Correct the position. Normally, samples are positively charged
Therefore, the measured peak position of Au4f3 / 5 is about 85 eV.
(It will shift by 1.2 eV due to charge up)
So C1 _SIf the measured peak position of 286 eV
For example, the corrected peak position is 284.8 eV. Then C
1_SPerform peak waveform analysis.

Commercially available software may be used for the waveform analysis. Usually, the Cl _S peak is separated into three peaks derived from C—C bond, C—O bond, and C—O—O bond. The parameters of each peak include peak position, half-width, and distribution form.
C—C bond: 284.70 ± 0.15 eV, C—O bond: 286.45 ± 0.15 eV, C—O—O bond: 2
88.65 ± 0.20 eV was used, the full width at half maximum was set in the range of 1.50 to 2.00 eV for each peak, and the Gauss distribution was applied as the distribution form. FIG. 1 shows a specific example of waveform analysis. Peak 1 is C—C bond, peak 2 is C—O
Bond, C in which peak 3 is derived from C—O—O bond, respectively
The amount ratio of each peak can be calculated by calculating these areas. FIG. 1 is an example of the present invention, C-O-O
The amount of surface C containing bonds is 33.5% of the amount of surface C consisting of only C—C bonds.

In order to measure the amount of the metal element M and the amount of the organic substance C on the surface of the film by XPS, the usual quantitative analysis method may be used. What should be noted is how to set the background for quantitative calculation when the peak of the metal element is small. If the background noise is large enough to be ignored compared to the size of the peak, select a region with a length of 1 to 2 eV at both ends of the peak, and calculate the average value of the background signal intensity within this range. It is better to obtain the peak area by linearly approximating the background based on these values. Note that if the minimum value is selected instead of the average value, the peak area will be overestimated.

The thickness of the organic post-treatment coating defined in the present invention as described above is 0.3 to 5 μm. If it is less than 0.3 μm, the effect as a continuous film cannot be obtained, and if it is 5 μm or more, the effect is saturated. As a method for treating the metal, roll coater coating, ringer roll coating, dipping and air knife squeezing coating, bar coater coating, spray coating, brush coating and the like can be applied. Further, as long as the surface structure is within the scope of the present invention, the coating may be a single coating or a treatment of two or more coatings.

The steel sheet to which the present invention can be applied includes a galvanized steel sheet, a zinc-nickel plated steel sheet, a zinc-iron plated steel sheet, a zinc-chromium plated steel sheet, a zinc-titanium plated steel sheet, a zinc-magnesium plated steel sheet, a zinc-manganese sheet. Galvanized steel sheet, zinc-based electroplating such as zinc-aluminum plated steel sheet, hot dip plating, vapor deposition plated steel sheet, aluminum plated steel sheet, lead or lead alloy plated steel sheet, tin or tin alloy plated steel sheet, and even a small amount of these plated layers As a different metal element or impurity, for example, cobalt,
Molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead,
A plated steel sheet containing antimony, tin, copper, cadmium, arsenic, and / or a plated steel sheet in which an inorganic substance such as silica, alumina, and titania is dispersed, and a plated steel sheet in which an organic substance is dispersed are included. Further, it can be applied to multilayer plating in which two or more of the above platings are sequentially applied, or multi-layer plating in which the above platings and other types of plating are combined, such as iron plating and iron-phosphorus plating. Is. Furthermore, zinc plate, zinc alloy plate, aluminum plate,
Aluminum alloy plates, steel plates, etc. can also be used.

[0019]

Next, the present invention will be described by way of examples. Example 1 (1) Type of metal plate: The following four types were used as the metal plate to be subjected to the chromate treatment. GI: hot-dip galvanized steel sheet (coating adhesion amount 90 g / m
² ) EG: Electrogalvanized steel sheet (coating weight 20g / m
² ) SZ: hot dip zinc-aluminum plated steel sheet (coating adhesion amount 120 g / m ² , AL / Zn = 5/95) GA: hot dip zinc-iron alloy plated steel sheet (coating adhesion amount 20
g / m ² , Zn / Fe = 85/15)

(2) Kind of rust preventive agent: Chromic anhydride partially reduced with starch was used. The concentration of chromic acid was 30 g / l (calculated as CrO ₃ ). (3) Type of resin: propyl acrylate, styrene,
An emulsion obtained by copolymerizing vinylphenol and acrylic acid was used. The concentration of solid content was 100 g / l. (4) Other additives: Phosphoric acid and colloidal silica were added. The concentration was 50 g / l for all pure components.

(5) Post-treatment method: A rust preventive agent, a resin, and other additives were all mixed to form an aqueous solution, which was applied to a metal plate using a roll coater and dried. The thickness of the post-treatment film was 0.2 to 3 μm. (6) Control of surface functional group: The surface structure of the post-treatment film was changed by controlling the composition of each component in the resin and the heating pattern during drying. (7) Surface analysis: The obtained sample was cut into 5 mm x 5 mm and analyzed by a commercially available X-ray photoelectron spectrometer.

(8) Performance Evaluation Method Paint Adhesion: 20 μm of melamine alkyd paint was applied to the sample.
After being coated and dried, it was immersed in boiling water for 30 minutes. Immediately cross-cut test (1mm cross-cut 10 x 10, tape peeling)
The peeled area ratio of the coating film was examined by. ◎ No peeling 〇 Peeling area ratio less than 5% △ Peeling area ratio 5% or more, less than 20% × Peeling area ratio 20% or more

Corrosion resistance: The white rust occurrence area ratio was measured after spraying 5% salt water at 35 ° C. for 72 hours on the sample. ◎ No rust occurrence 〇 White rust occurrence rate less than 5% △ White rust occurrence rate 5% or more, less than 20% × White rust occurrence rate 20% or more The results are shown in Table 1. As is clear from the table, the organic post-treated steel sheet of the present invention has excellent paint adhesion and corrosion resistance.

[0024]

[Table 1]

Example 2 (1) Type of metal plate: The same four types as in Example 1 were used. (2) Kind of rust preventive agent: Sodium molybdate was used. The concentration was 30 g / l. (3) Type of resin: A mixture of polyacrylic acid modified with acrylamide and polyethylene glycol was used. The concentration in the bath was 100 g / l in total in terms of solid content. (4) Other additives: Colloidal silica was added at 50 g / l in terms of SiO ₂ .

(5) Post-treatment method: First, an aqueous solution containing a rust preventive agent is applied with a roll coater, dried, and then an aqueous solution containing a resin and colloidal silica is applied using a roll coater.
Dried. The total thickness of the post-treatment coating was 0.5 μm. (6) Control of surface functional group: The same as in Example 1. (7) Surface analysis: The same as in Example 1. (8) Performance evaluation method: As in Example 1, paint adhesion,
The corrosion resistance was evaluated. The corrosion resistance was evaluated by salt spray for 24 hours. Table 2 shows the results. Although the coating method and the type of rust preventive agent are different from those of Example 1, when the surface structure of the post-treatment film is within the range defined by the present invention, excellent coating adhesion and corrosion resistance are also exhibited.

[0027]

[Table 2]

[0028]

Industrial Applicability According to the present invention, it is possible to provide an organic post-treatment metal plate having excellent paint adhesion, particularly durability after painting, and corrosion resistance.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example in which a C1 _S peak waveform analysis is performed on a surface C measurement value by XPS.

Claims (2)

[Claims] 1. A chemical conversion treatment in which a zinc-based plated steel sheet, an aluminum-based plated steel sheet, a zinc alloy plate, an aluminum alloy plate, or a steel sheet has a thickness of 0.3 to 5 μm and contains an organic resin. A film is formed, and C-O- detected by XPS on the outermost surface of the treated film.
An organic post-treatment metal plate, wherein the amount of surface C containing O bonds is 25% or more of the amount of surface C consisting of C—C bonds. 2. A chemical conversion treatment layer containing Cr, Mo, W, Ti,
Amount of metal element M containing one or more metal compounds of Zr and detected on the outermost surface of the treated film by XPS (in the case of two or more, the total value thereof)
The organic post-treatment metal plate according to claim 1, wherein the ratio of C to the amount of organic matter C is C / M ≧ 70.