JP2001049152A - Anticorrosion paints and painted metal plates with excellent corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chromium-free anticorrosion coating material having a low toxicity and excellent in corrosion resistance, and a coated metal plate treated with the above coating material. SOLUTION: This anticorrosion coating material contains one kind, or two or more kinds of a polyphosphoric acid, orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, hypophosphoric acid, phosphorous acid and hypophosphorous acid as a rust proof additive by >=0.1 wt.% in total. It is possible to obtain a coated metal plate excellent in corrosion resistance by having a coating film consisting of the above anticorrosion coating material at least one of its surfaces, and to have a colored coating film as an upper layer of the coating film consisting of the anticorrosion coating material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coated steel sheet.
More specifically, the present invention relates to a coated metal sheet which is excellent in corrosion resistance and low in toxicity because it does not contain toxic chromium, and is suitable for building materials and home appliances.

[0002]

2. Description of the Related Art In the fields of home appliances and building materials, the use of post-coated steel sheets, which are coated before cutting and processing, are increasing in place of post-coated steel sheets which are coated after cutting and processing. This is because the use of a pre-coated steel sheet to be painted by a steel maker eliminates the need for a home appliance maker or the like to have a painting line, and that a pre-coated steel sheet has a smoother and more beautiful appearance than a post-coated steel sheet.

[0003] It is generally known that when a painted steel plate such as a pre-coated steel plate is subjected to severe processing, the coating is damaged and the corrosion resistance is reduced. In addition, when the precoated steel sheet is cut, a bare steel sheet is exposed, and there is a concern that corrosion will occur at that portion. That is, the precoated steel sheet needs to have excellent corrosion resistance. As an example of improving the corrosion resistance of such a pre-coated steel sheet, see, for example, JP-A-8-168.
No. 723 discloses a technique for obtaining a precoated steel sheet having excellent workability, stain resistance, and hardness by defining the structure of a film. Also, Japanese Patent Application Laid-Open No. Hei 3-100180
Japanese Patent Application Laid-Open Publication No. H11-139,086 discloses a precoated steel sheet having improved end face corrosion resistance by using a specific chromate treatment liquid.

[0004] In any case, a plated steel sheet having excellent corrosion resistance is subjected to a base treatment called chromate treatment, which is excellent in corrosion resistance and adhesion, and an undercoat layer containing a chromium-based rust preventive pigment having excellent corrosion resistance is provided thereon. It has a structure having a colored overcoat layer thereon.

[0005]

The hexavalent chromium contained in these chromate-treated and chromium-based rust preventive pigments is water-soluble, and has the property of inhibiting the corrosion of zinc-based plated steel sheets by being eluted. For example, even if the coating film is cracked due to severe processing or if a bare steel plate is exposed at the cut part, it is extremely excellent, such as suppressing the corrosion of that part. It has been widely used in precoated steel sheets.

[0006] However, due to the chromate treatment and the toxicity of hexavalent chromium which may be eluted from the chromium-based rust preventive pigment, there has recently been an increasing demand for a chromium-free base treatment and a chromium-free rust preventive pigment. Therefore,
An object of the present invention is to provide a chromium-free low-toxic anticorrosion paint excellent in corrosion resistance and a coated metal sheet treated with the paint in response to such a demand.

[0007]

Means for Solving the Problems The present inventors have repeated various studies on the corrosion resistance of the cut end surfaces of various plated steel sheets under the conditions of various chromium-free base treatments and various chromium-free primers. As a result, it is possible to produce a low-toxic chromium-free pre-coated metal plate having excellent end face corrosion resistance by applying a paint containing phosphoric acid instead of a chromium-based rust preventive pigment as a rust preventive paint. This led to the present invention.

That is, the gist of the present invention is as follows.
It is as follows. (1) Polyphosphoric acid, orthophosphoric acid,
An anticorrosion paint comprising one or more of pyrophosphoric acid, metaphosphoric acid, hypophosphoric acid, phosphorous acid, and hypophosphorous acid in a total amount of 0.1 wt% or more. (2) A coated metal plate having excellent corrosion resistance, characterized in that at least one surface of the metal plate has a coating film made of the anticorrosive paint described in (1).

(3) The coated metal sheet having excellent corrosion resistance according to the above (2), further comprising a colored coating film as an upper layer of the coating film made of the anticorrosive paint.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the polyphosphoric acid, orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, hypophosphoric acid, phosphorous acid, and hypophosphorous acid of the present invention will be generically referred to as phosphorus oxyacid. In addition, polyphosphoric acid is a kind of polyoxoacid, and 1
Refers to those containing three or more phosphorus per molecule.

As the oxyacid of phosphorus of the present invention, a commercially available product can be used without special pretreatment. The mechanism by which the corrosion resistance of the coated metal sheet is improved by using the oxygen acid of phosphorus of the present invention as a rust preventive additive has not been clarified, but is presumed as follows. That is, phosphate ions are eluted when the cut end face of the coated metal plate of the present invention is placed in an environment where corrosion is likely to occur, that is, in a wet environment,
It is presumed that the reaction of the phosphate ion with the bare metal on the end face to form a stable phosphate contributes to the improvement of corrosion resistance.

The amount of the oxyacid of phosphorus to be added to the anticorrosion paint of the present invention is 0.1 wt% or more when added alone or when two or more kinds are mixed and added. 0.
If it is less than 1 wt%, the effect of improving corrosion resistance due to the addition is not recognized. No upper limit is set, but 4
If the content exceeds 0 wt%, it becomes difficult to form a film.
Less than is preferred.

[0013] The anticorrosion paint of the present invention is characterized by containing an oxygen acid of phosphorus and a resin capable of forming a film. As the resin used for the rust preventive paint of the present invention, generally known resins can be applied according to the application. That is, polyolefin resin, acrylic resin, urethane resin, epoxy resin, polyester resin, vinyl chloride resin, fluorine resin, butyral resin, polycarbonate resin, phenol resin and the like. These mixtures and copolymers can also be used. In addition, an isocyanate resin, an amino resin, a silane coupling agent, a titanium coupling agent, or the like can be used together as an auxiliary component.

Since the precoated metal sheet according to the present invention is often used as it is without any repair after processing,
In applications where severe processing is applied, resin systems that crosslink polyester resins with melamine, resin systems that crosslink polyester resins with urethane resins (isocyanates, isocyanate resins), vinyl chloride resins, fluororesins (solvent-soluble, (Dispersion mixed type with acrylic resin) is desirable.

The form of the paint is not particularly limited, and examples thereof include organic solvent-based paints, water-based paints, colloid-dispersed paints, powder paints, and electrodeposition paints. The rust preventive paint of the present invention may contain other rust preventive pigments as needed. Examples of the rust preventive pigment include phosphoric acid rust preventive pigments such as zinc phosphate, iron phosphate, aluminum phosphate, and zinc phosphite; molybdic acid such as calcium molybdate, aluminum molybdate, and barium molybdate. Vanadium-based rust preventive pigments, such as vanadium oxide
Silicate-based pigments such as calcium silicate, chromium-based rust preventive pigments such as strontium chromate, zinc chromate, calcium chromate, potassium chromate, and barium chromate, and finely divided silica such as water-dispersed silica and fumed silica can be used. However, since the chromate-based rust-preventive pigment is environmentally toxic, it is desirable to use other than these.

The rust preventive paint of the present invention may be colored if necessary. Coloring is by a general pigment or dye. Known pigments can be used regardless of whether they are inorganic, organic, or a composite of the two, and include cyanine pigments such as titanium white, zinc yellow, alumina white, and cyanine blue, carbon black, and iron black. , Yellow iron oxide, molybdate orange, hansa yellow, pyrazolone orange,
Examples include azo pigments, navy blue and condensed polycyclic pigments. In addition, metal fragments, powders, pearl pigments, mica pigments, indigoid dyes, sulfur dyes, phthalocyanine dyes, diphenylmethane dyes, nitro dyes, acridine dyes and the like can be mentioned. The pigment concentration in the organic coating layer is not particularly limited, and may be determined depending on the required color and hiding power.

The anticorrosion paint of the present invention is applied on a metal plate by a known method. The metal plate may be subjected to a pretreatment for improving the adhesion as required. For example, zinc phosphate treatment,
Examples include a chromate treatment, a silane coupling treatment, a composite oxide film treatment, a tannic acid treatment, and a mixture thereof. Examples of the coating method include a roll coater, a curtain coater, electrostatic coating, spray coating, and dip coating. After that, hot air, induction heating, near infrared, far infrared,
It is dried and cured by heating such as. If the resin of the organic coating layer is curable by electron beams or ultraviolet rays, it is cured by these irradiations. These may be used in combination.

The coated metal sheet having excellent corrosion resistance according to the present invention is obtained by applying the above-mentioned rust-preventive paint on a metal sheet and curing and drying. The base metal plate of the coated metal plate is not particularly limited, and a generally known metal plate can be used. An alloy such as an aluminum alloy or a magnesium alloy may be used, or a metal plated with another metal may be used. The present invention is particularly effective for steel-based metals and plated steel. The steel component is not particularly limited, and examples thereof include IF steel to which Ti, Nb, B and the like are added, Al-k steel, Cr-containing steel, stainless steel, and high tensile steel. Examples of the galvanized steel sheet include a hot-dip galvanized steel sheet, a hot-dip zinc-iron alloy-coated steel sheet, a hot-dip zinc-aluminum alloy-coated steel sheet, a hot-dip zinc-magnesium alloy-coated steel sheet, a hot-dip zinc-aluminum-magnesium alloy-coated steel sheet, and a hot-dip aluminum sheet.
Hot-dip steel sheets such as silicon alloy-plated steel sheets, hot-dip-tin-plated steel sheets, electro-galvanized steel sheets, electro-zinc-nickel-plated steel sheets, electro-plated steel sheets such as electro-zinc-chromium alloy-plated steel sheets, etc., Zn, Al, Mg, Sn , N
A steel sheet having a plating layer composed of at least one of i, Cu, and Pb is effective.

The thickness of the anticorrosion coating is not particularly limited, but is preferably 0.2 μm or more and less than 100 μm. If it is less than 0.2 μm, the effect of improving corrosion resistance is unclear.
The coated metal plate of the present invention can be coated with the anticorrosive paint of the present invention and then a colored coating film. As the coloring paint, generally known ones can be applied. For example, polyolefin resin, acrylic resin, urethane resin, epoxy resin, polyester resin, vinyl chloride resin, fluorine resin, butyral resin, polycarbonate resin, phenol resin and the like. These mixtures and copolymers can also be used. In addition, an isocyanate resin, an amino resin, a silane coupling agent, a titanium coupling agent, or the like can be used together as an auxiliary component. The pre-coated metal sheet according to the present invention is often used as it is without repair after processing, so in applications where severe processing is performed,
Resin systems that crosslink polyester resins with melamine, resin systems that crosslink polyester resins with urethane resins (isocyanates, isocyanate resins), vinyl chloride resins, and fluororesins (solvent-soluble types and dispersion-mixed types with acrylic resins) desirable. Coloring is by a general pigment or dye. Known pigments can be used regardless of whether they are inorganic, organic, or a composite of the two, and include cyanine pigments such as titanium white, zinc yellow, alumina white, and cyanine blue, carbon black, and iron black. , Red iron oxide, yellow iron oxide,
Examples include molybdate orange, Hansa yellow, pyrazolone orange, azo pigments, navy blue, condensed polycyclic pigments, and the like. In addition, metal fragments, powders, pearl pigments, mica pigments, indigoid dyes, sulfur dyes, phthalocyanine dyes, diphenylmethane dyes, nitro dyes, acridine dyes and the like can be mentioned. The pigment concentration in the organic coating layer is not particularly limited, and may be determined depending on the required color and hiding power. The form of the paint is not particularly limited, and examples thereof include an organic solvent-based paint, a water-based paint, a colloid-dispersed paint, a powder paint, and an electrodeposition paint.

The thickness of the colored organic coating layer is not particularly limited, but desirably has a dry thickness of 5 μm or more in order to obtain a uniform appearance. There is no upper limit on the film thickness, but when coating continuously with a coil, the dry film thickness is often about 50 μm in a single coating. The upper limit of the film thickness is increased to about 200 μm. Further, when processing is performed on each sheet by spray coating or the like, the upper limit film thickness further increases.

The coated metal sheet of the present invention may be provided with a general coating layer other than the present invention as an undercoat layer, and the coating layer of the present invention may be provided thereon.

[0022]

EXAMPLES Commercially available reagents were used for polyphosphoric acid, orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, hypophosphoric acid, phosphorous acid and hypophosphorous acid. As the clear paint for the rust preventive paint, a commercially available polyester clear paint, epoxy clear paint, and urethane clear paint were used. The oxygen acids of each phosphorus were added to these clear coatings in the weight ratios shown in each table, and the coating was performed after sufficiently stirring with a stirrer.

As a metal plate to be coated, a hot-dip galvanized steel sheet having a galvanized coating weight of 120 g / m ^{2 on} both sides was used. The plate thickness is 0.6 mm. The hot-dip galvanized steel sheet was degreased, washed with water and dried. Next, as a chemical conversion treatment (base treatment), a silane coupling treatment (adhesion amount 200 m)
g / m ² ), zinc phosphate treatment (1.8 g / m ² ), or electrolytic chromate treatment (total Cr adhesion amount 45 mg / m ² ). On both surfaces of the steel plate subjected to the above treatment, the above rust-preventive paint was applied with a bar coater, baked in a hot-air drying furnace at a reaching plate temperature of 210 ° C. for a reaching time of 45 seconds, and water-cooled to form a rust-preventive film layer. . The film thickness is shown in each table.

Subsequently, FL100HQ (manufactured by Nippon Paint Co., Ltd., white) was applied as a polyester-based top coat using a bar coater to a dry film thickness of 15 μm. Baking,
Then, it was cooled with water to form an upper film layer. The back surface is all coated with a melamine alkyd paint with a bar coater with a dry film thickness of 7
It was applied so as to have a thickness of .mu.m, baked under the conditions of a reaching plate temperature of 230.degree. C. for 45 seconds, and cooled with water.

As comparative materials, those containing strontium chromate and calcium chromate as rust preventive pigments were also prepared. The coated metal plate prepared as described above was subjected to a cross-cut using a cutter knife to reach the base material on the evaluation surface side (the surface on which the polyester-based overcoating was applied) using a cutter knife, followed by JIS-K5400. The salt spray test was conducted for 240 hours according to the method described in 9.1. After the salt spray test, the maximum blister width on one side of the cross cut was measured, and a score was given according to the following criteria. ：: One-side swelling width of less than 1 mm ：: One-side swelling width of 1 mm or more and less than 5 mm ：: One-side swelling width of 5 mm or more Also, return (burr) at the time of cutting comes to the evaluation surface side of the coated steel sheet (upper burrs). ) The salt water spray test described above was also performed on the prepared test piece, and the swollen width of the coating film from the end face was measured. A score was given based on the following criteria. ：: swelling width from end face less than 3 mm ：: swelling width from end face not less than 3 mm and less than 5 mm △: swelling width on one side not less than 5 mm The evaluation results are described in detail below.

Tables 1 to 16 show the detailed conditions of the experiment and the results of the corrosion resistance test. It can be seen that the coated metal plate using the rust preventive paint of the present invention (the one described in the remarks column of the present invention) has excellent corrosion resistance. In addition, it can be seen that they have almost the same corrosion resistance as those using strontium chromate and calcium chromate, which are known chromium-based rust preventive pigments.

[0027]

According to the present invention, it is possible to provide an environmentally friendly rust-preventive paint and a coated metal sheet excellent in corrosion resistance, which do not contain a hexavalent chromium compound.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

[0034]

[Table 7]

[0035]

[Table 8]

[0036]

[Table 9]

[0037]

[Table 10]

[0038]

[Table 11]

[0039]

[Table 12]

[0040]

[Table 13]

[0041]

[Table 14]

[0042]

[Table 15]

[0043]

[Table 16]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 22/03 C23C 22/03 C23F 11/00 C23F 11/00 B // B32B 15/08 B32B 15/08 G (72) Inventor Hiroshi Kanai 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Headquarters (72) Inventor Hiroyasu Furukawa 1st Kimitsu, Kimitsu-shi, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (72) Inventor Takashi Iijima 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Kenichiro Tadokoro 20-1 Shintomi, Futtsu-shi, Chiba Prefecture Nippon Steel Corporation Technology Development Division F term (reference) 4D075 CA33 DA06 DC01 DC18 4F100 AA04H AB01B AB17 AK36 AK41 AK51 AK53 BA02 BA03 BA04 BA05 BA06 BA07 BA10A BA10C BA10D BA10E CA14 CC00A CC00C EH46 EH462 EH71 E J42 EJ422 EJ69 EJ691 GB08 GB48 HB00D HB00E JB02 JB02A JB02C JL10D JL10E 4J038 CB001 CD021 CD091 CE071 CG141 DA091 DB001 DD001 DE001 DG001 EA011 HA426 KA08 NA03 PA07 PC02 BA02A01A23A02A23A12A12A12A BC12 BC13 BC15 FA12 GA08

Claims (3)

[Claims] 1. As a rust preventive additive, one or more of polyphosphoric acid, orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, hypophosphoric acid, phosphorous acid, and hypophosphorous acid are added in a total amount of 0.1%.
An anticorrosion paint characterized by containing 1 wt% or more. 2. A coated metal plate having excellent corrosion resistance, characterized in that it has a coating film made of the anticorrosive paint according to claim 1 on at least one surface of the metal plate. 3. The coated metal sheet having excellent corrosion resistance according to claim 2, further comprising a colored coating film as an upper layer of the coating film made of the anticorrosive paint.