JPH11319702A - Surface treated steel sheet excellent in white rust resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface treated steel sheet, of which a treatment liquid used in the manufacturing process and a product do not contain a material harmful to a human body and to be manufactured and used with no pollution and safety, and which has excellent corrosion resistance comparable to that of a chromate treated steel sheet. SOLUTION: A composition containing one or more compounds each containing at least one trihydroxybenzene structure in one molecule, preferably containing an aqueous resin at the specific ratio per the above compounds, is applied and dried on a hot dip zinc-aluminum alloy plated steel sheet to form a protective film having dried film thickness of 0.01-5 μm. As a result, excellent corrosion resistance comparable to that of a chromate treated steel sheet can be obtained by a synergistic action of the zinc-aluminum alloy plating and the above compounds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet most suitable for use in building materials, home appliances, and automobiles, which affects workers and users who handle products, measures for wastewater treatment at the time of manufacturing, and furthermore, in a use environment. Environmentally-friendly surface treatment that does not contain any heavy metals such as chromium, lead, cadmium, and mercury that are harmful to the environment and the human body in manufacturing processes and products in order to adapt to environmental issues such as volatilization and elution of harmful substances from products. It relates to a steel plate.

[0002]

2. Description of the Related Art Steel sheets for home appliances, steel sheets for building materials,
In order to improve corrosion resistance (white rust resistance and red rust resistance), the surface of galvanized steel sheet is subjected to chromate treatment with a treatment solution containing chromic acid, dichromic acid or salts thereof as a main component. Surface-treated steel sheets are widely used. This chromate treatment is an economical treatment method that can impart excellent corrosion resistance to a steel sheet and can be performed relatively easily.

[0003] However, since chromate treatment uses hexavalent chromium, which is a pollution control substance, it is difficult for chromate salts to have an adverse effect on the human body in the treatment process, and it is difficult to dispose of chromium sludge after wastewater treatment. In addition, there are various problems, for example, that hexavalent chromium may be eluted from the product after the chromate treatment. For this reason, as the use control standards for chromic acids have become stricter, the management of chromate treatment plants, wastewater treatment, and secondary contamination by chromate treatment have become a problem. In addition, measures are taken to minimize the emission of chromium ions to the outside.
In addition, in the process of degreasing the rust-preventive oil and press oil attached to the chromate-treated steel sheet by the user, when using an alkaline degreasing solution, the elution of chromium into the degreasing solution is considerably increased. Dechrome treatment is required.

[0004] In view of such circumstances, in order to prevent the generation of white rust on a zinc-based plated steel sheet, many pollution-free treatment techniques not based on chromate treatment have been proposed. For example,
There is a method of using an inorganic compound, an organic compound, an organic polymer material, or a combination thereof to form a thin film by a method such as immersion, coating, or electrolytic treatment. In particular,
The following methods are known. (1) A method using an oxide of a metal such as molybdenum or tungsten (for example, JP-A-57-5875). (2) A method using tannic acid (for example, JP-A-51-5875).
(3) A method using a surface treating agent containing a polyhydric phenol carboxylic acid and its depside (JP-A-8-325760)
(4) Pollution-free chromate treatment method comprising only trivalent chromium and not containing hexavalent chromium (for example, see JP-A-61-5).
No. 87)

[0005]

However, in the above method (1), the stable area against corrosion of metal oxides such as molybdenum and tungsten is narrower than that of chromium.
It is impossible to obtain the same level of corrosion resistance as chromate treatment. Further, in the above methods (2) and (3), even if a coating is formed on the surface of a pure galvanized steel sheet such as an electrogalvanized steel sheet or a hot-dip galvanized steel sheet by using these treatment solutions,
Sufficient corrosion resistance cannot be obtained.

[0006] Furthermore, in the above method (4), since soluble chromium is used, it cannot fundamentally meet the need for chromium-free. Therefore, the object of the present invention is to solve the problems of the prior art, do not include substances harmful to the human body in the processing solution or product used in the manufacturing process, can be manufactured and used safely and pollution-free, Moreover, it is an object of the present invention to provide a surface-treated steel sheet having excellent corrosion resistance comparable to chromate treatment.

[0007]

Means for Solving the Problems As a result of intensive studies by the present inventors to solve the above-mentioned problems, a compound having a specific chemical structure on the surface of a specific zinc-aluminum alloy plated steel sheet, specifically, By applying and drying a composition containing a compound containing at least one trihydroxybenzene structure in one molecule to form a protective film,
Even without using a chromate treatment solution that is harmful to the environment and the human body,
It has been found that a surface-treated steel sheet having no pollution and excellent corrosion resistance can be obtained.

[0008] The present invention has been made based on such findings, and the features thereof are as follows. [1] Obtained by applying and drying a composition containing at least one compound having at least one trihydroxybenzene structure in one molecule on the surface of a hot-dip zinc-aluminum alloy-plated steel sheet Protective film, 0.01 ~
A surface-treated steel sheet having excellent white rust resistance, formed with a dry film thickness of 5 μm.

[2] A composition containing one or more compounds containing at least one trihydroxybenzene structure in one molecule and an aqueous resin is applied to the surface of a hot-dip zinc-aluminum alloy-plated steel sheet. A surface-treated steel sheet having excellent white rust resistance, wherein a protective film obtained by drying is formed with a dry film thickness of 0.01 to 5 μm. [3] In the surface-treated steel sheet according to the above [2], the weight ratio of the solid content of the compound (A) containing at least one trihydroxybenzene structure in one molecule contained in the composition and the aqueous resin (B) ( A) a surface-treated steel sheet having excellent white rust resistance, wherein A) / (B) is 99/1 to 2/98.

[4] One or more compounds containing at least one trihydroxybenzene structure in one molecule, an aqueous resin, silica, and polyphosphoric acid are coated on the surface of a hot-dip zinc-aluminum alloy-plated steel sheet. One or more rust-preventive additives containing one or more selected from salts, phosphates, molybdates, phosphomolybdates, phytic acid, phytate, phosphonic acid, and phosphonate, and one molecule The weight ratio of the solid content of the compound (A) containing at least one trihydroxybenzene structure and the aqueous resin (B) (A) /
(B) is 99/1 to 2/98, and the compounding amount of the rust inhibitor is based on 100 parts by weight of the total solid content (A) + (B) of the compound (A) and the aqueous resin (B). A protective film obtained by applying and drying a composition having a solid content of 1 to 100 parts by weight in a dry film thickness of 0.01 to 5 μm and having excellent white rust resistance. Surface treated steel sheet.

[5] In the surface-treated steel sheet according to any one of the above [1] to [4], the zinc-aluminum alloy plating film is
Al: A surface-treated steel sheet excellent in white rust resistance, containing 0.3 to 53 wt%. [6] In the surface-treated steel sheet according to any of the above [1] to [4],
Zinc-aluminum alloy plating film is Al: 2-1
0 wt%, misch metal: 0-1 wt%, Mg: 0
A surface-treated steel sheet having excellent white rust resistance, characterized by comprising 1.0 wt% and the balance consisting of Zn and unavoidable impurities. [7] In the surface-treated steel sheet according to any of the above [1] to [4],
Zinc-aluminum alloy plating film is Al: 2-1
0 wt%, misch metal: 0-1 wt%, Mg: 0
A surface-treated steel sheet having excellent white rust resistance, characterized by comprising 1.0 wt%, Si: 0 to 10 wt%, and the balance consisting of Zn and unavoidable impurities.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention and the reasons for limiting the same will be described below. The surface-treated steel sheet of the present invention has a composition of a base coated steel sheet and a protective film formed on the surface thereof, each of which is conventionally known. It has been found that a synergistic effect of forming a protective film having a specific composition on the surface of the above provides a remarkable effect of improving white rust resistance which could not be expected in the past.

The surface-treated steel sheet of the present invention essentially requires the use of a hot-dip coated steel sheet having a zinc-aluminum-based alloy plating film as a base coated steel sheet. This hot-dip coated steel sheet has Al and Zn as main plating components, and the Al content in the plating film is 0.3 to 0.3%.
53 wt% is particularly preferable from the viewpoint of corrosion resistance,
Among them, those having an Al content of 2 to 10 wt% are optimal.

[0014] The Al content in the plating film is 0.3 wt%
If it is less than 3, the white rust resistance is insufficient, and if the Al content exceeds 53% by weight, the white rust resistance decreases. This is because, in the surface-treated steel sheet of the present invention, excellent white rust resistance can be obtained by the synergistic action of the plating film component and the compound containing at least one trihydroxybenzene structure in one molecule existing in the upper layer. This is considered to be because there is an optimum concentration of Al necessary for obtaining excellent white rust resistance.

Further, as will be shown in Examples described later, the effect of the present invention can be obtained when a hot-dip zinc-aluminum alloy coated steel sheet having an Al content of 2 to 10% by weight in a plating film is used as an undercoated steel sheet. The most remarkable and the most excellent white rust resistance is obtained. When the Al content is 2 to 1
In a 0 wt% plating film, a misch metal may be added for the purpose of improving plating wettability, and Mg may be added for the purpose of improving corrosion resistance and suppressing intergranular corrosion. The film is A
l: 2 to 10 wt%, misch metal: 0 to 1 wt%
(Including the case of no addition), Mg: 0 to 1.0 wt
% (Including the case of no addition), with the balance being Zn and unavoidable impurities.

Further, in order to improve the adhesion at the interface between the plating layer and the steel sheet substrate, Si is added to the plating film in an amount of 0 to 10%.
wt% (including the case of no addition) may be added.
Inevitable impurities in the plating film include Pb and the like. The adhesion amount of the zinc-aluminum-based alloy plating film is appropriately selected depending on the use and purpose of use of the plated steel sheet. For example, the adhesion amount per side is 30 g / m ² , 6
Can be a ^{0g / m 2, 90g / m} 2, 120g / m 2 about each level, there is no particular limitation on the adhesion amount. However, 30 to 120 g per side from the viewpoint of corrosion resistance etc.
/ M ² .

Further, the zinc-aluminum alloy plating film may have a multilayer structure composed of two or more plating layers having different compositions. Also, as a plated steel sheet,
A thin metal plating may be applied between the zinc-aluminum alloy plating film and the base steel sheet. Further, as a plated steel sheet, for the purpose of preventing blackening of the zinc-aluminum-based alloy plating film surface, a known chemical displacement plating of Co, Ni, or the like is performed on the plating film, or Co, Ni, Fe Or the like may be obtained by spraying an aqueous solution of a metal salt onto a plating surface in a molten state immediately after plating.

A composition containing one or more compounds containing at least one trihydroxybenzene structure in one molecule is provided on the surface of the above-described hot-dip zinc-aluminum alloy plated steel sheet as a base. Is applied and dried to form a protective film obtained.

The compound containing at least one trihydroxybenzene structure in one molecule includes tannin, tannic acid, gallic acid and esters thereof (for example, 3,
4,5-trihydroxybenzoic acid, methyl gallate, propyl gallate, lauryl gallate, stearyl gallate and the like, pyrogallol and pyrogallol derivatives (for example, 1,2,3-hydroxybenzene, 2,3,4-trihydroxy Benzophenol, 2,3,4,4'-tetrahydroxybenzophenol and the like can be used.

By forming a protective film containing these compounds on the surface of the above-mentioned specific plating film, excellent white rust resistance is obtained because a plurality of OH groups contained in one molecule of these compounds are present on the plating surface. It is because hydrogen bonding with hydrogen provides excellent adhesion, and furthermore, when the composition is applied, the plating metal is eluted to become ions, forming a stable and dense complex with OH groups and carboxyl groups. Conceivable.

The greatest feature of the present invention is that excellent corrosion resistance (white rust resistance) is obtained by the synergistic action of the specific zinc-aluminum alloy plating and the specific compound having chelating ability. However, even if a protective film of the above compound is formed on the surface of a pure galvanized steel sheet such as electrogalvanized or hot-dip galvanized, the same performance cannot be obtained at all. Although the anticorrosion mechanism of the surface-treated steel sheet of the present invention is not always clear, both zinc (divalent) and aluminum (trivalent) are taken into the protective film and ionic cross-links are formed by bonding with OH groups and carboxyl groups. And
The formation of a denser film having a higher barrier property than zinc (divalent) alone is considered to be one of the reasons why excellent corrosion resistance is obtained.

In the present invention, in order to further enhance the barrier properties of the film, it is preferable to further blend an aqueous resin into the composition constituting the protective film. As the aqueous resin, for example, the following can be used. (1) Acrylic resin For example, polyacrylic acid and its copolymer, polyacrylic acid ester and its copolymer, polymethacrylic acid ester and its copolymer, polymethacrylic acid ester and its copolymer, urethane-acryl Acid copolymers (or urethane-modified acrylic resins), styrene-acrylic acid copolymers, and the like, and resins obtained by modifying these resins with other alkyd resins, epoxy resins, phenol resins, and the like can be used.

(2) Ethylene resin (polyolefin resin) For example, ethylene copolymers such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer and carboxyl-modified polyolefin resin, ethylene-unsaturated carboxylic acid copolymer For example, a resin obtained by modifying these resins with another alkyd resin, an epoxy resin, a phenol resin, or the like can be used.

(3) Alkyd resin For example, oil-modified alkyd resin, rosin-modified alkyd resin, phenol-modified alkyd resin, styrenated alkyd resin, silicon-modified alkyd resin, acrylic-modified alkyd resin, oil-free alkyd resin, high-molecular-weight oil-free alkyd Resin or the like can be used.

(4) Epoxy resin For example, straight epoxy resin such as epichlorohydrin type, glycidyl ether type, etc., fatty acid modified epoxy resin (epoxy ester resin), polybasic acid modified epoxy resin, acrylic resin modified epoxy resin, alkyd (or polyester) ) Modified epoxy resins, polybutadiene-modified epoxy resins, phenol-modified epoxy resins, amine or polyamine-modified epoxy resins, urethane-modified epoxy resins, and the like can be used. (5) Urethane resin For example, a polycarbonate-based polyurethane resin, a polyester-based polyurethane resin, a polyether-based urethane resin, or the like can be used.

In addition, 2 selected from the above aqueous resins
Two or more types of aqueous resins may be mixed and used. Further, for the purpose of lowering the drying temperature of the film, a core-shell type water-dispersible resin in which the core portion and the shell portion of the resin particles are formed of different resin types or resins having different glass transition temperatures can be used. Further, by providing an alkoxysilane group to a water-dispersible resin having a self-crosslinking property, for example, resin particles, a silanol group is generated by hydrolysis of the alkoxysilane during heating and drying of the film, and dehydration of the silanol group between the resin particles. A water-dispersible resin in which cross-linking between particles utilizing a condensation reaction is generated can also be used.

When the compound having at least one trihydroxybenzene structure in one molecule contains an anionic functional group, considering the stability of the coating when mixed with an aqueous resin, the above-mentioned aqueous resin Among them, it is particularly preferable to use a water-dispersible resin in which the ionicity of the particles is nonionic or cationic. Furthermore, in addition to these water-based resins, water-soluble epoxy resins, water-soluble phenolic resins,
Water-soluble butadiene rubber (SBR, NBR, MBR),
It is effective to use one or more of a melamine resin, a blocked isocyanate, an oxazoline compound and the like as a crosslinking agent.

The weight ratio (A) / (B) of the solid content of the compound (A) containing at least one trihydroxybenzene structure in one molecule and the aqueous resin (B) is 99/1.
To 2/98. If the amount of the aqueous resin (B) exceeds the above range, the white rust resistance is remarkably reduced. on the other hand,
If the amount of the aqueous resin (B) is less than the above range, the effect of improving the barrier property cannot be sufficiently obtained. From such a viewpoint, a particularly preferable weight ratio (A) / (B) is 30.
/ 70 to 10/90.

In the composition constituting the protective film, silica, polyphosphate, phosphate, molybdate, phosphomolybdate, phytic acid, phytic acid may be used, if necessary, to further enhance the anticorrosion effect. One or more rust-preventive additives selected from acid salts, phosphonic acids, and phosphonates can be blended.

As the silica, either colloidal silica or fumed silica may be used. Examples of the colloidal silica include Snowtex O, Snowtex N, Snowtex 20, Snowtex 30,
Snowtex 40, Snowtex C, Snowtex S (all manufactured by Nissan Chemical Industries, Ltd.) and the like can be used. Also, as a fume dredica, for example, A
EROSIL R971, AEROSIL R812, A
EROSIL R811, AEROSIL R974, A
EROSIL R202, AEROSIL R805, A
EROSIL130, AEROSIL 200, AER
OSIL 300, AEROSIL 300CF (or more,
Nippon Aerosil Co., Ltd.) can be used.

The silica added to the protective coating contributes to the formation of dense and stable metal corrosion products in a corrosive environment,
It is considered that this corrosion product is formed densely on the plating surface, thereby suppressing the promotion of corrosion. In addition, as a rust preventive additive other than silica, known polyphosphates (for example, aluminum polyphosphate: Teika K-WHITE)
80, Takeka K-WHITE 84, Takeka K-WHI
TE 105, Teika K-WHITE G105, Teika K-WHITE 90 (all manufactured by Teika Co., Ltd.), phosphates (eg, zinc phosphate, aluminum dihydrogen phosphate, zinc phosphite, etc.), molybdate Salt, phosphomolybdate (eg, aluminum phosphomolybdate), phytic acid, phytate, phosphonic acid, phosphonate, and the like can also be used.

The compounding amount of the rust preventive additive is determined according to the above compound (A)
And 100 to 100 parts by weight of the total solid content (A) + (B) of the water-based resin (B) and 1 to 100 parts by weight of the solid content.
If the amount of the rust-preventive additive is less than 1 part by weight, the effect of improving corrosion resistance is not sufficient, while if the amount exceeds 100 parts by weight, paint adhesion is reduced, and corrosion factors are protected by aggregation of pigments. It is not preferable because the film easily penetrates the film and the corrosion resistance is reduced. From the viewpoints described above, the more preferable amount of the rust preventive additive is 5 to 80 parts by weight. In addition to the above, a metal or metal ion may be added to the composition constituting the protective film for the purpose of densifying the film. For example, Ni, Co, Cr (metal), Al, Mo, etc. are added. be able to.

If necessary, a solid lubricant may be added to the composition constituting the protective film for the purpose of improving the processability of the film. As this solid lubricant,
Hydrocarbon compounds such as polyolefin wax (eg, polyethylene wax, synthetic paraffin, natural paraffin, microwax, chlorinated hydrocarbons, etc.), fluororesin compounds (eg, polyfluoroethylene resin (polytetrafluoroethylene resin, etc.) , Polyvinyl fluoride resin, polyvinylidene fluoride resin, etc.), fatty acid amide type compounds (for example, stearic acid amide, palmitic acid amide, methylene bis stearamide, ethylene bis stearoamide, oleic acid amide, esylamide, alkylene bis) Fatty acid amides), metal soaps (eg, calcium stearate, lead stearate, calcium laurate, calcium palmitate, etc.), metal sulfides (eg, molybdenum disulfide, tungsten disulfide, etc.), graphite, fluoride Lead, boron nitride, polyalkylene glycols, want to use the alkali metal sulfates.

Among the above solid lubricants, polyethylene wax, fluororesin compounds (among others, poly-4
Fluorinated ethylene resin fine particles) are preferred. Examples of the polyethylene wax include Seridust 9615A, Seridust 3715, and Seridust 36 manufactured by Hoechst.
20, Celidust 3910, Sunwax 131-P, Sunwax 161-P, manufactured by Sanyo Chemical Co., Ltd., Chemipearl W-100, Chemipearl W-200, Chemipearl W-500, Chemipearl W-500, Chemipearl manufactured by Mitsui Petrochemical Co., Ltd.
W-800, Chemipearl W-950 and the like can be used.

As the fluororesin-based compound, fine particles of tetrafluoroethylene are suitable. For example, Lubron L-2 and Lubron L-5 manufactured by Daikin Industries, Ltd., MP1100 and MP1200 manufactured by DuPont Mitsui, and Asahi IC Co., Ltd. Fluon Dispersion AD1, Fluon Dispersion AD2 manufactured by iFluoropolymers Co., Ltd.
Fullon L140J, Fullon L150J, Fullon L155J and the like can be used.

[0036] Of these solid lubricants, a particularly excellent lubricating effect can be expected by adding a polyolefin wax and tetrafluoroethylene in combination. The compounding amount of the solid lubricant is 1 to 40 parts by weight in terms of the solid content based on 100 parts by weight of the total solid content (A) + (B) of the compound (A) and the aqueous resin (B). If the amount of the solid lubricant is less than 1 part by weight, the lubricating effect is poor.
If it exceeds 40 parts by weight, the adhesion of the paint will be reduced. From the viewpoints described above, the more preferable compounding amount of the solid lubricant is 3 to 3
0 parts by weight.

Further, in the composition constituting the protective film, other additives such as a coloring dye (for example, a water-soluble azo metal complex dye) and an organic coloring pigment (for example, a condensed polycyclic organic pigment, Phthalocyanine-based organic pigments, etc.), inorganic pigments (eg, titanium oxide, etc.), chelating agents (eg, thiol, etc.), conductive pigments (eg, zinc, aluminum,
Metal powders such as nickel, iron phosphide, antimony-doped tin oxide, etc., coupling agents (eg, silane coupling agents, titanium coupling agents, etc.), melamine / cyanuric acid adducts and the like can be added.

The surface-treated steel sheet of the present invention can be applied to the surface of a hot-dip zinc-aluminum alloy-plated steel sheet, if necessary, to smooth the plating surface, control spangles, prevent blackening, improve corrosion resistance, improve workability, and improve adhesion. Upper layer plating, mist treatment, dissolution treatment, weak acid or alkali activation treatment (may contain metal ions such as Ni and Co),
After one or more treatments such as surface polishing, a composition containing at least one compound having a trihydroxybenzene structure in one molecule is applied without performing a chromate treatment, and dried. To be obtained.

The thickness of the protective film after drying is 0.01 to 5 μm.
m. If the thickness of the protective film is less than 0.01 μm, the corrosion resistance is insufficient, while in applications requiring weldability,
If the thickness exceeds 5 μm, weldability becomes impossible. In addition, from the viewpoints described above, the more preferable thickness of the protective film is 0.1 to
3 μm. Usually, the applied composition is dried without washing with water, but may be dried after washing with water in some cases.

As a method for applying the composition, any method such as a coating method, a dipping method, and a spraying method can be adopted. As a coating method, any method such as a roll coater (three-roll system, two-roll system, etc.), a squeeze coater, a die coater, and the like may be used. In addition, after the coating, dipping, or spraying with a squeeze coater or the like, it is also possible to adjust the coating amount, uniform the appearance, and uniform the film thickness by an air knife method or a roll drawing method.

In the heating and drying treatment, a dryer, a hot air oven,
A high-frequency induction heating furnace, an infrared furnace, or the like can be used.
The heat treatment is performed at a plate temperature of 50 to 300 ° C., preferably 8 ° C.
It is desirable to carry out in the range of 0 ° C to 250 ° C. If the heating temperature is lower than 50 ° C., a large amount of water in the film remains, and the corrosion resistance becomes insufficient. On the other hand, if the heating temperature exceeds 300 ° C., it is not only uneconomical, but also there is a possibility that a defect occurs in the film and the corrosion resistance is reduced.

The present invention includes a steel sheet having the above-described protective film on both sides or one side. Therefore, examples of the form of the steel sheet of the present invention include the following. (1) One side: Plating film-Protective film, One side: Plating film (2) Both surfaces: Plating film-Protective film

[0043]

EXAMPLES As surface-treated steel sheets for home appliances, building materials and automobile parts, the surfaces of various plated steel sheets were subjected to alkali degreasing treatment, washed and dried, and then a composition for a protective film was applied by a roll coater and dried by heating. . The thickness of the protective film was adjusted according to the solid content concentration of the coating composition or the application conditions (rolling force of a roll of a roll coater, rotation speed, etc.).
About the obtained surface-treated steel sheet, evaluation of the film appearance and each evaluation test of corrosion resistance (white rust resistance), paint adhesion, and workability were performed. The results are shown in Tables 7 to 27 together with the type of the plated steel sheet used, the composition of the protective film, the film thickness, and the drying temperature.

The conditions for producing the surface-treated steel sheet in this embodiment are shown below. (1) Plated steel plate A cold-rolled steel plate having a thickness of 0.8 mm was subjected to various platings and used as a base-plated steel plate. Table 1 shows the used plated steel sheets. (2) Composition for protective film The compounds shown in Table 2 and the aqueous resin shown in Table 3 were mixed, and if necessary, added with the rust-preventive additives shown in Tables 4 and 5;
Was added and dispersed for a required time using a paint dispersing machine (sand grinder) to obtain a desired composition.

The quality performance of the obtained surface-treated steel sheet was evaluated as follows. (1) Appearance of Film For each sample, the uniformity of the film appearance (with or without unevenness) was visually evaluated. The evaluation criteria are as follows. ：: uniform appearance without any unevenness △: appearance with some unevenness ×: appearance with unevenness

(2) Corrosion resistance (white rust resistance) For each sample, a salt spray test (JIS-Z-23)
71) was carried out, and evaluated by the area ratio of white rust occurrence after a predetermined time. In addition, the surface-treated steel sheet formed with the coating without the water-based resin and the rust-preventive additive, the surface-treated steel sheet formed with the coating without the water-based resin and the rust-preventive additive, and the film with the water-based resin and the rust-preventive additive added. The formed surface-treated steel sheet originally has a difference in white rust resistance, and no significant difference in white rust resistance appears in the same test time. The white rust resistance after time was evaluated, and the white rust resistance after 72 hours was evaluated for the above. The evaluation criteria are as follows. ◎: No white rust generated ○ +: White rust generated area rate less than 5% ○: White rust generated area rate 5% or more and less than 10% △: White rust generated area rate 10% or more and less than 50% ×: White rust generated Area ratio 50% or more

(3) Adhesiveness of paint For each sample, a melamine baking paint (film thickness 30
μm), immersed in boiling water for 2 hours, cut immediately into a grid (10 × 10 grids at 1 mm intervals), and adhered / peeled off an adhesive tape. Rate was evaluated. The evaluation criteria are as follows. ：: No peeling ○: Peeling area rate less than 5% △: Peeling area rate 5% or more, less than 20% ×: Peeling area rate 20% or more

(4) Workability Deep drawing was performed with a blank diameter of φ120 mm and a die diameter of φ50 mm (under no oiling conditions), and evaluated by the molding height until cracking occurred. The evaluation criteria are as follows. ◎: Draw-out ○: Molding height 30 mm or more △: Molding height 20 mm or more, less than 30 mm ×: Molding height less than 20 mm

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

[Table 5]

[0054]

[Table 6]

[0055]

[Table 7]

[0056]

[Table 8]

[0057]

[Table 9]

[0058]

[Table 10]

[0059]

[Table 11]

[0060]

[Table 12]

[0061]

[Table 13]

[0062]

[Table 14]

[0063]

[Table 15]

[0064]

[Table 16]

[0065]

[Table 17]

[0066]

[Table 18]

[0067]

[Table 19]

[0068]

[Table 20]

[0069]

[Table 21]

[0070]

[Table 22]

[0071]

[Table 23]

[0072]

[Table 24]

[0073]

[Table 25]

[0074]

[Table 26]

[0075]

[Table 27]

Apart from the examples shown in Tables 7 to 27, as a comparative example, a hot-dip galvanized steel sheet (with a coating weight of 90 g
/ M ² ) with a chromate treatment solution (“Zinchrome 3360H” manufactured by Nippon Parkerizing Co., Ltd.)
After drying, a surface-treated steel sheet having a chromate film having a Cr adhesion amount of 20 mg / m ² was produced. For this surface-treated steel sheet, the salt spray test (JIS-Z) shown in (2) above
-2371) for 24 hours, no white rust was generated (evaluation of the above (2): ◎).

In the examples shown in Tables 7 to 27, the composition was such that the surface of a hot-dip galvanized steel sheet (coating weight: 90 g / m ² ) contained at least one compound having a trihydroxybenzene structure in one molecule. The surface-treated steel sheet (No. 15 in Table 7) of the comparative example, in which a coating (film thickness: 1.0 μm) was formed by a material (does not contain hexavalent Cr), showed white rust after the salt spray test was performed for 24 hours. The area ratio was 10% or more, and sufficient white rust resistance was not obtained.

On the other hand, a composition containing at least one compound having at least one trihydroxybenzene structure in one molecule (having no hexavalent Cr) on the surface of a hot-dip Zn—Al alloy-plated steel sheet. Film (film thickness 1.0μm)
Formed surface-treated steel sheet of the present invention example (No. 1 to N in Table 7)
o. 14) has good white rust resistance. Among these, improvement of white rust resistance was observed even when the Al concentration in the Zn—Al alloy plating film was 0.3 wt% (No. 1 in Table 7), and the Al concentration in the Zn—Al alloy plating film was improved. Is 1 wt% (No. 2 in Table 7), white rust resistance is further improved, and in particular, A in the Zn—Al alloy plating film
l concentration is 2 to 10 wt% (No. 3 to No. 5,
No. 9-No. In 14), excellent white rust resistance comparable to the above-mentioned chromate-treated plated steel sheet was obtained.

On the other hand, Al in the Zn—Al alloy plating film
When the concentration is 20 wt% (No. 6 in Table 7), the white rust resistance is lower than when the Al concentration is 2 to 10 wt%,
Al concentration is 53 wt% or more (No. 7, No. 7 in Table 7).
In 8), the area ratio of white rust occurrence is 5% or more and less than 10%. From the above results, it can be seen that the effect of the present invention is most remarkable when the Al concentration in the Zn—Al alloy plating film is 3 to 10% by weight, and the most excellent white rust resistance is obtained.

[0080]

As described above, the surface-treated steel sheet of the present invention does not contain any hexavalent chromium in the processing solution or the coating composition of the product at the time of manufacture, and furthermore, the surface treatment for applications such as building materials, home appliances and automobiles. It has high corrosion resistance as a steel sheet,
Excellent paint adhesion.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaru Sagiyama 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (7)

[Claims] 1. A composition containing at least one compound having at least one trihydroxybenzene structure in one molecule is applied to the surface of a hot-dip zinc-aluminum alloy-plated steel sheet and dried. The resulting protective film
A surface-treated steel sheet having excellent white rust resistance, which is formed with a dry film thickness of 0.01 to 5 μm. 2. A composition containing one or more compounds having at least one trihydroxybenzene structure in one molecule and an aqueous resin is applied to the surface of a hot-dip zinc-aluminum alloy plated steel sheet. A surface-treated steel sheet having excellent white rust resistance, wherein a protective film obtained by drying is formed with a dry film thickness of 0.01 to 5 μm. 3. The weight ratio (A) / solid content of the compound (A) containing at least one trihydroxybenzene structure in one molecule contained in the composition and the aqueous resin (B).
The surface-treated steel sheet having excellent white rust resistance according to claim 2, wherein (B) is from 99/1 to 2/98. 4. One or more compounds containing at least one trihydroxybenzene structure per molecule on the surface of a hot-dip zinc-aluminum alloy plated steel sheet;
Aqueous resin and one or more rust preventives selected from silica, polyphosphate, phosphate, molybdate, phosphomolybdate, phytic acid, phytate, phosphonic acid, phosphonate The weight ratio (A) / of the solid content of the compound (A) containing an additive and containing at least one trihydroxybenzene structure in one molecule to the aqueous resin (B) /
(B) is 99/1 to 2/98, and the compounding amount of the rust inhibitor is based on 100 parts by weight of the total solid content (A) + (B) of the compound (A) and the aqueous resin (B). A protective film obtained by applying and drying a composition having a solid content of 1 to 100 parts by weight in a dry film thickness of 0.01 to 5 μm and having excellent white rust resistance. Surface treated steel sheet. 5. The surface excellent in white rust resistance according to claim 1, wherein the zinc-aluminum alloy plating film contains Al: 0.3 to 53 wt%. Treated steel sheet. 6. A zinc-aluminum alloy plating film comprising: Al: 2 to 10 wt%, misch metal: 0 to 1 w
4. The composition according to claim 1, wherein the content of Mg is 0 to 1.0 wt%, and the balance is made of Zn and unavoidable impurities.
Or a surface-treated steel sheet excellent in white rust resistance according to 4. 7. A zinc-aluminum alloy plating film comprising: Al: 2 to 10 wt%, misch metal: 0 to 1 w
t%, Mg: 0 to 1.0 wt%, Si: 0 to 10 wt%
5. The surface-treated steel sheet having excellent white rust resistance according to claim 1, wherein the balance consists of Zn and inevitable impurities. 5.