JP2000063707A - Anticorrosive coating for steel sheet coated with zinc- based coating and anticorrosive treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive non-chromium anticorrosive coating having more excellent corrosion resistance than that of a chromium-containing anticorrosive agent, and to provide a method for an anticorrosive treatment. SOLUTION: This anticorrosive coating contains one or more kinds of compounds selected from thiosulfate salt compounds and persulfate salt compounds in a total amount of 0.1-20 g per liter of a composition containing an aqueous resin and water as main components. The anticorrosive agent further preferably contains 0.1-5 g of phosphate ions. The method for the anticorrosive treatment comprises coating the above coating on a steel sheet coated a zinc- based coating or on a non-coated steel sheet. An anticorrosive metal is coated with the above anticorrosive coating.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface treatment composition and a surface treatment method for metal materials, particularly galvanized steel sheets, and provides a rust preventive agent which imparts sufficient corrosion resistance to metal materials.

[0002]

2. Description of the Related Art Galvanized steel sheets and alloyed galvanized steel sheets have white rust on the surface and significantly impair their appearance in an atmosphere containing salt such as seawater or in a hot and humid atmosphere.
The anticorrosiveness against the base iron surface may be reduced.

To prevent the occurrence of white rust, a chromate-based rust preventive treatment agent has been frequently used, for example, Japanese Patent Laid-Open No. 3-13.
Japanese Patent No. 1370 discloses a resin-based treatment agent in which an olefin-α, β-ethylenically unsaturated carboxylic acid copolymer resin dispersion contains a water-dispersible chromium compound and water-dispersible silica.

However, even the above chromium-containing resin type treating agents are not necessarily sufficient in corrosion resistance, and white rust occurs when exposed to salt water or a hot and humid atmosphere for a long time. In recent years, there has been an increasing demand for chromium-free anticorrosive treatment agents.

The present inventors have found that sulfide ions react with zinc to form a stable ZnS film, and already disclosed in JP-A-8-239776 and JP-A-8-67834. Discloses a chrome-free rust preventive treatment agent.

However, some sulfides give off a peculiar odor, and they have not always been easy to handle.

Further, a rust preventive agent using a triazine thiol compound containing a sulfur atom and having neither odor nor toxicity has been proposed. For example, Japanese Patent Application Laid-Open No. 53-31737 discloses "water-soluble anticorrosive paint" which discloses a water-soluble anticorrosive paint containing a dithiol-S-triazine derivative.

Further, in "Reactive Emulsion with Metal" of JP-A-61-223062, a reaction of a compound containing a thiocarbonyl group with a metal obtained by mixing a poorly soluble or insoluble organic compound in water Aqueous emulsions are disclosed.

However, the above-mentioned Japanese Patent Laid-Open No. 53-3173.
The water-soluble anticorrosive paint disclosed in Japanese Patent No. 7 is intended for anticorrosion of mild steel, copper, brass, copper wire, etc., and is particularly prepared so that the base material is more easily adhered to copper or brass. There is. Therefore, it is insufficient as a rust preventive for the surface of metals such as zinc.

The reactive emulsion disclosed in JP-A-61-223062 also includes copper, nickel,
Since it is an emulsion that reacts with tin, cobalt, aluminum and the like and its alloys, it was insufficient as a rust preventive for the surface of metals such as zinc.

The present inventors have studied a triazine thiol-containing rust-preventive coating agent effective for rust prevention of zinc-based plated steel sheets, and disclosed the triazine thiol-containing rust-preventive coating agent described in Japanese Patent Application No. 9-2557. . However, triazine thiol is an expensive compound, and a cheaper anticorrosive agent has been desired.

As a surface treatment method for zinc or zinc alloy containing no chromium and using no triazine thiol,
JP-A-54-71734 and JP-A-3-226584
The gazette is mentioned. Japanese Unexamined Patent Publication No. 54-71734 discloses that myo-inositol has 2 to 6 bound phosphoric acid esters or salts thereof in an amount of 0.5 to 100 g / l and one selected from the group consisting of titanium fluoride and zirconium fluoride. A zinc or zinc alloy, characterized in that surface treatment of zinc or a zinc alloy is carried out with an aqueous solution containing 0.5 to 30 g / l in terms of metal and 1 to 50 g / l of thiourea or its derivative. It is a surface treatment method. This technique requires titanium fluoride or zirconium fluoride to form a passivation film as a protective layer on the zinc surface. In addition, JP-A-3-226
No. 584 discloses one or two of Ni ²⁺ and Co ²⁺ .
Disclosed is a surface treatment agent which is an aqueous solution having a pH of 5 to 10 containing 02 g / l or more and one or two kinds of a compound having ammonia and a primary amine group. This requires Ni ²⁺ and / or Co ²⁺ to provide paint adhesion and post-paint corrosion resistance by precipitation of cobalt or nickel. As described above, the treatment agent containing metal ions has a disadvantage that the load at the time of wastewater treatment increases.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an inexpensive and non-chromium zinc or zinc alloy plated steel sheet having corrosion resistance equal to or higher than that of a chromium-containing rust preventive agent. It is to provide an anticorrosion coating agent and an antirust treatment method. Another object of the present invention is to provide a rust-preventive metal material which is rust-proofed with a chromium-free rust preventive agent and has excellent corrosion resistance.

[0014]

In order to achieve the above-mentioned object, the anticorrosive coating agent according to the present invention comprises a thiosulfate compound and a peroxide compound in 1 liter of a composition containing an aqueous resin and water as main components. It contains 0.1 to 20 g in total of one or more compounds selected from sulfate compounds. Further, the anticorrosive coating agent according to the present invention contains 0.1 liters of one or more compounds selected from thiosulfate compounds and persulfate compounds in a total amount of 0.1 liter in 1 liter of a composition containing an aqueous resin and water as main components. .About.20 g and 0.1 to 5 g of phosphate ion.

Further, the rustproofing method according to the present invention is a method of coating zinc-based coated steel or uncoated steel with the above rustproofing coating agent. Furthermore, the antirust treated metal according to the present invention is a metal coated with the above antirust coating agent.

Generally, in order to be effective as a rust preventive coating agent, (1) prevent penetration of a corrosive liquid,
(2) Adhesion of the rust preventive film to the metal substrate, (3) Improving the passivation of the metal surface by rust preventive ions, etc. (4)
It is necessary to satisfy the requirements that the anticorrosive film has water resistance, acid resistance, alkali resistance, and the like. If any of these is insufficient, the rust preventive property cannot be exhibited. Chromium compounds, which are conventional rust preventives, are mainly excellent in passivation of (3).
Here, passivation means that a metal or an alloy is in a state of retaining its inactivity, even though it is in an environment in which it is chemically or electrochemically activated.

It is known that sulfides, like chromic acid, are easily adsorbed on the metal surface and have an excellent oxidizing ability, so that the metal surface can be passivated.
The reason why good corrosion resistance can be obtained by applying the aqueous resin solution containing the thiosulfate compound and / or the persulfate compound of the present invention to the galvanized surface is not necessarily clear, but zinc is the aqueous solution. It is considered that a zinc thiosulfate and / or zinc persulfate film is formed on the galvanized surface by contact with, and these films are converted into a stable compound film close to zinc sulfide during heating and drying.

In addition, zinc thiosulfate and zinc persulfate, which are the above-mentioned sulfur compounds, are more stable because the formed film becomes a composite film with zinc phosphate when phosphate ions are present in the aqueous solution. It is presumed that the sex is increasing. That is, (1) a thiosulfate compound or a persulfate compound is not adsorbed on an inactive zinc surface site (for example, an oxide surface), but phosphoric acid is not adsorbed on such an inactive surface. The ions act to form zinc phosphate, which forms the active surface. Since the thiosulfate compound and / or the persulfate compound are adsorbed on the activated surface in this way, it is presumed that the rust preventive effect is exerted on the entire surface of zinc. Also, (2) thiosulfate compounds and persulfate compounds,
The phosphate ion also acts as a crosslinking accelerator for the resin film. It is presumed that the synergistic action of the two can reduce the micropores of the resin film and efficiently block harmful ions such as water and chlorine ions.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
First, the thiosulfate compound and / or persulfate compound-based anticorrosive coating agent according to the present invention will be described in detail.
The thiosulfate compound that can be used in the present invention may be any thiosulfate, and specific examples thereof include ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, barium thiosulfate, calcium thiosulfate and magnesium thiosulfate. can do. Ammonium thiosulfate is preferred.

The persulfate compound that can be used in the present invention may be any persulfate, and specifically, ammonium persulfate, sodium persulfate, potassium persulfate,
Examples thereof include magnesium persulfate and calcium persulfate. Ammonium persulfate is preferred. Of the above-mentioned thiosulfate compounds and persulfate compounds, those which are not directly dissolved in water can be blended in the anticorrosive coating agent after once dissolved in an alkaline solution.

The anticorrosive coating agent of the present invention contains an aqueous resin. In the present invention, the aqueous resin includes, in addition to the water-soluble resin, those that are essentially water-insoluble but are in a state in which the insoluble resin is finely dispersed in water, such as an emulsion and a suspension. Examples of resins that can be used as such aqueous resins include polyolefin resins, polyurethane resins, acrylic resins, polycarbonate resins, epoxy resins, polyester resins, alkyd resins, phenol resins, and other heat-curable resins. The resin and the like can be exemplified, and a crosslinkable resin is more preferable. Particularly preferred resins are polyolefin resins, polyurethane resins, and mixed resin systems of both. You may use the said aqueous resin in mixture of 2 or more types.

The anticorrosive coating agent according to the present invention comprises an aqueous resin (including a water-soluble resin and a water-dispersible resin) in a solid content of 1%.
.About.80 parts by weight, 99 to 20 parts by weight of water, 0.1 to 20 g of one or more compounds selected from thiosulfate compounds and / or persulfate compounds in 1 liter of the total amount of the aqueous resin and water, It is preferably 0.5 to 15 g, particularly preferably 1.0 to 10 g, and when it contains a phosphate ion,
0.1 to 5 g of phosphate ion, preferably 0.5 to 4.0 g
It is contained and the pH is adjusted to the range of 3-12. Here, if the total amount of the thiosulfate compound and / or the persulfate compound is 0.1 g / l or less, sufficient corrosion resistance cannot be obtained, while if it exceeds 20 g / l, the corrosion resistance decreases.

The rust preventive coating agent of the present invention preferably contains phosphate ions. Phosphate ions form a phosphate layer on the surface of the metal substrate to passivate it, accelerate the cross-linking reaction of the resin film derived from the water-based resin, and form a dense rust-preventive film. Further improve. The content of phosphate ion is 1
0.1-5 g per liter, preferably 0.25-4.0
g, more preferably 0.5 to 3.0 g. When the content of phosphate ion is less than 0.1 g / l, the effect of adding phosphate ion is not sufficiently exerted, while when it exceeds 5 g / l, the rust preventive property is deteriorated or the resin is gelled. As a result, the storage stability of the anticorrosive coating agent as a product deteriorates.

The phosphate ion that can be used in the present invention means phosphate ion, phosphite ion and hypophosphite ion. In order to allow such a phosphate ion to exist in the anticorrosive coating agent, any compound can be used in the present invention as long as it is a compound capable of releasing the phosphate ion in the anticorrosive coating agent. it can. Examples of such compounds include the following: phosphoric acid; 3 ammonium phosphate, 2 hydrogen phosphate
Ammonium, ammonium salts of phosphoric acid such as ammonium dihydrogen phosphate; alkali metal salts of phosphoric acid such as trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and potassium potassium phosphate; zinc phosphate, phosphoric acid Alkaline earth metal salts of phosphoric acid such as potassium and magnesium phosphate; iron phosphate; manganese phosphate; phosphomolbudenic acid; phosphorous acid; ammonium phosphite; sodium phosphite, potassium phosphite and other phosphites Alkali metal salts of; hypophosphorous acid; ammonium hypophosphite; alkali metal salts of hypophosphorous acid such as sodium hypophosphite and potassium hypophosphite.

Further, a rust preventive additive may be added to the rust preventive coating agent according to the present invention. Examples of the rust preventive additive include water dispersible silica and the like.

By adding water-dispersible silica to the anticorrosive coating agent according to the present invention, it is possible to improve the drying property, scratch resistance and coating film adhesion. The water-dispersible silica is not particularly limited as long as it contains few impurities such as sodium and is weakly alkaline. For example, "Snowtex N" (manufactured by Nissan Chemical Industries, Ltd.), "Adelite AT-
20N "(manufactured by Asahi Denka Kogyo Co., Ltd.) or the like, or commercially available Aerosil powder silica particles or the like can be used. The content of the water-dispersible silica is preferably 2 to 600 g in 1 liter of the anticorrosive coating agent. If the content of water-dispersible silica is less than 2 g,
The rust preventive effect is not sufficiently exerted, while when it exceeds 600 g / l, the rust preventive property is deteriorated.

Further, the rust preventive coating agent according to the present invention may further contain other components. Examples of such components include pigments and surfactants. Further, in order to improve the affinity between the aqueous resin and the silica particles and the pigment, and further improve the adhesion between the aqueous resin and the phosphorous oxide layer of zinc or iron, a silane coupling agent may be added. . Examples of the pigment include titanium oxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO), calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), alumina (Al ₂ O ₃ ), kaolin clay, Carbon black, iron oxide (Fe ₂ O ₃ , Fe ₃
Inorganic pigments such as O ₄ ) and various colored pigments such as organic pigments can be used.

Examples of the silane coupling agent include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane and N- [ 2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane and the like can be mentioned.

A solvent may be used in the rust-preventive coating agent according to the present invention in order to improve the film-forming property of the aqueous resin and form a more uniform and smooth coating film. The solvent is not particularly limited as long as it is commonly used in paints, and examples thereof include alcohol-based, ketone-based, ester-based and ether-based solvents.

In the present invention, the above rust-preventive coating agent can be used as a rust-preventive coating agent for zinc-coated steel or uncoated steel to prevent rust-prevention of zinc-coated steel or uncoated steel. The rust-preventing treatment may be a method of applying the rust-preventive coating agent of the present invention to an article to be coated, and heating the article to be coated with hot air to dry it after coating, heating the article to be coated in advance, and then A method of applying the anticorrosive coating agent of the present invention at the time of heating and drying it by utilizing residual heat may be used.

The heating temperature is 50 to 250 ° C. in any of the above methods. If the temperature is lower than 50 ° C., the evaporation rate of water is slow and a sufficient film-forming property cannot be obtained. On the other hand, when the temperature exceeds 250 ° C., thermal decomposition of the aqueous resin occurs, so that salt water spray (SST) resistance and water resistance are deteriorated, and the appearance is yellowed. It is preferably 70 to 100 ° C. The drying time when the coated object is dried with hot air after coating is 1
Seconds to 5 minutes are preferred.

In the rustproofing treatment, the coating thickness of the rustproofing coating agent of the present invention is preferably a dry film thickness of 0.1 μm or more. If it is less than 0.1 μm, the rust preventive power is insufficient. On the other hand, if the dry film thickness is too thick, it is uneconomical as a coating base treatment and is also inconvenient for coating. Therefore, it is more preferably 0.1 to 20 μm. More preferably, it is 0.1 to 10 μm. However, when used as a water-based anticorrosive paint, the film thickness may be 0.1 μm or more.

In the rust-preventing treatment, the method of applying the rust-preventing coating agent of the present invention is not particularly limited, and it can be applied by a commonly used roll coating, air spray, airless spray, dipping or the like.

The steel material to be coated with the anticorrosive coating agent of the present invention is zinc-coated steel or uncoated steel as described above.

Further, the anticorrosive coating agent of the present invention can be used as a coating base treating agent and a water-based anticorrosive paint as described above, and can also be applied as a so-called primary anticorrosive agent. In addition, in the field of coil coating, it can be used not only for the base treatment of the lubricating film of zinc-based plated steel sheet and the coating base treatment, but also as a lubricant rust preventive agent for lubricating steel plate by adding wax to this rust preventive agent. it can.

[0036]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

In the following examples, the corrosion resistance was evaluated by the following method. [Evaluation method] a) Salt water resistance (salt spray (SST) test); 5% saline solution was sprayed onto the coated surface of the test piece at 35 ° C., and 72
After the time (240 hours only in Example 8), the degree of white rust was 10
It was evaluated on a perfect score. The evaluation criteria are as follows. 10 points: No abnormality 9 points: Between 10 points and 8 points 8 points: Slight white rust occurred 7 to 6 points: Between 8 points and 5 points 5 points: White rust occurred to half of the area 4 to 2 points: 1 point between 5 points and 1 point: White rust occurs on the entire surface

B) Moisture resistance (hot water resistance test): After being immersed in constant temperature water of 40 ° C. for 20 days, the degree of white rust was evaluated on a scale of 10 points. The evaluation criteria are as follows. 10 points: No abnormality 9 points: Between 10 points and 8 points 8 points: Swelling slightly occurs on the coating 7 to 6 points: Between 8 points and 5 points 5 points: Swelling occurs to half of the area 4 to 2 points : 1 point between 5 points and 1 point: Swelling occurs on the entire surface

Examples 1 to 7 Pure water was charged with a thiosulfate compound and / or a persulfate compound and optionally phosphate ions (diammonium hydrogen phosphate was used as a phosphate ion source). 1 to be dissolved so that the concentration of the resin may be 20% by weight, and finally water-dispersible silica (“Snowtex N”, (Nissan Chemical Co., Ltd.) was added in the amount shown in Table 1, and the mixture was stirred and dispersed with a disper for 30 minutes and adjusted to have a pH of 8.4 to prepare an anticorrosive coating agent. After polishing the surface of the obtained anticorrosion coating agent with Scotch Bright, an alkaline degreasing agent (“Surf Cleaner 5
3 ", made by Nippon Paint Co., Ltd.), degreased, washed with water, dried,
Dry coating with bar coat # 3 was performed on a commercially available hot-dip galvanized steel sheet (Z-27, manufactured by Nippon Test Panel Co., Ltd., 70 × 15 × 1.6 mm) preheated to a plate temperature of 80 ° C. (heating before coating). The film was applied and dried to a thickness of 1 to 2 μm.
The corrosion resistance of the obtained rustproof metal plate was evaluated by the above method. The evaluation results are also shown in Table 1.

Example 8 The same antirust coating agent obtained in Example 4 was used in Example 1
After commercially available degreasing, washing with water and drying in the same manner as ~ 7, a commercially available electrogalvanized steel sheet (EG-MO, manufactured by Nippon Test Panel Co., 70 x 150 x 0.8 mm) is dried with Bar Coat # 3. Was 1 μm. This was heated to a plate temperature of 150 ° C. and dried, and then the above corrosion resistance evaluation was performed. However, the evaluation time for the SST test is 2
It was set to 40 hours.

Comparative Example 1 After the same hot-dip galvanized steel sheet as in Example 1 was washed in the same manner as in Example 1, a resin-containing coating type chromate treating agent was used in a bar coater # 3 to obtain a chromium deposition amount of 20.
It was applied so that the amount would be mg / m ² and dried at 80 ° C. for 2 minutes to obtain a galvanized steel sheet treated with an anticorrosion agent.

Comparative Examples 2 to 4 Table 1 shows the types and blending amounts of the components of the anticorrosive coating agent.
A rust-proof coated steel sheet was obtained in the same manner as in Example 1 except that the changes were made as described in 1.

The aqueous resins used in the examples and comparative examples are the following commercial products: Polyolefin resin: "Hitec S-7024"
(Manufactured by Toho Chemical Co., Ltd.) (used in Examples 1, 2, 4 and Comparative Examples 2, 4) and "PC2200" (manufactured by Shoei Chemical Co., Ltd.) (Examples 3, 5, 8, Comparative Example 3) Polyurethane resin: "Bontiter HUX-320"
(Asahi Denka Co., Ltd.) Acrylic resin: "EM1220" (Nippon Paint Co., Ltd.)
Epoxy resin: "Polysol 8500" (Showa High Polymer)
Polyester resin: "Pethresin A-124G" (manufactured by Takamatsu Yushi Co., Ltd.) Polycarbonate resin: "Superflex F817"
4D "(manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)

[0044]

[Table 1]

From these results, according to the anticorrosive coating agent containing the thiosulfate compound and / or persulfate compound and the anticorrosion treatment method of the present invention, the corrosion resistance and anticorrosion property are remarkably improved as compared with the conventional chromate system. It is clear to do.

[0046]

INDUSTRIAL APPLICABILITY As described above, according to the anticorrosive coating agent and the anticorrosive treatment method of the present invention, a thiosulfate compound and / or a persulfate compound which are less toxic to an aqueous resin,
And, if necessary, by combining phosphate ions in combination, the rust-preventing property is superior to that of the conventional chromate-containing aqueous resin-based rust-preventive agent. Therefore, it is possible to provide a chromium-free rust preventive coating agent having low pollution and excellent rust preventive ability. Further, since the anticorrosion-treated metal material coated with the anticorrosion coating agent according to the present invention has a film excellent in anticorrosion ability formed for the same reason as above, it is possible to suppress the occurrence of rust.

Claims (4)

[Claims] 1. A rust preventive coating containing 0.1 to 20 g in total of one or more compounds selected from thiosulfate compounds and persulfate compounds in 1 liter of a composition containing an aqueous resin and water as main components. Agent. 2. A total of 0.1 to 20 g of one or more compounds selected from thiosulfate compounds and persulfate compounds in 1 liter of a composition containing an aqueous resin and water as main components.
And an anticorrosive coating agent containing 0.1 to 5 g of phosphate ions. 3. A zinc-based coated steel or uncoated steel.
Alternatively, a rust preventive treatment method comprising coating with the rust preventive coating agent according to 2. 4. An anticorrosion-treated metal coated with the anticorrosive coating agent according to claim 1.