JPH09263714A - Primary anticorrosive coating material for steel product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a primary anticorrosive coating material which forms a coating film inhibiting the generation of a harmful zinc gas during welding while hardly causing welding defects and without detriment to anticorrosive properties by incorporating a silicon-based inorg. binder, a zinc powder, and a zinc gas trap agent into the material so that the resultant dried coating film contains specified amts. of the zinc powder and the trap agent. SOLUTION: Examples of the inorg. binder are a tetraalkoxysilicate, an alkyltrialkoxysilicate, their partial condensate, and precondensates formed by condensing them in the presence of water and an acid catalyst. The zinc powder is one comprising spherical particles having an average particle size of 1-15μm or one comprising flat particles having an average major axis of 5-30μm. A metal oxide which decomposes at 500-1,500 deg.C and/or its salt can be used as the trap agent, pref. examples being CoO, CuO, Cu2 O, and WO3 . The zinc powder and the trap agent are compounded so that they are contained each is an amt. of 10-70wt.% in the resultant dried coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a primary rust preventive coating material for steel materials, and more particularly, a coating film having excellent welding performance by suppressing the generation of zinc gas harmful to the human body during welding even in high speed welding. The present invention relates to a primary rust preventive coating material for steel materials capable of forming rust.

[0002]

2. Description of the Related Art Steel materials used in the construction of steel structures such as ships, bridges, tanks, plants, etc.
In order to prevent the generation of rust during the assembling period, a so-called zinc primer, which is a primary rust preventive paint excellent in rust preventive property, heat resistance, flexibility and welding performance, is usually applied after the blast treatment.

The zinc primer is characterized by an excellent rust preventive property based on the electrochemical action between the zinc dust contained in the coating film and the surface of the raw material iron. As the zinc shop primer, Examples thereof include an organic zinc shop primer using an epoxy resin as a binder and an inorganic zinc shop primer using a hydrolyzed condensate of an alkyl silicate as a binder.

[0004] In the case of welding and fusing of steel materials, the primer coating film is heated to a high temperature and organic decomposition gas or zinc is melted and vaporized to generate a lot of harmful gases such as zinc fume. Such gas tends to cause welding defects such as blow holes and pits.

In recent years, the welding work has been further speeded up due to the increase in welding lines due to the double hull structure of the hull and the rationalization / automation of the shipbuilding process. For this reason, the steel material at the welded portion is once softened. Since the time from the start to hardening becomes shorter, the gas such as zinc fume cannot be completely escaped, and the occurrence of welding defects such as blowholes and pits becomes more and more inevitable.

[0006] Therefore, as countermeasures against this, studies have been made to reduce the content of zinc dust, which is the cause of welding defects, or to improve the heat resistance of the binder, but they are insufficient. Satisfactory welding performance has not been obtained. Further, even if generation of zinc gas is suppressed to some extent by reducing the content of zinc dust, there is a problem in that rust prevention cannot be maintained.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a high-speed operation can be achieved by adding a trapping agent that suppresses / captures zinc gas generated during welding and fusing. The present invention has been found to be applicable to welding.

That is, the present invention contains (A) a silicon-based inorganic binder, (B) zinc dust, and (C) a zinc gas trapping agent, and the zinc dust (B) and the zinc gas trap are contained in a dry coating film. The present invention provides a primary rust preventive coating material for steels, characterized by containing 10 to 70% by weight of each agent (C).

Hereinafter, the present invention will be described in detail.

The silicon-based inorganic binder (A) used in the present invention is a tetraalkoxy silicate, an alkyl trialkoxy silicate, a partial condensate of these, and / or their presence in the presence of water and an acid catalyst. A hydrolytic initial condensate obtained by a condensation reaction under the following conditions can be used. Examples of the tetraalkoxy silicate include tetramethoxy silicate, tetraethoxy silicate, tetrapropoxy silicate, and tetraisopropoxy silyl. Kate, tetrabutoxy silicone
, Tetraisobutoxy silicate, ethyl silicate 40 (manufactured by Nippon Corcote) and the like. Examples of the alkyl trialkoxy silicate include methyl trimethoxy silicate and methyl triethoxy silicate. Kate, methyl tripropoxy silicate, ethyl trimethoxy silicate, ethyl triethoxy silicate and the like can be mentioned. These can be used alone or in combination of two or more. A water-dispersed colloidal silica may be used in combination with the above silicates.

As the binder component, if necessary, a metal alkoxide other than silicon may be added to the above silicon-based inorganic binder,
You may mix and use metal colloid, polyvinyl alcohol resin, etc.

As the zinc powder (B) used in the present invention, almost spherical particles having an average particle size of 1 to 15 μm and an average major axis of 5 used in a usual zinc rich shop primer are used.
Those composed of flat particles having a particle size of up to 30 μm can be used.

The zinc gas trapping agent (C) used in the present invention traps zinc which has been melted or gasified at high temperature during welding and fusing as an oxide, a fluoride, a eutectic mixture and the like.

As the zinc gas trapping agent, first, 50
A metal oxide that decomposes at 0 to 1500 ° C. and / or a salt containing the same can be used. Specifically, MnO ₂ , Co
₃ O ₄ , Sb ₂ O _{3 and the} like, of which MnO ₂ ,
Co ₃ O ₄ can be preferably used.

As the zinc gas trapping agent, an oxide of a metal having a higher potential than zinc and / or a salt containing the same can be used. Specifically, CoO, CuO, Cu ₂ O and W are used.
O ₃ , NiO, TiO ₂ , Fe ₃ O ₄ , Na ₂ WO ₄ ,
BaTiO _{3 and the} like can be mentioned. Of these, CoO, Cu
O, Cu ₂ O and WO ₃ can be preferably used.

Further, as the zinc gas trapping agent, a fluoride and / or a fluororesin powder of a metal having a higher potential than zinc can be used, and specifically, CuF ₂ , Teflon powder, etc. can be preferably used.

The above zinc gas trap agents may be used alone or in combination of two or more.

If desired, a metal carbonate which decomposes at 300 to 1000 ° C. may be used in combination with the zinc gas trapping agent. Examples of the metal carbonate include CaCO ₃ and
_{FeCO 3, CoCO 3, MgCO 3} , ZnCO 3, M
Examples include nCO ₃ and dolomite, of which CaC
O ₃ , FeCO ₃ , MgCO ₃ , and dolomite can be preferably used. When the metal carbonate is used in combination, the amount of the zinc gas trapping agent used can be reduced.

In the present invention, the zinc powder (B) and the zinc gas trapping agent (C) are added to the dry coating film in an amount of 10 to 70, respectively.
It is blended so as to contain 20% by weight, preferably 20 to 50% by weight.

The content of zinc powder (B) in the dry coating film is 10
If it is less than 10% by weight, good anticorrosion properties cannot be obtained. On the other hand, if it exceeds 70% by weight, white rust is increased and the adhesion to the topcoat is reduced, and the amount of zinc gas generated during welding and fusing is increased. However, the effect of the zinc gas trapping agent (C) is not exhibited, which is not preferable.

On the other hand, if the content of the zinc gas trapping agent (C) in the dry coating film is less than 10% by weight, the trapping effect on zinc is not sufficiently exhibited, while if it exceeds 70% by weight, the anticorrosive property is deteriorated. Absent.

In the present invention, if necessary, other extender pigments, rust preventive pigments and coloring pigments can be used as the pigment component in addition to the above, for example, talc, mica, barium sulfate,
Titanium oxide, iron phosphide, MIO, lead cyanamide, zinc chromate, zinc phosphate, calcium phosphate, barium metaborate, zinc molybdate, aluminum molybdate, red iron oxide, cyanine color pigments, carbon black, and the like, Furthermore, materials used for coating the welding rod, such as silica powder, rutile powder, and zircon powder, can also be used.

In the composition of the present invention, if necessary, an organic solvent, an anti-settling agent, an anti-sagging agent, a wetting agent, a reaction accelerator,
Ordinary paint additives such as adhesion promoters may be appropriately mixed.

The composition of the present invention can be prepared according to a conventional method,
Usually, it is prepared as a two-component paint comprising a binder component and a component containing zinc dust and a trapping agent, and both components are mixed and provided for coating before coating. As a coating method, conventionally known methods such as air spray, airless spray, brush coating, and roller can be adopted.

[0025]

The effect of the invention and the effect of the invention The coating film obtained by the composition of the present invention suppresses the occurrence of welding defects such as blowholes and pits at the time of welding in the presence of a specific metal oxide or metal carbonate
It is presumed that the metal fluoride or the fluororesin powder acts as a zinc gas trapping agent and suppresses the generation of zinc gas by oxidizing, eutectic mixture or fluorinating the molten or gasified zinc.

Therefore, by using the composition of the present invention containing the above-mentioned specific zinc gas trapping agent, it is possible to prevent the generation of zinc gas, which is harmful to the human body during welding, without deteriorating the rust preventive property for a long time. 3 compared to primer
0% or more can be suppressed and there are welding defects such as pits and blow holes.
It is possible to form a coating film having excellent welding performance with less generation of cracks.

[0027]

The present invention will be described below in more detail with reference to examples. Here, "parts" and "%" mean "parts by weight" and "% by weight", respectively.

Manufacture of Silicon Inorganic Binder 100 parts of "Ethyl silicate 40" (manufactured by Nippon Corcoat Co.) and 57 parts of isopropyl alcohol were placed in a reaction vessel and kept at 40 ° C. with stirring to 0.5N. Hydrochloric acid 0.5
Parts, 2.5 parts of water and 40 parts of "SNO-TEX 0" (Colloidal silica manufactured by Nissan Chemical Industries, Ltd.) were added dropwise over 1 hour. After completion of the dropping, stirring was continued for 1 hour while maintaining the temperature at 40 ° C. to obtain a binder (solid content 25%).

Examples and Comparative Examples Each of the components shown in Table 1 was mixed with the binder obtained above and mixed and stirred to obtain each rust preventive paint. Each rust-preventive paint was added with isopropyl alcohol as needed to adjust the viscosity, and then applied for coating and evaluated by the following performance test. Table 2 shows the results.

(Rust-prevention test) A steel plate (300 × 100 × 3 mm) that has been shot-blasted is spray-coated with each rust-preventive paint so that the dry film thickness is 15 μm, and after drying, the test-coated plate obtained is dried. Salt spray test (JIS 540
0 9.1) was carried out for 200 hours and the state of rust generation was evaluated (○: no rust, no swelling, Δ: rust, little swelling, x: rust, significantly swelling).

(Welding test) A steel plate (600 × 100 × 16 mm) shot-blasted was coated with each rust-preventive coating by air spray coating so that the dry film thickness was 15 μm, and after drying, carbon dioxide gas was applied to the test coated plate obtained. -Q welding was carried out using "SM-1F" (manufactured by Nippon Welding Co., Ltd.) as a welding wire at a welding speed of 80 cm / min.
It was evaluated by the number of pits generated on the screen and the generation rate (%) of blowholes. Further, the zinc gas generation amount was evaluated using Comparative Example 1 as a reference (100).

[0032]

[Table 1]

[0033]

[Table 2]

Claims (7)

[Claims] 1. A dry inorganic coating containing (A) a silicon-based inorganic binder, (B) zinc dust, and (C) a zinc gas trapping agent, and a dry coating film containing zinc dust (B) and a zinc gas trapping agent (C). 10% to 70% by weight of each of the above). 2. The zinc gas trapping agent (C) is 500 to
The primary anticorrosive paint according to claim 1, which is a metal oxide decomposing at 1500 ° C and / or a salt containing the same. 3. A metal oxide which decomposes at 500 to 1000 ° C. and / or a salt containing the same is MnO ₂ , Co.
_The primary anticorrosive paint according to claim 2, which is at least one selected from ₃ O ₄ , Sb ₂ O _{3 and the} like. 4. The primary anticorrosive paint according to claim 1, wherein the zinc gas trapping agent (C) is an oxide of a metal having a nobler potential than zinc and / or a salt containing the same. 5. An oxide of a metal whose potential is nobler than zinc and /
Alternatively, salts containing it are CoO, CuO, Cu ₂ O, W
O ₃ , NiO, TiO ₂ , Fe ₃ O ₄ , Na ₂ WO ₄ ,
The primary rust preventive coating material according to claim 4, which is at least one selected from BaTiO _{3 and the} like. 6. The primary anticorrosive paint according to claim 1, wherein the zinc gas trapping agent (C) is a metal fluoride and / or fluororesin powder having a higher potential than zinc. 7. The primary anticorrosive paint according to claim 6, wherein the metal fluoride is CuF ₂ .