JPH11116856A - Rustproofing coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition for ships or the like, occurring neither white rust even during welding process for steel materials at high temperatures nor weld defects due to zinc vapor, by including zinc powder as rustproofing pigment and a specific compound. SOLUTION: This rustproofing coating composition is obtained by incorporating (A) a silicon based inorganic compound as binder with (B) zinc powder as rustproofing pigment, and (C) a crystal water-free cyclic aluminum metaphosphate, and pref. furthermore, (D) aluminum powder and/or (E) ferroaluminum alloy powder; wherein, it is preferable that the amounts of the components C, D and E to be used are 0.2-20 pts.wt., 5-50 pts.wt. and 10-50 pts.wt., respectively, based on 100 pts.wt. of the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rust-preventive coating composition having excellent white rust resistance, and more particularly, to a steel material used for ships, bridges, marine iron structures, etc. No problem even in processes involving high heat, such as welding, fusing, and strain removal when processing into a finished product. Also, even if exposed to the outdoors after this process, the painted film does not peel and exhibits sufficient rust prevention. In addition, the present invention relates to a rust-preventive coating composition capable of further suppressing the generation of white rust.

[0002]

2. Description of the Related Art Generally, steel materials used for the construction of large-scale steel structures such as ships, bridges, tanks, and plants are prevented from being rusted during processing and assembling operations, and are not reduced in welding workability. For this purpose, a steel plate before processing is subjected to blast treatment in advance to remove mill scale and rust, and then a primary rust preventive paint is applied.

[0003] As such a primary rust preventive paint, a wash primer composed of phosphoric acid-chromate using butyral resin as a binder, an organic zinc-rich paint composed of an epoxy resin as a binder and zinc dust, a silicon-based inorganic binder have been used. There are known inorganic zinc-rich paints comprising an agent and a large amount of zinc dust, and new inorganic zinc-rich paints obtained by further adding a rust preventive pigment or an organic resin to a silicon-based inorganic binder and zinc dust.

[0004] Such primary rust preventive paints include:
Characteristics such as (1) excellent rust resistance, (2) excellent workability in welding, and (3) adhesion to any top coating are required. Among the above-mentioned paints, inorganic zinc-rich paint is most often used as a primary rust preventive paint for steel materials for steel structures.

[0005]

However, in the construction of large-sized steel structures described above, work steps involving high heat such as welding, fusing, and strain removal have become indispensable in recent years. However, in the above-mentioned conventional inorganic zinc-rich paint, the content of zinc powder is very large, so that the sacrificial corrosion protection effect of zinc is strong and the rust prevention power is high, but the coating film is heated to high heat in the welding, fusing, and strain removing operations. Melting of zinc, if
Zinc whiskers are generated by vaporization and are rapidly oxidized, causing white rust consisting of zinc oxide to reduce the adhesion to the top coating, or becoming zinc vapor and diffusing into the molten pool, resulting in blowholes, pits, etc. The problem that a welding defect of No. occurs occurs. If the amount of zinc dust is reduced in order to avoid this, the rust resistance is reduced, the coating film becomes hard and brittle, and cracks are easily generated, making it difficult to form a coating film.

[0006] From the above, while maintaining the good rust prevention properties of the conventional inorganic zinc-rich paint,
There is a demand for rust-preventive paints that exhibit excellent properties such as paintability, heat resistance, and weldability.For example, by specifying the composition of a silicate-based binder, the amount of zinc dust is reduced while maintaining heat-resistant rust resistance. (JP-A-60-51756, JP-A-60-235871, JP-A-61-2)
No. 04282, Japanese Patent Application Laid-Open No. 61-204283), one that maintains rust resistance during high-temperature heating by using zinc powder surface-treated with conductive particles, a flow inhibitor or the like (Japanese Patent Application Laid-Open No. 61-76570). No., JP-A-63-179
No. 76), a material which maintains the rust resistance during high-temperature heating by using a zinc alloy powder as a rust preventive pigment (Japanese Patent Application Laid-Open No.
No. 2,358,872), using zinc dust and ferrosilicon to maintain rust resistance during high-temperature heating (JP-A-5-11)
No. 7553), a method for achieving high-temperature weldability using zinc powder and a molybdenum-containing pigment (Japanese Patent Application Laid-Open No. 5-339521), a method using zinc powder and a molybdenum compound to prevent oxidation of zinc during heating ( Japanese Patent Application Laid-Open (JP-A) No. 6-100803) and those which improve weldability by including at least one of a phosphate pigment and feldspar in a paint component (JP-A-6-200188). Has been made.

[0007] However, although each of these proposed rust preventive coating compositions has its own advantages, when it is exposed to high temperatures in welding, fusing, strain relief, etc., white rusting occurs, The problem of welding defects caused by steam has not been solved yet.

[0008] In view of the above, the present invention has a rustproof property that does not cause white rust or weld defects due to zinc vapor even in processing steps such as welding, fusing, and strain removal under high heat of steel. It is an object of the present invention to provide a rust-preventive coating composition capable of providing a coating film excellent in rust resistance.

[0009]

That is, the invention according to claim 1 of the present invention uses a silicon-based inorganic compound as a binder,
A rust-preventive paint composition containing zinc dust and cyclic aluminum metaphosphate having no water of crystallization as a rust-preventive pigment, wherein the invention according to claim 2 uses a silicon-based inorganic compound as a binder, The present invention is characterized by a rust-preventive paint composition comprising zinc dust and cyclic aluminum metaphosphate having no crystallization water as a rust-preventive pigment, and further comprising aluminum powder and / or ferroaluminum alloy powder.

[0010]

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention relates to a rust preventive coating composition comprising a silicon-based inorganic binder mixed with zinc dust and a cyclic aluminum metaphosphate having no water of crystallization as a heat-resistant rust preventive pigment. By adding aluminum powder and / or ferroaluminum alloy powder to the above composition to form a rust-preventive coating composition, the zinc content can be reduced without decreasing the rust-preventive property, and the zinc content in the cured coating film can be reduced. Provided is a rust-preventive coating composition that can reduce the generation of welding defects by reducing powder and suppress the oxidation of zinc powder due to high heat by the action of aluminum powder or ferroaluminum alloy powder and also prevent the generation of white rust. Things.

The silicon-based inorganic compound used as the binder solution in the present invention includes tetramethoxysilicate, tetraethoxysilicate, tetrapropoxysilicate,
Tetraalkoxysilicate such as tetraisopropoxysilicate and tetrabutoxysilicate or methyltrimethoxysilicate, methyltriethoxysilicate, methyltripropoxysilicate, ethyltrimethoxysilicate, ethyltriethoxysilicate, butyltrimethoxysilicate, amyltriethoxysilicate, etc. Hydrolysis-condensation products of silicate esters obtained by hydrolyzing and condensing alkyltrialkoxysilicates singly or as a mixture of two or more thereof, or compounds such as alkali silicates, silica sols, and polysiloxanes, and the like are used. Is suitably 30 to 50 parts by weight.

As the zinc powder, a commercially available product may be used, but a product having an average particle size of 3 to 15 μm is preferable. A suitable amount is 20 to 40 parts by weight. If the amount is less than 20 parts by weight, good rust prevention cannot be obtained, and if the amount exceeds 40 parts by weight, workability at the time of coating is reduced, and a large amount of zinc vapor is generated at the time of welding, leading to welding defects or white defects. This is because the generation of rust increases, and the adhesion to the top coat decreases.

As the heat-resistant rust-preventive pigment, Al (PO)
₃ ) Compounds such as aluminum tri (or tetra) metaphosphate having no water of crystallization in the molecule, such as ₃ or Al ₄ (P ₄ O ₁₂ ) ₃ , are preferred.
Type is used. With respect to 100 parts by weight of zinc dust, the effect of suppressing white rust is small at 0.2 parts by weight or less, and the effect of suppressing white rust is large at 20 parts by weight or more. Because it may lower it,
A range of 0.2 to 20 parts by weight is preferred.

Until now, aluminum phosphate has been used as one of the rust preventive pigments.
Or a orthophosphate containing water of crystallization indicated by ₄ · 2H ₂ O made formula, in order to be _{AlH 2 P 3 O 10 · 2H} 2 O made Formula polyphosphates containing crystal water represented by, In addition to the melting and vaporization of zinc that occurs when steel materials coated with rust-preventive paint using aluminum phosphate and zinc dust as rust-preventive pigments, hydrogen gas generated by water of crystallization is taken into the molten pool and welded. However, there is a problem that pits and blowholes are generated and welding defects easily occur.

Therefore, the present invention is characterized in that a cyclic aluminum tri (or tetra) metaphosphate having no water of crystallization in the molecule as described above is used as the heat resistant rust preventive pigment.

Aluminum powder is used in combination with zinc powder because it has better thermal stability than zinc powder and generates less white rust even when exposed to the outdoors.
This aluminum powder is atomized by spraying molten aluminum into granular powder by spraying, and wet ball milling method (machine) is to flake aluminum powder as a flake-like powder by pulverizing the raw aluminum powder with a ball mill using an organic substance such as stearic acid or oleic acid as a grinding aid. Crushing method), etc., but in the present invention, the average particle size obtained by the atomizing method is 5 to 2
An aluminum powder of 0 μm is used, and its amount is suitably 5 to 50 parts by weight (preferably 5 to 15 parts by weight) per 100 parts by weight of zinc dust. This is because less than 5 parts by weight has little effect on suppressing welding defects.
If the amount is more than the weight part, the cohesive strength of the coating film is reduced.

Since the organic substance remains in the aluminum powder using an organic substance such as stearic acid or oleic acid as a grinding aid, when such an aluminum powder is used, the applied rust-preventive coating film Since hydrogen atoms contained therein may become hydrogen gas and cause welding defects, the present invention uses aluminum powder by the atomizing method as described above.

The ferroaluminum alloy powder, which is a further essential component in the present invention, is an alloy of iron and aluminum, which is generally used as a deoxidizing agent for steel materials. The ferroaluminum alloy powder preferably has an average particle size of 20 μm or less (preferably 10 μm or less) in view of the stability of the added rust-preventive paint and the workability of the coating, and is used in an amount of 100 parts by weight of zinc dust. When the amount is less than 10 parts by weight, the expected effects on heat resistance and welding resistance are not obtained. On the other hand, when the amount is more than 50 parts by weight, rust resistance is reduced.

In obtaining the rust-preventive coating composition of the present invention, pigments, solvents and other additives may be added as necessary in addition to the above-mentioned essential components, as in the case of ordinary rust-preventive paints. Similarly, pigments include silica powder, talc, clay, calcined kaolin, mica powder, zinc white, barium sulfate, calcium carbonate, body pigments such as alumina, red iron oxide, titanium dioxide, carbon black, organic blue, organic yellow. And organic pigments such as organic green, and rust preventive pigments such as borate and chromate.

Suitable solvents are alcohol solvents such as isopropyl alcohol and isobutyl alcohol, and aromatic solvents such as toluene and xylene. As other additives, anti-settling agents such as organic bentonite, polyethylene oxide and Aerosil, anti-sagging agents, wetting agents, stabilizers and the like may be used according to the purpose.

The rust-preventive coating composition of the present invention comprises a binder solution as a main ingredient and a component (paste component) such as zinc dust, heat-resistant rust-preventive pigments such as aluminum metaphosphate, aluminum powder, and ferroaluminum alloy powder. It may be prepared separately, and both components may be sufficiently mixed and stirred with a stirrer at the time of coating on a steel material and used in a uniform state. The coating on the steel material may be performed by a normal coating method such as airless spray, air spray, brush coating, roll coater and the like, and after the coating, it may be dried by natural drying or hot air drying.

[0022]

Next, the present invention will be described in detail with reference to examples. The present invention is not limited by the following embodiments. All parts are parts by weight.

(Preparation of Binder Solution) A 1 liter reaction vessel charged with 304 g of tetraethoxysilicate (trade name ethyl silicate 40, manufactured by Nippon Colcoat Co., Ltd.) and 304 g of isopropyl alcohol was heated and maintained at 60 ± 3 ° C. 0.6 g of 35% hydrochloric acid and deionized water
2 g and a mixed solution obtained by mixing 75.2 g of isopropyl alcohol were gradually added with stirring over 1 hour.
Thereafter, stirring was continued at the same temperature for another 1 hour, and finally, 86.4 g of isopropyl alcohol was added, and the mixture was allowed to cool, whereby a binder solution composed of an isopropyl alcohol solution of a hydrolyzed condensate of tetraethylsilicate was prepared.

(Preparation of Paste) The raw materials constituting the pastes shown in the following Comparative Example 1 and Examples 1 to 15 were placed in a 1-liter container and sufficiently stirred and dispersed to prepare a paste.

The following materials were used as the raw materials constituting the paste. Zinc powder (Honjo Chemical Co., zinc powder F-1000) Heat resistant rust preventive pigment, aluminum metaphosphate (Taika Co., K White 94) Aluminum powder (A) (Toyo Aluminum Co., AC5000) Aluminum powder (B) (Daiwa Metal Powder Co., Ltd., NO.1112) Ferroaluminum alloy powder (Kinseimatic Co., Ltd., Ferroaluminum) Silica powder (Maruo Calcium Co., Ltd., silica powder MC-O) Organic bentonite (NL Chemical Co., Benton SD- 2) Aero Seal (Aero Seal COK80, manufactured by Nippon Aerosil Co., Ltd.)

(Preparation of Rust Preventive Paint) The binder solutions and pastes in the amounts shown in Table 1 below were sufficiently mixed to prepare each rust preventive paint used in Comparative Examples and Examples. And
The following coating film performance tests were performed using the obtained rust preventive paint.

[0027]

[Table 1]

(1) Rust Prevention Test Using a 2 × 70 × 150 mm sandblasted steel plate as a test piece, each paint shown in Table 1 was applied by air spray to a dry film thickness of 15 μm. 75R
The sample was dried in a constant temperature and humidity chamber of H for 7 days. Thereafter, horizontal exposure was performed outdoors for three months, and the rusting state and white rusting state of the coating film were evaluated. The results are shown in Table 2.

The rusting state and white rusting state of the coating film were visually observed. 5 points: No rust was observed at all. 4 points: Very slight rust was observed. 3 points: Slight rust was observed. Point: Rust is recognized. 1 Point: Very much rust is recognized.

(2) Heat resistance and rust resistance test Each of the test pieces coated and dried in the same manner as in the rust resistance test of the above (1), 800
Heated with a gas burner at 2 ° C. for 2 minutes. Thereafter, horizontal exposure was performed outdoors for three months, and the rusting state and white rusting state of the coating film were evaluated in the same manner as in the above (1). The results are shown in Table 2.

(3) Weldability test 12 × 100 × 1000 mm and 12 ×
Using a 200 × 1000 mm shot-blasted mild steel sheet, each paint shown in Table 1 was applied by air spray so that the dry coating thickness became 15 μm, and the cut surface was also applied with a brush to 15 μm at 20 ° C. After drying for 7 days under the condition of 75% RH, horizontal fillet welding was performed under the following welding conditions with one set of both test pieces.

Regarding the evaluation of weldability, defects on the welding surface (pits, gas grooves, etc.) are determined by determining the total length of the defects generated on the welding surface as a percentage (%) of the total welding length. Was not confirmed, that is, 0% was regarded as a pass.
For defects (blowholes) inside the weld, the total length of blowholes generated in the fractured surface by breaking the welded part is judged as a percentage (%) of the total weld length, and a value of 10% or less is passed. And The results are shown in Table 2.

Welding conditions Welding wire: SF-1F φ = 1.2 mm (manufactured by Nittetsu Welding Industry Co., Ltd.) Welding method: carbon dioxide gas shielded arc welding method Welding machine: LOBSTER C-85 (manufactured by Riken Koki Co., Ltd.) Welding speed: 800 mm / min welding current voltage: 280 A / 38 V

[0034]

[Table 2]

As can be seen from Table 2, in Examples 1 to 3 in which a binder solution, zinc dust and aluminum metaphosphate were blended as a heat-resistant rust preventive pigment, in Example 1 where the amount of aluminum metaphosphate to zinc dust was small, rust prevention was performed. Although the test results of the heat resistance and the weldability were not much different from those of Comparative Examples 1 and 2, which did not use the heat-resistant rust preventive pigment, Example 2 showed a very good result. Also, it was recognized that even if the amount of aluminum metaphosphate slightly exceeded the range of use of the present invention, by reducing the amount of zinc dust, quite good results were obtained as in Example 3.

On the other hand, in Examples 4 to 5 in which the reduced amount of zinc dust was replaced by aluminum powder or ferroaluminum alloy powder.
7. In Examples 10 to 18, good results were obtained in both rust prevention and weldability. In addition, Example 19 is similar to Example 1
3. An aluminum powder (B) obtained by adding an organic solvent and a grinding aid such as stearic acid or oleic acid as a wet powder method while using the same composition as in 3, and adsorbing the aluminum powder (B). It has been proved that the test results of the weldability are inferior due to the acid component used, which clearly shows the grounds for using the aluminum powder by the atomizing method in the present invention.

[0037]

As described above, according to the present invention, aluminum metaphosphate is added as a heat-resistant rust-preventive pigment to a conventional inorganic zinc-based primary rust-preventive paint, or aluminum powder, By using a rust-preventive paint composition with a predetermined amount of ferroaluminum alloy powder added, it improves white rust resistance and rust-preventive properties, and further suppresses the generation of zinc vapor during welding work to reduce coating defects. Can be provided.

Claims (5)

[Claims] A rust preventive having excellent white rust resistance, characterized in that a silicon-based inorganic compound is used as a binder, and zinc aluminum and a cyclic aluminum metaphosphate having no water of crystallization are blended with the binder as a rust preventive pigment. Paint composition. 2. A silicon-based inorganic compound as a binder, zinc dust as a rust-preventive pigment, a cyclic aluminum metaphosphate having no crystallization water, and an aluminum powder and / or a ferroaluminum alloy powder. A rust preventive paint composition having excellent white rust resistance. 3. The white rust resistance according to claim 1, wherein 0.2 to 20 parts by weight of cyclic aluminum metaphosphate having no crystallization water is used based on 100 parts by weight of zinc dust. Excellent rust preventive paint composition. 4. The rust-preventive coating composition according to claim 2, wherein the aluminum powder is used in an amount of 5 to 50 parts by weight based on 100 parts by weight of zinc dust. 5. A ferroaluminum alloy powder containing zinc powder 1
The rust preventive paint composition having excellent white rust resistance according to claim 2, wherein the composition is used in an amount of 10 to 50 parts by weight based on 00 parts by weight.