JP2001089867A - Surface-treated steel with excellent weather resistance - Google Patents

Abstract

(57) [Summary] [Problem] To provide a surface-treated steel material having excellent weather resistance that can form stable rust at an early stage while preventing the generation of flowing rust even when used in a coastal area where the corrosive environment is severe. A surface-treated steel material comprising a steel material surface and a butyral resin coating layer containing an inorganic compound in a total amount of 150% by weight or less based on a resin solid content. A surface-treated steel material excellent in weather resistance, one of which is a first effective component of a heteropolyacid or a salt thereof having a chemical formula containing at least two of phosphorus, molybdenum, vanadium, silicon, and tungsten. Further, it is preferable that one of the inorganic compounds other than the first active ingredient is a second active ingredient composed of a zinc-based compound, and that the inorganic compound other than the first and second active ingredients be a zinc-based compound. It is more preferable that one kind is the third active ingredient composed of one or more of a nickel compound, a copper compound, a phosphoric acid compound, and a sulfuric acid compound.

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 material having excellent weather resistance useful for bridges and buildings, and more particularly, to a weather resistance that prevents flow rust and forms stable rust on the surface of a steel base material at an early stage. It relates to excellent surface-treated steel.

[0002]

2. Description of the Related Art Weather-resistant steel, which has a steel composition containing a small amount of Cu, P, Cr, etc., is used as a steel material in an outdoor environment where the amount of flying salt particles is small. A stable rust layer (called stable rust) is formed,
It is known that this stable rust layer keeps suppressing the corrosion progress of the steel material for a long time. Although the essence of this stable rust has not always been fully elucidated, it is also known that the addition of a small amount of Cu, P, Cr, etc. is indispensable for forming dense stable rust. Because of these properties, weathering steel has been widely used in bridges, steel towers, and the like, and has contributed to prolonging its life.

However, in conventional weathering steel, it takes 5 to 10 years for stable rust to be formed, and the flowing rust generated during that time significantly impairs the appearance of the steel material and the surrounding landscape. Therefore, it has been desired to form stable rust at the early stage on the surface of the weathering steel and to suppress the generation of flowing rust during the stable rust formation period. As a conventional technique for the purpose of early formation of stable rust and prevention of flow rust, Japanese Patent Publication No. 52-22530,
A technique disclosed in Japanese Patent Application Laid-Open No. 6-226198 is mentioned.

The technology disclosed in Japanese Patent Publication No. 52-30530 is iron oxide (Fe ₃ O ₄ + Fe ₂ O ₃ ): 5 to 50%, phosphoric acid: 0.01 to 5%.
%, Pb, Ni, Cu, P, Zn, Cr simple substance or compound 1
More than kind: Butyral resin containing 0.01 to 10% is applied to the surface of weathering steel. According to this,
In an exposure test in an industrial area, the initial flow rust amount is reduced to about 1/10 that of bare exposed material, and the stable rust formation period is reduced to about 10 to 18 months. However, in a coastal zone where the amount of flying salt particles is larger than in an industrial zone and thus a more severe corrosive environment is formed, the effect of reducing the amount of flowing rust is insufficient, and a stable rust layer is not formed.

[0005] Japanese Patent Application Laid-Open No. 6-226198 discloses a technique in which one or two of chromium sulfate and copper sulfate: 1 to 65% by weight is contained on the surface of a steel ingot or a rust layer formed thereon. That is, a resin paint is applied. According to this, in a one-year exposure test in a coastal zone, although the generation of flowing rust can be prevented, the stable rust ratio (the amount of stable rust with respect to the total rust amount of 100) is only about 50 at most, which is not always sufficient.
Further, when a chromium sulfate-containing resin paint is applied, there is a problem that Cr ³⁺ elutes out of the system from the resin absorbed by rainfall or dew condensation, and contaminates the surrounding environment.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to prevent the occurrence of flowing rust and prevent the occurrence of stable rust at an early stage even when used in a coastal area where the corrosive environment is severe. An object of the present invention is to provide a surface-treated steel material that can be formed and has excellent weather resistance.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, by coating a steel material surface with a surface treatment agent obtained by mixing a specific compound with a specific resin, The inventors have found that stable rust can be formed at an early stage without flowing rust, and the present invention has been completed. That is, the gist of the present invention resides in the following surface-treated steel materials.

(1) A surface-treated steel material having a butyral resin coating layer containing one or more inorganic compounds in a total amount of 150% by weight or less based on the resin solid content on the surface of the steel material. Wherein one of the inorganic compounds is
A surface-treated steel material having excellent weather resistance, which is a first effective component comprising a heteropolyacid or a salt thereof having a chemical formula containing at least two of phosphorus, molybdenum, vanadium, silicon, and tungsten.

(2) The surface-treated steel material according to (1), wherein one of the inorganic compounds other than the first active ingredient is a second active ingredient composed of a zinc-based compound. (3) One of the inorganic compounds other than the first and second active ingredients comprises one or more of a nickel compound, a copper compound, a phosphoric acid compound, and a sulfuric acid compound. The surface-treated steel material according to (2), which is a third active ingredient.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention will be described below in detail. In general, when a chemical conversion treatment or painting is performed on a steel material surface, it is important to previously perform a base treatment for removing oil, dirt, scale, and the like and keeping the steel material surface clean.
The method of such a base treatment is not particularly limited in the present invention, but for example, a steel blast method and a steel grit method are preferable. In the base treatment, the surface of the steel material is preferably adjusted to an average surface roughness (ten-point average roughness Rz): 20 to 80 μm in order to increase the adhesion area of the surface treatment agent. If the Rz is less than 20 μm, it is difficult to increase the bonding area.
If it exceeds μm, it is difficult to uniformly coat the surface treating agent. In addition, it is more preferably 20 to 50 μm.

In the present invention, the base resin of the surface treating agent must be a butyral resin. The purpose of the surface treatment according to the present invention is to quickly form stable rust under the coating layer, and a resin meeting this purpose has excellent hydrophilicity, high water absorption (several tens%), and stable rust formation. Must be able to supply sufficient water to the steel surface, and the only suitable material is butyral resin. On the other hand, epoxy resin type generally used as base resin of steel material application paint,
Acrylic resin and urethane resin materials have low water absorption (several percent), so that water required to form stable rust cannot be supplied to the surface of the steel matrix in a short period of time. The period until formation is long, and it is not possible to prevent the generation of flowing rust during that period.

When used in a severely corrosive environment, especially in an extremely high humidity environment, butyral resin is reacted and cross-linked with an isocyanate-based curing agent, or mixed with a phenol-based resin to form a hydroxyl group. The water absorption of the entire system may be reduced to an appropriate value by applying a resin having a reduced concentration as a base resin. That is, in the present invention, the term "butyral resin" refers to a concept encompassing a simple substance of butyral resin, a substance obtained by adding an isocyanate-based curing agent to the simple substance, and a substance obtained by mixing a phenolic resin with the single substance. .

When butyral resin is used outdoors for a long time, the film thickness of the resin layer gradually decreases due to light deterioration. However, the purpose of this resin layer is to adjust the amount of water and oxygen supplied during the period when stable rust is formed at the boundary with the steel, to prevent the outflow of flowing rust generated during The purpose of the present invention is to hold an active ingredient (described later) necessary for stabilizing the garment and to continuously supply it to the boundary portion. Therefore, it takes a period of time until stable rust is formed at the boundary portion (less than one year). Period only), and the reduction in film thickness due to the photodegradation does not pose a problem.

The surface treating agent according to the present invention is a butyral resin containing an active ingredient (first active ingredient) necessary for stabilizing rust. The first active ingredient is phosphorus, molybdenum, vanadium, A heteropolyacid or a salt thereof having a chemical formula containing two or more of silicon and tungsten. When the surface of the surface-treated steel material of the present invention is wetted by rainfall or dew condensation, the butyral resin absorbs water, the first active ingredient in the resin is ionized, and heteropolyacid ions are generated, and the ions are bonded to the steel material and the resin layer. At the interface, Fe ²⁺ generated by a corrosion reaction at the adhesive interface is oxidized to Fe ³⁺ . Fe ³⁺
Is necessary for forming α-FeOOH which is a stable rust component effective for improving weather resistance and corrosion resistance of steel. Therefore, in order to form stable rust at an early stage and to impart excellent weather resistance to a steel material, it is important to rapidly oxidize Fe ²⁺ generated by a corrosion reaction to Fe ³⁺ , which is the first method. The reason is that butyral resin to which an active ingredient is added is used as a surface treatment agent.

Further, the heteropolyacid ion, which is an ionization product from the first active ingredient, has a property of imparting cation selectivity to the formed rust layer. It is also effective for enhancing barrier properties. As described above, the surface-treated steel material obtained by applying the butyral resin containing the first active ingredient to the surface of the steel material (coating stratification) can form stable rust under the coating layer at an early stage. The amount of rust is remarkably reduced, the progress of corrosion is suppressed from the initial stage of exposure, and a longer life of the steel material can be achieved.

Further, in the present invention, it has been found by the present inventors that, in stabilizing rust, a second active ingredient which coexists with the first active ingredient and exhibits a synergistic effect therewith.
Specifically, it is preferable to add a zinc compound to the butyral resin together with the first effective element. The zinc-based compound has the effect of enhancing the cation selectivity imparted to the rust layer by the heteropolyacid ion, which is an ionization product from the first active ingredient, and further improves the resistance to chloride ions. The weather resistance and corrosion resistance of the surface-treated steel material used in a coastal area where the amount is large and the corrosive environment is severe can be further improved.

In the present invention, the first active ingredient, the second active ingredient,
The third active ingredient found by the present inventors to further promote the early formation of stable rust in the presence of the active ingredient of the present invention, specifically, a nickel-based compound, a copper-based compound, a phosphate-based compound, and sulfuric acid. It is further preferable to add one or more of the system compounds to the butyral resin together with the first active ingredient and the second active ingredient.

The nickel-based compound and the copper-based compound have a property of densifying the generated rust and enhancing the barrier property of the rust layer, and are therefore effective for further improving the weather resistance and corrosion resistance of the steel material. In particular, nickel-based compounds are effective for forming dense rust in coastal areas where the amount of flying salt particles is large. Phosphate compounds are formed because phosphate ions ionized by resin absorption combine with metal ions such as Zn ²⁺ , Cu ²⁺ , and Fe ²⁺ to form a chemically stable phosphate film. It is considered to be effective in protecting the stable rust layer.

Sulfuric acid compounds are considered to be effective in promoting the formation of stable rust because sulfate ions ionized by water absorption of the resin accelerate the iron corrosion reaction at the bonding interface between the steel material and the coating layer. The second active ingredient is
Its effect can be exhibited in the coexistence with the first active ingredient, and the effect is poor when added alone to the butyral resin.
Further, the third active ingredient can exert its effect in the presence of the first active ingredient and the second active ingredient,
Single addition to the butyral resin or the first active ingredient,
The combined addition with only one of the second active ingredients has a poor effect.

Further, the gist of the present invention is to apply a surface treating agent combining a butyral resin and a first active ingredient to a steel material in order to achieve rust stabilization and flow rust prevention. And as long as the function of the first active ingredient is not impaired, it does not prevent the combination of an appropriate inorganic compound and additives other than the second and third active ingredients, and for example, for the purpose of harmonizing with the surrounding environment A coloring pigment such as iron oxide or carbon black may be added, and an ultraviolet absorber or an anti-settling agent may be added.

The composition of the heteropolyacid or a salt thereof as the first active ingredient according to the present invention is not particularly limited as long as it has a chemical formula containing at least two of phosphorus, molybdenum, vanadium, silicon and tungsten. However, for example, phosphotungstic acid (H ₃ (PW ₁₂ O ₄₀ ) · nH ₂ O), silicotungstic acid (H ₄ (SiW
₁₂ O ₄₀ ) · nH ₂ O), phosphomolybdic acid (H ₃ (PMo ₁₂ O ₄₀ )
nH ₂ O), sodium phosphomolybdate (Na ₃ (PMo ₁₂ O
₄₀ ) · nH ₂ O), Lintangostomolybdic acid (H ₃ (PW
_12-x Mo _x O ₄₀ ) · nH ₂ O, 0 <x <12), limvanado molybdic acid (H _15-x (PV _12-x Mo _x O ₄₀ ) · nH ₂ O, 6 <x <12) , Molybdenum silicic acid (H ₄ (SiMo ₁₂ O ₄₀ ) .nH ₂ O) and the like.

As the zinc compound as the second active ingredient, for example, zinc oxide is suitable, and as the third active ingredient, as the nickel compound, for example, nickel carbonate or the like, and as the copper compound, as the copper compound. For example, cupric oxide or the like, a phosphoric acid compound such as phosphoric acid, and a sulfuric acid compound such as calcium sulfate are preferable.

In the present invention, the total amount of the inorganic compound added to the butyral resin must be 150% by weight or less based on the solid content of the resin. The total amount of inorganic compounds is
When the content exceeds 150% by weight, the inorganic compounds come into direct contact with each other without the intervention of a resin, so that a through-hole from the surface of the coating layer to the steel surface is easily formed, thereby preventing rust outflow (flow rust). Becomes difficult.

The first active ingredient to be added to the butyral resin is preferably blended so as to be 0.01% by weight or more based on the solid content of the resin. It is more preferably at least 1% by weight. The second active ingredient is 0.01% by weight based on the resin solid content.
It is preferable to mix them in such a manner. It is more preferably at least 1% by weight. The third active ingredient is preferably blended so as to be 0.01% by weight or more based on the solid content of the resin.
It is more preferably at least 1% by weight.

In the present invention, the thickness of the coating layer on the surface of the steel material is not particularly limited.
m is preferred. If the dry film thickness is less than 10 μm, it is insufficient to suppress flow rust, and if it exceeds 50 μm, the amount of permeation of water and oxygen is too small to delay stable rust formation. In the present invention, the type of steel to which the surface treatment agent is applied is not particularly limited. That is, even if it is applied not only to ordinary weather-resistant steel but also to ordinary steel, stable rust formation can be accelerated and flow rust can be prevented. This is because the first active ingredient in the surface treatment agent according to the present invention is:
This is because it acts on the rust layer of ordinary steel formed below the coating layer to promote the formation of stable rust. Nevertheless, in coastal areas where the amount of incoming salt particles is high and corrosive environments are severe, when ordinary steel is used as the steel type, the period until stable rust is formed is considerably longer than when inland industrial areas are used. Since it becomes longer, it is desirable to adopt weather-resistant steel, nickel-added steel, or the like.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. A steel material having the chemical composition shown in Table 1 was used for 150 × 70 × 6 (m
m), the scale on both sides is removed by steel blasting, and the average surface roughness (10-point average roughness R
z): A sample base material having a surface roughness of about 40 μm was used.

On the other hand, a butyral resin (BM-1 manufactured by Sekisui Chemical Co., Ltd.) was dissolved in a solvent mainly composed of isopropyl alcohol so as to have a solid content of 15%. The inorganic compound as the first to third active ingredients was dispersed by a batch type sand mill to prepare a surface treatment agent. The average secondary particle size of these inorganic compounds was in the range of several to 10 μm. In addition, a surface treating agent in which an inorganic compound was dispersed in a bisphenol A type epoxy resin (manufactured by Yuka Shell, Epicoat 828) with three rolls was also prepared for forming a coating layer of a comparative example. The epoxy-based surface treatment agent was applied to the sample base material after adding an equivalent amount of an amine-based curing agent.

The produced surface treating agent was applied to the surface of the sample base material by a spray coating method while controlling the spray amount so that the dry film thickness became 30 μm to form a coating layer. After the coating layer was formed, the sample was dried all day and night, and at a location about 10 m away from the coast, the coating layer side was set to the front side and the longitudinal direction was inclined at 30 ° to the ground, and in that state for one year It was subjected to a holding exposure test. During the exposure test, the presence or absence of flowing rust was evaluated over time. In addition, samples were collected every month, and the cross section was observed with a polarizing microscope. The stable rust observed as the quenching layer showed that 80% or more of the interface between the rust layer formed under the coating layer and the steel matrix was obtained. The duration of exposure required to cover was determined.

Table 2 shows the composition (combination of resin type and inorganic compound) of the surface treating agent applied to the sample base material and the results of the exposure test. The first active ingredient (phosphorus,
2 of molybdenum, vanadium, silicon and tungsten
(Examples 1 to 7) to which a heteropolyacid or a salt thereof having a chemical formula containing at least one or more species is added, and a second active ingredient (zinc-based compound) or a third active ingredient ( Nickel compounds, copper compounds,
In the system (Examples 8 to 12) to which a phosphoric acid compound and a sulfuric acid compound were added, good results were obtained in which no flowing rust was generated and stable rust was formed early.

On the other hand, in the system in which the first active ingredient was not added to the butyral resin (Comparative Examples 1 to 5), flowing rust was generated and did not lead to early formation of stable rust. Further, a system in which an epoxy resin was used in place of the butyral resin (Comparative Example 6)
Did not generate flow rust, but did not lead to early formation of stable rust.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

As described above, the surface-treated steel material of the present invention has an excellent effect of preventing flow rust and forming stable rust at an early stage even in a coastal area where the corrosive environment is severe. By applying to bridges, it is possible to achieve thorough aesthetic maintenance and environmental preservation.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B32B 15/08 B32B 15/08 G C23C 22/12 C23C 22/12 22/40 22/40 22/42 22/42 22 / 50 22/50 (72) Inventor Tsutomu Komori 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. (No address) Inside Mizushima Works, Kawasaki Steel Corporation (72) Inventor Ryoichi Nomura 1382-12 Shimoishigami, Otawara City, Tochigi Prefecture Inside Nasu Plant, Dainippon Paint Co., Ltd. (72) Inventor Hidenori Matsuno Shimoishigami, Otawara City, Tochigi Prefecture 1382−12 Dai Nippon Paint Co., Ltd. Nasu Factory F-term (reference) CA18 CA23 CA27 CA29 CA30 CA31 CA33 CA39 DA02 DA03 DA06 EA02 EB11

Claims (3)

[Claims] 1. A surface-treated steel material having a butyral resin coating layer containing, on a steel material surface, one or more inorganic compounds in a total amount of 150% by weight or less based on a resin solid content. And a surface having excellent weather resistance, wherein one of the inorganic compounds is a first active ingredient of a heteropolyacid or a salt thereof having a chemical formula containing at least two of phosphorus, molybdenum, vanadium, silicon and tungsten. Treated steel. 2. The surface-treated steel material according to claim 1, wherein one of the inorganic compounds other than the first active ingredient is a second active ingredient composed of a zinc-based compound. 3. One of the inorganic compounds other than the first and second active ingredients is one or two of a nickel compound, a copper compound, a phosphoric acid compound, and a sulfuric acid compound.
3. The surface-treated steel material according to claim 2, which is a third active ingredient composed of a mixture of at least one kind.