JP2001164386A - Corrosion preventive for weather resistant steel and corrosion preventing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion preventive for weather resistant steel and a corrosion preventing method, in a corrosion preventing technique for weather resistant steel used for a steel structure, capable of easily and inexpensively performing the application while maintaining its corrosion resistance over a superlong period. SOLUTION: A corrosion preventive essentially consisting of one or two or more kinds among alkoxy group-containing silane compound and/or the partial condensation products thereof is applied on the surface of a rust layer of weather resistant steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preventing corrosion of weather-resistant steel used for steel structures such as bridges, steel towers, and buildings, and more particularly, to preventing deterioration of stable rust and generation of unstable rust. Alternatively, the present invention relates to an anticorrosion agent and an anticorrosion method for promoting stabilization of rust.

[0002]

2. Description of the Related Art Steel structures such as bridges, steel towers, elevated water tanks, tanks, and buildings as they are cause corrosion to cause red rust, yellow-brown floating rust, and flow rust, which not only impair the scenery but also cause corrosion. Since the strength of the structure is reduced due to the decrease in wall thickness, some anticorrosion measures are required. Conventionally, as a method of preventing corrosion of these structures, a painting method is generally used, and a heavy-duty anticorrosive coating with improved long-term durability is known, but the coating cost is high and the service life is limited. In addition, there is a problem that maintenance cost is high since regular repainting is necessary.

On the other hand, by adding a small amount of elements such as P, Cu, Cr and Ni to steel materials, dense rust (stable rust) having protection against corrosion is formed in the air in several years. A weather-resistant steel is known as a steel material having a very low corrosion rate. Since weather-resistant steel is a so-called maintenance-free steel that has a permanent anticorrosive effect without being painted after stable rust is formed, its use in structures such as bridges and steel towers has been increasing in recent years. In addition, the Ministry of Construction recommends an area where the amount of incoming salt is 0.05 mdd (mg / dm ² / day) or less as an area where the weather-resistant steel can be used without painting.

[0004] However, it is known that rust of weather-resistant steel is difficult to stabilize and practical corrosion resistance is difficult to obtain in an environment where the amount of flying salt is relatively high, such as a coastal area or a snow-melting salt spray area. In addition, for example, a portion that becomes a humid environment due to water leakage from an upper road, a floor slab, such as a bridge girder end portion,
Or in a so-called poor environment part, such as a part with a structure in which corrosive substances such as flying salt attached to the surface are not washed away by rainfall, such as the lower surface of the flange,
Unstable rust is generated and stable rust is hardly formed, so that the anticorrosion effect does not appear, which is not preferable. Furthermore, floating rust and flowing rust, such as red rust and yellow rust, not only have a problem in appearance, but also cause environmental pollution in the surroundings, and have a problem that the area where they can be used is limited.

[0005] Regarding these problems, for a newly-built structure, for example, Japanese Patent Publication No. 56-33991 discloses a method in which a resin layer containing a stable rust component is formed in a lower layer, and the upper layer has weather resistance and corrosion resistance. A surface treatment method by two-layer coating provided with a resin layer having excellent properties and the like is disclosed. In addition, Japanese Unexamined Patent Publication No.
JP-A-226198 discloses that a structure is covered with an organic resin paint containing at least one of chromium sulfate and copper sulfate in a total amount of 1 to 65% by mass. Further, in repairing an existing steel structure, a method of applying a coating to a portion where stable rust is unlikely to be formed is generally used.

[0006]

However, Japanese Patent Publication No. 56-33991 and Japanese Patent Application Laid-Open No. 6-226198 have been disclosed.
The invention of the publication No. is not an effective means for a portion where an unstable rust is formed in an existing structure using weathering steel, and a stable rust is not obtained even when painted on a portion where the unstable rust is formed. There is a problem that it is not formed.

Further, in the method of applying a coating to a portion where stable rust is unlikely to be formed, periodic repainting is inevitable.
At that time, it is necessary to perform rust removal treatment such as blast treatment as pretreatment, and work on site requires installation of equipment and power source, collection work of abrasives, dust scattering measures, etc. There is a problem that the cost becomes excessive.

Therefore, the present invention relates to a corrosion-resistant technique for weather-resistant steel used in steel structures, which is characterized in that it is easy and inexpensive to construct while maintaining super-long-term corrosion resistance. It is intended to provide an anticorrosion method.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors maintain the super-long-term corrosion resistance of the weather-resistant steel used for the steel structure, and at the same time, make the construction easy and easy. We examined the corrosion prevention method of weathering steel which can be manufactured at low cost. As a result, by applying an anticorrosive containing one or more of the alkoxy group-containing silane compound and / or its partial condensate to the surface of the rust layer of the weather-resistant steel,
We have found that the above problems can be solved. That is, by applying an anticorrosive agent containing one or more of the alkoxy group-containing silane compound and / or its partial condensate as a main component to the surface of the rust layer of the weather-resistant steel, it is unstable even in a poor environment part. It has been found that the formation of rust is prevented, the formation of stable rust is promoted, and furthermore, the stable rust is prevented from being deteriorated due to the addition of salt such as snow melting salt. Further, an alkoxy group-containing silane compound and / or
Alternatively, it has been found that an anticorrosive containing one or more of its partial condensates as a main component also has an effect of stabilizing unstable rust. As a result, even when repairing existing weather-resistant steel structures, a time-consuming blasting process and a base treatment process such as a two-type keren that exposes the steel surface by removing rust with an electric or air blast tool are used. It can be omitted, and the super long-term corrosion resistance is maintained even with a simple base treatment that removes floating rust with a brush.

The present invention has been made based on such findings, and is an anticorrosion agent and a method for anticorrosion for weathering steel having the following features. [1] An anticorrosion agent for weather-resistant steel comprising one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof as a main component. [2] A weather-resistant steel, characterized in that an anticorrosive containing one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof as a main component is applied to the surface of a rust layer of the weather-resistant steel. Anticorrosion method.

In the description of the present invention, unstable rust means rust that does not have a protective effect against atmospheric corrosion and generates floating rust such as red rust and yellow rust. Means dense rust which has a protective action against atmospheric corrosion.

[0012]

DETAILED DESCRIPTION OF THE INVENTION One or two of an alkoxy group-containing silane compound and / or a partial condensate thereof used in the present invention.
The anticorrosive containing at least one species as a main component is a paint obtained by mixing (for example, dispersing, emulsifying or dissolving) it in water or an organic solvent. A paint in which one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof is dispersed, emulsified or dissolved in water is called an aqueous type, and a paint which is dispersed, emulsified or dissolved in an organic solvent is referred to as an organic solvent. Called type. The aqueous type is more preferable than the organic solvent type in terms of working environment.

Here, the alkoxy group-containing silane compound is represented by the following general formula. R _n Si (OR) _4-n
In the formula, n is an integer of 0 to 3. R is a stable hydrophobic group such as a hydrocarbon-based substituent such as an alkyl group or a phenyl group, and usually has 1 to 8 carbon atoms.

Examples of the alkoxy group as OR include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentanoxy group, a hexanoxy group, an octyloxy group, a phenoxy group, an acryloyloxyethoxy group and a glycidyloxy group.

Specific examples of the alkoxy group-containing silane compound represented by the general formula include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltrimethoxysilane, and the like. Ethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane,
Octyltrimethoxysilane, octyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, methyltriisobutoxy Silane, methyltributoxysilane, methylSEC-trioctyloxysilane, methyltriphenoxysilane, methyltri (acryloyloxyethoxy) silane, methyltri (glycidyloxy) silane, lauryltriethoxysilane, stearyltrimethoxysilane, stearyltriethoxysilane, etc. Can be mentioned. In addition, these can be used individually by 1 type or in mixture of 2 or more types. In addition to the above compounds, their partial condensates can also be used.

As the organic solvent, for example, mineral spirit, toluene, isopropyl alcohol and the like can be used. The preferred proportion of water or organic solvent is 10-90% by weight of the total weight, more preferably 50-80% by weight. In addition, it is preferable to add a dispersant to water or the organic solvent in order to keep the components uniform. The dispersant is not particularly limited, and for example, trioxyethyloctylphenyl ether or the like can be used.

The anticorrosive for weather-resistant steel of the present invention comprises one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof as a main component. A silane compound containing a hydrolyzable substituent such as a hydroxyl group, a halogen atom, an acetoxy group, a carboxyl group, and an isocyanate group may be used. In addition, it is preferable to use an alkoxy group from storage stability and easy handling.

Next, in the anticorrosion method of the present invention, the above anticorrosion agent is applied to the surface of a rust layer of a steel material of a weather-resistant steel structure for performing anticorrosion.

When applying the above-mentioned anticorrosive to the surface of the rust layer of the steel material of the weather-resistant steel structure to be subjected to anticorrosion, usually, a base treatment is performed on the surface of the steel material, and thereafter, the application is performed.

Generally, the surface treatment of the rust layer of the steel material may be performed by removing floating rust with a brush or the like.

The application of the above-mentioned anticorrosive is carried out by a method such as brush coating, airless spray coating, air spray coating or roller coating. The coating amount is not particularly limited as long as the coating amount is sufficient to sufficiently impregnate the rust layer and substantially cover the surface of the rust layer. For example, when the proportion of water or an organic solvent is about 20% by weight, It is preferably about 0.1 to 0.7 liter / m ² , and the number of coatings is preferably about 1 to 5 times. The drying is preferably performed at room temperature for about 1 day to 2 weeks.

Hereinafter, the action of the anticorrosive containing an alkoxy group-containing silane compound as a main component will be described. Note that a partial condensate of an alkoxy group-containing silane compound has a similar effect.

FIG. 1 is a schematic view showing the reaction mechanism of an anticorrosive containing an alkoxy group-containing silane compound as a main component on the surface of a weather-resistant steel material on which unstable rust is formed in an existing steel structure. When an anticorrosive containing an alkoxy group-containing silane compound as a main component is applied to the surface of the weather-resistant steel material on which unstable rust is formed, a higher alkylalkoxysilane monomer as the main component penetrates into pores of the rust layer, and the compound is removed. And the condensation reaction between the compound and the hydrophilic group in iron rust,
Forms a hydrophobic alkyl group on the surface of iron rust. This changes the water-absorbing rust layer into a hydrophobic or water-repellent anti-water-absorbing layer. In addition, even when the anticorrosive is applied to the steel surface of a new steel structure in which unstable rust is not formed, the compound has the same action as described above on a very thin rust layer on the steel surface. Then, the rust layer is changed to a water absorption preventing layer having hydrophobicity or water repellency. The remainder of the compound forms a hydrophobic or water-repellent anti-water absorption layer by mutual condensation reaction.

The water absorption preventing layer prevents moisture from penetrating into the rust layer, and also prevents the invasion of corrosive substances such as chloride ions, which cause the formation of unstable rust, and prevents the formation of unstable rust. I do. Furthermore, the water absorption prevention layer has an effect of promoting the formation of stable rust by allowing water vapor and oxygen necessary for the formation of stable rust to permeate the steel material surface in an appropriate amount, and condensing moisture at the interface between the steel material and the rust layer.

The anticorrosive containing at least one of an alkoxy group-containing silane compound and / or a partial condensate thereof is preferably applied to the entire surface of the weathering steel structure. It may be partially applied only to a poor environment part of a steel structure. Even if it is applied only to a poor environment part of the weather-resistant steel structure, it has an effect of maintaining the long-term durability of the entire weather-resistant steel structure.

Here, the anticorrosive containing one or more of the alkoxy group-containing silane compound and / or its partial condensate as a main component can be a clear coating. Even if the clear paint is applied, the color tone of the rust surface of the weather-resistant steel is not impaired, and even when partially applied, there is no difference in appearance between the parts that do not use the clear paint and the sense of incongruity. Because it will not be given.

The anticorrosive containing one or more of the alkoxy group-containing silane compound and / or a partial condensate thereof as a main component is a mixture of one or more of rust preventive pigments or color pigments. Can be done. In particular, it is more preferable to mix a pigment having a rust stabilizing effect because the rust stabilizing effect is promoted. Examples of pigments that promote the rust stabilizing effect include copper oxide, copper sulfate, chromium phosphate, chromium sulfate, chromium nitrate, nickel phosphate, nickel sulfate, nickel nitrate, and the like. One or more of these are used. can do.

The anticorrosive containing one or more of alkoxy group-containing silane compounds and / or partial condensates thereof as a main component may be used in addition to, or instead of, the above-mentioned rust preventive pigments or coloring pigments. , One of inorganic or organic desalting agents
Species or a mixture of two or more species can also be used. By mixing this desalting agent, it is possible to remove corrosion factors such as chloride ions in rust that cause unstable rust generation, and to more effectively prevent the generation of unstable rust. .

Here, as an inorganic desalting agent capable of removing anions such as chloride ions, for example, Al ₂ O _3.
hydrous oxides such as nH ₂ O, SiO ₂ .nH ₂ O, Bi ₂ O ₃ .3H ₂ O, acidic salts such as zirconium phosphate and hydroxyapatite, basic salts such as hydrotalcites, Complex hydroxide, hexacyanoiron (III) salt and the like can be used.

As an organic desalting agent capable of removing anions such as chloride ions, ion exchange resins and chelate resins can be used. The ion exchange resin is not particularly limited as long as it has a skeleton of a hydrocarbon or a polymer such as fluorocarbon and has an ion exchange group introduced therein. In addition, as an ion exchange group of the ion exchange resin, for example, those having one or more anion exchange groups such as quaternary ammonium and primary to tertiary amines can be used.

Further, anticorrosives containing one or more of alkoxy group-containing silane compounds and / or partial condensates thereof as main components include the above-mentioned rust-proof pigments or color pigments, inorganic or organic desalinated salts. In addition to or instead of the agents, a resin having a multilayer coating forming function can be mixed and used. This resin has a lower penetrating power into the rust layer than the anticorrosive agent, and forms a multi-layered film on the surface of the anticorrosive agent film.

By mixing a resin having a function of forming a multilayer coating with an anticorrosion agent containing one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof as a main component, the anticorrosion agent becomes a rust layer. Is stabilized and densified, and the mixed resin forms a tough protective film with excellent adhesion on the anticorrosive film, thereby effectively preventing the invasion of corrosive substances from the outside. In addition, the physical strength is increased by the protective film, and a protective layer effective against external impact is formed.

Examples of the resin having the function of forming a multilayer coating include:
For example, a silane crosslinked acrylic resin can be used. An example of the silane crosslinked acrylic resin is an acrylic copolymer having an alkoxysilyl group. When an acrylic copolymer having an alkoxysilyl group is used, the following radical polymerizable components a to c
Is preferably copolymerized by emulsion polymerization or microsuspension polymerization. a: an alkoxysilane having a radical polymerizable group b: a vinyl monomer copolymerizable with the above component a c: an average degree of condensation having a radical polymerizable group copolymerizable with the above component a at one end of the molecule is 3 The above polyester or polyalkylene oxide

From the above, preferred forms of the anticorrosive of the present invention are as follows. (1) One or more of alkoxy group-containing silane compounds and / or partial condensates thereof and one or more of rust preventive pigments or color pigments (preferably, pigments having a rust stabilizing effect, For example, copper oxide, copper sulfate, chromium phosphate, chromium sulfate, chromium nitrate, nickel phosphate, nickel sulfate,
One or more kinds such as nickel nitrate) in water or an organic solvent.

(2) One or more of an alkoxy group-containing silane compound and / or a partial condensate thereof and one or more of an inorganic or organic desalting agent (for example, Al ₂ O
Hydrous oxides such as ₃ · nH ₂ O, SiO ₂ · nH ₂ O, Bi ₂ O ₃ · 3H ₂ O, acidic salts such as zirconium phosphate and hydroxyapatite, and basicities such as hydrotalcites Salt, composite hydroxide, hexacyanoiron (III)
One or more of a salt, an ion exchange resin, a chelate resin and the like) mixed with water or an organic solvent.

(3) One or more of an alkoxy group-containing silane compound and / or a partial condensate thereof and a resin having a multilayer coating forming function (for example, a silane crosslinked acrylic resin) are mixed with water or an organic compound. What was mixed with solvent.

(4) One or more of alkoxy group-containing silane compounds and / or partial condensates thereof, and one or more of the above-mentioned (1) rust-preventive pigment or colored pigment, and A mixture of one or more inorganic or organic desalting agents of 2) in water or an organic solvent.

(5) One or more of an alkoxy group-containing silane compound and / or a partial condensate thereof, and one or more of the above-mentioned (1) rust preventive pigment or colored pigment, and the above ( A resin obtained by mixing the resin having the function of forming a multilayer coating of 3) with water or an organic solvent.

(6) One or more of an alkoxy group-containing silane compound and / or a partial condensate thereof, and one or more of the inorganic or organic desalting agent of (2); A resin obtained by mixing the resin having the function of forming a multilayer coating of the above (3) with water or an organic solvent.

(7) One or more of an alkoxy group-containing silane compound and / or a partial condensate thereof, and one or more of the above-mentioned (1) rust preventive pigment or colored pigment, and the above ( 2) one or more inorganic or organic desalting agents and a resin having a multilayer coating forming function (for example,
Silane-crosslinked acrylic resin) mixed with water or an organic solvent.

[0041]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

As a test steel material, a weather-resistant steel on which unstable rust was formed was prepared. The size of the test piece is 150 mm x 70
mm × 6 mm. As a base treatment of the test steel material, only floating rust on the rust surface was removed using a nylon brush.

In the present embodiment, as an anticorrosive containing one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof as a main component, an aqueous type (Example 1,
3, 4, 5) and organic solvent type (Example 2). In addition, a silane crosslinked acrylic resin (Example 3) was used as the resin for forming the multilayer coating. Further, as a pigment having a rust stabilizing effect, a mixture of chromium phosphate (Example 4) and a hydrous bismuth oxide (Bi ₂
O ₃ · 3H ₂ O) a mixture was used (Example 5).

An anticorrosive agent, a resin for forming a multilayer coating, a pigment having a rust stabilizing effect, and a desalinating agent, which are mainly composed of one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof, are mixed. The test pieces of Examples 1 to 5 were prepared by applying a brush to the base treated surface of each of the test steel materials at a coating amount of 0.1 l / m ² and drying at room temperature for 3 days.

As comparative examples, a test piece coated with a commercially available oil-based paint (Comparative Example 1) and a test piece not subjected to any treatment (Comparative Example 2) were used.

The test pieces of Examples 1 to 5 and Comparative Examples 1 and 2 obtained as described above were exposed at an exposure test site for 6 months. This exposure test site is located about 200 m away from the shoreline, and is in an environment suitable for generating unstable rust because sea salt particles fly from the sea side.

The test piece was exposed at an angle of about 45 ° with respect to the ground so that the test surface on which the test piece was coated was not easily dried by sunlight and unstable rust was likely to occur. The lower surface of the test piece was set.

After exposing the test piece for 6 months, the amount of floating rust was measured by a tape peeling test. In this tape peeling test, a 50 mm × 50 mm adhesive tape was used, and the total amount of floating rust peeled off when the test was repeated three times on the same portion of the test piece was measured.

Further, the number of defects in the rust layer was counted based on the number of coloring points by performing a ferroxyl test, and the formation of stable rust was evaluated.

Table 1 summarizes the results of the floating rust evaluation and the ferroxyl test of each of the examples and comparative examples.

[0051]

[Table 1]

As shown in Table 1, test pieces (Examples 1 to 5) coated with an anticorrosive containing one or more of the alkoxy group-containing silane compound of the present invention and / or its partial condensate as a main component were prepared. ) Indicates that the amount of floating rust is less than 0.03 g in all cases despite the exposure in a severe corrosive environment where sea salt particles fly near the coast, and the number of defects is 150 / dm ^{2 in the} ferroxyl test. Is less than. Therefore, it is understood that stable rust is formed on the test piece.

On the other hand, a commercially available oil-based paint was
The amount of floating rust was 0.03 g between the sample applied to the sample (Comparative Example 1) and the sample not subjected to any treatment (Comparative Example 2).
As described above, the number of defects in the ferroxyl test evaluation was 200 / dm ² or more, indicating that no stable rust was formed.

[0054]

As described above, according to the present invention, it is possible to prevent the formation of unstable rust even in an environment where the amount of flying salt is relatively high, such as a coastal area or a snowmelt salt spray area, or in a poor environment. It has the effect of promoting the formation of stable rust and preventing the deterioration of the once formed stable rust. Further, it has an effect of stabilizing unstable rust. As a result, even when repairing existing weather-resistant steel structures, a time-consuming blasting process and a base treatment process such as a two-type keren that exposes the steel surface by removing rust with an electric or air blast tool are used. Ultra-long-term corrosion resistance can be easily maintained even with a simple base treatment that can be omitted and removes floating rust with a brush. Thereby, in the anticorrosion technology of a weathering steel structure, an anticorrosion agent and a method for anticorrosion of a weathering steel structure which can be easily and inexpensively constructed while maintaining the corrosion resistance for an extremely long period of time are provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic diagram of a reaction mechanism of an anticorrosive containing an alkoxy group-containing silane compound as a main component.

Claims (2)

[Claims] 1. An anticorrosive for weathering steel comprising one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof as a main component. 2. A weather resistance characterized in that an anticorrosive containing one or more of an alkoxy group-containing silane compound and / or a partial condensate thereof as a main component is applied to the surface of a rust layer of weather resistant steel. Steel corrosion protection method.