JPH055900B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for rust-preventing steel materials among inorganic materials with a high chloride ion concentration. <Prior Art> It is known that steel materials are originally extremely resistant to corrosion in a highly alkaline environment contained in inorganic materials such as concrete. Therefore, steel materials usually do not rust even if no rust prevention measures are taken. However, it is known that when the chlorine ion concentration in the inorganic material surrounding the steel material is high, the steel material corrodes relatively easily even in a highly alkaline environment that has not been neutralized. This is usually explained as follows. In a highly alkaline environment, steel materials form an oxide film of γ-Fe ₂ O ₃ on their surfaces, which prevents corrosion of the steel materials. This is called passivation. However, if chloride ions are present here due to contamination with chlorides, this passive film will be destroyed. In this case, the passive film is usually locally destroyed and the steel material is exposed. Then, this narrow part becomes the anode, and the wide part covered with another passive film becomes the cathode, and since a large potential difference is generated between the two, corrosion concentrates on the anode in the narrow part.
As a result, a form of corrosion often called pitting corrosion occurs at various locations on the steel surface. This pitting corrosion rapidly reduces the effective cross section of the steel material and is dangerous even if the number of occurrences is small. Furthermore, if the number of corrodes increases significantly, the surface of the steel material will be covered with continuous corroded parts. When steel corrodes, the first step is to produce ferrous hydroxide, Fe(OH) ₂ . Since it is unstable and easily oxidized, it quickly turns into iron oxides, such as α-FeOOH and Fe ₃ O ₄ , which are the main components of rust. Volumetric expansion occurs during this rust formation process. Then, when the inorganic material reinforced by steel material is reinforced concrete, the above-mentioned expansion is restrained by the concrete, so that a large expansion pressure acts on the concrete around the reinforcing bars. This expansion pressure often causes cracks to develop in the covered concrete along the reinforcing bars. If this progresses further, this cover (covering) concrete will be missing. Then, the rusting of the reinforcing bars progresses more and more, and the cross-sectional defects of the reinforcing bars become even larger, eventually leading to the collapse of the structural members. The reasons why chlorine ions are introduced into inorganic materials that cause serious damage to inorganic materials containing steel (hereinafter also referred to as reinforced concrete) are listed below. Use of sea sand as fine aggregate Expansion of concrete structures into the marine environment Spraying of ice-melting agents Use of chemical admixtures containing large amounts of chloride Among these, when sea sand is used as fine aggregate, Salt can be removed by washing with water. However, its complete implementation is difficult in practice and is often not implemented in reality. Furthermore, in the past, calcium chloride and the like containing a large amount of chlorine ions were frequently used as concrete admixtures to impart hardening properties to concrete. Although the use of chlorine-based admixtures is now on the decline, reinforced concrete that has been used over the past 20 years and contains large amounts of chlorine ions still remains. Furthermore, the number of concrete structures used in the marine environment is expected to increase in the future as they are highly valued for their ease of maintenance. However, in this case, since salt is constantly supplied from the outside, there is no way to prevent salt intrusion other than applying a completely water-impermeable coating. <Problems to be solved by the invention> Now, if it is not possible to prevent salt from entering the structure of structures such as reinforced concrete, then
It is necessary to consider and implement methods to prevent steel materials from rusting even when salt enters. Concrete admixtures for the purpose of rust-preventing the reinforcing bars in reinforced concrete, etc., which are made of sea sand and other materials and in which harmful amounts of chlorine ions cannot be avoided, have already been developed in patents No. 937065 and No. 937065.
It is publicly known from No. 941253, No. 554656, No. 987505, etc. And based on this
JIS A6205 "Rust preventive agent for reinforced concrete" has been established, and its effectiveness has been well-received. However, this type of rust preventive agent has conventionally been used by mixing it with other inorganic agents when pouring concrete. Therefore, it has never been considered as a repair (reinforcement) treatment agent or repair treatment method for existing reinforced concrete or the like. The present inventors have proposed (i) rust prevention of reinforcing steel by coating and impregnating the surface of inorganic materials with this type of rust preventive agent when a harmful amount of salt is contained in already placed reinforced concrete, etc.; method, (ii) a reinforcing steel rust prevention method by coating and impregnating an aqueous solution of a water-soluble silicate compound in addition to the rust preventive agent when the reinforced concrete etc. is neutralized and deteriorated; 3. the rust preventive agent;
We previously filed a patent application for a method for preventing rust on reinforcing steel by coating it with a cement-based composition to prevent water-soluble silicate compounds from leaking out. Subsequently, the inventors researched ways to more completely and easily prevent the leakage of these rust preventives and water-soluble silicate compounds, and found that silicone-based and/or He learned that it would be better to top coat with a silane-based primer and completed the invention. <Means for Solving the Problem> That is, the present application consists of the following four inventions. First invention: A first step of coating and impregnating the surface of an inorganic material containing a steel material with an aqueous solution of inorganic salts having a rust-preventing effect on the steel material. After the first step, a silicon-based ,or/
and a second step of overcoating with a silane-based primer. Second invention: Sequentially performing a third step of further coating the surface of the inorganic material after implementing the first invention with a paint. Third invention: An invention in which a (second) step of applying and impregnating an aqueous solution of a water-soluble silicate compound is added before or after the first step of the first invention. Fourth invention: Sequentially performing a fourth step of further coating the surface of the inorganic material after carrying out the third invention with a paint. Consists of four inventions. The purpose of these inventions is to prevent steel materials among inorganic materials with a high chlorine ion concentration from rusting by performing the treatment of the present invention even after reinforced concrete etc. have been placed, and to prevent the rusting. It is an object of the present invention to provide a method for rust-preventing steel materials among inorganic materials, which makes it possible to make the rust effect permanent. In this invention, the inorganic material containing steel refers to reinforced concrete, steel reinforced concrete, lath mortar, steel fiber concrete, etc. In this invention, inorganic salts (corrosion inhibitors for concrete, etc.) that have a rust-preventing effect are used to prevent corrosion on the anode and cathode formed on the steel surface by adding a small amount of them to a corrosive environment (in the presence of chlorine ions). A chemical that can suppress electrochemical corrosion reactions by forming a film. Moreover, these drugs are specifically classified into the following two types. (1) Anodic rust inhibitors Nitrite, chromate, etc. These agents directly or indirectly oxidize the steel surface, forming a dense film of metal oxide on the surface and forming an anode. suppress the reaction. (2) Cathode-type rust inhibitors Carbonates, phosphates, polyphosphates, etc. These agents act with other ions coexisting in the corrosive environment to form a film of salts that are sparingly soluble in water on the steel surface (cathode). ) to suppress the cathode reaction. Next, the application amounts of these rust preventives are shown below in relation to the amount of chlorine ions (converted into common salt) contained in inorganic materials such as existing concrete. Calcium nitrite 3% or more Sodium nitrite 3% or more Calcium phosphate (Ca ₃ (PO ₄ ) ₂ ) 4% or more Sodium chromate 2% or more The amounts of these rust inhibitors are neutral for inorganic materials such as concrete. When carbonation is not progressing and the pH is high, a small amount is sufficient, but when neutralization is progressing, a large amount is required. Since the rust preventive agent of this application is strongly alkaline (the pH of a 30% solution of calcium nitrite, which is most commonly used, is 11 to 12), it can be applied to concrete that is undergoing neutralization. It becomes possible to return the internal atmosphere to strong alkalinity. 30 of calcium nitrite, which is most commonly used as a rust preventive agent in this application.
When the solution was applied to mortar (cement to aggregate ratio of 1:3) or concrete, the penetration depth was more than 4 mm, but over time, ions diffused into the interior. It was found that it penetrated gradually. In this invention, the water-soluble silicate compound is a single silicate or a mixture of silicate represented by the general formula M ₂ O.nSiO ₂ . However, in the above general formula, M is Li, Na, K, Cs or ammonium component, and n is an integer. Examples of the ammonium component include primary amines such as methylamine and ethylamine, secondary amines such as dimethylamine and diisopropylamine, trimethylamine,
Examples include tertiary amines such as triethanolamine, quaternary ammoniums such as monomethyltriethanolammonium and tetraethanolammonium, and ammonia. Also, the value of n is preferably 1
~5, but is not particularly limited. It may be within a range that does not interfere with water solubility and permeability during actual use. Furthermore, additives such as curing agents to increase the water resistance of the water-soluble silicate compound after drying and curing may be added to the extent that they do not affect workability or permeability, but they should not be used alone. In this case, it is preferable to use lithium silicate, which has relatively good water resistance.
Therefore, the concentration of the aqueous solution of the silicate compound in use is not particularly limited, but is usually 30% or less. In this invention, the reason why the solution of inorganic salts such as nitrites and the aqueous solution of water-soluble silicate compounds applied to the surface of the inorganic material containing the steel material has a synergistic effect in rust prevention is considered as follows. Originally, an aqueous solution of a water-soluble silicate compound is a substance that is unstable to chemicals, so an aqueous solution of a water-soluble silicate compound and an aqueous solution of a rust preventive agent containing nitrite etc. are mixed in liquid form. In this case, a gelation reaction immediately occurs and a solid substance is precipitated. Therefore, when these two aqueous solutions are individually and continuously impregnated into concrete, a gelation reaction occurs in the concrete structure, and both chemical components are fixed in the concrete structure. For this reason, when an aqueous solution of a water-soluble silicate compound and a rust preventive agent are applied and impregnated in succession, the expected effects of using each alone, such as imparting alkalinity to neutralized concrete, enhancing solidification of deteriorated concrete areas, and chlorine ion It is expected that it will not only effectively prevent damage caused by rusting of reinforcing steel, but also fill voids in the concrete structure, fill cracks that occur in concrete, and repair sutures at the same time. It is. Next, in order to understand the rusting status of steel materials in inorganic materials with a high chlorine ion concentration and the rust-preventing effects of the inorganic salts and water-soluble silicate compounds used in the present invention, which have rust-preventing effects, on steel materials, the following steps were taken. We conducted a model experiment and present the results. [1] Experimental method (a) Prepare 12 types of solutions in each beaker containing calcium nitrite in the range of 0 g/~24 g/ and lithium silicate in the range of 0 g/~16 g/ in 1.3% (13 g/) saline solution. , and reinforcing bars of the same shape and weight (d=10mm, L=
100mm). The reason why this experiment was conducted in 1.3% saline water was because the amount of chlorine ions contained in reinforced concrete constructed in the past was low, based on actual analysis data, and due to the use of sea sand and chemical admixtures. From the numerical value calculated theoretically from the amount, it is 2.4 as table salt.
This is because it is around Kg/ ^m3 or less (assuming the unit water volume is 180Kg, it is 2.4Kg/180Kg).
=0.013). (b) Create 12 types of aqueous solutions with the same composition as the 12 types in (a), saturated with calcium hydroxide,
Immerse the reinforcing steel in the same way (calcium hydroxide is added to approximate the atmosphere inside the concrete). (c) After 8 days, pull up the soaked reinforcing bars and measure the amount of rust. [2] Experimental results The results of the above experiments are shown in Table 1. The amount of rust is 1
Expressed in mg of rust per cm ² . From the above table, it is known that lithium silicate and calcium nitrite synergistically prevent rusting of steel materials. The primer used in this invention refers to a primer that is applied to modify the surface condition of porous materials prior to adhesion, or to promote the effectiveness of an adhesive that is applied afterwards. Examples of silane compounds used in the silane primer used in this invention are listed below. (a) Vinyltrichlorosilane CH ₂ =CHSiCl ₃ (b) Vinyl-tris (β-methoxyethoxy)
Silane CH ₂ =C(CH ₃ )C(=O)O(CH ₂ ) ₃ Si
(OCH ₃ ) ₃ (c) Vinyltriethoxysilane CH ₂ =CHSi(OC ₂ H ₅ ) ₃ (d) γ-methacryloxypropyltrimethoxysilane CH ₂ =C( _CH3 )C(=O)O(CH ₂ ) _3Si
(OCH ₃ ) ₃ (e) β-(3,4-epoxycyclohexyl)
Ethyltrimethoxysilane (f) γ-glycidoxypropyltrimethoxysilane (g) Vinyltriacetoxysilane CH ₂ =CHSi(OCOCH ₃ ) ₃ (h) γ-Mercaptopropyltrimethoxysilane HSCH ₂ CH ₂ CH ₂ Si(OCH ₃ ) ₃ (i) γ-Aminopropyltriethoxysilane NH ₂ CH ₂ CH ₂ CH ₂ Si(CO ₂ H ₅ ) ₃ (j) γ-[bis(β-hydroxyethyl)]aminopropyltriethoxysilane (HOCH ₂ CH ₂ ) ₂ N(CH ₂ ) ₃ Si(OC ₂ H ₅ ) ₃ (k) N-β-(aminoethyl)-γ-aminopropyltriethoxysilane NH ₂ CH ₂ CH ₂ CH ₂ Si(OC ₂ H ₅ ) ₃ (l) γ-(β-aminoethyl) Aminopropyldimethoxymethylsilane NH ₂ (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₂ CH ₃ (n) N-(trimethoxysilylpropyl)ethylenediamine NH ₂ (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si(OCH ₃ ) ₃ (m) N-(dimethoxymethylsilylisopropyl)ethylenediamine (CH ₃ O) ₂ Si(CH ₃ )CH ₂ CH(CH ₃ )
CH ₂ NH (CH ₂ ) ₂ NH _2The silicon-based paint used in this invention is:
silicone (organopolysiloxanes) resin,
Modified silicone resin (as a modifier, alkyd,
epoxy, phenol, acrylic, melamine,
Refers to paints whose main components are urethane resins, etc.). Silicon-based or/
Examples of silane-based primers are listed below. (a) (b) Epoxy resin modified silicone resin (50%
xylene solution) 20 parts as solid content (b) Mercapto group-containing silane (Hs(CH ₂ ) ₃ Si
(OCH ₃ ) ₃ ) 10 parts (c) Methyl ethyl ketone 30 parts (d) Isocyanurate ring-containing urethane prepolymer 100 parts as a solid substance Note that the above epoxy resin-modified silicone resin 1
is a silicone resin made of polymethylphenylsiloxane obtained by hydrolyzing a mixture of dimethyldichlorosilane, methyltrichlorosilane, diphenyldichlorosilane, phenyltrichlorosilane etc. equivalent weight
100 to 500) and modified by a conventional method. Further, as the isocyanurate ring-containing urethane prepolymer, a reaction product of tris(2-hydroxyethyl)isocyanurate and hexamethylene diisocyanate, or a reaction product of tolylene diisocyanate and hexamethylene diisocyanate was used. (b) (a) Organopolysiloxane resin (50% xylene solution) 200 parts (b) HS (CH ₂ ) ₃ Si (OCH ₃ ) ₃ 10 parts (c) Ethyl orthosilicate, (or propyl polysilicate, ethyl Polysilicate) 15 to 25 parts (iv) Toluene, xylene, acetone, isopropanol, etc. 100 to 500 parts The organopolysiloxane resin has (CH ₃ ) ₂ SiO units as molecular constituent units: 5 to 500 parts.
It has 30 mol% units, _{CH3SiO3 /2} units: 50 to 90 mol% units, and _{C6H5SiO3 /2 units} : 5 to 20 mol% units. Moreover, HS(CH ₂ ) ₄ Si(OC ₂ H ₅ ) ₃ is often used for (b). (c) (a) α,ω-dihydroxypolydimethylsiloxane 70 to 100 parts (b) Fumed silica (surface area 170 to 250 m ² /g)
5 to 15 parts (c) Methyl ethyl ketone 30 parts (d) Methyltrissilane (ethylketoxime silane) 3 to 10 times (e) γ-aminopropyltriethoxysilane
0.5 to 2 parts (f) Dibutyltin diacetate 0.5 to 2 parts (d) (a) Chlorinated rubber 0.5 to 50 parts (b) Acrylic acid-methyl methacrylate copolymer 0.5 to 50 parts (c) γ-mercaptopropyltri Methoxysilane 0.1 to 5 parts (d) Toluene (organic solvent 50 to 200 parts) The following substances can be used in place of the substances (a), (b), and (c) above. (a) Chloroprene polymer, Chloroprene-acrylonitrile copolymer, etc. (b) Acrylic acid-methyl methacrylate copolymer, acrylic acid-methyl methacrylate-styrene copolymer, acrylic acid-2-hydroxyethyl acrylate copolymer, acrylic acid-2- Hydroxyethyl acrylate
Styrene copolymer, ethyl-α-hydroxymethyl acrylate polymer, ethyl-α-hydroxymethyl acrylate-α-methylstyrene polymer, methacrylic acid-ethyl acrylate-styrene copolymer, acrylic acid-ethyl acrylate-styrene copolymer , methyl acrylate-acrylamide-styrene copolymer, ethyl acrylate-acrylonitrile-styrene copolymer, etc. (copolymerization of acrylic unsaturated compounds such as acrylic acid, acrylic acid derivatives, methacrylic acid, and methacrylic acid derivatives and styrene compounds) combination). (c) Methyltrimethoxysilane-γ-aminopropyltriethoxysilane cohydrolyzate, dimethyldiethoxysilane-γ-methacryloxypropyltrimethoxysilane-γ-mercaptopropyltrimethoxysilane cohydrolyzate, γ-aminopropyl Triethoxysilane (including partial hydrolysates), γ-aminopropyl group-containing polysiloxane, vinyltriacetoxysilane, phenyltrimethoxysilane
γ-mercaptopropyltrimethoxysilane cohydrolyzate, vinyltriethoxysilane
γ-mercaptopropyltrimethoxysilane cohydrolyzate, γ-glycidoxypropyltrimethoxysilane, etc. can be used. Example 1 A building with 7 floors above ground and 1 floor underground finished with exposed concrete (ordinary concrete for 3rd floor and above, lightweight concrete for 4th floor and above) that has been constructed for 15 years has turned into powder, cracks, floating concrete, etc. Repair work was carried out because there were many exposed areas of reinforcing steel. The concrete in this building has a salt content of 0.042
% (0.16% for fine aggregate), and the carbonation depth is
It was 25-35mm. In this construction, the concrete surface was washed with high pressure water and dried, then calcium nitrite was applied.
A reinforcing steel rust preventive agent containing 30% was applied twice with a roller brush for impregnation (400 g/m ² ). Then dry and apply the primer (a) above (300g/m ² )
Then, on top of that, apply a futsuso resin paint (product name:
It was finished by applying New Germet #500 (Toa Paint Co., Ltd.) (400 g/m ² ). When we conducted an investigation one year after the repair, no abnormalities were found. Example 2 In the same manner as in Example 1, the building of Example 1 was washed with high pressure water, coated with rust preventive agent and impregnated with reinforcing steel, then coated with the primer (b) (350 g/m ² ), and then coated with acrylic. Apply resin-based paint (product name: Onoda Top Coat Type, Onoda Kenzai Co., Ltd.) (350g/
^m2 ) and finished. When we conducted an investigation one year after the repair, no abnormalities were found. Example 3 A building with 7 floors above ground and 1 floor underground finished with exposed concrete (ordinary concrete for 3rd floor and above, lightweight concrete for 4th floor and above) that has been constructed for 15 years has turned into powder, cracks, floating concrete, etc. Repair work was carried out because there were many exposed areas of reinforcing steel. The concrete in this building has a salt content of 0.042
% (0.16% for fine aggregate), and the carbonation depth is
It was 25-35mm. In this construction, the concrete surface was washed with high-pressure water and dried, and then a surface reinforcing/alkalinizing agent containing 12% lithium silicate was applied twice with a roller brush and impregnated (400 g/m ² ). Next, add 30% calcium nitrite
% of reinforcing steel rust preventive agent was applied twice with a roller brush (400 g/m ² ), then dried.
Topcoat with the primer (300g/m ² ) of (c) above,
Furthermore, a silica-based inorganic paint (product name: Dice Coat 900P, Dainichiseika Kagyo Co., Ltd.) was applied (400
g/m ² ) and finished. When we conducted an investigation three years after the repair, no abnormalities were found. Example 4 In the building of Example 3, high-pressure water cleaning, surface reinforcement, alkali imparting agent application and impregnation,
Apply and impregnate the reinforcing steel with a rust preventive agent, then apply the primer (400g/m ² ) from (d) above, and then apply silicone paint (product name: Aqua Seal 190S, Steel Chemical Industry Co., Ltd.). )) applied (250g/
^m2 ) and finished. When we conducted an investigation one year after the repair, no abnormalities were found. <Effects of the Invention> As described above, according to the method of rust-preventing steel materials in inorganic materials according to the present invention, salt (chlorine ions) in existing inorganic materials with a high salt content can be easily rendered harmless. Through simple repair work, the reinforcing bars (steel materials) in inorganic materials can be easily protected and rust-proofed, and the effect can be made permanent.

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Claims (1)

[Scope of Claims] 1. A first step of coating and impregnating the surface of an inorganic material containing a steel material with an aqueous solution of inorganic salts having a rust-preventing effect on the steel material. After the first step, the surface of the inorganic material is A method for rust-preventing steel materials among inorganic materials, characterized by sequentially passing through a second step of overcoating with a silicone-based and/or silane-based primer. 2. A method for rust-preventing steel materials among inorganic materials according to claim 1, wherein the inorganic salt is a nitrite. 3. The method for rust-preventing steel materials among inorganic materials according to claim 1, wherein the nitrite is calcium nitrite. 4. The first step of applying and impregnating the surface of the inorganic material containing the steel material with an aqueous solution of inorganic salts having a rust-preventing effect on the steel material, and after the first step, the surface of the inorganic material is coated with silicon-based or/ A method for rust-preventing steel materials among inorganic materials, characterized by sequentially passing through a second step of top-coating a silane-based primer, and a third step of top-coating a paint on the surface of the inorganic material after the second step. 5. A method for rust-preventing steel materials among inorganic materials according to claim 4, wherein the inorganic salt is a nitrite. 6. The method for rust-preventing steel materials among inorganic materials according to claim 4, wherein the nitrite is calcium nitrite. 7. The method for rust-preventing steel materials among inorganic materials according to claim 4, wherein the main component of the paint is an acrylic resin. 8. The method for rust-preventing steel materials among inorganic materials according to claim 4, wherein the main component of the paint is a fluorine resin. 9. The method for rust-preventing steel materials among inorganic materials according to claim 4, wherein the main component of the paint is silicone resin. 10. The method for rust-preventing steel materials among inorganic materials according to claim 4, wherein the main component of the paint is a silica-based inorganic paint. 11 After passing through the following first and second steps in any order on the surface of the inorganic material containing the steel material, the third step of coating with a silicone-based or/and silane-based primer is performed in sequence. Features: A method for rust-proofing steel among inorganic materials. First step: A step of applying and impregnating the steel material with an aqueous solution of inorganic salts having a rust-preventing effect. 2nd step: A step of applying and impregnating an aqueous solution of a water-soluble silicate compound. 12. A method for rust-preventing steel materials among inorganic materials according to claim 11, wherein the inorganic salt is a nitrite. 13. The method for rust-preventing steel materials among inorganic materials according to claim 11, wherein the nitrite is calcium nitrite. 14. The method for rust-preventing steel materials among inorganic materials according to claim 11, wherein the silicate compound is lithium silicate. 15 After passing through the following first and second steps in any order on the surface of the inorganic material containing the steel material, the third step is to further apply a silicone-based or/and silane-based primer, and to top-coat the paint. A method for rust-preventing steel materials among inorganic materials, the method comprising sequentially performing a fourth step. First step: A step of applying and impregnating the steel material with an aqueous solution of inorganic salts having a rust-preventing effect. 2nd step: A step of applying and impregnating an aqueous solution of a water-soluble silicate compound. 16. The method for rust-preventing steel materials among inorganic materials according to claim 15, wherein the inorganic salt is a nitrite. 17. The method for rust-preventing steel materials among inorganic materials according to claim 15, wherein the nitrite is calcium nitrite. 18. The method for rust-preventing steel materials among inorganic materials according to claim 15, wherein the silicate compound is lithium silicate. 19. The method for rust-preventing steel among inorganic materials according to claim 15, wherein the main component of the paint is an acrylic resin. 20. The method for rust-preventing steel materials among inorganic materials according to claim 15, wherein the main component of the paint is a fluorine resin. 21. The method for rust-preventing steel materials among inorganic materials according to claim 15, wherein the main component of the paint is silicone resin. 22. The method for rust-preventing steel materials among inorganic materials according to claim 15, wherein the main component of the paint is a silica-based inorganic paint.