Rust-proofing agents and rust-proofing method
A rust preventive agent with controlled nitrite and nitrate ion content and ratios addresses workability and delay in rust development, providing effective rust prevention with maintained fluidity.
Patent Information
- Application Number
- JP2023114277
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-07-12
- Publication Date
- 2025-01-24
AI Technical Summary
Nitrite-based rust inhibitors used in cross-section repair methods face issues with poor workability due to increased viscosity and reduced fluidity, and they may not effectively prevent rust if the repair is not immediate, leading to premature rust development.
A rust preventive agent containing a binder with specified amounts and ratios of nitrite and nitrate ions, along with other components, is formulated to maintain fluidity and extend the time before rust development.
The agent maintains fluidity and significantly prolongs the time before rust appears while ensuring effective rust prevention, even when immediate repair is not possible.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present invention relates to a rust inhibitor and a rust prevention method thereof, and more particularly to a rust inhibitor and a rust prevention method thereof that inhibits corrosion of steel materials inside concrete, such as reinforcing bars, steel frames, steel plates, and steel wires inside precast concrete, and prevents the occurrence of rust. [Background technology]
[0002] When repairing concrete structures, cross-section repair work is carried out by removing deteriorated sections and pouring new repair mortar in their places. At that time, anti-rust treatment is carried out to prevent the exposed steel materials such as reinforcing bars from rusting.
[0003] Known conventional rust inhibitors include inorganic types such as nitrites, chromates, silicates, and phosphates, and organic types such as organic phosphates, ester salts, organic acids, sulfonic acids, amines, alkylphenols, mercaptans, and nitro compounds (see Non-Patent Document 1).
[0004] When carrying out cross-section repair methods, nitrite-based rust inhibitors are often used as rust inhibitors for reinforcing bars. They are applied directly to the reinforcing bars, mixed with a polymer emulsion, or mixed with a hydraulic substance such as cement. When mixed with cement, a coating containing a cement-mixing polymer may be applied to retain the nitrite on the rebar surface for a long period of time and to reduce the permeability of chloride ions and oxygen, thereby maintaining a stronger rust-preventing effect. [Prior art documents] [Non-patent literature]
[0005] [Non-Patent Document 1] "IX Rust Inhibitors", Development Technology of Concrete Admixtures, pp.119-134, CMC Publishing, 2000 Summary of the Invention [Problem to be solved by the invention]
[0006] However, nitrite-based rust inhibitors, which are often used in cross-section repair methods, can be applied directly to rebars, but rust may occur if the cross-section is not repaired immediately after application. In addition, nitrite-based rust inhibitors have the problem of poor workability because nitrite accelerates hardening, and the viscosity increases and fluidity decreases after adding nitrite. Therefore, an object of the present invention is to provide a rust inhibitor and a rust prevention treatment method that contain a nitrite, which extends the time until rust occurs, has fluidity and is easy to apply. [Means for solving the problem]
[0007] As a result of intensive research to solve the above problems, it was found that the above problems can be solved by specifying the total mass of nitrite ions and nitrate ions contained in the rust inhibitor, and the mass ratio of nitrite ions to nitrate ions. The present invention was completed based on the above findings. The present invention is as follows.
[0008] [1] A rust inhibitor containing a binder including cement, nitrite ions, and nitrate ions, wherein the total mass of the nitrite ions and the nitrate ions is more than 2 parts by mass and not more than 30 parts by mass per 100 parts by mass of the binder, and the mass ratio of the nitrite ions to the nitrate ions (nitrite ions / nitrate ions) is 0.1 or more and 3 or less. [2] The rust inhibitor according to [1], wherein the content of the nitrite ions is 0.8 parts by mass or more and 22 parts by mass or less per 100 parts by mass of the binder. [3] The rust inhibitor according to [1] or [2], wherein the content of the nitrate ions is 0.8 parts by mass or more and 22 parts by mass or less per 100 parts by mass of the binder. [4] The rust inhibitor according to any one of [1] to [3], wherein the content of chloride ions is 0.04 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the binder. [5] A rust prevention method using the rust inhibitor according to any one of [1] to [4]. Effect of the Invention
[0009] The present invention can provide a rust inhibitor and a rust prevention treatment method containing a nitrite that extends the time until rust occurs, has fluidity, and is easy to apply. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] The present invention will be described in detail below. In the present invention, parts and percentages are based on mass unless otherwise specified.
[0011] The rust inhibitor according to an embodiment of the present invention (hereinafter, sometimes simply referred to as "the present embodiment") contains a binder containing cement, nitrite ions, and nitrate ions. The rust inhibitor according to the present embodiment is obtained by mixing a binder containing cement with an aqueous nitrite solution containing nitrite ions and nitrate ions, and is in the form of a slurry. Each component of the rust inhibitor will be described below.
[0012] [Binders containing cement] The binder in the rust inhibitor according to the present embodiment is a binder containing cement. The binder containing cement is preferably a mixture of cement and inorganic fine powder.
[0013] (cement) The cement contained in the binder is not particularly limited, but may be any of various Portland cements such as ordinary, early strength, super early strength, low heat, and moderate heat, any of various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica, filler cements obtained by mixing these Portland cements with limestone powder or blast furnace slag powder, and environmentally friendly cements (ecocements) produced using municipal waste incineration ash or sewage sludge incineration ash as raw materials. These cements may be used alone or in combination of two or more. Among these cements, ordinary Portland cement is preferred from the viewpoint of being easily incorporated with food materials.
[0014] The cement used in the present invention has a Blaine specific surface area (hereinafter also referred to as the Blaine value) of 2,500 cm from the viewpoint of production cost and strength development. 2 / g or more 7,000cm 2 / g or less, and 2 / g or more 6,000cm 2 / g or less is more preferable, and 2 / g or more 4,500cm 2 The Blaine value is determined in accordance with JIS R 5201 (physical testing method for cement).
[0015] (Inorganic fine powder) Examples of inorganic fine powders include finely ground quenched slag powder such as granulated blast furnace slag, fly ash, silica fume, and rice husk ash (rice husk ash), as well as finely ground limestone powder, finely ground silica powder, finely ground crushed stone, and finely ground annealed slag powder. Of these, finely ground limestone powder is preferred.
[0016] The fineness of the inorganic fine powder is not particularly limited, but is usually 3,000 cm in Blaine value. 2 / g or more 9,000cm 2 The fineness of the limestone powder is not particularly limited, but is preferably in the range of 3,000 cm 2 / g or more 9,000cm 2 / g or less, and 2 / g or more 8,000cm 2 / g or less, and more preferably 3,500 cm 2 / g or more 7,000cm 2 It is more preferable that the molecular weight is not more than 1 / g.
[0017] The blending ratio of the cement-containing binder and the inorganic fine powder is not particularly limited, but is preferably 30 parts by mass to 80 parts by mass, more preferably 35 parts by mass to 75 parts by mass, and even more preferably 40 parts by mass to 70 parts by mass, per 100 parts by mass of the cement-containing binder. By having the blending ratio of the cement-containing binder and the inorganic fine powder within the above range, the kneading resistance is reduced and the workability is improved.
[0018] [Nitrite ion] The nitrite ions used in the present invention are supplied in the form of nitrous acid and nitrite salts. Examples of nitrite salts include, but are not limited to, alkali and alkaline earth metal salts such as lithium salts, sodium salts, potassium salts, and calcium salts, and ammonium salts. The nitrite salts may be anhydrous salts or hydrated salts. The nitrite salts may be supplied as they are, or may be diluted with water to facilitate mixing with the medium.
[0019] The content of nitrite ions in the rust inhibitor according to this embodiment is preferably 0.8 parts by mass or more and 22 parts by mass or less, more preferably 1.2 parts by mass or more and 20 parts by mass or less, more preferably 1.6 parts by mass or more and 19.6 parts by mass or less, and even more preferably 2 parts by mass or more and 19.2 parts by mass or less, relative to 100 parts by mass of the binder. By having the content of nitrite ions within the above range, the rust inhibitor exhibits a sufficient rust prevention effect, the time until rust occurs is extended, and the agent has fluidity and improves workability. In order to adjust the content of nitrite ions in the rust inhibitor to fall within the above range, the content of nitrite ions in the aqueous nitrite solution used in preparing the rust inhibitor may be adjusted.
[0020] [Nitrate ion] The nitrate ions used in the present invention are supplied in the form of nitric acid and nitrates. Examples of nitrates include, but are not limited to, alkali and alkaline earth metal salts such as lithium salts, sodium salts, potassium salts, and calcium salts, aluminum salts, iron salts, copper salts, nickel salts, magnesium salts, zinc salts, manganese salts, and ammonium salts. The nitrates may be anhydrous salts or hydrated salts. The nitrates may be supplied as they are, or may be diluted with water to make them easier to mix with the medium.
[0021] The content of nitrate ions in the rust inhibitor according to the present embodiment is preferably 0.8 parts by mass or more and 22 parts by mass or less, more preferably 1.2 parts by mass or more and 20 parts by mass or less, more preferably 1.4 parts by mass or more and 16 parts by mass or less, even more preferably 1.6 parts by mass or more and 12 parts by mass or less, and even more preferably 1.8 parts by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the binder. By having the content of nitrate ions within the above range, the rust inhibitor exhibits a sufficient rust prevention effect, the time until rust occurs is extended, and the agent has fluidity and improves workability. The content of nitrate ions in the rust inhibitor can be obtained by collecting a supernatant of the rust inhibitor in a slurry form and measuring the content by anion chromatography. In order to adjust the nitrate ion content in the rust inhibitor to fall within the above range, the nitrate ion content in the aqueous nitrite solution used in preparing the rust inhibitor may be adjusted.
[0022] The total mass of the nitrite ion and the nitrate ion in the rust inhibitor according to the present embodiment is more than 2 parts by mass and not more than 30 parts by mass relative to 100 parts by mass of the binder. If the total mass of the nitrite ion and the nitrate ion is 2 parts by mass or less, the rust prevention effect is insufficient and the time until rusting is shortened. If the total mass of the nitrite ion and the nitrate ion is more than 30 parts by mass, the fluidity is reduced and the workability is poor. The total mass of the nitrite ion and the nitrate ion in the nitrite salt aqueous solution is preferably 5 parts by mass or more and 27 parts by mass or less, more preferably 7 parts by mass or more and 25 parts by mass or less, and even more preferably 10 parts by mass or more and 22 parts by mass or less relative to 100 parts by mass of the binder.
[0023] In the rust inhibitor according to the present embodiment, the mass ratio of nitrite ions to nitrate ions (nitrite ions / nitrate ions) is 0.1 or more and 3 or less. If the mass ratio of nitrite ions to nitrate ions is less than 0.1 and exceeds 3, the rust-preventing effect is insufficient, the time until rusting occurs is shortened, and the fluidity is reduced, resulting in poor workability. From these viewpoints, the mass ratio of nitrite ions to nitrate ions is preferably 0.15 or more and 2.9 or less, more preferably 0.2 or more and 2.8 or less, and even more preferably 0.25 or more and 2.7 or less.
[0024] The content of chloride ions in the rust inhibitor according to this embodiment is preferably 0.04 parts by mass or more and 3 parts by mass or less, more preferably 0.08 parts by mass or more and 2.5 parts by mass or less, and even more preferably 0.12 parts by mass or more and 2 parts by mass or less, relative to 100 parts by mass of the binder. By having the chloride ion concentration in the rust inhibitor within the above range, an initial rust prevention effect can be obtained.
[0025] [aggregate] It is also possible to use sand as an aggregate in addition to the rust inhibitor, and to mix the sand appropriately to use as mortar. The content of the aggregate is preferably 50 to 350 parts by mass, and more preferably 70 to 200 parts by mass, relative to 100 parts by mass of the binder. By keeping the content of the aggregate within the above range, it is possible to further increase the initial crack resistance.
[0026] [Other additives] The rust inhibitor according to this embodiment can be used in combination with pozzolanic substances, which are hydraulic substances other than cement that are stimulated and hardened by alkali, calcium aluminates that can impart rapid hardening properties, and mixtures of these, within a range that does not adversely affect the quality. In addition, the rust inhibitor of this embodiment can be used in combination with various additives such as calcium carbonate, magnesium silicate, slag powder, clay powder, carbon black, surfactants, fibers, thickeners, clay minerals, setting accelerators, setting retarders, waterproofing agents, water reducing agents, defoamers, hardening accelerators, foaming agents, pigments, gas foaming substances, expansion agents, shrinkage reducing agents, chelating agents such as sodium ethylenediaminetetraacetate, water-soluble sulfur-containing organic compounds or salts thereof, fragrances, deodorants, antibacterial agents, preservatives, etc., within the scope that does not adversely affect the quality.
[0027] The rust prevention treatment method according to this embodiment is a rust prevention treatment method using any of the rust inhibitors described above. The rust prevention treatment method according to this embodiment is not particularly limited, but since the rust prevention agent according to this embodiment is in a slurry form, it may be sprayed onto the object of the rust prevention treatment, such as reinforcing bars, using a sprayer or may be painted on with a brush, for example. EXAMPLES
[0028] The present invention will be further described below based on experimental examples of the present invention, but the present invention is not limited to these.
[0029] [Experimental Example 1] The rust inhibitor was prepared with a composition that would provide the total mass of nitrite ions and nitrate ions contained in the rust inhibitor, and the mass ratio of nitrite ions to nitrate ions, as shown in Table 1. The rust inhibitor was prepared by adding water to 100 parts by mass of the obtained rust inhibitor so that the water / rust inhibitor ratio was constant (water / rust inhibitor ratio: 50%). The prepared rust inhibitor was tested for fluidity and the time it took for rust to develop using the prepared rust inhibitor. The results are shown in Table 1 below.
[0030] [Materials used] Cement: Ordinary Portland cement (commercially available) Inorganic fine powder: limestone fine powder, Blaine value 4,000 cm 2 / g Nitrite ion: Calcium nitrite (commercially available) Nitrate ion: Calcium nitrate (commercially available) Chloride ions: Sodium chloride (commercially available) Water: Tap water
[0031] [Measurement method] <Liquidity> JIS flow: Compliant with JIS R 5201. <Time until rust occurs> The prepared anti-rust agent was applied to the surface of D16 reinforcing bar (JIS standard SD295) at a rate of approximately 150 g / m 2 The rebars coated with the rust inhibitor were placed in a constant temperature and humidity room at a temperature of 20°C and a relative humidity of 100%, and the time from application to when rust was visually confirmed on the rebars was measured. Three pieces were tested per example, and the average of the measured times was taken as the time until rust appeared.
[0032] [Table 1]
[0033] The results in Table 1 show that by specifying the total mass of nitrite ions and nitrate ions contained in the rust inhibitor, as well as the mass ratio of nitrite ions to nitrate ions, it is possible to increase the fluidity to 80 mm or more and extend the time until rusting occurs to 50 hours or more. [Industrial Applicability]
[0034] By specifying the total mass of nitrite ions and nitrate ions contained in the rust inhibitor of the present invention and the mass ratio of nitrite ions to nitrate ions, the rust inhibitor can have increased fluidity and improve the time until rust occurs, and can be used in a wide range of applications, such as inhibiting corrosion of steel materials inside concrete, such as reinforcing bars, steel frames, steel plates, and steel wires inside precast concrete, and preventing the occurrence of rust.
Claims
1. The cement-containing binder contains nitrite ions and nitrate ions, The total mass of the nitrite ion and the nitrate ion is more than 2 parts by mass and 30 parts by mass or less with respect to 100 parts by mass of the binder, A rust inhibitor in which a mass ratio of the nitrite ions to the nitrate ions (nitrite ions / nitrate ions) is 0.1 or more and 3 or less.
2. 2. The rust inhibitor according to claim 1, wherein the content of the nitrite ions is 0.8 parts by mass or more and 22 parts by mass or less relative to 100 parts by mass of the binder.
3. 2. The rust inhibitor according to claim 1, wherein the content of the nitrate ions is 0.8 parts by mass or more and 22 parts by mass or less with respect to 100 parts by mass of the binder.
4. 2. The rust inhibitor according to claim 1, wherein the content of the chloride ions is 0.04 parts by mass or more and 3 parts by mass or less relative to 100 parts by mass of the binder.
5. A method for rust prevention treatment using the rust inhibitor according to any one of claims 1 to 4.