Anti-rust cleaner, surface preparation method and repainting method

Abstract

To improve volatility of moisture after a substrate treatment of a treatment target so as to allow a swift transition to a next step such as a coating treatment after the substrate treatment, and to improve treatment efficiency.SOLUTION: An antirust cleanser is liquid to be used being added to treatment water for applying a substrate treatment onto a surface of a treatment target, and includes: 10 to 40 wt.% of a vehicle including an antirust agent and a nonionic surfactant of HLB 12 or higher; and 60 to 90 wt.% of water. The vehicle includes the antirust agent by 70 to 98 wt.% and the nonionic surfactant by 2 to 30 wt.%. The antirust cleanser is used being added to the treatment water by 0.05 to 10 wt.%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an anti-rust cleaner that is effective for use in surface preparation of a metal object, a surface preparation method using the same, and a recoating method using the anti-rust cleaner. [Background technology]

[0002] Conventionally, repainting has been a common maintenance practice for steel and other metal structures, such as painted bridges, pedestrian bridges, civil engineering structures, plant facilities, etc. In this case, rust and paint films are removed using a dry blasting method or a wet blasting method, and then a new coat of paint is applied. It is also well known that salt generally adheres to the surfaces of steel structures in cold regions and coastal areas. In the case of dry blasting, abrasives are fed into an air stream and sprayed onto the surface of the workpiece to remove salt. The steel surface is then washed with treatment water to remove salt. In the case of wet blasting, abrasives are mixed into treatment water, which is then sprayed onto the surface of the workpiece. However, both methods use water, which creates the problem that rust (so-called "return rust") is likely to occur on the base surface of the workpiece afterwards.

[0003] In order to solve this problem, a rust inhibitor technology has been proposed, which is used in the wet blasting method described above, and is described in JP-A-2001-181815 (Patent Document 1). This rust inhibitor is composed of an aqueous solution of potassium hydroxide. Alternatively, a rust inhibitor that is preheated and vaporized to easily form a compound with zinc, aluminum, etc., such as an acrylic acid polymer or oxyphenoxyethanol, has also been proposed. In this case, it is said that a surfactant may be added to make it easier to wet the abrasive. Then, when treating the surface of the workpiece by the wet blasting method, the rust inhibitor is added to water and sprayed onto the workpiece together with the abrasive to perform the blasting treatment. As a result, a thin film of the rust inhibitor is formed on the surface of the base material after blasting, preventing rust from occurring on the blasted surface of the base material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-181815 A Summary of the Invention [Problem to be solved by the invention]

[0005] Although the above-mentioned conventional rust inhibitors are effective in preventing rust from forming on the blasted surface, the water content of the aqueous solution containing the rust inhibitors evaporates slowly, and therefore the rust inhibitors are not sufficient for the application of paint to be applied immediately after the blasting process, which is particularly problematic during the rainy season and winter repainting processes.

[0006] For this reason, in the technology described in Patent Document 1, the rust inhibitor is preheated to 80°C to 130°C before the blast treatment. Alternatively, after the blast treatment, the blasted surface preparation is cleaned with an alcohol such as methanol or ethanol, or the surface preparation is heat-treated. However, preheating before the blast treatment, or cleaning with an alcohol or heat-treating the surface preparation is performed after the blast treatment, increases the number of steps and makes the process complicated, resulting in poor processing efficiency.

[0007] The present invention has been made in consideration of the above-mentioned points, and has an object to provide an anti-rust cleaning agent, a surface preparation method, and a recoating method which improve the volatility of water after the surface preparation of the object to be treated and enable the object to be quickly transferred to the next step, such as painting, after the surface preparation, thereby improving the processing efficiency. [Means for solving the problem]

[0008] In order to achieve the above object, the rust-preventive cleaning agent of the present invention is a liquid rust-preventive cleaning agent which is added to treatment water for preparing the surface of a workpiece, and The composition contains 10% by weight to 40% by weight of a medium having a rust inhibitor and a nonionic surfactant with an HLB of 12 or more, and 60% by weight to 90% by weight of water. Nonionic surfactants have an HLB of 12 or higher, so they have a high affinity with water and are translucent or transparent when dissolved.

[0009] For example, the process will be described below in the case of repainting a workpiece having a metal base coated with paint. <Dry blasting method> The surface of a workpiece, which is a metal substrate coated with paint, is sprayed with air mixed with an abrasive to remove the paint from the substrate surface, and then the substrate surface from which the paint has been removed is cleaned by spraying treated water, after which a new paint is applied to the substrate surface. In this case, the rust-preventive cleaning agent according to the present invention is added to the treated water used for cleaning.

[0010] <Wet blasting method> The surface of a workpiece, which is a metal substrate coated with paint, is sprayed with treated water mixed with an abrasive to remove the paint from the substrate surface, and then, after this process, a new paint is applied to the substrate surface. In this case, the rust-preventive cleaner according to the present invention is added to the treated water used for removing the paint.

[0011] During cleaning by this dry blasting method, or during peeling of paint by wet blasting method, paint chips and abrasives on the substrate surface are washed away with the treatment water, and a thin film of the rust inhibitor is formed on the substrate surface. When spraying of the treatment water is stopped, the water evaporates, but in combination with the nonionic surfactant, the water evaporates synergistically, and the substrate surface dries quickly. That is, the addition of the nonionic surfactant improves the surface wettability of the rust inhibitor, the rust inhibitor spreads wet, and a uniform thin film of water is formed, improving the water volatility (drying speed). As a result, it is possible to prevent rust (so-called reversion rust) from occurring on the substrate surface of the treated object. In addition, since it dries quickly, it becomes possible to apply a new coating to the substrate surface as quickly as possible. Therefore, it is not necessary to perform special treatments such as wiping with alcohol or heat treatment of the substrate surface to dry it, as in the past, which reduces the number of steps and significantly improves the processing efficiency, and shortens the time until repainting is completed, improving work efficiency.

[0012] If necessary, the rust inhibitor contains one or more types of nitrite, as well as one or more types of aromatic carboxylic acid having one or more carboxyl groups in its structure, a derivative of the aromatic carboxylic acid, an alkali metal salt of the aromatic carboxylic acid, an alkali metal salt of a derivative of the aromatic carboxylic acid, an ammonium salt of the aromatic carboxylic acid, or an ammonium salt of a derivative of the aromatic carboxylic acid.

[0013] The nitrites are not particularly limited, but examples thereof include sodium nitrite, potassium nitrite, calcium nitrite, magnesium nitrite, and nitrites of amines. Furthermore, examples of compounds related to aromatic carboxylic acids include, but are not limited to, benzoic acid, gallic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, acetylsalicylic acid, 3-nitrophthalic acid, 4-nitrophthalic acid, and alkali metal salts or ammonium salts thereof. Various rust inhibitors have been known in the art, but by selecting the above-mentioned compounds, the action and effect of the present invention can be reliably achieved.

[0014] If necessary, the nonionic surfactant may contain one or more of polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers. The polyoxyethylene alkyl ether is not particularly limited, but examples thereof include polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene isodecyl ether, polyoxyethylene oleyl ether, and the like. The polyoxyethylene alkylphenyl ether is not particularly limited, but examples thereof include polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene benzyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene naphthyl ether, polyoxyethylene bisphenol A ether, polyoxyethylene bisphenol F ether, polyoxyethylene nonylphenyl ether, polyoxyethylene cumylphenyl ether, polyoxyethylene polycyclic phenyl ether, and the like.

[0015] In general, nonionic surfactants include, for example, ester type in which polyhydric alcohol and fatty acid are ester-bonded, ether type made by adding ethylene oxide, and ester-ether type having both ester bond and ether bond in the molecule. Among these, polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether were selected in the present invention. This ensures that the action and effect of the present invention can be exerted. In particular, the synergistic effect with the rust inhibitor can improve the volatility of water.

[0016] Furthermore, if necessary, the medium contains 70% to 98% by weight of a rust inhibitor and 2% to 30% by weight of the nonionic surfactant. This ratio provides a good balance between the rust inhibitor effect and drying properties, ensuring the action and effect of the present invention.

[0017] Furthermore, the rust-preventive cleaner has a pH of 7 to 10, if necessary. This improves the liquid stability and ensures that the functions and effects of the present invention can be exhibited. The pH is preferably 7.5 to 9.5.

[0018] If necessary, the composition is configured to be added to the treated water at 0.05% by weight to 10% by weight, preferably 0.15% by weight to 5% by weight, and more preferably 0.25% by weight to 1% by weight. The action and effect of the present invention can be achieved with a relatively small amount of addition. If the amount is less than 0.05% by weight, the action and effect of the present invention cannot be achieved. If the amount exceeds 10% by weight, there is a risk of reducing the adhesion between the paint and the treated object when the next process is painting.

[0019] In order to achieve the above object, the present invention provides a surface preparation method for spraying treatment water onto the surface of a metal workpiece to prepare the surface of the workpiece, the method being configured to add the above-mentioned rust-preventive cleaning agent to the treatment water. The same effects and advantages as those described above can be achieved.

[0020] In order to achieve the above object, the recoating method of the present invention comprises a stripping step of blowing air mixed with an abrasive onto a surface of a workpiece, which is a metal substrate coated with paint, to strip the paint from the substrate surface, a cleaning step of spraying treated water onto the substrate surface from which the paint has been stripped after the stripping step to clean it, and a coating step of coating the substrate surface with new paint after the cleaning step, The rust-preventive cleaning agent is added to the treated water used in the cleaning step.

[0021] This is a recoating method that employs the so-called dry blasting method. According to this, during cleaning in the cleaning process, paint chips and abrasives on the substrate surface are washed away with the treatment water, and a thin film of the rust inhibitor is formed on the substrate surface. When the spraying of the treatment water is stopped, the water evaporates, but in combination with the nonionic surfactant, the water evaporates synergistically, and the substrate surface dries quickly. That is, the addition of the nonionic surfactant improves the surface wettability of the rust inhibitor, the rust inhibitor spreads wet, and a uniform thin film of water is formed, improving the water volatility (drying speed). As a result, it is possible to prevent the occurrence of rust (so-called reversion rust) on the substrate surface that has been blasted. In addition, since the drying is fast, the transition to the painting process can be performed as quickly as possible. That is, it becomes possible to apply a new coating to the substrate surface as quickly as possible. Therefore, it is no longer necessary to carry out special treatments such as wiping with alcohol to dry the surface or heat-treating the base surface, as was done in the past. This reduces the number of steps and significantly improves processing efficiency, and shortens the time required to complete repainting, thereby improving work efficiency.

[0022] In order to achieve the above object, the recoating method of the present invention includes a peeling step of spraying treated water mixed with an abrasive onto a surface of a workpiece, which is a metal substrate coated with paint, to peel off the paint from the substrate surface, and a coating step of coating a new paint on the substrate surface from which the paint has been peeled off after the peeling step, The rust-preventive cleaning agent is added to the treated water used in the stripping step.

[0023] This is a recoating method that employs the so-called wet blasting method. According to this method, during the peeling process, paint chips and abrasives on the substrate surface are washed away with the treatment water, and a thin film of anti-rust agent is formed on the substrate surface. After that, in the transition to the painting process, the same actions and effects as the recoating method employing the so-called dry blasting method described above are achieved. Effect of the Invention

[0024] According to the present invention, when the treated object is treated with the treatment water, a thin film of the rust inhibitor can be formed on the surface of the substrate of the treated object. In this case, the water evaporates, but in combination with the nonionic surfactant, the water evaporates synergistically, and the substrate surface can be dried quickly. That is, the addition of the nonionic surfactant improves the surface wettability of the rust inhibitor, the rust inhibitor spreads wet, and a uniform thin film of water is formed, thereby improving the water volatility (drying speed). As a result, it is possible to prevent the occurrence of rust (so-called reversion rust) on the substrate surface that has been blasted. In addition, since the drying is fast, it is possible to move to the next process, such as applying a new coat of paint to the substrate surface, as soon as possible, thereby improving the processing efficiency. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram showing the configuration of an antirust cleaning agent according to an embodiment of the present invention together with the configuration of treated water. [Diagram 2] FIG. 1 is a diagram showing a configuration of an anti-rust cleaning agent according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a process diagram showing a repainting method (a repainting method using a dry blasting method) according to an embodiment of the present invention. [Figure 4] FIG. 1 is a process diagram showing a repainting method (a repainting method using a wet blasting method) according to an embodiment of the present invention. [Diagram 5] 1 is a photograph showing the results of a comparison test on the wettability of treated water according to an embodiment and treated water according to a comparative example to a metal surface, in accordance with Test Example 1 of the present invention. [Figure 6]10 is a photograph showing the results of a comparative test on water volatility on a metal surface between treated water according to an embodiment and treated water according to a comparative example, relating to Test Example 2 of the present invention. [Figure 7] FIG. 11 is a graph showing the measurement results of the water volatilization rate from the metal surface of treated water according to the example and treated water according to the comparative example, relating to Test Example 3 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The rust-preventive cleaner, the surface preparation method, and the repainting method according to the embodiment of the present invention will be described in detail below with reference to the attached drawings. The surface preparation method according to the embodiment of the present invention is realized in the repainting method according to the embodiment of the present invention, so it will be described in the repainting method.

[0027] Figures 1 and 2 show the structure of an anti-rust cleaning agent according to an embodiment of the present invention, and Figures 3 and 4 show a recoating method according to an embodiment of the present invention. The anti-rust cleaning agent R according to the embodiment is a liquid that is added to treated water W for base treatment of the surface of a workpiece M. In the embodiment, the anti-rust cleaning agent is sprayed onto the surface of a metal workpiece M and added to treated water W for base treatment of the base surface of the workpiece M in a recoating method according to an embodiment described later.

[0028] As shown in Figs. 1 and 2, the basic composition of this anti-rust cleaner R contains 10 to 40% by weight of a medium having a rust inhibitor and a nonionic surfactant with an HLB of 12 or higher, and 60 to 90% by weight of water.

[0029] In one embodiment, the rust inhibitor comprises one or more types of nitrite salts, as well as one or more types of aromatic carboxylic acids having one or more carboxyl groups in their structure, derivatives of the aromatic carboxylic acids, alkali metal salts of the aromatic carboxylic acids, alkali metal salts of derivatives of the aromatic carboxylic acids, ammonium salts of the aromatic carboxylic acids, and ammonium salts of derivatives of the aromatic carboxylic acids.

[0030] The nitrites are not particularly limited, but examples thereof include sodium nitrite, potassium nitrite, calcium nitrite, magnesium nitrite, and nitrites of amines. Examples of the nitrites of amines include dicyclohexylammonium nitrite, diisopropylammonium nitrite, and nitronaphthaleneammonium nitrite. Furthermore, examples of compounds related to aromatic carboxylic acids include, but are not limited to, benzoic acid, gallic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, acetylsalicylic acid, 3-nitrophthalic acid, 4-nitrophthalic acid, and alkali metal salts or ammonium salts thereof.

[0031] Nonionic surfactants generally include, for example, ester types in which polyhydric alcohols and fatty acids are ester-bonded, ether types produced by adding ethylene oxide, ester-ether types having both ester bonds and ether bonds in the molecule, etc. In the embodiment, the nonionic surfactant is configured to contain one or more types of polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers. The polyoxyethylene alkyl ether is not particularly limited, but examples thereof include polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene isodecyl ether, polyoxyethylene oleyl ether, and the like. The polyoxyethylene alkylphenyl ether is not particularly limited, but examples thereof include polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene benzyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene naphthyl ether, polyoxyethylene bisphenol A ether, polyoxyethylene bisphenol F ether, polyoxyethylene nonylphenyl ether, polyoxyethylene cumylphenyl ether, polyoxyethylene polycyclic phenyl ether, and the like.

[0032] As shown in FIG. 2, the medium contains 70% to 98% by weight of a rust inhibitor and 2% to 30% by weight of a nonionic surfactant. The pH of the present anti-rust cleaner R is set to pH 7 to pH 10, preferably pH 7.5 to pH 9.5. The rust-preventive cleaning agent R according to the embodiment is used by adding it to the treatment water W in an amount of 0.05% by weight to 10% by weight, preferably 0.15% by weight to 5% by weight, and more preferably 0.25% by weight to 1% by weight.

[0033] Next, a repainting method according to the embodiment, which is carried out using the rust-preventive cleaning agent R according to the embodiment, will be described. The repainting method according to the embodiment has two aspects: (A) a repainting method using a dry blasting method, and (B) a repainting method using a wet blasting method. Each aspect will be described below.

[0034] (A) Repainting method using dry blasting As shown in Fig. 3, this method includes a peeling step (A1), a cleaning step (A2), and a coating step (A3). Each step will be described below.

[0035] (A1) Peeling process Air mixed with an abrasive K is sprayed onto the surface of the workpiece M, which is a metal substrate coated with paint T, to remove the paint T from the substrate surface. Well-known abrasives K are used, such as ferronickel slag, fused alumina, almandite garnet, copper slag, and steel grit. In this case, a well-known air blasting device equipped with a gun for spraying air mixed with the abrasive K is used.

[0036] (A2) Cleaning process After the peeling process, the surface of the substrate from which the paint T has been peeled off is sprayed with treated water W for cleaning. The treated water W used in this cleaning process is added with the rust-preventive cleaning agent R according to the above embodiment. In this cleaning process, a well-known cleaning device equipped with a gun for spraying treated water W from the gun is used. In this case, the paint chips and abrasives K on the surface of the substrate are washed away together with the treated water W, and a thin film of the rust-preventive agent is formed on the surface of the substrate. When the spraying of the treated water W is stopped, the water evaporates, but in combination with the nonionic surfactant, the water evaporates synergistically, and the substrate surface dries quickly. That is, the addition of the nonionic surfactant improves the surface wettability of the rust-preventive agent, the rust-preventive cleaning agent R spreads wet, and becomes a uniform thin film of water, improving the water volatility (drying speed). As a result, it is possible to prevent the occurrence of rust (so-called return rust) on the surface of the substrate. In addition, since the drying is fast, the transition to the painting process can be performed as quickly as possible. This eliminates the need for special treatments such as wiping with alcohol to dry the surface or heat treatment of the base material, as was done in the past, and reduces the number of steps, greatly improving treatment efficiency. Furthermore, the surface of corroded steel structures in cold regions and coastal areas has a high salt concentration, but this cleaning process ensures that the salt is removed.

[0037] (A3) Painting process After the cleaning process, new paint T (A) is applied to the substrate surface. The coating is carried out using a brush, roller, spray gun, or the like. In this case, the substrate surface that has been cleaned in the cleaning process is coated with a rust inhibitor, so rust (so-called reversion rust) is prevented from occurring, and coating can be carried out smoothly. In addition, the substrate surface of the workpiece M needs to be dried from the cleaning process to the coating process, but the action of the rust inhibitor R in the treated water W allows for quick drying, so that the transition to the coating process can be carried out as quickly as possible. In other words, a new coat of paint can be applied to the substrate surface as quickly as possible. This shortens the time until recoating is completed, improving work efficiency.

[0038] (B) Repainting method using wet blasting As shown in Fig. 4, this method includes a peeling step (B1) and a coating step (B2). Each step will be described below.

[0039] (B1) Peeling process Treatment water W mixed with abrasives K is sprayed onto the surface of a workpiece M, which is a metal substrate coated with paint T, to remove the paint T from the substrate surface. The rust-preventive cleaning agent R according to the above embodiment is added to the treatment water W used in this removal process. As the abrasives K, well-known materials such as ferronickel slag, molten alumina, garnet, copper slag, etc. are used. The weight ratio of the abrasives K to the treatment water W is abrasives K: 50% to 55% by weight, treatment water W: 45% to 50% by weight. In this process, a well-known wet blasting device equipped with a gun for spraying the treatment water W mixed with abrasives K is used.

[0040] In this stripping process, paint chips and abrasives K on the substrate surface are washed away with the treatment water W, and a thin film of the rust inhibitor is formed on the substrate surface. When spraying of the treatment water W is stopped, the water evaporates, but in combination with the nonionic surfactant, the water evaporates synergistically, and the substrate surface dries quickly. That is, the addition of the nonionic surfactant improves the surface wettability of the rust inhibitor, and the rust inhibitor cleaner R spreads and becomes a uniform thin film of water, improving the water volatility (drying speed). As a result, it is possible to prevent rust (so-called reversion rust) from occurring on the substrate surface that has been blasted. In addition, since it dries quickly, it is possible to move to the painting process as quickly as possible. Therefore, it is not necessary to perform special treatments such as wiping with alcohol or heating the substrate surface to dry it, as in the past, and the labor hours are reduced and the processing efficiency is greatly improved. In addition, the surface of steel structures with advanced corrosion in cold regions and coastal areas has a high salt concentration, but this stripping process also ensures that the salt is removed.

[0041] (B2) Painting process After the stripping process, new paint T (A) is applied to the base surface. The coating is carried out using a brush, roller, spray gun, or the like. In this case, the base surface blasted in the stripping process is coated with a rust inhibitor, so rust (so-called reversion rust) is prevented from occurring, and coating can be carried out smoothly. In addition, the base surface of the workpiece M needs to be dried from the stripping process to the coating process, but the action of the rust inhibitor cleaning agent R in the treated water W allows for quick drying, so that the transition to the coating process can be carried out as quickly as possible. In other words, a new coat of paint can be applied to the base surface as quickly as possible. This shortens the time until recoating is completed, improving work efficiency.

[0042] <Test Example> Next, a test example is shown. The rust-preventive cleaner R according to the embodiment was prepared and added to treated water W, and the following test was carried out on this treated water W together with the comparative example. The rust-preventive cleaner R according to the embodiment was prepared by mixing 15% by weight of sodium nitrite and 5% by weight of sodium benzoate as rust inhibitors, 3% by weight of polyoxyethylene cumyl phenyl ether as a nonionic surfactant, and 77% by weight of water. This rust-preventive cleaner R was mixed with 0.25% by weight of treated water W. The rust-preventive cleaner R according to the comparative example was prepared without adding the surfactant, and was mixed with 0.25% by weight of treated water W in the same manner.

[0043] (Test Example 1) The surface wettability of the treated water W containing the anti-rust cleaning agent R according to the embodiment on a test piece was confirmed by contact angle measurement. The test piece was a SUS304 material (70 mm x 150 mm, surface roughness Ra = 0.3) that had been ultrasonically cleaned with acetone for 10 minutes. A probe liquid was prepared as the treated water W using the above-mentioned anti-rust cleaning agent R, and this was dropped onto the test piece. A droplet volume of 1 μl was used. The same procedure was carried out for the comparative example. The results are shown in Figure 5. It can be seen that the treated water W according to the embodiment has a larger wetting spread and improved water volatility (drying speed) compared to the treated water W according to the comparative example.

[0044] (Test Example 2) A comparative test was conducted on the water volatility of the treated water W of the embodiment to the metal surface with the treated water of the comparative example. The treated water W containing the rust-preventive cleaning agent R of the embodiment was applied to the entire surface of a test piece made of SM400 material (70 mm x 70 mm, surface roughness Ra = 2.9), and the surface condition of the test piece immediately after application was compared with the surface condition of the test piece one hour after application. The same test was also conducted for the comparative example.

[0045] 6, the results of observation of the surface showed that immediately after application of the treated water W, there was almost no difference between the treated water W according to the comparative example and the treated water W according to the example, and the treated water W spread approximately uniformly on the metal plate surface. One hour after application, some of the treated water W according to the comparative example remained on the metal surface, while the treated water W according to the example had volatilized and no longer remained on the metal surface.

[0046] (Test Example 3) A comparative test was conducted on the water volatilization rate of the treated water W of the Example to the metal surface, in comparison with the treated water of the Comparative Example. The treated water W containing the rust-preventive cleaning agent R of the Example was applied to a test piece in the same manner as in Test Example 2 above, and the water volatilization rate was measured one hour after application while the water was left in the air. The same test was also conducted for the Comparative Example. The measurements were performed using a Fourier transform infrared spectrophotometer (FT-IR). The results are shown in FIG. 7. It was found that the treated water W of the Example had significantly better water volatility (drying speed) than the treated water of the Comparative Example. The rust-preventive effect was confirmed to be rust-preventive for at least 24 hours.

[0047] In the above embodiment, the method is applied to repainting as a surface preparation method, but the present invention is not limited to this. The method may be applied to other surface preparations such as surface preparation for new painting, surface preparation for various linings, thermal spraying and plating, and surface preparation for cleaning various buildings, and may be modified as appropriate. The rust-preventive cleaner R is not limited to being added to the treatment water W for repainting, and may be added to any treatment water used for surface preparation of the surface of a metal object. The rust inhibitor and surfactant of the rust-preventive cleaner R may also be modified as appropriate. In short, the present invention is not limited to the above-mentioned embodiment of the present invention, and those skilled in the art can easily make many modifications to these exemplary embodiments without substantially departing from the novel teachings and effects of the present invention, and many of these modifications are included in the scope of the present invention. [Explanation of symbols]

[0048] R Rust prevention cleaning agent W Treated water M Processing object T-paint K abrasive (A) Repainting method using dry blasting method (A1) Peeling process (A2) Cleaning process (A3) Painting process (B) Repainting method using wet blasting method (B1) Peeling process (B2) Painting process

Claims

1. A liquid rust-preventive cleaning agent that is added to treatment water for preparing the surface of a workpiece, The medium contains 10% by weight to 40% by weight of a rust inhibitor and a nonionic surfactant having an HLB of 12 or more, and 60% by weight to 90% by weight of water; The rust inhibitor is a rust-preventive cleaning agent characterized in that it contains one or more types of nitrite and is composed of one or more types of aromatic carboxylic acid having one or more carboxyl groups in its structure, a derivative of the aromatic carboxylic acid, an alkali metal salt of the aromatic carboxylic acid, an alkali metal salt of a derivative of the aromatic carboxylic acid, an ammonium salt of the aromatic carboxylic acid, or an ammonium salt of a derivative of the aromatic carboxylic acid.

2. 2. The rust-preventive cleaner according to claim 1, wherein said nonionic surfactant comprises at least one of polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether.

3. 3. The rust-preventive cleaning agent according to claim 2, wherein said medium contains 70% by weight to 98% by weight of the rust-preventive agent and 2% by weight to 30% by weight of said nonionic surfactant.

4. 4. The rust-preventive cleaner according to claim 3, wherein the pH is from 7 to 10.

5. 5. The rust-preventive cleaning agent according to claim 1, which is added to the treatment water in an amount of 0.05% by weight to 10% by weight.

6. A surface preparation method for preparing a base surface of a metal workpiece by spraying treated water onto the surface of the workpiece, comprising: A surface preparation method comprising adding the rust-preventive cleaning agent according to claim 5 to the treatment water.

7. A recoating method comprising a stripping step of blowing air mixed with an abrasive onto a surface of a workpiece, which is a metal substrate coated with paint, to strip the paint from the substrate surface, a cleaning step of spraying treated water onto the substrate surface from which the paint has been stripped after the stripping step to clean it, and a coating step of coating the substrate surface with new paint after the cleaning step, A recoating method comprising adding the rust-preventive cleaning agent according to claim 5 to the treated water used in the cleaning step.

8. A repainting method comprising a stripping step of spraying treated water mixed with an abrasive onto a surface of a workpiece, the surface being a metal substrate coated with paint, to strip the paint from the substrate surface, and a coating step of applying new paint to the substrate surface from which the paint has been stripped after the stripping step, A recoating method comprising adding the rust-preventive cleaning agent according to claim 5 to the treated water used in the stripping step.

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