JPH0118995B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to metal corrosion inhibitors. More specifically, it can suppress corrosion of various metals in aqueous media, such as ferrous metals such as steel, mild steel, and cast iron, copper metals such as copper and brass, and aluminum metals, and is suitable for cooling water systems and boiler water systems. The present invention also relates to a metal corrosion inhibitor that is low in toxicity and does not contain phosphorus. Conventionally, systems in which an aqueous medium is introduced or passed through, such as various cooling systems and heat exchange systems in petrochemicals, synthetic chemicals, food chemicals, steel manufacturing, paper manufacturing, textile factories, etc., diesel engines,
It is desired to prevent corrosion of various metals used in cooling systems such as radiators of automobiles, etc., and various anticorrosive agents have been proposed. Such anticorrosive agents include those mainly containing heavy metal ions such as chromium and zinc, and anionic components such as phosphoric acid, polymerized phosphoric acid, phosphonic acid, molybdic acid, tungstic acid, aliphatic oxycarboxylic acids, and polyphenols. Various materials have been proposed, including those mainly composed of cationic components such as amine compounds, those mainly composed of cationic components such as amine compounds, and those containing these in combination. However, the above-mentioned heavy metal ions such as chromium and zinc have problems in terms of pollution, and in particular, chromium-based compounds are currently hardly used due to their toxicity. The use of phosphorus compounds is also a problem from the viewpoint of eutrophication. In this regard, the inventors of the present invention first focused on the use of zirconium and tin, which have particularly low toxicity among heavy metals, as active ingredients in anticorrosive agents. Zirconium is originally known as a heavy metal with low toxicity (J. Schubert. Science 105.389-390
(1947) and J. Nutr 95.95-101 (1968), etc.).
It is known that such zirconium can be used as part of the active ingredient in the field of so-called rust inhibitors, which prevent corrosion by applying a preparation with an appropriate viscosity to metal surfaces (Japanese Patent Publication No. 39-1989).
(See Publication No. 29946 and Japanese Patent Publication No. 52-38973).
However, in the field of so-called anticorrosive agents in which active ingredients are directly added to aqueous systems, only those in combination with polymerized phosphates (see column CA Vol. 52.18153i) are known. Furthermore, tin is also known to have low toxicity. In other words, tin is not regulated in the Ministerial Ordinance on Water Quality Standards (Ministry of Health and Welfare Ordinance No. 11 of May 6, 1965 (Act No. 117 of 1965)), and tin is not subject to wastewater standards. Not mentioned. In addition, tin is painted on the inner surfaces of edible canned goods, and tin tableware is also used, making it extremely safe. In view of the above, the inventors of this invention
As a result of studying various zirconium and tin compounds, we first confirmed that generally, adding zirconium and tin compounds alone to an aqueous system does not provide nearly any effective anticorrosion effect. Furthermore, tests were also conducted on the above-mentioned anticorrosion agent that combines a polymerized phosphate and a zirconium compound, but although some anticorrosion effect was obtained, excellent anticorrosion effect was not obtained at low concentrations, and it was not sufficient for practical use. We have confirmed that this is not the case. Various tests were also conducted on the use of anionic components such as phosphonic acids and oxycarboxylic acids, and cationic components such as amines in place of polymerized phosphates, but although some anticorrosion effects were still exhibited, they were not found to be superior. It was not possible to obtain an anticorrosion effect, and in addition, the storage stability as a preparation was insufficient, and there was a risk that zirconium or tin would gradually form an insoluble salt and precipitate. The inventors of this invention aimed to develop an anticorrosive agent containing zirconium or tin as a component that exhibits an excellent anticorrosive effect and has good storage stability.As a result of further research and consideration, the inventors of the present invention discovered a zirconium or tin compound. The inventors have discovered that a three-component anticorrosive agent consisting of a combination of an aliphatic oxycarboxylic acid and an aliphatic lower unsaturated carboxylic acid polymer or a salt thereof exhibits the desired effect, and has thus arrived at the present invention. According to the present invention, zirconium or tin contained in the form of a compound or ion, an aliphatic oxycarboxylic acid or a salt thereof, and an aliphatic lower unsaturated carboxylic acid polymer or a salt thereof are contained as active ingredients. A metal corrosion inhibitor is provided. Zirconium or tin used in this invention is contained in the form of a compound or in the form of an ion. The above ion form refers to normal free ions such as zirconium ions, zirconyl ions, and tin ions, and also includes complex ions with aliphatic oxycarboxylic acids. In this invention, as such a zirconium-containing compound, it is usually appropriate to use a halide of zirconium or zirconyl, or an inorganic acid or an organic acid salt, and of course, a salt with the other two components of the invention described below may also be used. You can. Specific examples of these compounds include zirconium chloride, zirconyl chloride, zirconium iodide, zirconyl iodide, zirconium sulfate, zirconyl sulfate, zirconium nitrate, zirconyl nitrate, zirconium carbonate, zirconyl carbonate, zirconium ammonium carbonate, zirconyl ammonium carbonate, Examples include zirconium acetate, zirconyl acetate, zirconyl sulfamate, and the like. Further, examples of the tin compound used in this invention include stannous chloride, stannous chloride, stannous sulfate, and the like. Generally, these compounds are often added to an aqueous medium for use, so it is convenient to use compounds with high water solubility. Preference is given to using zirconyl or stannous chloride. On the other hand, examples of aliphatic oxycarboxylic acids or salts thereof used in the present invention include gluconic acid, glycolic acid, citric acid, malic acid, tartaric acid, lactic acid, hydroxyacrylic acid, oxybutyric acid, and alkali metal salts or ammonium salts thereof. Generally, it is preferable to use gluconic acid, citric acid, malic acid, or a sodium salt thereof from the viewpoint of anticorrosion effect. In addition, the aliphatic lower unsaturated carboxylic acid polymer or its salt used in this invention has the following formula (): (In the formula, R ₁ to _{R 3} each independently represent a hydrogen atom, a methyl group, or a carboxyl group, and n is 0 or 1.
(representing an integer of (However, the molecular weight of each of these homopolymers and copolymers is 500 to 100,000) or salts thereof. Depending on the case, it may be a mixed polymer of each of these homopolymers and copolymers. Specific examples of the compound represented by formula () include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, methylmaleic acid, fumaric acid, and the like. Other compounds having an ethylenic double bond that can be copolymerized with any of the monomers of formula () include acrylamide, methacrylamide, methylolacrylamide, acrylonitrile, methyl acrylate, ethyl acrylate, isopropyl acrylate, and methacrylic acid. Examples include methyl, ethyl methacrylate, styrene, and acrolein. Polymers of the present invention defined above include polyacrylic acid, polymethacrylic acid, polymaleic acid, polyitaconic acid, polymethylmaleic acid,
Polyfumaric acid, acrylic acid methacrylic acid copolymer, acrylic acid maleic acid copolymer, acrylic acid itaconic acid copolymer, acrylic acid fumaric acid copolymer, acrylic acid methylmaleic acid copolymer, methacrylic acid itaconic acid copolymer, acrylic acid acrylamide copolymer, acrylic acid methacrylamide copolymer , methylol acrylate acrylamide copolymer, acrylonitrile acrylate copolymer, methyl acrylate acrylate copolymer, ethyl acrylate acrylate copolymer, isopropyl acrylate copolymer, styrene acrylate copolymer, acrolein acrylate copolymer, methyl acrylate methacrylate copolymer, Ethyl acrylic acid methacrylate copolymer, acrylonitrile methacrylate copolymer, methacrylic acid acrylamide copolymer, methacrylic acid methacrylamide copolymer, methacrylic acid methylolacrylamide copolymer, acrylonitrile methacrylate copolymer, methacrylic acid methyl acrylate copolymer, methacrylic acid ethyl acrylate copolymer,
Examples include acrolein methacrylate copolymer. More preferred among these are polyacrylic acid, polymethacrylic acid, polymaleic acid, acrylic acid methacrylic acid copolymer, acrylic acid maleic acid copolymer, acrylic acid itaconic acid copolymer, acrylic acid acrylamide copolymer, and methacrylic acid methylol acrylamide copolymer. The molecular weight of these polymers is suitably from 500 to 100,000, more preferably from 1,000 to 20,000, from the viewpoint of corrosion resistance and solubility. These polymers may be used in their sodium, potassium, or ammonium salts if necessary. In addition, when using a copolymer, at least the monomer component represented by formula () is included in the polymer.
It must be contained in an amount of 40 mol% or more. If the monomer component represented by the formula () is less than 40 mol%, the anticorrosion effect will be insufficient and the product will be unsuitable. Note that these polymers and copolymers can be produced by known methods such as radical polymerization. The content ratio of the above three components of this invention is: (a) 1 to 200 parts by weight of aliphatic oxycarboxylic acid or its salt, and (b) aliphatic lower unsaturated carboxylic acid, per 1 part by weight of zirconium or tin. Coalescence or its salt 0.1～
It is appropriate to set the amount to 30 parts by weight, especially for 1 part by weight of zirconium or tin, (a) 5 to 60 parts by weight,
(b) It is preferable to use 1.0 to 10 parts by weight from the viewpoint of anticorrosion effect. The composition of the present invention consisting of these three components can be used as a powder, slurry or paste preparation, glass-like solid preparation or aqueous solution, optionally containing a filler etc., but it can be used for convenience and dispersibility when added. From the viewpoint of solubility, etc., it is suitable to use it as an aqueous solution. When preparing an aqueous solution, usually
It is preferable to first dissolve the aliphatic oxycarboxylic acid or its salt in water, and then mix and dissolve the zirconium or tin compound, and then the polymer or its salt, in this order while heating as desired. Changing the above order may cause precipitation in the preparation, which is not preferable. The total concentration of the active ingredients when preparing an aqueous solution depends on the solubility of each component, but is usually 5 to 55% by weight, preferably 20 to 45% by weight. The anticorrosive agent of the present invention has a total amount of active ingredients of 0.1 to 0.1 in the system to be treated for anticorrosion, that is, in water.
It achieves the purpose by adding 10,000 mg/equivalent, preferably 5 to 5,000 mg/equivalent, and in general cooling water systems and boiler systems, an excellent corrosion prevention effect is usually obtained by adding the equivalent of 5 to 200 ppm, and it is used in cooling systems such as radiators. In aqueous systems, an excellent anticorrosion effect can be obtained by adding 500 to 5000 mg/. Therefore, from another point of view, the present invention consists of adding a zirconium or tin compound, an aliphatic oxycarboxylic acid or a salt thereof, and an aliphatic lower unsaturated carboxylic acid polymer or a salt thereof to a system to be treated for corrosion protection. A corrosion protection method is also provided. The above-mentioned anticorrosive agent of the present invention, due to the combined effect of zirconium ions or tin ions, aliphatic oxycarboxylic acid anions, and the polymer, can be applied not only to iron-based metals but also to the surface of copper-based metals, aluminum, etc. It forms a strong anti-corrosion film even under relatively mild temperature conditions and exhibits excellent anti-corrosion effects. The heavy metals contained are also low-toxic zirconium or tin, which is advantageous.
In addition, it has a remarkable anticorrosive effect compared to the effect of each active ingredient alone or the combination thereof, and is useful in reducing the amount of added chemicals in industry. Moreover, it is advantageous in that it does not particularly require a large number of anticorrosive agents even in systems where various metals are present. It has been found that the anticorrosive agent of the present invention using tin has an excellent anticorrosive effect particularly in boiler water systems. In addition, when using the anticorrosive agent of the present invention, other known anticorrosive agents may be used in combination, for example, hydrazine may be added to perform oxygen-scavenging corrosion protection. Hereinafter, the anticorrosive agent of the present invention will be described in detail with reference to Examples, but the present invention is not limited thereby. Example 1 Formulation example 1 Zirconium sulfate (Zr(SO ₄ ) _{2.4H 2} O) 2 parts by weight Sodium gluconate 30 Sodium polyacrylate (molecular weight 8000)
2 Sodium hydroxide (PH adjuster) 1 Water 65 After dissolving sodium gluconate in water at the above blending ratio, zirconium sulfate, sodium polyacrylate, and sodium hydroxide were sequentially mixed and dissolved to create a uniform and stable solution. A liquid preparation was obtained. (The molecular weight is an approximate value based on the Ostwald method. The same applies hereinafter.) Formulation example 2 Zirconyl chloride (ZrOCl _{2.8H 2} O) (zirconium oxychloride) 5 parts by weight Sodium gluconate 25 Sodium polymethacrylate (molecular weight 7000)
3. Water 67. After dissolving sodium gluconate in water at the above mixing ratio, zirconyl chloride and then sodium polymethacrylate were mixed and dissolved to obtain a uniform and stable liquid preparation. Formulation example 3 Zirconyl nitrate (ZrO (NO ₃ ) ₂・2H ₂ O) (zirconium oxynitrate) 5 parts by weight Gluconic acid 30 Polymaleic acid (molecular weight 1000) 10 Water 55 Dissolve gluconic acid in water at the above mixing ratio After letting
Zirconyl nitrate and then polymaleic acid were mixed and dissolved to obtain a uniform and stable solution. Formulation example 4 Zirconium sulfate (Zr(SO ₄ ) ₂・4H ₂ O) 5 parts by weight citric acid 25 Acrylic acid methacrylic acid copolymer (molecular weight
4000, reaction molar ratio 1:1) 5 Water 65 After dissolving citric acid in water at the above mixing ratio, zirconium sulfate and then acrylic acid methacrylic acid copolymer were mixed and dissolved to obtain a uniform and stable liquid agent. Formulation Example 5 Zirconium sulfate (Zr(SO ₄ ) ₂・4H ₂ O) 15 parts by weight Gluconic acid 20 〃 Polymaleic acid (molecular weight 1000) 10 〃 Water 55 〃 After dissolving gluconic acid in water at the above mixing ratio,
Mix and dissolve zirconium sulfate, then lower the liquid temperature to 60~
After heating to 70°C, polymaleic acid was mixed and dissolved to obtain a uniform and stable solution. Formulation example 6 Zirconyl nitrate (ZrO(NO ₃ ) ₂・2H ₂ O) 20 parts by weight Sodium malate 70 〃 Methylolacrylamide methacrylate copolymer (molecular weight 1000, reaction molar ratio 3:1) 10 〃 Each component was mixed at the above mixing ratio. After uniformly mixing, the mixture was dried to obtain a powder. Formulation example 7 Zirconyl chloride (ZrOCl _{2.8H 2} O) 5 parts by weight Sodium gluconate 50 Acrylic acid itaconic acid copolymer (molecular weight 6000,
Reaction molar ratio 2:1) 20 〃 Sodium sulfate (anhydrous salt) (weight gain stabilizer)
25 After uniformly mixing each component at the above mixing ratio, the mixture was dried to obtain a powder. Formulation example 8 Zirconium sulfate (Zr(SO ₄ ) ₂・4H ₂ O) 10 parts by weight Sodium citrate 80 Acrylic acid acrylamide copolymer (molecular weight
6000, reaction molar ratio 3:1) 10 Each component was mixed uniformly at the above mixing ratio and then dried to obtain a powder. Each of the thus obtained formulations contains 5.2 to 58.8 parts by weight of aliphatic oxycarboxylic acid or its salt and 1.5 to 14.2 parts by weight of polycarboxylic acid or its salt, calculated based on 1 part by weight of zirconium. be. Formulation example 9 Stannous chloride (SnCl _{2.2H 2} O) 2 parts by weight Sodium gluconate 30 〃 Sodium polyacrylate 5 〃 Water 63 〃 After dissolving sodium gluconate in water at the above mixing ratio, stannous chloride Tin and then sodium polyacrylate were mixed and dissolved to obtain a uniform and stable solution. Formulation example 10 Stannic chloride (SnCl _{4.3H 2} O) 10 parts by weight Sodium gluconate 15 〃 Polymaleic acid (molecular weight 1000) 10 〃 Water 65 〃 After dissolving sodium gluconate in water at the above mixing ratio, chloride The stannic and then the polymaleic acid were mixed and dissolved to obtain a uniform and stable solution. Formulation example 11 Stannous sulfate (SnSO ₄ ) 4 parts by weight Sodium citrate 30 Acrylic acid methacrylic acid copolymer (molecular weight
4000, reaction molar ratio 1:1) 5 〃 Water 61 〃 After dissolving sodium citrate in water with the above mixing ratio, stannous sulfate and then acrylic acid methacrylic acid copolymer were mixed and dissolved to form a uniform and stable liquid agent. Obtained. Formulation example 12 Stannous chloride (SnCl _{2.2H 2} O) 20 parts by weight Sodium gluconate 15 Acrylic acid acrylamide copolymer (molecular weight
6000, reaction molar ratio 3:1) 10 〃 Water 55 〃 After dissolving sodium gluconate in water with the above mixing ratio, mixing and dissolving stannous chloride, and then heating the liquid temperature to 50 to 60 ° C. A homogeneous and stable solution was obtained by mixing and dissolving the acrylic acid acrylamide copolymer. Formulation example 13 Stannous chloride (SnCl ₂ 2H ₂ O) 2 parts by weight Sodium malate 15 Sodium polyacrylate (molecular weight 8000)
3 Sodium hydroxide 3 Water 77 After dissolving sodium malate and sodium hydroxide in water at the above mixing ratio, stannous chloride and then sodium polyacrylate were mixed and dissolved to obtain a uniform and stable liquid preparation. Formulation example 14 Stannous chloride (SnCl ₂ 2H ₂ O) 1 part by weight Sodium gluconate 30 Sodium polyacrylate (molecular weight 8000)
5. Water 64. After dissolving sodium gluconate in water at the above mixing ratio, stannous chloride and then sodium polyacrylate were mixed and dissolved to obtain a uniform and stable solution. Each of the thus obtained formulations contains 1.4 to 57 parts by weight of aliphatic oxycarboxylic acid or its salt and 1.0 to 9.5 parts by weight of polycarboxylic acid or its salt, calculated based on 1 part by weight of tin. It is something. Example 2 A standing test by immersion was conducted using a test piece. That is, an aqueous solution containing a predetermined amount of drug
cc in a beaker and immerse a test piece of copper, aluminum, or mild steel (commercial product name: SPCC). The shape of the test piece is 30 x 50 x 1 mm. This is left for 10 days while maintaining the liquid temperature at 30°C ± 3°C. After finishing, pull up the test piece and observe the condition of the test piece with the naked eye. The water used was Osaka city tap water with a liquid volume of 500c.c. The table shows the water quality and the results obtained.

【table】

【table】

[Table] *The numbers in brackets in the concentration column indicate the active ingredient concentration.
In this way, zirconium sulfate, stannous chloride,
Sodium gluconate, sodium polyacrylate, and sodium polymethacrylate alone
Even when 50mg/m was added, there was no significant difference in the anticorrosive effect on mild steel, copper, and aluminum compared to when no addition was made. In addition, two-component systems of zirconium sulfate or stannous chloride and sodium gluconate, zirconium sulfate or stannous chloride and sodium polyacrylate also exhibit some corrosion-preventing effect, but no excellent corrosion-preventing effect can be obtained. Ta. However, for formulation examples 1 to 14 in Example 1, mild steel,
It can be seen that it exhibits excellent anticorrosion effects against copper and aluminum. Example 3 A corrosion prevention test in hot water was conducted using a test piece. A mild steel test piece having the same shape as that used in Example 2 and having a hole with a diameter of 4 mm in the upper part was attached to a stainless steel stirring rod and immersed in Test Solution 1 containing a predetermined amount of drug. The liquid is contained in a flat-bottomed beaker below a separable flask fitted into an annular mantle heater. While keeping the water temperature at 50℃ using a thermostat and mantle heater, the stirring bar linked to the motor rotates the water at 100rpm.
(100 rotations per minute) for 5 days. The water used was Osaka City tap water. Test end prognosis MDD (mg loss of corrosion per 1 dm ² day, mg/dm ² day) was determined in accordance with JIS K0100. The results obtained are shown in the table.

【table】

【table】

[Table] Indicates component concentration.
In this way, as in Example 2, each component may be used alone or in combination.
Compared to the component-based anticorrosive agent, the three-component anticorrosive agent of the present invention has
It can be seen that it exhibits excellent anticorrosion effects despite the low additive concentration. Furthermore, it can be seen that an excellent anti-corrosion effect can be achieved with a lower additive concentration than the conventionally known two-component system of a zirconium compound and a condensed phosphate. Example 4 The effect of chemicals in a soft water boiler was investigated using an autoclave. That is, a predetermined amount of the drug was added to 800 ml of 5 times concentrated Osaka city water softened water, and the mixture was placed in an autoclave. A mild steel test piece similar to that in Example 3 is suspended from a stirring rod, linked to a motor, immersed in the liquid, and rotated at 100 rpm. After sealing the autoclave, under stirring, 15Kgf/ ^cm2 approx. 200
Test for 3 days under pressurized and heated conditions at ℃. Since this soft water contained 10 _to 11 mg of dissolved enzyme, hydrazine (N ₂ H ₄ ) was used as _an oxygen scavenger in all cases tested _.
12mg/added. After the test was completed, MDD was determined in the same manner as in Example 3. The quality of the soft water used is shown in the table, and the results obtained are shown in the table.

【table】

【table】

[Table] *The numbers in brackets in the concentration column indicate the concentration of the active ingredient.
In this way, even in soft water and high temperature water, the three-component anticorrosive agent of the present invention has 136
It can be seen that excellent anti-corrosion effects can be achieved with amounts smaller than 200 mg/~156 mg/. Example 5 The dispersion effect of chemicals on iron in a soft water boiler was tested using an autoclave (high pressure cooker).
A predetermined amount of chemicals was added to Test Water 1, and the mixture was placed in an autoclave. After sealing the autoclave, a test is conducted for 3 days under pressure and heating conditions of 15 kg/cm ² and approximately 200°C while stirring at 100 rpm using a stirrer. After the test, let it cool to room temperature, let it stand for 1 hour, and then remove the supernatant liquid of the test water.
100ml was collected and the total iron concentration was measured. The table shows the quality of the soft water used and the results obtained. The test water used was synthetic soft water modeled after the quality of water that causes scaling problems in actual soft water boilers.

【table】

【table】

【table】

[Table] *The numbers in brackets in the concentration column indicate the active ingredient concentration.
Note that the dispersion rate was calculated using the following formula. Dispersion rate (%) = Total iron concentration after test (mg/) / Total iron concentration before test (mg/) x 100 As described above, the three-component corrosion inhibitor of the present invention has a sufficient iron dispersion effect. It turns out that there is something. This means that, for example, in a boiler can or heat exchanger system, iron brought into the can or heat exchanger system by water supply can be sufficiently removed from the system by blowing. In this way, scale does not form inside the can or heat exchanger system, preventing energy loss due to inhibition of heat transfer, and can prevent accidents due to pipe blockage or bursting.

Claims (1)

[Claims] 1. Zirconium or tin (contained in the form of a compound or ion), an aliphatic oxycarboxylic acid or a salt thereof, and an aliphatic lower unsaturated carboxylic acid polymer or a salt thereof A metal corrosion inhibitor characterized by containing as an active ingredient. 2. A patent claim containing 1 to 200 parts by weight of aliphatic oxycarboxylic acid or its salt and 0.1 to 30 parts by weight of aliphatic lower unsaturated carboxylic acid polymer or its salt per 1 part by weight of zirconium or tin. The anticorrosive agent according to item 1. 3. A patent claim containing 5 to 60 parts by weight of aliphatic oxycarboxylic acid or its salt and 1.0 to 10 parts by weight of aliphatic lower unsaturated carboxylic acid polymer or its salt per 1 part by weight of zirconium or tin. The anticorrosive agent according to item 1. 4. The anticorrosive agent according to any one of claims 1 to 3, wherein zirconium is contained in the form of a halide or inorganic acid salt of zirconium or zirconyl. 5. The anticorrosive agent according to claim 4, wherein zirconium is contained in the form of zirconyl chloride, zirconium sulfate, or zirconyl nitrate. 6 Claim 1 in which tin is contained in the form of stannous chloride, stannic chloride or stannous sulfate
The anticorrosive agent according to any one of items 1 to 3. 7. The anticorrosive agent according to any one of claims 1 to 3, wherein the aliphatic oxycarboxylic acid is gluconic acid, citric acid, malic acid, or a sodium salt thereof. 8 The aliphatic lower unsaturated carboxylic acid polymer has the following formula (): (In the formula, R ₁ to _{R 3} each independently represent a hydrogen atom, a methyl group, or a carboxyl group, and n is 0 or 1.
(representing an integer of (However, the molecular weight of each of these homopolymers and copolymers is 500 to 100,000.)
The anticorrosive agent according to any one of claims 1 to 3. 9 The molecular weight of the aliphatic lower unsaturated carboxylic acid polymer
1000 to 20000 polyacrylic acid, polymethacrylic acid, polymaleic acid, acrylic acid maleic acid copolymer, acrylic acid methacrylic acid copolymer, acrylic acid itaconic acid copolymer, acrylic acid acrylamide copolymer or methacrylic acid methylol acrylamide copolymer The anticorrosive agent according to any one of items 1 to 3. 10. The anticorrosive agent according to any one of claims 1 to 9, which is used in a cooling water system or a boiler water system.