JP2005097701A - Antirust - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antirust capable of forming a protective film for rust prevention having corrosion resistance equal to that by chromate treatment using a hexavalent chromium compound on various metals without depending on the kinds of metals, and further comprising no harmful metals such as hexavalent chromium. <P>SOLUTION: A protective film having durability equal to that of a chromate film can be formed on a metal surface without depending on the kinds of metals by using the antirust comprising a phosphate, an oxidizing agent and a nonionic surfactant, and the balance water and preferably having the pH of 8 to 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rust inhibitor. The rust inhibitor of the present invention is useful for rust prevention treatment of various metals, particularly nickel, copper and alloys thereof, tin and alloys thereof, chromium, gold, silver and palladium.

  Conventionally, ornaments such as rings, necklaces and bracelets, home appliances such as TVs and video recorders, acoustic products such as CD players and DVD players, electronic products such as computers, communication devices such as mobile phones and mobiles, watches, etc. On the surface of metal parts or synthetic resin parts used in a wide range of industrial products such as precision instruments, cameras, electron microscopes, telescopes and other optical equipment, automobiles, motorcycles, trains and other transportation equipment, leisure and sports equipment In order to improve decoration and design, and improve corrosion resistance, wear resistance, etc., a plating film made of metal or alloy such as nickel, copper, copper alloy, tin, tin alloy, gold, silver, palladium, etc. is formed In addition, the surface of the plating film is protected by a plating film, and a rust prevention protective film is formed to prevent rusting of the plating film. It is.

  For the formation of the rust-preventing protective film, a chemical conversion treatment solution containing a hexavalent chromium compound is mainly used. When the surface of the plating film is treated with the chemical conversion solution, hexavalent chromium and the metal constituting the plating film are partially replaced, and a chromate film having high corrosion resistance is formed. Substitution with hexavalent chromium varies depending on the metal species, and the most easily substituted metal is zinc. Therefore, chromate treatment is used exclusively for the treatment of plating films containing zinc. A protective film having the same durability as that formed cannot be formed.

  In addition, hexavalent chromium is not only a causative agent for nasal septum, chromium allergy, ulcers, etc., but also has been suspected of having carcinogenicity, and there is a strong movement to restrict or prohibit its use. Yes. Furthermore, hexavalent chromium is leached out from the chromate film on the surface of parts such as automobiles and electrical equipment that are left outdoors, resulting in a problem of polluting the environment.

  In view of such problems, there is a need for a rust preventive solution that exhibits excellent rust preventive effects on metal or alloy surfaces such as plating films and does not contain harmful metals such as hexavalent chromium. .

  A typical example of a substitute for hexavalent chromium is phosphate. Phosphate is used for rust prevention treatment of various metals.

As a technique using phosphate for the treatment of the zinc-based plating film, recently, for example, a phosphate (Zn ₃ (PO ₄ ) ₂ .4H ₂ O), phosphophyllite (Zn) is formed on one surface of a zinc-based plated steel sheet. A method of forming a film made of an amorphous phosphate such as ₂ Fe (PO ₄ ) ₂ .4H ₂ O) and forming a film made of a phosphate on the other surface (see, for example, Patent Document 1), A method in which a phosphate film is formed on a Zr—Cr plating film and the film is oxidized with an oxidizing agent such as hydrogen peroxide or nitric acid (for example, see Patent Document 2), phosphoric acid on a zinc-based plating film A method of forming a film made of a salt crystal and further forming a film made of an amorphous phosphate thereon (see, for example, Patent Document 3), manganese compound, titanium compound, phosphate, fluoride, and organic Contains acid, pH A chemical conversion treatment liquid having a pH of 0.5 to 4 (for example, including a tetravalent titanium compound, phosphate and tannic acid or tannic acid salt (for example, see Patent Document 4) Patent document 5) etc. are mentioned.

  In addition, as a technique using phosphate for the treatment of the Al-based plating film, for example, oxides of bubble metals (Ti, Zr, Hf, V, Nb, Ta, Mo, W) in which oxides exhibit high insulation resistance Alternatively, a chemical conversion treatment solution containing hydroxide, fluoride and phosphate (for example, Patent Document 6), Al or Al alloy surface is selected from alkali hydroxide and one selected from Zn, Fe, Ni, Co and Cu, or Treatment with an aqueous solution containing two or more, then alkaline earth metal, one or more selected from phosphoric oxyacids and oxyacid salts, and Mo, W, V and Ti oxygen acids and oxygen acids Examples include a method of treating with an aqueous solution containing one or more selected from salts and having a pH of 1 to 5 (for example, Patent Document 7).

  However, since the protective film formed by including a phosphate essentially has a low corrosion resistance when not coated, it cannot provide a metal with the same corrosion resistance as a chromate film.

  In addition, it has been proposed to treat an electroless nickel-phosphorous plating film with an alkaline aqueous solution containing a phosphate, an oxidizing agent and an alkali metal hydroxide (see, for example, Patent Document 8). Here, as the phosphate, an alkali metal salt of phosphoric acid, tripolyphosphoric acid or pyrophosphoric acid is used. As the oxidizing agent, hydrogen peroxide, an alkali metal salt of persulfuric acid, an alkali metal peroxide, an alkali metal salt of permanganic acid, or the like is used. When the electroless nickel-phosphorus plating film is treated with this alkaline aqueous solution, the corrosion resistance of the film can be improved. However, the corrosion resistance is not as excellent as that of the chromate film, and further improvement of the corrosion resistance is desired.

Japanese Patent Laid-Open No. 8-67989 JP-A-7-258822 JP 2000-309880 A JP 2002-30459 A JP 2002-60959 A JP 2002-146551 A JP 2003-193253 A JP 11-323567 A

  An object of the present invention is a rust-proofing solution for metals that does not contain harmful metals such as hexavalent chromium, and imparts corrosion resistance equivalent to that a chromate film imparts to zinc or a zinc alloy regardless of the metal type. It is to provide a rust inhibitor that can be used.

  This invention is a rust preventive agent characterized by including a phosphate, an oxidizing agent, and a nonionic surfactant, and the remainder being water.

  Further, the rust preventive agent of the present invention has a phosphate content of 0.1 to 15 wt% (0.1 wt% or more, 15 wt% or less), an oxidizing agent of 0.01 to 5 wt% (0.01 wt% or more, 5 wt% or less) and a nonionic surfactant 0.005 to 1 wt% (0.005 wt% or more and 1 wt% or less), with the balance being water.

  Furthermore, the rust preventive agent of the present invention has a pH of 8 to 11 (8 or more, 11 or less).

  Further, in the rust preventive agent of the present invention, the above-mentioned phosphate is one or more selected from phosphoric acid, pyrophosphoric acid, ammonium salt of polyphosphoric acid, alkali metal salt and alkaline earth metal salt. Features.

  Furthermore, the rust inhibitor of the present invention is characterized in that the above-mentioned oxidizing agent is one or more inorganic oxidizing agents selected from hydrogen peroxide, persulfates, nitrates and permanganates.

  Furthermore, the rust preventive agent of the present invention is characterized in that the oxidizing agent is one or more selected from oxyacid salts, oxides and sulfates of manganese, cerium, vanadium and tin.

  Furthermore, the rust preventive agent of the present invention is characterized in that the above-mentioned nonionic surfactant is an aliphatic alcohol nonionic surfactant.

  According to the present invention, by treating a metal surface with a rust inhibitor containing phosphate, an oxidant and a nonionic surfactant as active ingredients, the balance being water, the discoloration of the metal surface, etc. It is possible to form an anticorrosive protective film on the metal surface that has excellent corrosion resistance, maintains corrosion resistance for a long period of time without adverse effects, and does not contain hexavalent chromium or other harmful metals.

  According to the research of the present inventor, the rust preventive agent of the present invention does not form a protective film by substitution with a metal to be treated like a chemical conversion treatment solution containing hexavalent chromium, but the above three kinds of effective Since the protective film is formed by the reaction between the component and the metal, especially the reaction between the phosphate and the metal, the same corrosion resistance as the chromate film imparts to zinc and zinc alloys on the metal surface, regardless of the type of metal. Can be granted.

  Further, the rust preventive agent of the present invention contains other components, such as an oxidizing agent and a nonionic surfactant, particularly an oxidizing agent, even though it contains phosphate as a main component of the protective film. Significantly promotes the chemical reaction between the phosphate and the metal to be treated, and the phosphate and the metal to be treated are firmly bonded to each other. A protective film with high corrosion resistance that cannot be obtained can be formed. In addition, a protective film excellent in corrosion resistance is formed by allowing an oxidizing agent to act on the surface of the metal to be treated in the process of forming a protective film containing phosphate as a main component. Even if an oxidizing agent is allowed to act after forming a protective film containing the main component, the desired corrosion resistance cannot be obtained.

  The rust inhibitor of the present invention is effective for rust prevention of various metals, but is particularly effective for nickel, copper, copper alloy, tin, tin alloy, chromium and the like. Furthermore, unlike conventional chemical conversion solutions or rust inhibitors containing phosphate, it is extremely effective for precious metals such as gold, silver and palladium.

  According to the present invention, by using specific amounts of each of the phosphate, the oxidizing agent and the nonionic surfactant, which are effective components of the rust preventive agent of the present invention, each component acts efficiently, and the metal to be treated Corrosion resistance of the protective film formed on the surface is further improved.

  According to the present invention, the corrosion resistance of the protective film formed on the surface of the metal to be treated is further improved by adjusting the pH of the rust inhibitor of the present invention to a specific range of 8 to 11.

  According to the present invention, among the above-mentioned phosphates, in particular, by using one or more selected from phosphoric acid, pyrophosphoric acid and ammonium salts of polyphosphoric acid, alkali metal salts and alkaline earth metal salts Since these phosphates are highly reactive with various metals in the presence of an oxidizing agent, a protective film with very good corrosion resistance can be formed on the surface of the metal to be treated.

  According to the present invention, among the above-mentioned oxidizing agents, by using one or more inorganic oxidizing agents selected from hydrogen peroxide, persulfates, nitrates and permanganates, phosphates and coatings can be obtained. Since the reaction with the treated metal proceeds more smoothly, a protective film having very good corrosion resistance can be formed on the surfaces of various metals.

  According to the present invention, among the aforementioned oxidizing agents, phosphates and treated materials are used by using one or more selected from oxyacid salts, oxides and sulfates of manganese, cerium, vanadium and tin. Since the reaction with the metal proceeds more smoothly, a protective film with very good corrosion resistance can be formed on the surface of various metals.

  According to the present invention, among the aforementioned nonionic surfactants, by using an aliphatic alcohol-based nonionic surfactant, the uniformity of the protective film formed on the surface of the metal to be treated can be further improved, The excellent corrosion resistance of the protective film can be maintained for a longer period.

  The rust preventive agent of the present invention is an aqueous composition containing a phosphate, an oxidizing agent and a nonionic surfactant as active ingredients, with the balance being water.

  The rust preventive agent of the present invention preferably has a pH of 8 to 11, more preferably a pH of 9 to 10. If the pH is much lower than 8 or significantly higher than 11, the reaction between the phosphate and the metal to be treated may be inhibited, and a protective film having sufficient corrosion resistance may not be formed.

  Known phosphates can be used, and examples thereof include salts of orthophosphoric acid, triphosphoric acid, metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, tetraphosphoric acid, hexaphosphoric acid, and other condensed phosphoric acids. Among these, phosphates rich in reactivity with various metals, for example, orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid salts and the like are preferable, and alkali metal salts, alkaline earth metal salts, ammonium salts and the like are further included. preferable. Specific examples include sodium phosphate, calcium phosphate, ammonium phosphate, potassium pyrophosphate, sodium pyrophosphate, sodium tripolyphosphate, and the like. Particularly preferred are normal phosphates and pyrophosphates having 2 to 3 alkali metals or alkaline earth metals in one molecule such as sodium phosphate, calcium phosphate, potassium pyrophosphate and sodium pyrophosphate. A phosphate can be used individually by 1 type, or can use 2 or more types together.

  The content of phosphate in the rust inhibitor of the present invention is not particularly limited, and the type of phosphate, the type and content of other components used in combination, the type of metal treated with the rust inhibitor of the present invention, and the like. Although it can be appropriately selected from a wide range, it is usually 0.1 to 15% by weight, preferably 3 to 10% by weight, based on the total amount of the rust inhibitor of the present invention. If the phosphate content is less than 0.1% by weight, the protective film formed on the surface of the metal to be treated may be uneven or the protective film may be too thin, resulting in insufficient corrosion resistance. . On the other hand, if it greatly exceeds 15% by weight, the effect of the oxidant used in combination may be reduced.

  As the oxidizing agent, one or more selected from inorganic oxidizing agents, oxyacid salts, oxides and sulfates can be used. As the inorganic oxidizing agent, known ones can be used. For example, peroxides such as hydrogen peroxide, alkali metal persulfates such as potassium persulfate and sodium persulfate, and alkaline earth metals persulfate such as barium persulfate. Preferred are salts, persulfates such as ammonium persulfate, nitrates such as potassium nitrate, copper nitrate, silver nitrate, and ammonium nitrate, and alkali metal permanganates such as potassium permanganate. Although known oxyacid salts, oxides and sulfates can also be used, tungsten, vanadium, cerium and tin oxyacid salts, oxides and sulfates are preferred, tungsten, vanadium and cerium oxyacid salts, oxidation And sulfates are particularly preferred. Specific examples include tungstate, vanadate, vanadium pentoxide, cerium sulfate, and the like. Moreover, formation of a protective film can be further accelerated | stimulated by using together 1 type, or 2 or more types of an inorganic oxidizing agent, and 1 type or 2 or more types chosen from an oxyacid salt, an oxide, and a sulfate.

  The content of the oxidizing agent in the composition of the present invention is not particularly limited and can be appropriately selected from a wide range depending on the type of oxidizing agent, the type and content of other components used in combination, the type of metal to be treated, etc. Is 0.1 to 5% by weight, preferably 1 to 3% by weight, based on the total amount of the composition of the present invention. If it is less than 0.1% by weight, the reaction between the phosphate and the metal to be treated does not proceed smoothly, and the corrosion resistance of the protective film may be insufficient. If it greatly exceeds 5% by weight, the oxidant may be self-decomposed and the effect of adding the oxidant may be reduced.

  As the nonionic surfactant as the component (c), known ones can be used. For example, aliphatic alcohol nonionic surfactants such as polyethylene glycol and ethylene glycol, polyoxyethylene alkyl ether, polyoxyethylene Examples include ethylene alkyl phenyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene fatty acid ester. Among these, aliphatic alcohol-based nonionic surfactants are preferable. A nonionic surfactant can be used individually by 1 type, or can use 2 or more types together.

  The content of the nonionic surfactant in the composition of the present invention is not particularly limited, and is wide depending on the type of nonionic surfactant, the type and content of other components used in combination, the type of metal to be treated, and the like. Although it can be appropriately selected from the range, it is usually 0.005 to 1% by weight, preferably 0.01 to 1% by weight of the total amount of the composition of the present invention. If it is less than 0.005% by weight, the uniformity of the protective film to be formed is insufficient, which may adversely affect the corrosion resistance of the protective film. If it exceeds 1% by weight, salting out of the surfactant occurs, and the effect of adding the surfactant may be reduced.

  The rust preventive of the present invention may contain various additives conventionally used in this field in addition to the essential components as long as the preferable characteristics are not impaired. Examples of the additive include metal salts such as aluminum, molybdenum and manganese, silane compounds such as polyalkylsiloxane, phosphorus compounds such as alkyl phosphate esters and alkanolamine phosphate, nitrogen compounds such as imidazole, tannic acid, boron Examples thereof include organic acids such as acid, gluconic acid and citric acid. These additives can be used alone or in combination of two or more.

  The rust preventive of the present invention includes, for example, an appropriate amount of an essential component which is a phosphate, an oxidizing agent and a nonionic surfactant, and other additives as required, and an amount of water in which the total amount becomes 100% by weight. And each component can be dissolved or dispersed in water according to a known method.

  A general alkali is used for pH adjustment of the rust inhibitor of the present invention. Examples of the alkali include alkali metal hydroxides such as ammonia water, sodium hydroxide, and potassium hydroxide, alkali metal carbonates such as sodium carbonate and potassium carbonate, and alkali metal hydrogen carbonates such as sodium bicarbonate and potassium bicarbonate. Etc. An alkali can be used individually by 1 type, or can use 2 or more types together as needed. Moreover, common acids, such as phosphoric acid, hydrochloric acid, sulfuric acid, and acetic acid, are used.

  The rust preventive agent of the present invention can be suitably used for rust prevention treatment of plating films formed containing various metals and various metals. Particularly effective for nickel, copper, copper alloy, tin, tin alloy, chromium and the like. Examples of the copper alloy include copper-silver, copper-cadmium, copper-chromium, copper-beryllium, copper-aluminum, and copper-nickel. Examples of tin alloys include tin-nickel, tin-cobalt, and tin-copper. Moreover, it can be particularly preferably used for rust prevention treatment of noble metals such as gold, silver and palladium.

  The metal rust prevention treatment using the rust inhibitor of the present invention can be carried out in the same manner as in the conventional method except that the rust inhibitor of the present invention is used.

FIG. 1 is a flowchart for explaining a metal rust prevention method using the composition of the present invention.
In the start step a0, an article to be processed is prepared in which at least a part or the whole of the surface is made of one or more kinds of arbitrary metals.

A degreasing process, a pickling process, etc. are given to a to-be-processed product as needed.
Degreasing can be performed according to a known method. For example, it is performed by supplying an alkaline aqueous solution to the surface of the article to be processed. The supply of the alkaline aqueous solution is performed, for example, by spraying the alkaline aqueous solution onto the article to be treated or immersing the article to be treated in the alkaline aqueous solution. As the alkali, those commonly used for metal degreasing can be used, and examples include alkali metal phosphates such as sodium phosphate and potassium phosphate. The alkali concentration in the aqueous alkali solution is appropriately determined according to, for example, the type of metal to be treated and the degree of contamination of the metal to be treated. Furthermore, the alkaline aqueous solution may contain an appropriate amount of a surfactant such as an anionic surfactant and a nonionic surfactant. Degreasing is performed at a temperature of about 20 to 50 ° C. (liquid temperature of the alkaline aqueous solution) and is completed in about 1 to 5 minutes. After degreasing, the product to be treated is washed with water and subjected to the next pickling process. In addition, degreasing to be immersed in an acidic bath, bubbling immersion degreasing, electrolytic degreasing, and the like can be appropriately combined.

  Pickling can be performed according to a known method. For example, it is performed by supplying an acid aqueous solution to the surface of the article to be processed. The supply of the acid aqueous solution is performed by spraying the acid aqueous solution onto the article to be treated, immersing the article to be treated in the acid aqueous solution, and the like, similarly to the supply of the alkaline aqueous solution in the degreasing treatment. As the acid, those commonly used for metal pickling can be used, and examples thereof include sulfuric acid, nitric acid, and phosphoric acid. The acid concentration in the acid aqueous solution is appropriately determined according to, for example, the type of metal to be treated. The pickling is performed at a temperature of about 20 to 30 ° C. (liquid temperature of the acid aqueous solution) and is completed in about 15 to 60 seconds.

  In step a1, the surface of the article to be treated is rust-prevented with the rust inhibitor of the present invention. The rust prevention treatment is performed, for example, by supplying the rust inhibitor of the present invention to the surface of the article to be treated. The supply of the rust inhibitor of the present invention includes, for example, immersion of the article to be treated in the rust preventive agent of the present invention, spraying of the rust inhibitor of the present invention to the article to be treated, application of the rust inhibitor of the present invention to the article to be treated, etc. Is done by. The rust preventive treatment time and the liquid temperature of the rust preventive agent of the present invention during the rust preventive treatment are not particularly limited and can be appropriately selected from a wide range depending on the type of metal to be treated, the composition of the rust preventive agent of the present invention, etc. The rust prevention treatment is performed at a temperature of about 15 to 35 ° C., preferably about 20 to 30 ° C. (liquid temperature of the rust preventive agent of the present invention), and is about 10 seconds to 3 minutes, preferably about 30 to 90 seconds. End with. By this treatment, a protective film having excellent corrosion resistance is formed on the metal portion on the surface of the article to be treated. After the rust prevention treatment, the article to be treated is washed with water and subjected to the subsequent post-drying step.

  In step a2, the article to be processed is dried. The article to be processed is dried at a temperature of about 70 to 120 ° C.

  Subsequently, it progresses to the end of step a3 and the article | item with which the protective film was formed on the metal surface is obtained.

The present invention will be specifically described below with reference to examples and test examples.
(Examples 1-3)
Each component was used in the ratio (% by weight) shown in Table 1, and the phosphate, oxidizing agent and surfactant were dissolved in water to prepare the composition of the present invention. In addition, sodium hydroxide or phosphoric acid was used for pH adjustment.

(Test Example 1)
Tin-copper alloy plating (product name: Royal White, manufactured by Shimizu Corporation, plating temperature 50 ° C., plating time 5 minutes), tin-nickel alloy plating (product name: 100 × 70 × 0.3 mm) Nobleloy SNC, manufactured by Shimizu Corporation, temperature 30 ° C., plating time 3 minutes) and tin-cobalt alloy plating (trade name: Black Beauty, manufactured by Shimizu Corporation, temperature 30 ° C., plating time 3 minutes), A sample was prepared.

  The obtained plated sample plate was immersed in 1 liter of the composition of the present invention obtained in Example 1 for 1 minute at room temperature, and then the plated sample plate was taken out of the composition of the present invention, washed with water, and washed at 80 ° C. for 20 minutes. It was dried for a minute, and the plated sample plate was subjected to rust prevention treatment.

The obtained rust-proof treated plated sample plate was continuously subjected to a salt spray test (sodium chloride concentration 5%, pH 7.0, spray amount 1 ml / 80 cm ² , temperature 35 ° C.) in accordance with JIS Z2371 for 36 hours. Thereafter, the surface condition of the plating of the sample plate was visually observed.

  For comparison, a plated sample plate not subjected to rust prevention treatment (Comparative Example 1) and a commercially available chromate chemical conversion treatment solution (trade name: metal passivation ELC, manufactured by Shimizu Corporation) are used instead of the composition of the present invention. A salt spray test similar to the above was also performed on the plated sample plate (Comparative Example 2) subjected to chemical conversion treatment. The results are shown in Table 2.

  From Table 2, it is clear that the antirust treatment to the tin alloy plating by the composition of the present invention is very effective. It is apparent that the plated sample plate treated with rust prevention by the composition of the present invention has corrosion resistance equivalent to or higher than that of the plated sample plate subjected to the chemical conversion treatment with the chromate chemical conversion treatment solution.

(Test Example 2)
A salt spray test was conducted in the same manner as in Test Example 1 except that the composition of the present invention of Example 2 was used and two commercially available trivalent chromium plating baths (plating temperature 50 ° C., plating time 2 minutes) were used as the plating bath. Went. The results are shown in Table 3.

Specifically, the trivalent chromium plating bath is as follows.
Trivalent chromium plating bath A: Trade name Envirochrome, manufactured by Canning Japan Co., Ltd. Trivalent chromium plating bath B: Product name, Twilight, manufactured by Canning Japan Co., Ltd.

  From Table 3, it is clear that the antirust treatment to the trivalent chromium plating by the composition of the present invention is very effective. It is apparent that the plated sample plate treated with rust prevention by the composition of the present invention has corrosion resistance equivalent to or higher than that of the plated sample plate subjected to the chemical conversion treatment with the chromate chemical conversion treatment solution.

(Test Example 3)
A salt spray test was conducted in the same manner as in Test Example 1 except that the composition of the present invention of Example 3 was used and two types of commercially available silver plating baths (plating temperature 30 ° C., plating time 10 minutes) were used as plating baths. It was. The results are shown in Table 4.

Specifically, the silver plating bath is as follows.
Silver plating bath X: Trade name Silver Glow 3KBK, manufactured by Meltex Co., Ltd. Silver plating bath Y: Trade name Algarx 64, manufactured by Atotech Japan Co., Ltd.

  From Table 4, it is clear that the rust prevention treatment to silver plating by the composition of the present invention is very effective. It is apparent that the plated sample plate treated with rust prevention by the composition of the present invention has corrosion resistance equivalent to or higher than that of the plated sample plate subjected to the chemical conversion treatment with the chromate chemical conversion treatment solution.

It is a flowchart explaining the antirust processing method of the metal using this invention antirust agent.

Claims (7)

  A rust preventive agent comprising a phosphate, an oxidizing agent and a nonionic surfactant, the balance being water.   2. A phosphate comprising 0.1 to 15% by weight, oxidizing agent 0.01 to 5% by weight and nonionic surfactant 0.005 to 1% by weight, the balance being water. Rust preventive as described.   pH is 8-11, The rust preventive agent of Claim 1 or 2 characterized by the above-mentioned.   The phosphate is one or more selected from ammonium salt, alkali metal salt and alkaline earth metal salt of phosphoric acid, pyrophosphoric acid and polyphosphoric acid. The rust preventive according to any one.   The oxidizing agent is one or more inorganic oxidizing agents selected from hydrogen peroxide, persulfates, nitrates and permanganates, according to any one of claims 1 to 4. Rust preventive.   The oxidizing agent is one or more selected from oxyacid salts, oxides and sulfates of manganese, cerium, vanadium and tin, according to any one of claims 1 to 4. Antirust agent.   The rust preventive agent according to any one of claims 1 to 6, wherein the nonionic surfactant is an aliphatic alcohol-based nonionic surfactant.

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