JP2006281186A - Rust prevention method for steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stencil, to prevent slight rust during the period until the stencil is applied, and to exhibit a long-term rust prevention effect, particularly in the coastal area The present invention provides a method for preventing rust of a steel material, which can effectively prevent rust from being generated even under severe environmental conditions such as outdoor storage and sea transportation.
A step of applying an acrylic resin emulsion containing a rust preventive additive as a rust preventive for an undercoat, a step of applying a stencil after the undercoat rust preventive is dried, and a rust preventive for a top coat, A method for preventing rust of a steel material comprising a step of applying an alkyd resin solution containing an additive.
[Selection figure] None

Description

  The present invention relates to a method for preventing rust generated in a steel material during storage or transportation of the steel material, and more particularly to a method for preventing rust of the steel material in a steel material that needs to be provided with a stencil.

  In general, a steel material is coated with a rust preventive agent in order to prevent rust from being generated on the surface and maintain the quality of the product after being manufactured and before reaching the consumer. In particular, when steel materials are stored in coastal areas or during ocean transport, rust is likely to occur on the steel material surface due to the influence of salt water. Therefore, under such circumstances, it is more important to sufficiently rust prevent the steel material.

  As a method for rust-proofing steel materials, Patent Document 1 discloses that an alkyd resin-based rust-preventing oil is used to quickly dry the rust-preventing oil by setting the atmospheric temperature of the process to a predetermined temperature. A method for drying rust preventive oil is described.

  In Patent Document 2, a water-based zinc rich paint using a water-based urethane resin having a carboxyl group as a binder is applied to a preheated cast iron pipe outer surface, and then an acrylic resin-based emulsion is applied. A method for coating the outer surface of a cast iron pipe, characterized by drying by preheating, is described.

  Patent Document 3 is coated with an inexpensive temporary rust preventive agent that cures within a short time of 5 minutes within a temperature range of 40 to 60 ° C. and that can self-repair the roll wrinkles by the transport roll and the temporary rust preventive agent. A temporary rust preventive coated steel material is described.

Patent Document 4 describes a steel pipe rust inhibitor raw material containing one or more natural resins such as rosin and guaiac resin or modified products thereof, and a steel pipe rust preventive composition obtained by diluting this raw material with a solvent. ing.
Japanese Patent Laid-Open No. 54-101551 JP-A-8-141498 JP-A-10-157003 JP 2002-339086 A

  In the manufactured steel material, the stencil for displaying the manufacturer, specification, dimension, etc. of the steel material is attached. In steel materials with such a stencil, if rust occurs on the surface of the steel material, not only does the quality of the steel material deteriorate due to the occurrence of rust, but the stencil for product identification disappears due to the effect of rust and cannot be read. A further problem arises.

  In a normal factory environment (there are heating furnaces, cooling facilities, etc., and the environment is relatively high in temperature and humidity), rust is generated little by little immediately after the manufacture of the steel material. Therefore, it is necessary to prevent the generation of rust by applying a rust prevention treatment (hereinafter sometimes referred to as “primary rust prevention”) as soon as possible after the production of the steel material.

  Further, in order to inspect the quality of the steel material before applying the stencil, the steel material is subjected to a quality inspection test such as an ultrasonic flaw detection test or a wet magnetic particle flaw detection test. Therefore, the primary rust prevention described above prevents the steel material from rusting even if the steel material is stored indoors or outdoors for a short period (about 100 days) until these test results are obtained. There is a need.

  In the above quality inspection test, water is used as the contact medium or the solvent of the inspection solution, so that the rust-preventive coating produced by the primary rust prevention has good wettability with water. is required.

  Moreover, secondary processing may be given to the manufactured steel materials. For example, a threaded joint is processed at the end of a steel pipe, which is a kind of steel material, but a phosphate coating treatment or the like may be applied to impart lubricity or the like to the threaded joint. In this way, even when secondary processing is performed in a later step, the steel material is subjected to primary rust prevention immediately after manufacturing. Therefore, the surface of the rust preventive film is not discolored by the phosphoric acid film treatment in the subsequent process, or the rust preventive film component is dissolved and the phosphoric acid film treatment liquid ( The degreasing solution is strongly alkaline, and the phosphoric acid solution is strongly acidic.

  Moreover, the above-described stencil is attached to the steel material after the quality inspection. Therefore, the rust preventive film produced by the first rust prevention in the steel material needs to be able to impart this stencil. In other words, even if the rust-preventing film has good rust-preventing properties, it should not repel stencil ink on the rust-preventing film.

  Furthermore, after the primary rust prevention, the steel material may be applied with a rust preventive for overcoating and subjected to rust prevention treatment (secondary rust prevention) to obtain a long-term (several months or more) rust prevention effect. . Therefore, it is necessary that the rust preventive film produced by the primary rust prevention can be applied with a rust preventive agent for overcoating.

  However, the invention described in Patent Document 1 is a method for drying rust preventive oil at an early stage, and is not intended to provide a stencil on the rust preventive coating. Further, in the present invention, an alkyd resin-based rust preventive agent is used. However, when a stencil is applied on a rust preventive film made of an alkyd resin, the paint is repelled on the resin, making it difficult to confirm characters. In addition, since there is no rust preventive film on the stencil paint, the stencil is directly exposed to the outside air or the stencil part is directly rubbed, so that it may be difficult to read the stencil due to deterioration and wear. Therefore, the present invention cannot solve the above-described problem.

  The invention described in Patent Document 2 is a coating method for the outer surface of a cast iron pipe that is dried by preheating a cast iron pipe heated with a multilayer coating film, and is intended to prevent air pollution and save resources. It is not intended to provide a stencil on the rust preventive coating. Therefore, the above-described problem cannot be solved by the present invention.

  The invention described in Patent Document 3 is a rust preventive agent containing a specific solvent, which is excellent in low-temperature rapid curability and self-healing property, but provides a stencil on the rust preventive coating. It is not intended. The main component of the resin is preferably a urethane-modified alkyd resin. The stencil paint may be difficult to read when the paint is bounced on the resin and the stencil character cannot be confirmed, because the stencil paint is exposed to the outside air and rubbed because there is no rust preventive film on the stencil paint. The stencil cannot be applied. Therefore, the above-described problem cannot be solved by the present invention.

  The invention described in Patent Document 4 is a steel pipe rust preventive raw material containing one or more natural resins and a raw material diluted with a solvent, and has been conventionally used mainly from the viewpoint of environmental problems. Even if a desiccant (lead soap) is not used, it is intended to improve the drying property of the rust-preventive coating and provide good rust-prevention properties, and to provide a stencil on the rust-preventive coating. Absent. Therefore, the above-described problem cannot be solved by the present invention.

  The present inventors can also impart a stencil, can prevent even a slight rust during the period from immediately after producing the steel material until the stencil is imparted, and further provides a long-term rust prevention effect In particular, the inventors have found a method that can effectively prevent the occurrence of rust even under harsh environmental conditions such as long-term outdoor storage in coastal areas and marine transportation, and have completed the following invention.

  The present invention is a step of applying an acrylic resin emulsion containing a rust preventive additive as a rust preventive for an undercoat, a step of applying a stencil after the undercoat rust preventive is dried, and a rust preventive for a top coat. It is a method for preventing rust of a steel material having a step of applying an alkyd resin solution containing an additive.

In the above rust prevention method, the undercoat rust inhibitor is 100% by mass of the entire undercoat rust inhibitor, 0.1 to 4.0% by mass of the rust additive, and 0 to 0 of the viscosity modifier. It is preferably an acrylic emulsion containing 5.0% by mass and 20-50% by mass of an acrylic resin, with the balance being water.
The antirust additive is preferably one or more selected from the group consisting of organic acids, amines, sodium molybdate and sodium nitrite,
The viscosity modifier is preferably an ammonium salt or an amine salt of a polymer or copolymer having acrylic acid and / or methacrylic acid as a monomer unit,
The acrylic resin is a polymer obtained by polymerizing a monomer mixture containing 50 to 80% by weight of methacrylic acid ester and 20 to 50% by weight of acrylic acid ester, with the whole monomer mixture being 100% by weight. Preferably there is.

  In the rust prevention method, the undercoat rust inhibitor preferably contains 0.1 to 5% by mass of a film-forming aid, with the total of the undercoat rust preventive being 100% by mass.

In the above rust prevention method, the rust preventive agent for topcoat is 100% by mass of the entire rust preventive agent for topcoat, 0.1 to 10.0% by mass of the additive, 30 to 70% by mass of alkyd resin, It is preferably an alkyd resin solution containing 28 to 68% by mass of a petroleum hydrocarbon,
The additive is preferably one or more selected from the group consisting of sodium sulfonate, barium sulfonate, calcium sulfonate, bismuth abietic acid, cobalt naphthenate and lead naphthenate.

  In the above rust prevention method, the temperature of the steel material when applying the rust preventive agent for undercoating is 15 to 99 ° C, and the temperature of the steel material when applying the rust preventive agent for overcoating is 0 to 100 ° C. preferable.

  In the above rust prevention method, the acrylic resin in the rust preventive agent for undercoat is 50 to 79% by weight of methacrylic acid ester, 20 to 49% by weight of acrylic acid ester, 1% of styrene, based on 100% by weight of the whole monomer mixture. A polymer obtained by polymerizing a monomer mixture containing ˜20% by mass is preferable.

  According to the present invention, a rust preventive agent for undercoating can be applied immediately after the production of a steel material to form a rust preventive coating, and slight rust during the period until the stencil is applied can be prevented. Moreover, after the undercoat rust inhibitor is dried, a stencil can be applied on the rust preventive film. Furthermore, by applying a rust preventive agent for overcoating, it gives a long-term rust-preventing effect, and rust is generated in steel materials even in harsh environmental conditions such as long-term outdoor storage in coastal areas and sea transportation. This can be effectively prevented. In addition, according to the present invention, since the stencil is provided between the rust preventive film by the undercoat rust preventive and the rust preventive film by the top coat rust preventive, the stencil is clearly maintained for a long period of time. can do.

  The method for preventing rust of a steel material of the present invention comprises a step of applying an undercoat rust preventive, a step of applying a stencil, and a step of applying a top coat rust preventive.

  Hereinafter, the method for preventing rust of a steel material of the present invention will be described in the order of steps.

<Process of applying an undercoat rust preventive>
In the method for preventing rust of a steel material according to the present invention, a rust preventive for undercoating is applied immediately after a steel material such as a steel plate or a steel pipe is manufactured through processes such as casting, rolling, and heat treatment.

  The method for applying the rust preventive for undercoating is not particularly limited, and examples thereof include spray coating and brush coating. However, spray coating is preferable because it can be applied uniformly and efficiently to a steel material. In the case of brush coating, no bubbles are generated when the anticorrosive agent is applied. However, in the case of spray coating, there is a possibility that bubbles are generated depending on the pressure during spraying. Therefore, in order to prevent the generation of such bubbles, the spray pressure is preferably 0.5 MPa or less.

  The undercoat rust inhibitor is applied to the entire surface of the steel material. For example, in the case of a steel plate, it is applied to all of the back, front and side, and in the case of a steel pipe, it is also applied to the outer peripheral surface and the end surface of the steel pipe, and in some cases, the inner surface of the steel pipe.

  The temperature of the steel material when applying the rust preventive for undercoating is preferably 15 to 99 ° C, and more preferably 50 to 80 ° C. If the temperature of the steel material is too low, it takes a long time to dry the rust preventive for the undercoat. Moreover, when the temperature of steel materials is too high, the water which is a solvent will boil, the film-forming property of a rust prevention film will worsen, and it will become difficult to attach a stencil on a rust prevention film.

  The rust preventive for undercoating is an acrylic resin emulsion containing a rust preventive additive as an essential component and a viscosity modifier as an optional component.

  In order to prevent the rust-preventive agent from dripping and flowing until the rust-preventive coating is formed after applying the rust-preventive agent for the undercoat, the rust-preventive coating exerts the rust-preventive effect It is necessary to be able to maintain the required film thickness. For this reason, a viscosity modifier described below is added to the rust preventive for undercoating.

  The viscosity modifier can be used without limitation as long as it has such an effect, but the rust preventive film formed by applying the rust preventive for undercoat is made of an acrylic resin. Therefore, an ammonium salt or amine salt of a polymer or copolymer having acrylic acid and / or methacrylic acid as monomer units, which hardly affects the moldability of such a rust-preventive coating, is preferable. Moreover, the ammonium salt or amine salt of the copolymer which further has an acrylic ester and / or a methacrylic ester as a monomer unit may be sufficient.

  It is preferable that the rust preventive film formed by applying the rust preventive agent for undercoating has a dry film thickness of 5 to 20 μm. In order to maintain such a film thickness, the amount of the viscosity modifier added to the rust preventive for the undercoat is adjusted. The addition amount of the viscosity modifier is preferably 5.0% by mass or less, and preferably 0.2 to 2.0% by mass based on the mass of the entire undercoat rust inhibitor (100% by mass). More preferred.

  It is necessary to prevent the rust from being generated in the steel material even during the period from when the rust preventive for the undercoat is dried to form a rust preventive film. In general, even if the effect of preventing rust by the rust preventive coating after the rust preventive agent has dried is sufficient, if rust has already occurred in the steel material, this rust becomes the starting point even after film formation. And rust diffuses. Therefore, in the present invention, the rust preventive additive is added to the rust preventive agent for the undercoat, and the rust preventive agent is exerted with the rust preventive effect until the rust preventive agent for the undercoat is dried to form the rust preventive film. Rust is sufficiently prevented.

  Any anti-rust additive can be used without limitation as long as it has an effect of preventing rust generation in the steel in the presence of water. Among them, as a rust preventive additive that hardly affects the film forming property of the rust preventive coating after the undercoat rust preventive is dried, a kind selected from the group consisting of organic acid, amine, sodium molybdate and sodium nitrite, Or the mixture of 2 or more types can be mentioned.

  Examples of the organic acid include saturated or unsaturated aliphatic monocarboxylic acid or aliphatic dicarboxylic acid having 6 to 12 carbon atoms, and benzoic acid.

  Examples of the amine include C2-C12 amino alcohols such as monoethanolamine, diethylmonoethanolamine, and monoisopropanolamine, C1-C6 alkylamines such as monomethylamine and diethylamine, and cyclohexylamine. Can be mentioned.

  Sodium molybdate and sodium nitrite act more effectively as rust preventive additives when used in combination with the above organic acids and amines. These can be used as rust preventive additives within a range that does not affect the film formability.

  The addition amount of the rust preventive additive is preferably 0.1 to 4.0% by mass based on the mass (100% by mass) of the entire rust preventive agent for undercoat, and 0.2 to 2.0% by mass. It is more preferable that If the additive amount of the rust preventive additive is too small, the rust preventive effect until the rust preventive film is formed becomes insufficient, and if the additive amount of the rust preventive additive is excessive, the film forming property and water resistance of the resin are reduced. This is because the rust preventive properties deteriorate as a result.

  As the rust preventive agent for undercoat, an acrylic resin emulsion containing the above-described rust preventive additive and a viscosity modifier as an optional component is used. Here, the performance required for the rust-preventive coating formed after applying and drying the rust-preventing agent is rust-preventive for a short period (for example, about 100 days), but it is stored not only indoors but also outdoors, and it is wind and rain. Even when exposed to rust, it must retain rust resistance. Therefore, the antirust coating formed by applying the rust preventive for undercoating needs water resistance and light resistance. Therefore, in the present invention, in order to maintain these functions, an acrylic resin is used in the rust preventive for undercoat.

  Examples of the acrylic resin include a polymer obtained by polymerizing a monomer mixture containing a methacrylic acid alkyl ester, a methacrylic acid cyclohexyl ester, and an acrylic acid alkyl ester. The methacrylic acid alkyl ester and the acrylic acid alkyl ester may each be one kind or a mixture of two or more kinds, and the alkyl group is an alkyl group having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, A propyl group, a butyl group, 2-ethylhexyl group, etc. can be mentioned.

  As a blending ratio of the monomer mixture, based on the mass of the entire monomer mixture (100% by mass), the methacrylic acid alkyl ester is 50 to 80% by mass, and the acrylic acid alkyl ester is 20 to 50% by mass. It is preferable to do.

  Moreover, in order to increase the strength of the dry film, styrene can be blended to adjust the strength. The blending amount of styrene is preferably 1 to 20% by mass with respect to 99 to 80% by mass of acrylic based on the mass of the whole monomer mixture (100% by mass).

  The rust preventive agent for undercoat used in the present invention is based on the total mass of the rust preventive agent for undercoat (100% by mass), 0.1 to 4.0% by mass of the rust preventive additive, and 0 for the viscosity modifier. It is preferable that it is an acrylic emulsion which contains -5.0 mass%, acrylic resin 20-50 mass%, and the remainder is comprised with water. In addition, water-based emulsions are safer than organic solvents for fires, air pollution, and work environments.In addition, there is a risk of large-scale local exhaust devices and explosions caused by volatilized gases after application. Therefore, there is an effect that the primary rust inhibitor can be applied at a relatively low cost.

  In addition, the rust preventive for undercoating contains a film-forming aid to compensate for the difficulty in forming an appropriate film depending on the temperature of the steel material during application of the rust preventive. Also good. Examples of the film forming aid include ethylene glycol mono-2-ethylhexyl ether, dipropylene glycol monobutyl ether and the like. The blending ratio of the film-forming auxiliary is preferably 0.1 to 5% by mass based on the mass of the entire undercoat rust inhibitor (100% by mass).

  It is also possible to add a preservative, an antifoaming agent, etc. to the rust preventive agent for undercoating as required, as long as the performance of the rust preventive coating is not impaired. Moreover, it is necessary to select what does not affect a rust preventive film as a kind of antiseptic | preservative, an antifoamer, etc.

  A rust-preventing film formed by applying a rust-preventing agent for undercoating and drying it is formed with an rust-preventing additive, and in some cases, an acrylic resin containing a viscosity modifier and a film-forming aid. Yes. The stencil described below can be satisfactorily imparted to the rust preventive coating.

  Further, the rust preventive coating has good wettability with water. Therefore, in the quality inspection performed on the steel material, when water is used as a solvent, the quality inspection can be easily and appropriately performed.

  Moreover, even if the above-mentioned rust preventive film is subjected to a phosphoric acid film treatment or the like, the surface is not discolored and the rust preventive film component does not melt out.

  Moreover, the rust preventive film can be coated with a rust preventive agent for top coating described below.

<Step of applying stencil>
An undercoating rust preventive agent is applied to a steel material, and a stencil is provided on the anticorrosive coating formed by drying the undercoating rust preventive agent. Here, the stencil refers to printing that displays the manufacturer (manufacturer name, etc.), standard, dimensions, weight, etc. of the steel material that has passed the quality inspection.

  The ink used in the stencil needs to be compatible with both the undercoat rust preventive and the top coat rust preventive. For example, an ink made of a cellulose resin or the like can be used.

<Process of applying top coat rust preventive>
After the stencil is applied to the rust preventive film made of the undercoat rust preventive agent, the top coat rust preventive agent is applied thereon.

  The method of applying the top coating rust inhibitor is not particularly limited, and examples thereof include spray coating and brush coating. However, the spray coating method is desirable because uniform coating is possible.

  The top coating rust preventive is an alkyd resin solution containing additives. Moreover, it is preferable that the rust preventive for topcoat contains 0.1 to 10.0% by mass of the additive based on the total mass of the rust preventive for topcoat (100% by mass), and 0.2 to 5%. More preferably, the content is 0.0% by mass. Moreover, it is preferable to contain 30-70 mass% of alkyd resins, and it is more preferable to contain 40-60 mass%. Moreover, it is preferable to contain 28-68 mass% of petroleum hydrocarbons.

  Examples of the additive include one or a mixture of two or more selected from the group consisting of sodium sulfonate, barium sulfonate, calcium sulfonate, bismuth abietic acid, cobalt naphthenate, and lead naphthenate. be able to.

  The above alkyd resin refers to a polycondensation product of a polyhydric alcohol and a polyvalent carboxylic acid. For example, a polycondensation polymer composed of phthalic acid and glycerin can be used, and other oil-modified alkyd resins and rosin-modified alkyd resins. Various modified alkyd resins such as phenol-modified alkyd resins can also be used, but linseed oil-modified alkyd resins are particularly preferable.

  Examples of the petroleum hydrocarbon include lanterns, petroleum spirit, xylene, and isoparaffin.

  Moreover, in order to maintain a long-term rust prevention effect, the rust-preventing film formed by applying the anti-rusting agent for overcoating needs to be a uniform film having a dry film thickness of 10 to 50 μm. In order to form such a coating film, it is necessary to set four factors: steel material temperature, drying time, viscosity of the topcoat rust inhibitor, and concentration of the topcoat rust inhibitor.

  After applying the top coating anticorrosive agent, the petroleum-based hydrocarbons evaporate to form a rustproof coating. At this time, if the temperature of the steel material at the time of application of the anticorrosive agent for top coating is high, the viscosity of the anticorrosive agent for top coating decreases and droops, resulting in a problem that a required film thickness cannot be obtained. Moreover, if the temperature of the steel material at the time of application | coating of the anticorrosive agent for topcoat is still higher, since petroleum-type hydrocarbon will immediately evaporate and dry, it will become a nonuniform rust-proof film. Moreover, when the temperature of steel materials is too low, drying time will become long and the problem that the rust preventive agent for topcoat will drips will arise. From the above, it is necessary to determine the drying time, viscosity, and concentration of the rust preventive agent for overcoating according to the steel material temperature, in addition to the predetermined steel material temperature.

  Steel material temperature is 0-100 degreeC, and is determined by normal operation | work, and the process which heats or cools steel material in order to apply | coat the antirust agent for topcoat is not performed. The drying time of the top coating rust inhibitor is determined by the steel material temperature and the boiling point (or volatilization point) of the petroleum hydrocarbon. The viscosity of the top coating rust inhibitor is determined by the viscosity and concentration of the alkyd resin and the viscosity of the petroleum hydrocarbon. The concentration of the rust preventive for top coating is determined by the amount of additive and alkyd resin.

Based on these factors, the present invention has been achieved by making the components of the top coating anticorrosive agent as follows.
The boiling point range of the petroleum hydrocarbon is 120 to 200 ° C.
The viscosity of the rust preventive for top coating is 30 to 100 (mPa · sec, 25 ° C.),
The blending amount of the alkyd resin is 48 to 65%,
The compounding quantity of an additive shall be 3.5 mass%.

<Adjustment of rust preventive for undercoat>
Samples 1 to 8 and comparative samples 1 to 4 having the respective components shown in Table 1 and Table 2 below were prepared as rust preventives for undercoating. In addition, the compounding quantity of each component is the mass%.

The types of resins, rust preventive additives, viscosity modifiers, and film increasing aids shown in Tables 1 and 2 are shown below.
Resin (A): Copolymer of methyl methacrylate and butyl acrylate (copolymerization ratio (molar ratio) = 70: 30 (methyl methacrylate: butyl acrylate)),
Resin (B): Copolymer of methyl methacrylate, butyl acrylate and styrene (copolymerization ratio (molar ratio) = 45: 45: 10 (methyl methacrylate: butyl acrylate: styrene)),
Resin (C): Copolymer of methyl methacrylate, cyclohexyl methacrylate and butyl acrylate (copolymerization ratio (molar ratio) = 35: 38: 27 (methyl methacrylate: cyclohexyl methacrylate: butyl acrylate)),

Antirust additive (A): a mixture of caprylic acid (20% by mass), monoisopropanolamine (50% by mass) and sodium nitrite (30% by mass),
Antirust additive (B): Caprylic acid (30% by mass), Triethanolamine (70% by mass) mixture,
Antirust additive (C): a mixture of dodecadioic acid (25% by mass), triethanolamine (50% by mass), and molybdate Na (25% by mass),
Antirust additive (D): Na nitrite (100% by mass),
Antirust additive (E): a mixture of triethanolamine (50% by mass) and Na molybdate (50% by mass),
Antirust additive (F): a mixture of monoisopropanolamine (70% by mass) and sodium nitrite (30% by mass),

Viscosity modifier: ammonium salt of RHEOLATE 430 (Elementis Specialties, Inc.),
Film-forming aid: ethylene glycol mono 2-ethylhexyl ether

<Adjustment of rust preventive for top coat>
Samples 9 to 11 and comparative samples 5 to 6 having the respective components shown in Table 3 and Table 4 below were prepared as rust preventives for top coating. In addition, the compounding quantity of each component is the mass%.

<Examples 1-15>
A sample cut to 150 mm × 100 mm from a steel tube having an outer diameter of 178 mm and a wall thickness of 10.4 mm as it is hot-rolled is spray-coated with a rust preventive agent for undercoat shown in Table 5, and after drying, the following wettability Evaluation and film deterioration evaluation by phosphoric acid treatment were performed.
Subsequently, a stencil was formed by spraying a cellulose resin-based paint on the sample using a template. After the stencil, the top coating rust preventive shown in Table 5 was applied and stored outdoors for 180 days, and then the state of rust generation on the coated surface was confirmed, and the following rust generation / stencil discrimination evaluation was performed.

<Comparative Examples 1-10>
In the same manner as in the examples, the undercoat rust preventive agent shown in Table 5 was spray-coated, and after drying, water wettability evaluation shown below and film deterioration evaluation by phosphoric acid treatment were performed. Subsequently, the stencil was applied in the same manner, and the top coating anticorrosive agent shown in Table 5 was applied. After the storage for 180 days outdoors, the state of rust generation on the coated surface was confirmed, and the following rust generation / stencil discrimination evaluation Went.
In Comparative Example 1 and Comparative Example 8, the top coating rust preventive was not applied. Moreover, in Comparative Example 9 and Comparative Example 10, the rust preventive for undercoating was not applied.

<Evaluation method>
Evaluation was performed by the following evaluation methods. The evaluation results are shown in Table 5.
(Water wettability evaluation)
Water wettability was evaluated visually by applying an undercoat rust preventive in each of the above-mentioned Examples and the like and then watering it.

(Evaluation of coating deterioration by phosphoric acid treatment)
In each of the above examples, an undercoating rust preventive agent was applied, and after drying, half of the dried sample was degreased with a commercially available alkaline degreasing agent, and then the commercial phosphate was adjusted to a predetermined concentration and subjected to chemical conversion treatment (temperature 80 ° C. For 5 minutes). Then, after storage outdoors for 30 days, the phosphoric acid-treated part and the untreated part were visually compared, and the presence or absence of rust in the phosphoric acid-treated part was investigated to evaluate the presence or absence of film deterioration due to phosphoric acid. . In Comparative Examples 9 and 10, since the undercoat rust preventive was not applied, this evaluation was not performed.

(Evaluation of stencil printing)
It was judged visually whether the stencil was clearly printed.

(Rust generation / stencil discrimination evaluation)
After applying a rust preventive for top coating and storing it outdoors for 180 days, the rust occurrence state of the coated surface was confirmed, and rust generation / stencil discrimination evaluation was performed according to the following criteria.
(Double-circle): Rust hardly generate | occur | produced and the stencil remained clear.
○: Extremely thin or slightly spot rust was generated and the stencil remained clear.
(Triangle | delta): About 10 to 50% rust generate | occur | produced and stencil discrimination | determination was a little difficult.
X: Rust occurred by 50% or more, and stencil discrimination was difficult.

(Evaluation results)
In the case where the rust prevention method of the present invention was applied (Examples 1 to 15), good results were shown in all evaluation items. On the other hand, in the methods of Comparative Examples 1 to 10, the steel material could not be rusted.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the present invention can be appropriately changed without departing from the gist or the idea of the invention that can be read from the claims and the entire specification, and a method for preventing rust of a steel material with such a change is also included in the technical scope of the present invention. Must be understood.

Claims (6)

Applying an acrylic resin emulsion containing an antirust additive as an antirust agent for undercoating;
A method for preventing rust of a steel material comprising a step of applying a stencil after the undercoat rust preventive has been dried, and a step of applying an alkyd resin solution containing an additive as a rust preventive for overcoating. The undercoat rust preventive is 100% by mass of the entire undercoat rust preventive,
An acrylic resin comprising 0.1 to 4.0% by mass of the rust preventive additive, 0 to 5.0% by mass of the viscosity modifier, 20 to 50% by mass of an acrylic resin, and the balance being water. System emulsion,
The rust preventive additive is one or more selected from the group consisting of organic acids, amines, sodium molybdate and sodium nitrite,
The viscosity modifier is an ammonium salt or amine salt of a polymer or copolymer having acrylic acid and / or methacrylic acid as a monomer unit,
The acrylic resin is a polymer obtained by polymerizing a monomer mixture containing 50 to 80% by weight of methacrylic acid ester and 20 to 50% by weight of acrylic acid ester, with the whole monomer mixture being 100% by weight. The method for preventing rust of a steel material according to claim 1.   The method for preventing rust of a steel material according to claim 1 or 2, wherein the undercoat rust preventive comprises 100% by mass of the entire undercoat rust preventive and further contains 0.1 to 5% by mass of a film forming aid. The top coat rust preventive is 100% by weight of the top coat rust preventive,
An alkyd resin solution containing 0.1 to 10.0% by mass of the additive, 30 to 70% by mass of alkyd resin, and 28 to 68% by mass of petroleum hydrocarbon,
The additive is one or more selected from the group consisting of sodium sulfonate, barium sulfonate, calcium sulfonate, bismuth abietic acid, cobalt naphthenate and lead naphthenate. The rust prevention method of the steel materials in any one of.   The temperature of the steel material at the time of apply | coating the rust preventive agent for undercoat is 15-99 degreeC, The temperature of the steel material at the time of apply | coating the rust preventive agent for topcoat is 0-100 degreeC, Any one of Claims 1-4 The rust prevention method of the steel materials as described in 4.   The acrylic resin in the undercoat rust preventive contains 50 to 79% by weight of methacrylic acid ester, 20 to 49% by weight of acrylic acid ester, and 1 to 20% by weight of styrene, based on 100% by weight of the entire monomer mixture. The method for preventing rust of a steel material according to any one of claims 1 to 5, wherein the method is a polymer obtained by polymerizing a monomer mixture.