JP2011056737A - Surface-treated steel material excellent in corrosion resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel material capable of affording sufficient corrosion resistance by inexpensively improving the corrosion resistance of an organic coated steel material in an environment severer in corrosive condition. <P>SOLUTION: The surface-treated steel material excellent in corrosion resistance is characterized by having a surface-treated layer including following (a)-(c) on the surface of the steel material: (a) a gas phase silica of 1,000 nm or smaller in mean particle size, (b) an amino-based or epoxy-based silane coupling agent and (c) at least one oxide selected from oxides of molybdenum, vanadium, zirconium and tungsten and/or at least one oxysalt selected from oxysalts of molybdenum, vanadium, zirconium and tungsten. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface-treated steel material having excellent corrosion resistance.

  As a base treatment of an organic coated steel material, a surface treatment layer of a thin film made of a phosphate treatment, a chromate treatment or an organic resin and an inorganic substance is known as a coating treatment base. These roles are to increase the adhesion between the paint and the steel material, and to suppress the corrosion of the steel material under the organic layer and to increase the durability of the organic coated steel material in the corrosive environment.

  Since silica is almost insoluble in both acid and alkali and is a stable substance, it is often used by being added to various surface treatment agents. An organic composite-coated steel sheet having a resin layer in which a binder resin is blended is disclosed.

  Further, since the silane coupling agent has a high ability to form a surface treatment layer on the steel surface by reaction with the steel surface or by self-condensation reaction, for example, Patent Document 2 discloses fine particle silica, silane coupling agent, vanadic acid compound. And the like, and a chromate-free surface-treated zinc-based plated steel sheet is disclosed.

Japanese Patent No. 2988822 JP 2008-169470 A

  However, silica hardly reacts with steel plates, and some kind of binder is necessary to treat silica as a surface treatment layer on the steel surface. As shown in Patent Document 1, steel materials such as resin and chromate layers are used. Requires ingredients to adhere to.

  On the other hand, the silane coupling agent has a high ability to form a surface treatment layer on the steel surface by reaction with the steel surface or self-condensation reaction, but (1) it is expensive and (2) forms a certain thickness on the surface layer. For this purpose, there are problems such that a considerable amount of the silane coupling agent is required, and (3) there are few methods for applying a considerable amount of the silane coupling agent to the surface of the steel material.

  For example, even if it is supplied as an aqueous solution of a silane coupling agent, if the concentration becomes high, the solution gels due to a self-condensation reaction, which may limit the usable time and may inhibit the adsorption to the steel surface. It is difficult to technically and technically form a silane coupling layer as a binder.

  An object of the present invention is to provide a steel material that can improve the corrosion resistance of an organically coated steel material in a more severe corrosive environment at a low cost and obtain sufficient corrosion resistance.

  Inventors have found that the change in the environment (pH) associated with the corrosion reaction of the steel material causes peeling of the organic coating layer and adhesion deterioration, and reduces the corrosion resistance life of the organic coating layer. It has been found that the formation of is more effective against peeling of the organic coating layer and adhesion deterioration.

  However, as described above, efficiently forming the silica layer on the surface of the steel material is difficult and has many technical problems. Accordingly, the inventors diligently studied a method for forming a silica layer on the steel material surface, and obtained the following knowledge.

  Vapor phase silica was used as the main forming material of the silica layer. There are many OH groups that accompany hydration on the surface of vapor phase silica, which can react with silane coupling agents, and OH groups formed by hydration on the surface of steel materials are also silane coupled. This is because the reaction with the agent is possible.

  Therefore, the main material of the layer structure is gas phase silica, and the silane coupling agent acts on the coupling between the gas phase silica particles and the coupling between the steel material and the gas phase silica, and the surface of the steel material mainly composed of silica. A treatment layer can be formed.

  A silane coupling agent layer is formed on the vapor phase silica by a reaction between the silane coupling agent and the silica surface. The end of the silane coupling agent has an amino group, an epoxy group, or a silanol group, and this polar group further forms a hydrogen bond or an acid-base bond with the organic resin layer formed in the upper layer, and the surface treatment layer There is also an advantage that the adhesion between the organic resin layer and the organic resin layer is improved.

  Furthermore, if such a silica layer contains oxides or oxyacid salts such as molybdenum, vanadium, zirconium, etc., this suppresses the corrosion reaction of the steel material and further improves the durability of the organic coating layer. It has also been found that it has the properties of

  The present invention is based on the findings described above, and the present invention has the following features in order to solve the above problems.

1st invention is the surface treatment steel material excellent in corrosion resistance characterized by having the surface treatment layer containing the following a) -c) on the surface of steel material.
a) Gas phase silica having an average particle size of 1000 nm or less b) Amino or epoxy silane coupling agent c) At least one oxide selected from oxides of molybdenum, vanadium, zirconium, tungsten, and / or Or at least one oxyacid salt selected from oxyacid salts of molybdenum, vanadium, zirconium, and tungsten

  The second invention is an organic coated steel material excellent in corrosion resistance, characterized by having an epoxy-based, polyurethane-based, or acrylic-based organic resin layer on the surface treatment layer described in the first invention.

3rd invention is the surface treatment composition characterized by including the following a) -d).
a) Gas phase silica having an average particle size of 1000 nm or less b) Amino or epoxy silane coupling agent c) At least one oxide selected from oxides of molybdenum, vanadium, zirconium, tungsten, and / or Or at least one oxyacid salt selected from molybdenum, vanadium, zirconium, and tungsten oxyacid salts d) a solvent containing water

4th invention is the manufacturing method of the surface treatment steel material excellent in corrosion resistance characterized by heating after apply | coating the surface treatment composition containing the following a) -d), and evaporating the following d) solvent. .
a) Gas phase silica having an average particle size of 1000 nm or less b) Amino or epoxy silane coupling agent c) At least one oxide selected from oxides of molybdenum, vanadium, zirconium, tungsten, and / or Or at least one oxyacid salt selected from molybdenum, vanadium, zirconium, and tungsten oxyacid salts d) a solvent containing water

  The fifth invention is characterized in that an epoxy-based, polyurethane-based or acrylic-based organic resin layer is formed on the surface-treated steel obtained by the method for producing a surface-treated steel according to the fourth invention. It is the manufacturing method of the organic covering steel material excellent in corrosion resistance.

  Compared to conventional organic-coated steel materials, the steel materials manufactured according to the present invention can suppress the progress of corrosion of the damaged part of the film, for example, to about ½ or less, and can suppress the anticorrosion cost low. . Moreover, the steel structure which has the organic coating layer comprised with the steel material of this invention can be used as a steel structure which has long-term durability also in a severe corrosive environment.

It is a figure explaining the relationship between crosscut and crosscut peeling distance A1-A8.

  The present invention will be described in detail below.

  The silica in the surface treatment layer formed on the steel material mainly has a network structure formed by vapor phase silica particles and an amino or epoxy silane coupling agent. Vapor phase silica particles have many OH groups on the surface, so they have a higher probability of reacting with silane coupling agents on the surface than silica made by other production methods, and are suitable for this structure. ing.

  Further, the larger the surface area of the silica particles is advantageous for the same reason, but the surface area basically depends on the particle size and is considered to be more advantageous by reducing the particle size. This is achieved by using a silica of a diameter. If the average particle diameter exceeds 1000 nm, there are many gaps in the silica network structure, and a layer having a large defect is formed as the surface treatment layer. Therefore, the average particle diameter is preferably 1000 nm or less. More preferably, vapor phase silica particles having a maximum particle size of 1000 nm or less are preferable.

  The average particle diameter can be determined, for example, by the following method. First, an enlarged image of a small amount of vapor phase silica is obtained with a scanning electron microscope (hereinafter abbreviated as SEM). The magnification is preferably 1000 times or more and 5000 times or less. In the obtained enlarged image, 40 or more arbitrary gas phase silicas are selected, and the maximum length of each particle is measured. And let the arithmetic mean value of all the measured values be an average particle diameter.

  Although various types of silane coupling agents are known, most of them have silanol groups and organic polar groups. As organic polar groups, (1) epoxy widely used for upper organic layers Assuming that amino groups and epoxy groups are excellent in reactivity with polyurethane resins and polyurethane resins, and (2) other than silanol groups form bonds with the steel surface or silica surface, amino groups and epoxy These are preferred because the system is believed to form better bonds with them.

  Typical examples of these are γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyl. Examples include triethoxysilane.

  Since these all have a plurality of silanol groups, a cross-linked structure is formed between the vapor phase silica, between the vapor phase silica and the steel material, or between the vapor phase silica and the organic resin, so that the vapor phase silica is fixed on the steel surface. , And fixation between vapor phase silica and fixation between organic resin layers can be expected.

  As described above, a basic layer resistant to acids and alkalis is formed. However, when an inorganic material that inactivates steel or acts as an inhibitor is added thereto, a more effective surface treatment layer is formed. Inorganic materials used in the present invention include molybdenum oxide, vanadium oxide, zirconium oxide, tungsten oxide, molybdenum oxyacid salt, vanadium oxyacid salt, zirconium oxyacid salt, and tungsten oxide. Oxyacid salt. One type may be selected and used from the oxide and the oxyacid salt, or a plurality of types may be selected from the oxides and used. Or a plurality of types selected from the oxide and the oxyacid salt may be used.

  Preferred examples of these compounds include sodium molybdate, ammonium molybdate, sodium vanadate, sodium metavanadate, sodium zirconate, sodium tungstate, molybdenum trioxide, vanadium trioxide, vanadium pentoxide, zirconium oxide, and tungsten oxide. It is.

  Under the organic coating layer, as an action for mainly destroying the interface under the organic coating layer, there is destruction of the interface with an alkali or an acid generated as a result of a corrosion reaction caused by oxygen or water permeating the organic coating layer. Unlike the phosphoric acid or chromate treatment layer, the surface treatment layer formed of silica is basically insoluble in acids and alkalis. In addition to being strong to these, the inorganic substance is added to the surface treatment layer, The caustic corrosion reaction can also be fundamentally suppressed and is more effective.

These surface treatment layers can be generated on the steel material by the following method.
First, a surface treatment composition containing the following a) to d) is prepared. Here, a) gas phase silica having an average particle diameter of 1000 nm or less, b) an amino or epoxy silane coupling agent, c) at least one oxide selected from oxides of molybdenum, vanadium, zirconium, and tungsten Oxides and / or at least one oxyacid salt selected from molybdenum, vanadium, zirconium, and tungsten oxyacid salts, and d) a solvent containing water.

  The d) solvent of the surface treatment composition in the present invention always contains water. In order to mix the vapor-phase silica into the surface treatment composition to some extent without precipitation, it is desirable that the surface of the vapor-phase silica in the solvent has a polarity. Repulsive force is generated by this surface polarity, and the vapor phase silica can be mixed in the solvent uniformly to some extent without precipitation. If water is used as the solvent, the surface polarity of the gas phase silica can be generated most effectively. If the surface polarity of the vapor phase silica can be generated, the solvent may contain an organic solvent other than water, such as ethanol, methanol, and the like. In order to obtain the effect of this surface polarity, it is desirable that water accounts for 50 parts by mass or more when the total amount of the solvent is 100 parts by mass. The water used may be pure water (including ion exchange water), purified water, tap water, or the like.

  A) a surface-treating composition comprising: a) gas phase silica, b) a silane coupling agent, and c) at least one selected from the above oxides and the above oxyacid salts. To do. These may be input at a time or may be input individually.

  Furthermore, although not essential, an acid or the like for controlling the stability of the silane coupling agent may be added to the surface treatment composition.

  After applying the surface treatment composition thus obtained to the steel surface, the solvent is evaporated. As a method of evaporating the applied solvent, specifically, a method of heating a steel material is desirable because it is the simplest and most efficient.

  Hereinafter, the present invention will be described in detail with reference to examples.

1. About preparation of test steel plate As the steel material, ordinary steel (SS400) was used. The size was 100 mm × 50 mm × 6 mmt, and the black skin was removed by blasting.

  The surface treatment composition applied to the surface was prepared by the following procedure. Vapor phase silica was put into ion-exchanged water and stirred so as not to precipitate. To this stirring liquid, an inorganic material (sodium vanadate, sodium metavanadate, sodium zirconate, ammonium molybdate, sodium tungstate, vanadium pentoxide, molybdenum trioxide, all of which use a reagent having a purity of 99.9%) and Aminopropyltriethoxysilane or 3-glycidylpropyltriethoxysilane was added as a silane coupling agent and stirred vigorously with a stirrer. This was made into the surface treatment composition. In addition, the inorganic material was crushed with a mortar so as to be easily dissolved, and a powder having a particle size of approximately 1 μm or less was used.

  And this surface treatment composition was poured on the steel material surface, continuing stirring. At this time, the thickness of the solution film of the surface treatment composition was made substantially constant by maintaining the steel material at an angle of 45 degrees. Then, it left still for about 1 minute, it heated until the steel materials temperature reached 100 degreeC in the electric furnace hold | maintained at 140 degreeC, and the surface treatment layer was formed by evaporating the solvent in a surface treatment composition.

Then, on this surface treatment layer,
A) Polyurethane paint (Permguard 330 Primer, manufactured by Daiichi Kogyo Seiyaku) was applied by 40 μm spray, and polyurethane paint (Permguard 137, manufactured by Daiichi Kogyo Seiyaku) was sprayed to a thickness of 1 mm and cured for 1 week.
A) Epoxy resin (Epicoat 828 / P002 blended at 100: 50) was applied with a 300 μm bar coater and baked at 180 ° C. for 10 minutes,
An organic-coated steel material coated with a two-level coating material was prepared.

  In addition, it shows in Table 1 and Table 3 about the composition of a solvent in a surface treatment composition, the average particle diameter and content of a gaseous-phase silica, the composition of a silane coupling agent, and the composition of an inorganic material.

2. About investigation of corrosion resistance About investigation of corrosion resistance of steel materials, masking was performed so that the back and end faces of the steel materials coated with the organic resin layer were not corroded by seal tape. Thereafter, a cross cut (see FIG. 1) reaching the steel surface was formed in a size of 30 mm × 30 mm by a saw blade on the organic coating layer of the test material. Then, using a combined cycle tester, 4 hours of drying (50 ° C. × 30% RH or less), 2 hours of salt spray (35 ° C./5% NaCl solution), 2 hours of wetness (60 ° C. × 98% RH or more) is 1 cycle. The combined corrosion test was performed 300 cycles.

  After completion of the test, the test material was collected, the bulge and the peeled portion around the crosscut were forcibly peeled, and the peel width from the crosscut portion was measured. An example of a sample that is forcibly peeled is shown in FIG. In FIG. 1, when the vertical distance from the crosscut to the edge of the peeling area is A, eight distances A1 to A8 in the figure are measurement points for one crosscut. The value obtained by arithmetically averaging the measurement distances at these eight locations was taken as the peel width from the crosscut.

  In this example, as an evaluation of the corrosion resistance of the coating material, the peel width of the cross cut was shown as a representative value. From the cross cut portion, the cross section of the coating film is directly exposed to the environment. Mass transport is performed in this portion, and a corrosion reaction occurs under the coating film. Due to the direct result of this corrosion reaction or corrosion products, blistering and peeling occur. It is considered that the size of swelling and peeling depends on the size of the corrosion reaction occurring under the coating film. This is considered to have a direct correlation with the corrosion suppression effect by the surface treatment layer. Therefore, it is considered that the superiority or inferiority of the surface treatment layer is determined by the magnitude of the peeling width.

3. Results Table 1 shows the composition of the surface treatment composition and the peel distance (mm) from the crosscut in the case of an organic coated steel material coated with a polyurethane resin, and Table 3 shows the case of an organic coated steel material coated with an epoxy resin.

  As a comparative example using the conventional method, an organically coated steel material directly coated by the above methods a) and a) without surface treatment, and coated by the above methods a) and a) after phosphating with Palbond. An organic coated steel material is prepared, and 2. The peel distance (mm) from the cross cut was measured by the method. The results are shown in Table 2 when the polyurethane resin is coated, and Table 4 when the epoxy resin is coated.

  In addition, content in the surface treatment composition of Table 1 and Table 3 was shown by the mass part when the solvent whole quantity is 100 mass parts.

  In the case of polyurethane resin coating, the separation distance from the cross-cut is reduced in the example of the present invention compared to the sample 28 not subjected to the surface treatment and the sample 29 treated by the typical iron phosphate treatment. is doing. In samples 1 to 24, which are examples of the present invention, the peel distance is 2.7 to 3.9 mm, but in sample 28, it is 8.8 mm, and in sample 29, it is 5.8 mm. Moreover, when the composition of the surface treatment composition deviates from the definition of the present invention (samples 25 to 27), the separation distance is also increased. In particular, it can be seen that when the silane coupling agent is not contained, the peel distance is greatly increased.

  On the other hand, in the case of the epoxy resin coating, the peeling width is 5.6 to 7.4 mm in the samples 30 to 41 which are the examples of the present invention, whereas 17.8 mm of the sample 45 and 10 of the sample 46 in Table 4. .6 mm, which is suppressed similarly to the case of polyurethane resin coating. In addition, when the composition of the surface treatment composition deviates from the definition of the present invention (samples 42 to 44), the separation distance is also increased. In particular, when no silane coupling agent is contained, the peel distance is greatly increased as in the case of polyurethane resin coating.

  From the above results, in any case of the same type of coating material after the surface treatment, the improvement of the corrosion resistance is recognized by the application of the surface treatment layer using the surface treatment composition of the present invention, and more excellent corrosion resistance performance. It is secured.

Claims (5)

A surface-treated steel material excellent in corrosion resistance, comprising a surface-treated layer containing the following a) to c) on the surface of the steel material.
a) Gas phase silica having an average particle size of 1000 nm or less b) Amino or epoxy silane coupling agent c) At least one oxide selected from oxides of molybdenum, vanadium, zirconium, tungsten, and / or Or at least one oxyacid salt selected from oxyacid salts of molybdenum, vanadium, zirconium, and tungsten   An organic coated steel material excellent in corrosion resistance, comprising an epoxy, polyurethane or acrylic organic resin layer on the surface treatment layer according to claim 1. A surface treatment composition comprising the following a) to d):
a) Gas phase silica having an average particle size of 1000 nm or less b) Amino or epoxy silane coupling agent c) At least one oxide selected from oxides of molybdenum, vanadium, zirconium, tungsten, and / or Or at least one oxyacid salt selected from molybdenum, vanadium, zirconium, and tungsten oxyacid salts d) a solvent containing water A method for producing a surface-treated steel material having excellent corrosion resistance, which comprises applying a surface treatment composition containing the following a) to d) and then heating to evaporate the following d) solvent.
a) Gas phase silica having an average particle size of 1000 nm or less b) Amino or epoxy silane coupling agent c) At least one oxide selected from oxides of molybdenum, vanadium, zirconium, tungsten, and / or Or at least one oxyacid salt selected from molybdenum, vanadium, zirconium, and tungsten oxyacid salts d) a solvent containing water   5. An organic coated steel material having excellent corrosion resistance, wherein an epoxy, polyurethane or acrylic organic resin layer is formed on the surface treated steel obtained by the method for producing a surface treated steel according to claim 4. Manufacturing method.

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