JP2008274400A - Anticorrosive coated steel material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anticorrosive coated steel material having an excellent alkali resistance as compared with the conventional anticorrosive coated steel. <P>SOLUTION: The anticorrosive coated steel includes a base material steel and an anticorrosive coated layer laminated directly or via an intermediate layer on the base material steel and based on an inorganic compound containing sulfur or silicon, wherein a substance having a pH buffer action is incorporated into at least the steel side part or the intermediate layer of the anticorrosive coated layer, coming into contact with the base material steel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an anticorrosion-coated steel material excellent in alkali resistance, which is mainly applied to civil engineering and construction materials.

In a corrosion-resistant coated steel material, when the steel material is exposed to the environment due to scratches on the coating layer, the exposed steel material becomes the anode, and the interface between the coating layer and the steel material becomes the cathode. For example, in an alkaline environment, the cathode reaction (reduction reaction) It is known that hydroxide ions (OH ⁻ ) are easily generated by the reaction, and that the anticorrosion coating layer is easily peeled by the reaction between the generated hydroxide ions and the anticorrosion coating layer. Therefore, when the cathodic protection method is used for the anticorrosion coated steel material in marine steel structures and the like, it is normal that the corrosion of the base steel material is reduced, but the hydroxide ions (OH ⁻ ) generated in the same manner as described above, There is a problem that the anticorrosion coating layer is easily peeled off (cathode peeling) due to the reaction of the anticorrosion coating layer.

  In addition, inorganic compounds mainly composed of silicon or sulfur have been attracting attention as anticorrosion coatings because they are superior in weather resistance and scratch resistance due to their high hardness compared to organic coatings, such as binders for inorganic zinc rich paints. Part of it has been applied as an anticorrosion coating layer for steel.

In addition, a civil engineering / building material using sulfur having excellent acid resistance and strength has been proposed. For example, Patent Document 1 discloses a material having excellent acid resistance and strength made of a modified sulfur and silicon-containing inorganic material. It has been proposed and is considered suitable for anticorrosion coating materials. However, these materials also have acid resistance but have a drawback of being dissolved in alkali (OH ⁻ ).

  As a means for suppressing cathode peeling, for example, as shown in Patent Document 2, a chromate treatment is performed as a base treatment of a steel material, and as shown in Patent Document 3, generated hydroxide ions are captured. For this purpose, a method for coating a paint using a resin containing a resin having a negative fixed charge has been proposed.

  The above methods are all methods for suppressing cathode peeling, but are not particularly intended for cathode peeling under an alkaline environment, and have a problem that cathode peeling under an alkaline environment cannot be sufficiently suppressed. In addition, the method of Patent Document 1 is not preferable from an environmental viewpoint.

Therefore, an anticorrosion-coated steel material excellent in alkali resistance that can solve the above problems is desired.
JP 2001-163649 A JP 2001-288588 A JP 2003-147555 A

  An object of the present invention is to provide a corrosion-resistant coated steel material excellent in alkali resistance.

  As a result of repeated studies to solve the above problems and obtain a corrosion-resistant coated steel material excellent in alkali resistance, the present inventors have laminated the base steel material and the base steel material directly or via an intermediate layer. In addition, an inorganic compound-based anticorrosion coating layer or an organic compound-based anticorrosion coating layer containing sulfur or silicon, and a pH buffering action on at least a steel material side portion or an intermediate layer of the anticorrosion coating layer that comes into contact with the base steel material As a result, the pH of the coated steel surface can always be maintained in a neutral range when hydroxide ions are generated on the coated steel surface due to corrosion in an alkaline atmosphere. It has been found that an anticorrosion-coated steel material excellent in alkalinity can be obtained.

  The present invention has been made based on such findings, and the gist thereof is as follows.

  (1) An anticorrosion coating comprising a base steel material, and an inorganic compound-based anticorrosion coating layer containing sulfur or silicon, which is laminated directly or via an intermediate layer on the base steel material, and is in contact with the base steel material An anticorrosion-coated steel material, wherein a substance having a pH buffering action is contained in at least a steel material side portion of the layer or an intermediate layer.

  (2) A base steel material, and an inorganic compound-based anticorrosion coating layer containing an inorganic material containing sulfur and silicon, laminated on the base steel material through an intermediate layer, and in contact with the base steel material The intermediate layer contains a substance having a pH buffering action, which is an anticorrosion-coated steel material.

  (3) A base steel material, and an inorganic compound-based anticorrosion coating layer that is laminated on the base steel material and contains sulfur and an inorganic material containing silicon, and has a pH buffering action on the anticorrosion coating layer. An anti-corrosion-coated steel material containing a certain substance.

  (4) At least a steel material side portion of the anticorrosion coating layer, which is laminated on the base steel material directly or via an intermediate layer and has an organic compound-based anticorrosion coating layer and is in contact with the base steel material Alternatively, an anticorrosion-coated steel material comprising a substance having a pH buffering action in an intermediate layer.

  (5) In the above (1) to (4), substances having a pH buffering action are potassium hydrogen phthalate, sodium citrate, potassium dihydrogen phosphate, calcium hydrogen phosphate, aluminum tripolyphosphate and vanadium pentoxide. 1 type or 2 types or more selected from these, The anticorrosion coating steel material characterized by the above-mentioned.

  According to the present invention, there is provided a base steel material, and an inorganic compound-based or organic compound-based anticorrosion coating layer that is laminated directly or via an intermediate layer on the base steel material and contains sulfur or silicon, By including a substance having a pH buffering action in at least the steel material side portion or the intermediate layer of the anticorrosion coating layer that comes into contact, it becomes possible to provide an anticorrosion coating steel material excellent in alkali resistance.

  Hereinafter, the configuration of the present invention and the reasons for limitation will be described.

  The anticorrosion-coated steel material of the present invention comprises a base steel material, and an inorganic compound-based or organic compound-based anticorrosion coating layer laminated on the base steel material directly or via an intermediate layer and containing sulfur or silicon, A corrosion-resistant coated steel material comprising a substance having a pH buffering action in at least a steel material-side portion or an intermediate layer of a corrosion-resistant coated layer that comes into contact with the steel material.

  The structural example of the coating layer of the anticorrosion coating steel material of this invention is shown in FIG. 1 and FIG. In FIG. 1, a corrosion protection coating layer 13 is directly laminated on the surface of a steel material 11. FIG. 2 shows a structure in which an intermediate layer 12 and an anticorrosion coating layer 13 are sequentially laminated on the surface of a steel material 11.

(Base steel)
Examples of the base steel material used as the base material of the anticorrosion-coated steel material of the present invention include carbon steel, low alloy steel, and stainless steel. Although there is no limitation in particular about a use, the thing applicable to a civil engineering building material, for example, a reinforcing bar, a steel pipe, a cast iron pipe, a steel plate (thick board etc.), a shape steel, etc. are preferable. Further, the base steel material may be subjected to surface treatment in advance, and may be subjected to blasting, keren, pickling, or the like as necessary.

(Anti-corrosion coating layer, intermediate layer)
The anticorrosion coating layer of the present invention is laminated on the base steel material directly or via an intermediate layer, and is formed as an inorganic compound-based or organic compound-based coating layer containing sulfur or silicon.

  The intermediate layer is formed mainly for improving the adhesion between the steel material and the anticorrosion coating layer. For example, a primer made of a thermosetting resin such as an epoxy resin or polyurethane, a chemical conversion film such as a phosphate film or a chromate film, silane Examples thereof include an adhesive layer of a coupling agent. Any material can be used as long as it improves adhesion, but not only adhesion but also corrosion resistance is preferable.

  From the viewpoint of adhesion and corrosion resistance, a primer made of a thermosetting resin such as an epoxy resin and / or polyurethane is more preferable. In this epoxy resin system, for example, as a combination of the main agent / curing agent, jER 828 / jER T, jER 828 / jER LV11, jER 828 / jER DC11 manufactured by Japan Epoxy Resin Co., Ltd. can be used. Moreover, as a polyurethane type | system | group, the perm guard 331 main ingredient / curing agent etc. by a 1st industrial pharmaceutical company can be used.

  When the intermediate layer is the primer described above, it can be formed by coating the above-described resin on a steel material, coating the anticorrosion coating layer before drying with the touch, and solidifying it together with the anticorrosion coating layer.

  The thickness of the intermediate layer is preferably 50 μm or more from the viewpoint of improving alkali resistance, and is preferably 500 μm or less from the viewpoint of economy.

  As an anticorrosion coating based on inorganic compounds containing sulfur, it is possible to melt sulfur and modify it by adding diene hydrocarbons such as dicyclopentadiene, hydroaromatic hydrocarbon compounds, etc. What knead | mixed with materials (henceforth a sulfur kneaded material) etc. can be used.

  The inorganic compound-based anticorrosive coating layer containing sulfur is first kneaded in order to disperse the inorganic material well if the sulfur kneaded material is heated and melted at 130 to 150 ° C. and contains the inorganic material. The kneaded material is directly applied to the surface of the steel material or the surface to which the intermediate layer is applied, and is formed by cooling and solidifying. As a coating method, a known method such as a pouring method using a mold or a spraying method using a spray can be used. In addition, when directly coating a steel material, the heated anticorrosion coating layer is preferably heated to 130 to 150 ° C. in advance in order to prevent the steel material from abruptly cooling and solidifying to prevent adhesion failure. . On the other hand, when the primer is applied as an intermediate layer, the primer is solidified by the heat of the anticorrosion coating layer, and the steel material does not have to be heated in order to exhibit good adhesion to the anticorrosion coating layer. The cooling method is not particularly limited, but cooling such as air cooling is preferable in order to prevent rapid shrinkage of the anticorrosion coating layer. The sulfur reforming method is as described in Patent Document 1. For example, when sulfur is melted and diene hydrocarbon is added and kneaded, the mixing ratio of sulfur and diene hydrocarbon is 100% sulfur. The diene hydrocarbon is preferably 2 to 20 parts by weight with respect to part by weight.

  The inorganic material is an inorganic fine powder that imparts strength and flame retardancy to the anticorrosion coating layer, an aggregate that imparts strength to the anticorrosion coating layer, and the like. As the inorganic fine powder, known inorganic fine powder such as coal ash, silica fume, glass powder, and alumina can be used, and as the aggregate, known aggregate such as dredged sand, silica, steelmaking slag, crushed stone, gravel and the like can be used. . The inorganic fine powder is more preferably coal ash from the viewpoint that it is easy to obtain a large amount of particles having a uniform particle size distribution, and the aggregate is more preferably quartz sand, crushed stone, or the like. In particular, when silica sand is used, there are advantages that the purity of silicon is high and the acid resistance is excellent. One or more inorganic fine powders or one or more aggregates may be used as the inorganic material, but excellent impact resistance can be obtained by using one or more inorganic fine powders and one or more aggregates. Is more preferable.

  When an inorganic material containing both inorganic fine powder and aggregate is added and kneaded together, the blending ratio is 20 to 70 for a mixture of modified sulfur and inorganic fine powder with respect to the entire anticorrosion coating layer. It is preferable from a viewpoint of improving intensity | strength and acid resistance that mass% and an aggregate are 30-80 mass%. Further, the mixing ratio between the modified sulfur and the inorganic fine powder is preferably 20 to 100 parts by mass of the inorganic fine powder with respect to 100 parts by mass of the modified sulfur from the same viewpoint.

  The film thickness of the inorganic compound-based anticorrosion coating containing sulfur is preferably 2 mm or more from the viewpoint of anticorrosion, and more preferably 10 mm or more from the viewpoint of impact resistance. Moreover, 50 mm or less is preferable from a viewpoint of economical efficiency. This is because even if the film thickness exceeds 50 mm, a beneficial improvement in corrosion resistance cannot be expected and it is not economical.

  As an anticorrosion coating based on an inorganic compound containing silicon, an alkyl silicate resin or polysilazane can be applied and then reacted with moisture in the air to form a coating containing silicon.

  When sulfur or silicon is used as a material, it is superior in scratch resistance and low cost compared to a coating layer made of an organic resin, but silicon and sulfur are weak against alkalis. By containing a substance having a pH buffering action in at least the steel material side portion or the intermediate layer of the anticorrosion coating layer that comes into contact with the anticorrosion coating layer, it is possible to obtain an anticorrosion coating steel material that is further excellent in alkali resistance.

  The film thickness of the inorganic compound-based anticorrosion coating containing silicon is preferably 0.5 μm or more from the viewpoint of anticorrosion, and is preferably 10 μm or less from the viewpoint of heat cycle resistance.

  The organic compound-based anticorrosion coating layer is not particularly limited, and may be coated with a thermoplastic resin such as polyethylene or polypropylene, or a thermosetting resin made of urethane elastomer or epoxy resin. Also, a coating film may be formed by coating regardless of organic solvent type, water type or solventless type made of polyurethane, drying oil, epoxy resin or the like. When using a commercial product, for example, jER 828 / jER T manufactured by Japan Epoxy Resin Co., Ltd. is applied to the steel as a primer, NE060 manufactured by Mitsui Chemical Co., Ltd. as adhesive polyethylene, and HiZEX 5100E manufactured by Mitsui Chemicals Co., Ltd. as high density polyethylene by hot pressing. It can be used by coating.

  The anticorrosion coating layer made of organic resin is more flexible than the anticorrosion coating layer made of inorganic compounds, so that the anticorrosion coating layer cracks in an environment where the steel material is subject to impact or bending deformation during transportation and construction. This is advantageous in that it is suppressed from being generated and hardly peeled off from the steel material.

  The thickness of the anticorrosion coating layer made of an organic resin is preferably 0.5 mm or more from the viewpoint of anticorrosion, and more preferably 2 mm or more from the viewpoint of impact resistance. Moreover, 6 mm or less is preferable from a viewpoint of economical efficiency. This is because even if the film thickness exceeds 6 mm, a beneficial improvement in corrosion resistance cannot be expected and it is not economical.

The present inventors pay attention to the fact that hydroxide ions (OH ⁻ ) generated by corrosion of the steel surface or the cathode reaction are the cause of peeling, deterioration and decomposition of the anticorrosion coating layer, and the anticorrosion coating in an alkaline environment. We have conducted intensive research on methods that can suppress layer peeling.

As a result, even when hydroxide ions are generated in the vicinity of the surface of the steel material by including a substance having a pH buffering action in at least the steel material side portion or intermediate layer of the anticorrosion coating layer that comes into contact with the steel material, It has been found that the pH change due to OH ⁻ can be minimized by the action of the pH buffer substance, and that peeling, deterioration and degradation of the anticorrosion coating layer can be suppressed.

The substance having a pH buffering action is not particularly limited as long as the substance has a buffering action that does not change the pH even when hydroxide ions are generated. from the viewpoint of excellent effect of keeping the suppression and pH to a neutral range, potassium hydrogen phthalate _{(C 6 H 4 (COOK)} (COOH)), sodium _{citrate, (Na 3 C 6 H 5} O 7 · 2H 2 O) One selected from potassium dihydrogen phosphate (KH ₂ PO ₄ ), calcium hydrogen phosphate (CaHPO ₄ ), aluminum tripolyphosphate (AlH ₂ PO ₁₀ ), and vanadium pentoxide (V ₂ O ₅ ), It is preferably a mixture of two or more, selected from potassium dihydrogen phosphate, calcium hydrogen phosphate, aluminum tripolyphosphate and vanadium pentoxide. One or more that are more preferred.

  The substance having a pH buffering action needs to be contained in a portion of the anticorrosion coating layer or intermediate layer in direct contact with the steel surface. Specifically, a method of containing a pH buffer substance in the anticorrosion coating layer or intermediate layer in contact with the steel surface, or a method of containing the pH buffer substance in the anticorrosion coating layer so as to be unevenly distributed on the steel surface side. is there.

  For example, in the case of a coating layer made of modified sulfur and an inorganic material, the pH buffer substance in the anticorrosion coating layer is unevenly distributed on the steel surface side by heating the steel material during coating on the steel material. Since the melting time of sulfur becomes longer, if a pH buffer substance having a density higher than that of sulfur is used, the coating layer is settled and can be unevenly distributed near the steel surface.

  The addition amount of the substance having a pH buffering action is not particularly limited, but when added to the anticorrosion coating layer, the content in the anticorrosion coating layer is within the range of 1 to 50% by mass in the anticorrosion coating layer. When added to the intermediate layer, the content in the intermediate layer is preferably in the range of 1 to 50% by mass in the intermediate layer. This is because if the amount is less than 1% by mass, the buffering effect is not sufficient, and even if the amount exceeds 50% by mass, the buffering effect does not change.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

  Examples of the present invention will be described below.

Example 1
In Example 1, a hot-rolled steel sheet (base steel material) (JIS SS400) having a size of 100 mm × 100 mm × 6 mm whose surface was made to have a surface roughness of about 50 μm by steel grid blasting was installed in a mold. 26 parts by mass of sulfur and 1 part by mass of dicyclopentadiene were melted at 150 ° C., 27 parts by mass of the melt and 13 parts by mass of coal ash were kneaded, 40 parts by mass of the kneaded material and 60 parts by mass of cinnabar No. 3 Kneaded. 10 parts by mass of potassium hydrogen phthalate is added to 90 parts by mass of the kneaded product (potassium hydrogen phthalate is 10% by mass in the anticorrosion coating) so that the kneaded product becomes an anticorrosion coating layer having a thickness of 10 mm on the steel plate. The steel sheet was poured and cooled to room temperature to obtain an anticorrosion coated steel sheet.

(Example 2)
In Example 2, an anticorrosion-coated steel sheet was obtained by the same process as in Example 1 except that potassium hydrogen phthalate was 5% by mass in the anticorrosion coating.

(Example 3)
In Example 3, the surface of a hot-rolled steel sheet having a size of 100 mm × 100 mm × 6 mm was pickled and neutralized with dilute sulfuric acid, and then, perhydroxypolysilazane (Aquarica manufactured by Clariant) was 5% by mass in the solution. After spray-coating a mixture of xylene solution and potassium hydrogen phthalate at 1% by mass in the solution, leave it in the atmosphere for 2 weeks to form an anticorrosion coating layer with an average film thickness of 2 μm. Then, an anticorrosion coated steel sheet coated with silica glass was obtained.

Example 4
Example 4 is a bisphenol A type epoxy resin in which 1% by mass of potassium hydrogen phthalate is added to a hot rolled steel sheet of size 100 mm × 100 mm × 6 mm whose surface is made to have a surface roughness of about 50 μm by steel grid blasting. JER 828 / jER T) manufactured by Japan Epoxy Resin Co., Ltd. was spray-coated on the surface of the steel sheet as an intermediate layer having an average film thickness of 70 μm, and allowed to cure at room temperature for 24 hours. On top of that, an acid-modified polyethylene is used as an adhesive layer (NE060 manufactured by Mitsui Chemicals), and high-density polyethylene (HiZEX5100E manufactured by Mitsui Chemicals) is used as an anticorrosive coating layer having an average thickness of 2 mm. Pressing was performed to obtain a corrosion-resistant coated steel sheet.

(Example 5)
Example 5 obtained a corrosion-proof coated steel sheet by the same process as Example 1 except that potassium hydrogen phthalate was not contained and 1 mass% of sodium citrate was contained.

(Example 6)
Example 6 obtained an anticorrosion coated steel sheet by the same process as Example 2 except that potassium hydrogen phthalate was not contained and 4 mass% of sodium citrate was contained.

(Example 7)
Example 7 obtained a corrosion-proof coated steel sheet by the same process as Example 3 except that potassium hydrogen phthalate was not contained and 2 mass% of sodium citrate was contained.

(Example 8)
Example 8 obtained an anticorrosion coated steel sheet by the same process as Example 4 except that potassium hydrogen phthalate was not contained and 2 mass% of sodium citrate was contained.

Example 9
Example 9 did not contain potassium hydrogen phthalate and obtained an anticorrosion-coated steel sheet by the same steps as in Example 1 except that it contained 5% by mass of potassium dihydrogen phosphate.

(Example 10)
Example 10 obtained an anticorrosion-coated steel sheet by the same process as Example 2 except that potassium hydrogen phthalate was not contained and 7 mass% potassium dihydrogen phosphate was contained.

(Example 11)
Example 11 obtained an anticorrosion-coated steel sheet by the same process as Example 3 except that potassium hydrogen phthalate was not contained and 2 mass% potassium dihydrogen phosphate was contained.

(Example 12)
Example 12 obtained an anticorrosion coated steel sheet by the same process as Example 4 except that potassium hydrogen phthalate was not contained and 2 mass% potassium dihydrogen phosphate was contained.

(Comparative Example 1)
In Comparative Example 1, an anticorrosion-coated steel sheet was obtained by the same process as in Example 1 except that a substance having a pH buffering action shown in Table 1 was not contained in the anticorrosion coating layer.

(Comparative Example 2)
In Comparative Example 2, an anticorrosion-coated steel sheet was obtained by the same process as Example 3 except that the substance having a pH buffering action shown in Table 1 was not contained in the anticorrosion coating layer.

(Comparative Example 3)
In Comparative Example 3, a corrosion-proof coated steel sheet was obtained by the same process as Example 4 except that the intermediate layer did not contain a substance having a pH buffering action shown in Table 1.

  Various tests were performed on each of the anticorrosion coated steel sheets obtained as described above. The evaluation method of the test conducted in this example is shown below.

(Evaluation methods)
(1) Alkali resistance As shown in FIG. 3, each anticorrosion-coated steel sheet produced above was sealed with a silicon sealant so that the steel surface was not exposed except for one end, and a 3 mass% NaCl aqueous solution (60 C.) for 21 days, the coating was peeled from the steel sheet and the peel length of the coating was measured.

(2) Weather resistance Each prepared anti-corrosion coated steel sheet was exposed to a sunshine weatherometer (carbon arc) manufactured by Suga Test Instruments Co., Ltd. for 2000 hours, and the 60-degree specular gloss before and after exposure was measured. The weather resistance was evaluated. The 60-degree specular gloss was measured with a gloss meter VG-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

(3) Surface hardness The surface hardness of each produced anti-corrosion coated steel sheet was evaluated by durometer hardness (D) based on JIS K7215 (Ueshima Seisakusho Co., Ltd.).

  Table 1 shows the evaluation results of the above tests.

  According to this, as for the anticorrosion coating steel materials of Examples 1-12, compared with Comparative Examples 1-3, all have the peeling length of a coating layer small, and it was a comparable value about weather resistance and hardness. . As a result, it can be seen that while having the same degree of weather resistance and hardness as the conventional anticorrosion-coated steel material, it has an alkali resistance superior to that of the conventional one.

(Invention Example 1)
Invention Example 1 is a calcium hydrogen phosphate as an intermediate layer on a hot-rolled steel sheet (base steel) of size 100 mm × 100 mm × 6 mm (JIS SS400) whose surface has a surface roughness of about 50 μm by steel grid blasting. 200 μm of bisphenol A type epoxy primer (JER 828 / jER DC11 manufactured by Japan Epoxy Resin Co., Ltd.) with 10% by mass added was applied, and this steel plate was heated on a hot plate at 150 ° C. for 4 minutes and then placed in a mold. 26 parts by mass of sulfur and 1 part by mass of dicyclopentadiene were melted at 150 ° C., and 27 parts by mass of the melt and 13 parts by mass of coal ash were kneaded. A kneaded mixture of 40 parts by mass of kneaded material, 30 parts by mass of cinnabar No. 3 and 30 parts by mass of cinnabar 7 is poured onto a steel sheet so as to form a 30 mm thick anticorrosion coating layer, and cooled to room temperature to provide an anticorrosion coating. A steel plate was obtained.

(Invention Example 2)
Invention Example 2 obtained an anticorrosion-coated steel sheet by the same process as Invention Example 1 except that the thickness of the intermediate layer was 100 μm and the thickness of the anticorrosion coating layer was 15 mm.

(Invention Example 3)
Invention Example 3 does not contain calcium hydrogen phosphate in the intermediate layer, contains 10 mass% of aluminum tripolyphosphate, the thickness of the intermediate layer is 300 μm, and the thickness of the anticorrosion coating layer is 20 mm. An anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Invention Example 4)
Invention Example 4 does not contain calcium hydrogen phosphate in the intermediate layer, contains 10 mass% of aluminum tripolyphosphate, the thickness of the intermediate layer is 400 μm, and the thickness of the anticorrosion coating layer is 30 mm. An anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Invention Example 5)
Invention Example 5 does not contain calcium hydrogen phosphate in the intermediate layer, contains 10% by mass of vanadium pentoxide, the thickness of the intermediate layer is 60 μm, and the thickness of the anticorrosion coating layer is 12 mm. An anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Invention Example 6)
Invention Example 6 does not contain calcium hydrogen phosphate in the intermediate layer, contains 10% by mass of vanadium pentoxide, the thickness of the intermediate layer is 200 μm, and the thickness of the anticorrosion coating layer is 45 mm. An anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Invention Example 7)
In Invention Example 7, an anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1, except that the thickness of the intermediate layer was 100 μm and the thickness of the anticorrosion coating layer was 30 mm.

(Invention Example 8)
Invention Example 8 In Comparative Example 2, an anticorrosion-coated steel sheet was obtained in the same manner as in Invention Example 1, except that the thickness of the intermediate layer was 150 μm and the thickness of the anticorrosion coating layer was 15 mm.

(Invention Example 9)
Invention Example 9 does not contain calcium hydrogen phosphate in the intermediate layer, contains 10 mass% of aluminum tripolyphosphate, the thickness of the intermediate layer is 150 μm, and the thickness of the anticorrosion coating layer is 20 mm. An anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Invention Example 10)
Invention Example 10 Comparative Example 4 did not contain calcium hydrogen phosphate in the intermediate layer, contained 10% by mass of aluminum tripolyphosphate, the intermediate layer had a thickness of 180 μm, and the anticorrosion coating layer had a thickness of 20 mm. Except for the above, an anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Invention Example 11)
Invention Example 11 does not contain calcium hydrogen phosphate in the intermediate layer, contains 10% by mass of vanadium pentoxide, the thickness of the intermediate layer is 100 μm, and the thickness of the anticorrosion coating layer is 30 mm. An anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Invention Example 12)
Invention Example 12 Comparative Example 6 did not contain calcium hydrogen phosphate in the intermediate layer, contained 10% by mass of vanadium pentoxide, the intermediate layer had a thickness of 200 μm, and the anticorrosion coating layer had a thickness of 20 mm. Except for the above, an anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1.

(Comparative Example 1)
In Comparative Example 1, the intermediate layer does not contain a pH buffer substance, the thickness of the intermediate layer is 200 μm, and the thickness of the anticorrosion coating layer is 50 mm. Got.

(Comparative Example 2)
In Comparative Example 2, an intermediate layer was not provided, and the anticorrosion coating layer was provided by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer was 50 mm, to obtain an anticorrosion coated steel sheet.

(Comparative Example 3)
Comparative Example 3 provided an anticorrosion coating layer by the same process as in Invention Example 1 except that the intermediate layer was not provided and the thickness of the anticorrosion coating layer was 5 mm, to obtain an anticorrosion coated steel sheet.

(Evaluation methods)
(1) Alkali resistance Each of the anticorrosion coated steel sheets prepared above was sealed with a silicon sealant so that the steel surface was not exposed except for one end, and immersed in a 3% by mass NaCl aqueous solution (60 ° C.) for 28 days. After that, the coating was peeled off from the steel sheet, and the peeling length of the coating was measured.

(2) Surface hardness The surface hardness of each anti-corrosion coated steel sheet produced was evaluated by durometer hardness (D) based on JIS K7215 (Ueshima Seisakusho Co., Ltd.).

(3) Impact resistance Based on ASTM G14, a falling weight impact test at −20 ° C. was performed using a falling weight having a tip diameter of 15.9 mm and a weight of 5 kgf. The destruction of the anticorrosion coating layer was confirmed visually and by a 20 kV energization test, and the impact strength was determined from the limit height at which no destruction occurred.

  Table 2 shows the evaluation results of the above tests.

  According to this, compared with the anticorrosion coating steel materials of Comparative Examples 1 and 2, the anticorrosion coating steel materials of Invention Examples 1 to 12 each have a small peeling length of the anticorrosion coating layer and are excellent in alkali resistance.

(Invention Example 1)
Inventive example 1 is a hot rolled steel sheet (base steel material) of size 100 mm × 100 mm × 6 mm (JIS SS400) whose surface is made to have a surface roughness of about 50 μm by steel grid blasting with JIS SS400 and heated for 4 minutes on a hot plate at 150 ° C. In a mold, 24.2 parts by mass of sulfur and 0.8 parts by mass of dicyclopentadiene are melted at 150 ° C., 25 parts by mass of the melt, 29 parts by mass of cinnabar 3, 29 parts by mass of cinnabar 7 A kneaded product (calcium hydrogen phosphate content 5 mass%) kneaded with 12 parts by weight of coal ash, 12 parts by mass of coal ash, and 5 parts by mass of calcium hydrogen phosphate so as to form a 10 mm thick anticorrosion coating layer on the steel sheet, The steel sheet was cooled to room temperature to obtain a corrosion-resistant coated steel sheet.

(Invention Example 2)
Invention Example 2 obtained an anticorrosion-coated steel sheet by the same process as Invention Example 1 except that the thickness of the anticorrosion coating layer was 30 mm.

(Invention Example 3)
Invention Example 3 does not contain calcium hydrogen phosphate, contains 5% by mass of aluminum tripolyphosphate, and the corrosion-resistant coated steel sheet in the same manner as in Invention Example 1 except that the thickness of the corrosion-resistant coating layer is 15 mm. Got.

(Invention Example 4)
Invention Example 4 does not contain calcium hydrogen phosphate, contains 5% by mass of aluminum tripolyphosphate, and the anticorrosion coated steel sheet is formed by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer is 40 mm. Obtained.

(Invention Example 5)
Invention Example 5 does not contain calcium hydrogen phosphate, contains 5% by mass of vanadium pentoxide, and the anticorrosion-coated steel sheet is formed by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer is 20 mm. Obtained.

(Invention Example 6)
Invention Example 5 does not contain calcium hydrogen phosphate, contains 5% by mass of vanadium pentoxide, and the anticorrosion-coated steel sheet is formed by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer is 35 mm. Obtained.

(Invention Example 7)
Invention Example 7 obtained an anticorrosion-coated steel sheet by the same process as Invention Example 1 except that the thickness of the anticorrosion coating layer was 15 mm.

(Invention Example 8)
Invention Example 8 obtained an anticorrosion-coated steel sheet by the same process as Invention Example 1, except that the thickness of the anticorrosion coating layer was 60 mm.

(Invention Example 9)
Invention Example 9 does not contain calcium hydrogen phosphate, contains 5% by mass of aluminum tripolyphosphate, and the anticorrosion coated steel sheet is formed by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer is 20 mm. Obtained.

(Invention Example 10)
Invention Example 10 does not contain calcium hydrogen phosphate, contains 5% by mass of aluminum tripolyphosphate, and the anticorrosion coated steel sheet is formed by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer is 60 mm. Obtained.

(Invention Example 11)
Invention Example 11 does not contain calcium hydrogen phosphate, contains 5% by mass of vanadium pentoxide, and the anticorrosion-coated steel sheet is formed by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer is 20 mm. Obtained.

(Invention Example 12)
Invention Example 12 does not contain calcium hydrogen phosphate, contains 5% by mass of vanadium pentoxide, and the anticorrosion-coated steel sheet is formed by the same process as in Invention Example 1 except that the thickness of the anticorrosion coating layer is 15 mm. Obtained.

(Comparative Example 1)
In Comparative Example 1, an anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1, except that the anticorrosion coating layer did not contain a pH buffer substance and the thickness of the anticorrosion coating layer was 50 mm.

(Comparative Example 2)
In Comparative Example 2, an anticorrosion-coated steel sheet was obtained by the same process as in Invention Example 1 except that the anticorrosion coating layer did not contain a pH buffer substance and the thickness of the anticorrosion coating layer was 5 mm.

Various tests were performed on each of the anticorrosion coated steel sheets obtained as described above. The evaluation method of the test conducted in this example is shown below.
(Evaluation methods)
(1) Alkali resistance Each of the anticorrosion coated steel sheets prepared above is sealed with a silicon sealant so that the steel surface is not exposed except for one end, and immersed in a 3% by mass NaCl aqueous solution (60 ° C.) for 14 days. After that, the coating was peeled off from the steel sheet, and the peeling length of the coating was measured.

(2) Surface hardness The surface hardness of each anti-corrosion coated steel sheet produced was evaluated by durometer hardness (D) based on JIS K7215 (Ueshima Seisakusho Co., Ltd.).

(3) Impact resistance In accordance with ASTM G14, impact strength was evaluated by a falling weight impact test at −20 ° C. using a falling weight having a tip diameter of 15.9 mm and a weight of 5 kgf. The destruction of the anticorrosion coating layer was confirmed visually and by a 20 kV energization test, and the impact strength was determined from the limit height at which no destruction occurred.

  Table 3 shows the evaluation results of the above tests.

  According to this, the anticorrosion coating steel materials of Invention Examples 1 to 12 all have a smaller peeling length of the anticorrosion coating layer than the anticorrosion coating steel material of Comparative Example 1, and are excellent in alkali resistance.

  According to the present invention, there is provided a base steel material, and an inorganic compound-based anticorrosion coating layer containing sulfur or silicon, which is laminated directly or via an intermediate layer on the base steel material, and is in contact with the steel material. By including a substance having a pH buffering action in at least the steel material side portion or the intermediate layer of the coating layer, it is possible to provide an anticorrosion coated steel material having excellent alkali resistance.

It is sectional drawing which shows the structural example of the coating layer of the anticorrosion coating | coated steel material of this invention. It is sectional drawing which shows another structural example of the coating layer of the anti-corrosion coating steel material of this invention. It is the figure which showed typically the evaluation method about the alkali resistance of the anti-corrosion coating steel plate produced in each Example.

Explanation of symbols

11 Steel material 12 Intermediate layer 13 Anticorrosion coating layer

Claims (5)

A base steel material, and an inorganic compound-based anticorrosion coating layer containing sulfur or silicon, which is laminated directly or via an intermediate layer on the base steel material, and is in contact with the base steel material, at least of the anticorrosion coating layer An anticorrosion-coated steel material comprising a steel material side part or an intermediate layer containing a substance having a pH buffering action. The intermediate steel layer, which is laminated on the base steel material via an intermediate layer, has an inorganic compound-based anticorrosion coating layer containing sulfur and an inorganic material containing silicon, and is in contact with the basic steel material An anticorrosion-coated steel material comprising a layer containing a substance having a pH buffering action. A base steel material, and an inorganic compound-based anticorrosion coating layer containing sulfur and silicon-containing inorganic material laminated on the base steel material, and a substance having a pH buffering action on the anticorrosion coating layer. An anticorrosion-coated steel material characterized by containing. At least a steel material side portion or an intermediate layer of the anticorrosion coating layer which has a base steel material and an organic compound-based anticorrosion coating layer which is laminated on the base steel material directly or via an intermediate layer and which is in contact with the base steel material An anticorrosion-coated steel material comprising a substance having a pH buffering action. The pH buffering substance is one or more selected from potassium hydrogen phthalate, sodium citrate, potassium dihydrogen phosphate, calcium hydrogen phosphate, aluminum tripolyphosphate, and vanadium pentoxide. The anticorrosion-coated steel material according to any one of claims 1 to 4, wherein:

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