JP2009275247A - Steel material provided with rust-preventive and corrosion-preventive coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel material provided with a rust-preventive and corrosion-preventive coating, which shows superior corrosion-preventive properties when used in a state that one part of the steel material is buried in concrete or in the ground. <P>SOLUTION: The steel material provided with the rust-preventive and corrosion-preventive coating has a zinc-base plated film on a steel material and one or more layers of an organic painted film coated thereon. The outermost surface layer of the organic paint film contains a phosphate-based rust-preventive pigment, a sulfate of an alkaline earth metal, and a non-silver and non-copper type antibacterial agent. Thereby, the rust-preventive and corrosion-preventive coating can form a corrosion-preventive structure on the coated steel material that is used in the state that the one part is buried in concrete or in the ground. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coated steel material, and more particularly, to a rust and corrosion resistant coated steel material that is used by being partially embedded in concrete or the ground.

  Zinc-based plating is widely adopted as a technique for preventing corrosion of steel materials. In order to further increase the anticorrosion ability, an organic resin coating is often applied on the galvanizing. However, it is also well known that the adhesion between the plating and the organic resin is not always good even if the coating is directly performed on the zinc plating. For this reason, the so-called phosphate treatment, chromate treatment, etc. are performed on the plating. It is common to perform chemical conversion treatment.

  Steel structures are often used outdoors in the form of being embedded in concrete or the ground. However, it is known that steel structures that are used in this way have severe corrosion directly above the buried portion, that is, at the ground.

The cause of this “inter-surface corrosion” has not been completely clarified, but the following factors are listed.
1) The steel material in concrete is passivated by the alkali of the concrete, and this passivated part and the iron on the ground surface form a local battery.
2) The ground part has a structure that is easy to get wet because the dew condensation attached to the steel material falls, and the dew condensation water has agglomerated salt attached to the steel material.

  It is also said that the excrement of animals, especially dogs, has an effect on the ground corrosion. As a method of preventing such corrosion, focusing on the fact that the dew condensation water at the buried portion interface shows alkalinity, a method of providing a corrosion protection layer above and below the buried portion interface has been proposed (see, for example, Patent Document 1). . This method presupposes that it is used as it is except for the ground part of a structure. However, the current steel structures are generally used after being subjected to a phosphate chemical treatment after zinc-based plating, and further painted, in terms of both aesthetics and corrosion resistance. A general coating method is a method in which a binder layer is directly coated on the plating. When the technique of Patent Document 1 is applied to a steel structure based on normal coating, only the ground part is completely different. Therefore, there is a problem that productivity is remarkably lowered.

  The inventor has paid attention to the marking of dogs as a factor that promotes corrosion at the ground. As a result of examining the reaction when the excrement of dogs is decomposed by humus or the like, it has been reported that ammonia is first generated (for example, see Non-Patent Document 3). Furthermore, it turned out that the produced | generated ammonia is oxidized and nitric acid produces | generates. And in the film | membrane structure called hot dip galvanization-phosphate chemical conversion treatment-painting which is a general anti-corrosion structure, it turned out that a zinc phosphate chemical conversion treatment film and a zinc plating layer are weak to ammonia. The reason why the chemical conversion film is dissolved in ammonia is that ammonia extracts zinc ions as zinc-ammonia complexes from zinc phosphate in the chemical conversion film. When the chemical conversion film disappears, the organic film loses adhesion with the steel material. In addition, ammonia reacts with zinc, which is the main component of plating, by forming a zinc-ammonia complex, thereby facilitating the disappearance of the plating layer and accelerating the corrosion of the steel material.

  It was thought that ammonia promotes corrosion of steel materials by such a mechanism.

  However, even if a reproduction experiment based on the reported pH, composition, etc. of compost is carried out, or even if humus, animal excrement, insect carcasses, etc. are mixed in the soil, the amount of ammonia produced is small. Therefore, it was found that the possibility of directly dissolving the chemical conversion film and the galvanized layer was low. Nevertheless, experimentally, it was confirmed that the presence of a small amount of ammonia promotes corrosion of the plated and painted steel. This is because zinc corrosion products such as zinc chloride, zinc carbonate, and zinc oxide, which are generated and accumulated during normal corrosion reactions and suppress the progress of corrosion, are dissolved by ammonia. It was found that it was halved.

  For this reason, although the white rust of zinc is not observed at all and looks healthy, it is thought that zinc is consumed quickly and corrosion of the steel material itself proceeds. However, in the academic presentation, dog urine is pointed out as the cause, and although the generation of ammonia is mentioned, it is only concluded that the increase in pH promotes corrosion. The claim that ammonia generation has an effect on ground corrosion has also been reported in patents. However, as countermeasures, paints or anticorrosion techniques that have excellent corrosion resistance in the local environment have been proposed. For example, Patent Document 3 describes that a copper alloy cannot be used as a coating material because it reacts with ammonia.

JP 2002-371372 A JP 2006-348109 A JP 2006-132128 A Proceedings of the 47th Materials and Environmental Discussion Meeting p195 (2000) Mie Prefectural Science and Technology Promotion Center Lecture Engineering Department Research Report no. 26 (2002) Proceedings of Material and Environmental Discussion p4007 (2004)

  Accordingly, an object of the present invention is to provide a rust and corrosion-resistant coated steel material that exhibits excellent anti-corrosion properties when used by being partially embedded in concrete or the ground, which solves the above problems.

  The inventor examined a more effective and drastic countermeasure against ground corrosion. As a result, we have come up with the idea that suppressing the generation of ammonia in the soil is more effective than developing a paint and film structure that is resistant to ammonia. If ammonia is not present, the original anticorrosion function of zinc can be exerted, and the problem of ground corrosion of steel materials can be solved. In order to suppress the generation of ammonia, it is effective to suppress the activity of microorganisms in the soil, and this purpose can be achieved by adding a compound having an antibacterial action to the paint film. It was confirmed. In general, examples of the substance having an antibacterial action include Ag ions and Cu ions. However, even when these metal ions were included in the paint, the effect of suppressing the generation of ammonia was hardly seen. As a result of investigating this cause, both the Ag ion and the Cu ion are metal ions having high reactivity with ammonia, and they react with a slight amount of generated ammonia quickly to form a complex. Was found to be almost lost. For this reason, by arranging an antibacterial agent that has low reactivity with ammonia and does not depend on Ag ions or Cu ions in the anticorrosion film, it suppresses the generation of ammonia and exhibits an excellent anticorrosion function on the ground. Is a successful one.

That is, the present invention is as follows.
(1) A corrosion-resistant and corrosion-resistant coated steel material having an organic coating film on the surface of a zinc-based plated steel material, wherein the outermost coating film of the organic coating film is composed of a phosphate-based anticorrosive pigment and an alkaline earth metal sulfuric acid. An anti-corrosion and anti-corrosion coated steel material comprising a salt and a non-silver non-copper type antibacterial agent.
(2) The rust and corrosion-proof coated steel material according to (1), wherein a phosphate chemical conversion treatment layer is provided between the zinc-based plated steel material and the organic coating film.

  According to the present invention, an excellent anticorrosion structure can be formed on a coated steel material that is partially embedded in concrete or the ground, so that it is possible to extend the life of a structure using the anticorrosive anticorrosive coated steel material. .

  Hereinafter, the present invention will be described in detail.

  First, the steel material used in the present invention is structural steel represented by SS400 as a material, or other low carbon steel, and as a product type, H-shaped steel, I-shaped steel, steel pipe, steel sheet pile, or, for example, It is a civil engineering construction hardware or the like for fixing an anchor, and is a steel material that may be used by being embedded in concrete or the ground. Moreover, it is a steel material that is installed in contact with the ground, and as a result, a part of the steel material is covered with soil or the like and may be in contact with the soil.

  The components of the anticorrosion coating of the rust and corrosion prevention steel material according to the present invention will be described below.

  The plating layer is zinc-based plating that has a sacrificial anticorrosive action on steel. Although it is possible to use alloy plating, zinc-aluminum alloy plating whose production volume has been increasing in recent years is widely used for structures, but reports that it has a short life in concrete (for example, non-patent literature) 2), and attention is required for application to the present invention. The plating method may be any of electroplating, hot dipping, etc. However, it is usually plating after forming a shape as a structure, and in order to increase corrosion resistance, for example, thick plating of 50 μm, 100 μm is desirable. The hot dip galvanizing is suitable.

  Next, the organic coating film will be described. Epoxy resin, polyester resin, acrylic resin, and the like can be applied as the type of organic resin that serves as the binder of the film, and the type of resin is not particularly limited. However, when a special resin such as a fluororesin is used, there may be a problem with compatibility with the pigment, and therefore sufficient prior study is required. In addition, when the organic coating film is applied by local construction, it is required to be cured at room temperature, and therefore the type of resin is limited.

  Next, the antibacterial agent added to the organic coating film will be described. It is a non-silver, non-copper type antibacterial compound that reduces the generation of ammonia by suppressing the activity of microorganisms and improves the anticorrosion properties, and many types are commercially available. . In particular, as a non-silver non-copper antibacterial agent contained in the organic coating film of the present invention, a quaternary ammonium salt, 2- (4-thiazoline) benzimidazole (TBZ), which is an imidazole compound, 2 -Methyl benzimidazole carbamate (BCM), 2- (4-thiocyanomethylthio) benzthiazole (TCMTB) which is a thiazole compound, 2,3,5,6-tetrachloro-4- (methyl) which is a pyridine compound Sulfone) pyridine, triazine compound hexahydro 1,3,5-tris (2-hydroxyethyl) -S-triazine, phenol compound 2,4,4'-trichloro-2'-hydroxydiphenyl ether (triclosan) Disulfide compounds such as tetramethylthiuram disulfide, thio -Sodium N-methyldithiocarbamate (carbam) nitrile compound 2,4,5,6-tetrachloroisophthalonitrile (TPN), organometallic 10,10-oxybisphenoxyarsine (OBPA) ) And the like. Antibiotics such as phenoxymethylpenicillin, cephalothin, streptomycin sulfate and the like are also suitable as non-silver non-copper antibacterial agents to be contained in the organic coating film of the present invention.

  All of these are commercially available products, exhibiting antibacterial properties when introduced into an organic coating film, and suppressing the generation of ammonia. As a method for adding the antibacterial agent, a method of dispersing and kneading the antibacterial agent at the time of manufacturing the paint in a powder state, a method of adsorbing the antibacterial agent to an inorganic powder such as silica and adding a pigment so that the pigment is added, There is a method in which an antibacterial agent is pasted together with an appropriate medium and mixed after manufacturing the paint. As content with respect to the whole organic coating film after drying of an antibacterial agent, 0.1 to 20 mass% is desirable. If the content of the antibacterial agent is less than 0.1% by weight, sufficient antibacterial action cannot be obtained. Further, when the content exceeds 20% by weight, the antibacterial effect does not increase so much even if it is added more than this, and the economic disadvantage is increased.

  As an anti-corrosion pigment, an organic coating film is added with a phosphoric acid anti-corrosion pigment and an alkaline earth metal sulfate. As the phosphoric acid-based anticorrosive pigment, magnesium salt, calcium salt, aluminum salt, molybdate, etc. of phosphoric acid, phosphorous acid, polyphosphoric acid can be added. As alkaline earth metal sulfates, sulfates such as Ca, Ba and Sr can be added. As for the content of phosphate anticorrosive pigments and alkaline earth metal sulfates, 20% by mass is sufficient for the entire organic coating film after drying. Considering the membrane performance, 5% by mass or more and 15% by mass or less is desirable. The total content including the above-mentioned non-silver non-copper antibacterial agent is desirably 75% by mass or less based on the entire organic coating film.

  The reason for this combination of phosphate and alkaline earth metal sulfate is unknown, but it has been found to improve the ammonia resistance of the entire anticorrosion coating, and the anticorrosion performance of steel materials on the ground is improved. Greatly improve. However, for the addition of phosphate-based anticorrosive pigments and alkaline earth metal sulfates, a combination in which the pigments used do not react with each other must be selected.

  In the present invention, first, since the antibacterial agent exhibits anticorrosion performance by suppressing the activity of microorganisms that generate ammonia, the organic coating film containing the antibacterial agent is not always the outermost layer coating film. must not.

  If the outermost layer is a film containing the antibacterial agent, the organic coating film of the present invention may be a single layer or a multilayer structure.

  In addition, when making an organic coating film into a multilayer structure, although it does not prescribe | regulate especially about the structure and thickness of films other than the outermost layer, the thickness of the whole organic coating film is desirably 50 μm or more and less than 3 mm. When a plurality of organic coating films are industrially performed, the thickness naturally exceeds 50 μm. Moreover, in the case of a thick film of 3 mm or more, the life of the entire organic coating film is prolonged, and thus the effect of the present invention cannot be confirmed.

  The advantage of having a multi-layer coating film is that the amount of paint containing an antibacterial agent is minimized by overcoating only the part that contacts the ground. As a result, the cost can be reduced and the discharge of the antibacterial agent to the environment can be minimized.

  Moreover, if the anticorrosion requirements of the present invention can be satisfied by combining existing paints, it is possible to suppress ground corrosion without producing new paints or minimizing the production of new paints. It is also possible to exert an effect.

  The coating method may be a general method such as spray coating, fluid bath immersion, powder coating, or the like.

  The rust and corrosion preventive steel material of the present invention can have a phosphate chemical conversion treatment layer between the zinc-based plated steel material and the organic coating film.

  In general, the zinc phosphate chemical conversion coating in galvanization is mainly composed of opium crystals, but when the ammonia concentration is very high, zinc ions in the crystals are extracted as zinc-ammonia complexes. If the emphasis is on the prevention of abnormal corrosion due to ammonia at the ground, if there is no chemical conversion coating, the corrosion resistance (ammonia resistance) is higher. There is also. However, the dissolution of the chemical conversion film by ammonia is limited to a case where the pH is very high as 11 or more, and in terms of the overall corrosion resistance by the adhesion of the coating film and the coating film, the chemical conversion film, and the plating layer, Chemical conversion treatment is useful.

This is the amount of zinc phosphate conversion coating. Actually, there are various types of phosphate conversion coatings, and the size of crystals varies depending on the type and ratio of metals. The amount of adhesion is not uniquely determined. However, in order to uniformly coat the steel surface, at least 300 mg / m ² is necessary. In addition, the chemical conversion treatment film may be intentionally formed thick for the purpose of impregnating with a rust preventive oil, etc., but in the case of the present invention, when the adhesion amount becomes large, the crystal becomes coarse. Adhesion after painting, which is the original purpose of chemical conversion treatment, cannot be ensured. For this reason, the maximum adhesion amount is desirably 8000 mg / m ² or less.

  Hereinafter, the present invention will be described in detail using examples.

Example 1
The SS400 steel having a plate thickness of 4.5 mm, a width of 100 mm, and a length of 200 mm was subjected to plating, chemical conversion treatment and coating treatment having the composition and composition shown in Table 2. Incidentally, pure zinc plating is carried out by grooved hot dipping with flux, it was 300g ^{/ m 2} ~380g ^/ m 2 at a coating weight of zinc terms. The zinc-aluminum alloy plating was performed by a two-step plating method in which after pure zinc plating was applied, zinc-10% aluminum alloy plating was performed. Adhesion amount is 250g ^{/ m 2} ~360g ^/ m 2 by plating a total of 2 times, as calculated from the amount of aluminum, the second stage of zinc -10% aluminum alloy plating 80 mass as a plating composition of the average % Or more. These galvanized steel pieces were painted and used as test materials. In addition to the direct coating, the coating was also performed by applying a normal immersion type phosphate chemical conversion treatment for the coating base. The painting method was spray coating.

  In addition, as a non-silver non-copper type antibacterial agent, a vinylazine (manufactured by Morton), which is an organic antibacterial agent and has 10,10'-oxybisphenoxyarsine as a main component, was used. On the coated surface of this test piece, a sword reaching a 150 mm long plating layer was put with a cutter knife, and then embedded in concrete to about 1/3 of the total length, and an additional 50 mm thick humus layer was formed on the concrete layer. . This was installed outdoors, and at 9 and 17 o'clock twice a day, 50 ml of a solution simulating dog urine having the composition shown in Table 1 was sprayed for each test material. After performing this test for nine months from March to December, the humus was removed, and the buttocks of the portion buried in the humus were observed. Furthermore, the paint film that floated was peeled off, and the spread of corrosion under the paint film was investigated. The results are summarized in Table 1. It can be seen that all of the examples of the present invention are good, white rust of zinc is generated in the collar portion, and the steel material itself is not corroded. Moreover, the corrosion width under a coating film is also slight. On the other hand, in the comparative example, red rust is generated in all the test pieces, and the sacrificial anticorrosive function of galvanization has been lost, and it can be clearly seen that undercoat corrosion occurs.

(Example 2)
The same steel as that used in Example 1, by a melting method ^were pure zinc plating ^{450g / m 2 ~530g / m 2} . The test piece was painted to give a test material. In addition to the direct coating, the coating was also applied to those subjected to the usual immersion-type phosphate chemical conversion treatment for the coating base. Coating was performed by spray coating, with coating A having the composition shown in Table 3 and coating B thereon. Similarly, coating A, coating B, and coating C having the composition shown in Table 4 were performed in this order by the spray method, and a test piece having a three-layer coating film was produced.

  In addition, as a non-silver non-copper type antibacterial agent, UNICHEM FLEX (manufactured by Union Chemical Co., Ltd.) which is an isothiazoline antibacterial agent which is an organic antibacterial agent was used. About these test pieces, the same test as Example 1 was done, and the buttocks from the part directly above the embedding part to the part buried in the humus were observed. The test results are shown in Tables 3 and 4. It can be seen that all of the examples of the present invention are good, white rust of zinc is generated in the collar portion, and the steel material itself is not corroded. Moreover, the corrosion width under a coating film is also slight. On the other hand, in the comparative example, red rust is generated in all the test pieces, and the sacrificial anticorrosive function of galvanization has been lost, and it can be clearly seen that undercoat corrosion occurs.

As mentioned above, although preferred embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

Claims (2)

A rust and corrosion-resistant coated steel material having an organic coating film on the surface of a zinc-based plated steel material,
The outermost coating layer of the organic coating film comprises a phosphoric acid anticorrosive pigment, an alkaline earth metal sulfate, and a non-silver non-copper antibacterial agent, Coated steel. The rust and corrosion-resistant coated steel material according to claim 1, further comprising a phosphate chemical conversion treatment layer between the zinc-based plated steel material and the organic coating film.