Technical field
[0001]
　The present invention is anticorrosive steel and a method of manufacturing the same, a corrosion protection methods as well as the ballast tanks of steel.
Background technique
[0002]
　When used for a long period of time the steel in a corrosive environment containing chloride ions, or to improve corrosion resistance by optimizing the components of the steel material, such as or painted, are required corrosion protection. In particular, the inside of the ballast tank of the ship, to become a severe corrosive environment of the repetition of the wet atmosphere, including the immersed state and salinity of sea water, painted with international treaties have been mandatory.
[0003]
　However, the goal corrosion-resistant life mandates have been painted standard in the international treaty is 15 years, shorter than the 25 years that is the ship of life. Thus, since 15 years is considered to be required repair replacement or paint corroded steel. Therefore, in order to suppress the economic loss of maintenance costs and the dog extension of time (time loss), and the development of new anti-corrosion technology a need to achieve corrosion resistance over a longer period.
[0004]
　Conventionally, the request that the performance improvement of corrosion-resistant steel material having an inorganic zinc coatings, or properly control the component composition and surface properties of the steel material, the method or to properly control the properties of the inorganic zinc coating are proposed and have (for example, see Patent documents 1-12.).
CITATION
Patent literature
[0005]
Patent Document 1: Publication Patent Publication No. 51-028650
Patent Document 2: Unexamined Patent Publication No. 51-106134
Patent Document 3: JP Publication No. 51-123229
Patent Document 4: JP Publication No. 59-051951
Patent Document 5 : Laid-open Publication No. 2002-285102
Patent Document 6: JP Publication No. 2003-531924
Patent Document 7: JP Publication No. 2005-510584
Patent Document 8: JP Publication No. 2007-191730
Patent Document 9: JP 2008-144204 No. Publication
Patent Document 10: Unexamined Publication No. 2010-018846
Patent Document 11: Unexamined Publication No. 2011-021247
Patent Document 12: Unexamined Publication No. 2011-021248
Summary of the invention
Problems that the Invention is to Solve
[0006]
　The have been corrosion protection method described in the above patent documents and the like, of the component composition of the steel affect thing to corrosion resistance, the performance of the inorganic zinc coating corrosion-resistant steel having a is a sacrificial protection effect primarily due to the zinc particles, inorganic zinc other components contained in the coating film and the like, affect the performance of corrosion-resistant steel having a inorganic zinc coating is not assumed. Therefore, capture the inorganic zinc coating and the steel material as an integral, it attempts drastically improve the performance of corrosion-resistant steel having a inorganic zinc coating is not performed.
[0007]
　Further, in general, in order to obtain a long-term corrosion resistance of the ballast tanks of ships, topcoat of further organic resin layer or the like on an inorganic zinc coatings are provided. However, with the corrosion protection method described in the above patent documents and the like, long-term corrosion resistance in the case of not providing the top coat is still insufficient.
[0008]
　Accordingly, the present invention has been made in view of the circumstances as described above, which can maintain excellent corrosion resistance over a long period of time, corrosion protection steel and a production method thereof, a corrosion prevention method and ballast tanks of steel and to provide.
Means for Solving the Problems
[0009]
　The present invention is focused on the synergistic effect of the components included in the component and the steel contained in the inorganic zinc coating is in the performance of corrosion-resistant steel having a inorganic zinc coating which improved drastically and has as its gist , it is as follows.
[0010]
　[1] and steel, it is a corrosion steel and a paint film thickness of 10μm or more formed on the surface of the steel material; the steel material, by mass%, C: 0.001% ~ 0.20%, Si : 0.01% ~ 3.0%, Mn: 0.1% ~ 3.0%, Cr: 0.1% ~ 9.99% to contain respectively; the coating film, alkali silicate-based inorganic zinc paint is formed by curing the composition, wherein during the coating, and a silicon atom, it contains at least one kind of atoms selected from alkali metal atom and a nitrogen atom, {silicon atoms Si in the coating film molar ratio expressed in moles} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film} is located at 2.0 to 125; wherein the inorganic zinc coating composition, the alkali silicate and zinc particles containing the door, in the "mass of solids mass / zinc particles of the binder component" Anticorrosive steel mass ratio being, characterized in that from 0.01 to 0.35.
[0011]
　[2] and the Cr content in said steel material, and wherein the molar ratio in the coating film satisfies the following conditional expression (1), anticorrosive steel according to [1]. Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material in (μm)) × a / b [ condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 7, b is 6. ]
　[3] and the Cr content in said steel material, the coating film the molar ratio in the satisfies the following conditional expression (1), anticorrosive steel according to [1]. Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material in (μm)) × a / b [ condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 17, b is 6. ]
　[4] above in the coating film include a silicon atom and an alkali metal atom, wherein [1] to anticorrosive steel of any one of [3].
[0012]
　[5] above in the coating film include a silicon atom and a nitrogen atom, wherein [1] to anticorrosive steel of any one of [4].
[0013]
　[6] The alkaline silicate, M 1 2 O · NSiO 2 [wherein, M 1 is an alkali metal or an amine component or ammonium component, n represents a positive number. A compound represented by, the [1] anticorrosive steel according to any one of [5].
[0014]
　[7] The alkaline silicate, lithium silicate, contains at least one selected from sodium silicate and potassium silicate, wherein [1] to anticorrosive steel of any one of [6].
[0015]
　[8] The alkaline silicate is the primary amine is selected from quaternary ammonium silicate consisting of secondary amine or a tertiary amine and ammonium silicate consisting of silicic acid, and quaternary ammonium silicate, that at least one, said [1] to anticorrosive steel of any one of [7].
[0016]
　[9] The alkaline silicate comprises a quaternary ammonium silicate consisting of a quaternary ammonium silicate, said [1] to anticorrosive steel of any one of [8].
[0017]
　[10] the inorganic zinc coating composition, anticorrosion steel according to any one of [1] to [9], wherein the substantially free of alkyl silicate-based binder and an organic solvent.
[0018]
　[11] The thickness of the coating film, wherein characterized in that at 200μm or less [1] anticorrosive steel according to any one of [10].
[0019]
　[12] consists of the the steel material and the coating film, according to the coating without providing a top coating film on the film, any one of said which is a ballast tank [1] to [11] anticorrosive steel.
[0020]
　[13] The steel product, in mass%, Cr: 0.3% - above [1] which is characterized by containing 3.0% ~ anticorrosive steel of any one of [12].
[0021]
　[14] In the steel material, C, Si, other Mn and Cr, by mass%, Al: 2.0% or less, Cu: 1.0% or less, Ni: 2.0% or less, Mo: 0.5 % or less, W: 0.5% or less, Sn: 0.5% or less, Sb: 0.5% or less, V: 0.2% or less, Nb: 0.08% or less, Ti: 0.1% or less Mg: 0.01% or less, Zr: 0.05% or less, B: 0.0050% or less, Ca: 0.02% or less, REM: 0.02% or less, P: 0.03% or less, S: 0.01% or less, N: 0.02% or less, the balance being iron and anticorrosive steel according to any one of [1] to [13], wherein the unavoidable impurities.
[0022]
　[15] The [1] to the ballast tanks constructed with corrosion steel according to any one of [14].
[0023]
　[16] in terms of mass%, C: 0.001% ~ 0.20%, Si: 0.01% ~ 3.0%, Mn: 0.1% ~ 3.0%, Cr: 0.1% ~ 9.99% to the surface of the steel material containing, respectively, containing the alkali silicate and zinc particles, the mass ratio represented by "weight of solid content / zinc particles of the binder component" 0.01 to 0 the alkali silicate inorganic zinc-coating composition is .35, the thickness of the coating film after curing was applied so that the above 10 .mu.m, at least one and a silicon atom, is selected from an alkali metal atom and a nitrogen atom included with the atoms, and the molar ratio represented by {the number of moles of silicon atoms Si in the coating} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film} is 2.0 ~ the method of manufacturing corrosion steel, characterized in that it comprises a step of forming a coating film is 125
[0024]
　[17] and the Cr content in said steel material, the coating film the molar ratio in the satisfies the following conditional expression (1), the manufacturing method of anticorrosive steel according to [16]. Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material in (μm)) × a / b [ condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 7, b is 6. ]
　[18] the inorganic zinc coating composition to be to self-cure method of manufacturing a corrosion steel according to [16] or [17], wherein the forming a coating film on the surface of the steel material.
[0025]
　[19] in terms of mass%, C: 0.001% ~ 0.20%, Si: 0.01% ~ 3.0%, Mn: 0.1% ~ 3.0%, Cr: 0.1% ~ 9.99% to the surface of the steel material containing, respectively, containing the alkali silicate and zinc particles, the mass ratio represented by "weight of solid content / zinc particles of the binder component" 0.01 to 0 the alkali silicate inorganic zinc-coating composition is .35, the thickness of the coating film after curing was applied so that the above 10 .mu.m, at least one and a silicon atom, is selected from an alkali metal atom and a nitrogen atom included with the atoms, and the molar ratio represented by {the number of moles of silicon atoms Si in the coating} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film} is 2.0 ~ anticorrosion method of steel material characterized in that it comprises a step of forming a coating film is 125.
[0026]
　[20] and the Cr content in said steel material, the coating film the molar ratio in the satisfies the following conditional expression (1), corrosion prevention method of the steel according to [19]. Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material in (μm)) × a / b [ condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 7, b is 6. ]
　[21] the inorganic zinc coating composition to be to self-cure, corrosion protection method for steel according to [19] or [20], wherein the forming a coating film on the surface of the steel material.
Effect of the invention
[0027]
　According to the present invention described above, by providing the surface of the steel material comprising the specified ingredients, a coating film alkali silicate inorganic zinc-coating composition is formed by curing with a predetermined components in, it is possible to maintain excellent corrosion resistance over a long period of time.
Brief description of the drawings
[0028]
[1] Figure 1 atomic molar ratio in the coating film with respect to (Si / M), is a graph plotting Cr content in the steel.
FIG. 2 is for the film thickness of the coating film is a graph plotting the Cr content in the steel.
DESCRIPTION OF THE INVENTION
[0029]
　The following describes in detail preferred embodiments of the present invention.
[0030]
　[Anticorrosive steel and a manufacturing method thereof]
　anticorrosive steel of the present invention is a corrosion resistant steel having excellent corrosion resistance over a long period, the steel containing predetermined components to be used as a base material, formed on the surface of the steel material and a coating film. The coating is formed on a part or all of the surface of the steel material.
[0031]
　That anticorrosive steel of the present invention, a steel material, be a corrosion steel and a paint film thickness of 10μm or more formed on the surface of the steel material; the steel is 0.1% of Cr by weight% to 9. containing 99%; the coating film is formed by curing the alkali silicate inorganic zinc-coating composition, wherein during the coating, and a silicon atom, at least one selected from alkali metal atom and a nitrogen atom It includes the atom, {the mole number of silicon atoms Si in the coating} / mole ratio represented by {the alkaline total moles of metal atoms and nitrogen atoms in the coating film} is 2.0 to 125 in it; the inorganic zinc coating composition contains an alkali silicate and zinc particles, the mass ratio represented by "weight of solid content / zinc particles of the binder component" is from 0.01 to 0.35 and characterized in that.
[0032]
　Hereinafter, these steel materials and coatings will be described in detail.
[0033]
　
　describes components of the steel to be used as the base material. In the following description of the contained elements, notation "%" means% by weight (i.e. weight percent).
[0034]
　[C: 0.001 ～ 0.20 Pasento]
　C is an effective element in improving the strength of the steel. In the present invention, in order to maintain the required strength, C amount is set to 0.001% or more. C content is preferably at least 0.005%, 0.01% or more, and more preferably 0.03% or more, or 0.05% or more. On the other hand, when the C content exceeds 0.20%, the weldability and toughness may decrease, the upper limit is 0.20%. C amount, considering the weldability, and more preferably 0.16% or less, from the viewpoint of workability, more preferably 0.14% or less, or 0.12% or less.
[0035]
　[Si: 0.01 ~
　3.0%] Si acts as a deoxidizer and also is an element effective in improving the strength. The Si content is less than 0.01%, since there are cases where deoxidation is insufficient, in the present invention, the lower limit is set to 0.01%. Further, in order to perform the deoxidation more stably is, Si content is more preferably 0.05% or more, or 0.10% or more. On the other hand, when the Si content exceeds 3.0%, the ductility is reduced, and 3.0% the upper limit. In consideration of weldability and toughness of the steel material, Si content is more preferably 0.5% or less or 0.4% or less.
[0036]
　[Mn: 0.1 ~
　3.0%] Mn is an element effective for tissue control of the steel in the present invention, Mn amount is set to 0.1% or more. Further, in order to perform the tissue controlled stably, Mn amount is more preferably 0.5% or more. On the other hand, when the Mn content exceeds 3.0%, there is a case where the ductility or toughness is reduced to 3.0% the upper limit. Further, since the productivity and weldability of improvements such as rolling, Mn amount is more preferably equal to or less than 2.5%. Such as for weldability improvement, the upper limit of the amount of Mn, 2.0%, Sashitsukaenai even as 1.6% or 1.4%. For ductility or improving the toughness, 0.6% the lower limit of the Mn content may be 0.8% or 1.0%.
[0037]
　[Cr: 0.1 ~
　9.99%] Cr is effective in improving the steel corrosion, is an important element. In the present invention, in order to obtain a remarkable corrosion resistance improving effect by interaction with the alkali silicate-based inorganic zinc coating and a steel material formed as a coating film, Cr amount is set to 0.1% or more. For the purpose of improving corrosion resistance is, Cr amount is less than 0.2%, 0.3% or more, preferably 0.5% or more, or 0.7% or more, 1% or more is more preferable. On the other hand, when the Cr content is more than 9.99% does not occur is the transformation in the cooling process of the cast, become a ferrite single-phase structure, since the cast halves occurs, and 9.99% the upper limit. Further, Cr amount, for the alloy cost reduction is preferably 8.0% or less, more preferably 6.5% or less. Cr content, in consideration of the weldability, etc., 5.0% or less, 4.0% or less, 3.0% or less, 2.0% or less, 1.5% or less, 1.2% or less, or 1. it may be limited to less than 0%.
[0038]
　Steel used in the present invention, in order to further improve the corrosion resistance of the steel, Al, Cu, Ni, Mo, W, may contain one or more kinds of Sn and Sb. Hereinafter, Al, Cu, Ni, Mo, W, the reason for limiting the content of Sn and Sb is described.
[0039]
　[Al: 2.0% or less]
　Al is generally used as a deoxidizing agent, in the present invention, in order to further improve the corrosion resistance of the steel, steel material may contain, if necessary Al. On the other hand, when the Al content exceeds 2.0%, not occur transformation during cooling of the slab, become a ferrite single phase structure, because it can cast halves occurs, it is 2.0% upper limit It is preferred. Al content is more preferably 1.5% or less. For the reduction of Al-based inclusions, the upper limit of the Al content, 1.0%, 0.5%, 0.2%, may be 0.1% or 0.08%. The lower limit of the Al content need not be particularly defined, but may be 0% in order to further improve the corrosion resistance of the steel is preferably 0.002%, more preferably 0.01%. Further, Al content is more preferably set to 0.02% or more.
[0040]
　[Cu: 1.0% or less]
　Cu are the elements to improve the corrosion resistance of the steel, steel material may contain, if necessary Cu. On the other hand, when the Cu content exceeds 1.0%, since it may steel becomes brittle, so the upper limit is preferably made 1.0%. Cu content is more preferably 0.5% or less, more preferably 0.3% or less. The lower limit of the Cu content does not need to be particularly specified, but may be 0% in order to stably improve the corrosion resistance of the steel is preferably 0.05%. Further, Cu serves to improve the strength, since that is also an element to prevent cast halves, Cu amount is more preferably set to 0.10% or more.
[0041]
　[Ni: 2.0% or less]
　Ni is an element improving the corrosion resistance of the steel, and may steel is prevented at the same time the production of degradation containing Ni in the case of containing Cu. On the other hand, Ni is an expensive element, because it is saturated with the effect described above containing Ni exceeding 2.0% the steel material, it is preferable that the 2.0% limit. Ni content is more preferably 0.5% or less, more preferably 0.3% or less. The lower limit of the Ni amount is not particularly necessary to define, but may be 0% in order to obtain the effect of the stable is preferably 0.05%, more preferably from 0.10%.
[0042]
　[Mo: 0.5% or less] [W: 0.5% or
　less] Mo and W is an element improving the corrosion resistance of the steel, steel material may be contained if necessary these elements. On the other hand, Mo and W, since the steel material is saturated effect also contain more than 0.5% and the upper limit is preferably made 0.5%. Mo content and W content is more preferably 0.1% or less, respectively. The lower limit of the Mo content and W content need not be particularly defined, but may be 0% in order to improve the corrosion resistance of the steel in a stable manner is preferably 0.01%, respectively, more preferably 0.03% .
[0043]
　[Sn: 0.5% or less]
　Sn is an element that improves the corrosion resistance of the steel, steel material may contain, if necessary Sn. On the other hand, because they may impair the manufacturability and mechanical properties and the steel material is excessively containing Sn, it is preferable that 0.5% or the upper limit of the Sn content. Sn amount is more preferably 0.2% or less. The lower limit of the Sn content does not need to be particularly specified, but may be 0% in order to stably improve the corrosion resistance of the steel is preferably 0.01%, more preferably 0.05%.
[0044]
　[Sb: 0.5% or less]
　Sb is an element for improving the corrosion resistance of the steel, steel material may contain, if necessary Sb. On the other hand, because they may impair the manufacturability and mechanical properties and the steel material is excessively containing Sb, it is preferable that 0.5% or the upper limit of the Sb content. Sb content is more preferably 0.2% or less. Sb amount of the lower limit need not be particularly defined, but may be 0% in order to stably improve the corrosion resistance of the steel is preferably 0.01%, more preferably 0.05%.
[0045]
　Steel used in the present invention, mechanical properties, containing service performance, from the viewpoint of improvement of such production stability, further, V, Nb, Ti, Mg, Zr, B, 1 kind of Ca and REM or two or more it may be.
[0046]
　[V: 0.2% or less]
　V is, mechanical properties, use performance, an element for improving the production stability, the steel material may contain as necessary V. On the other hand, because it may impair the耐発rust resistance when the steel material is excessively containing V, the upper limit of the V content is preferably set to 0.2%. V amount is more preferably 0.05% or less. The lower limit of V content does not have to be particularly defined, but may be 0% in order to stably improve the properties of the steel is preferably 0.005%, more preferably 0.01%.
[0047]
　[Nb: 0.08% or less]
　Nb is mechanical properties, use performance, an element for improving the production stability, the steel material may contain, if necessary Nb. On the other hand, because it may impair the耐発rust resistance when the steel material is excessively contains Nb, it is preferable to 0.08% and the upper limit of Nb content. Nb amount is more preferably 0.03% or less. Nb amount lower limit need not be particularly defined, but may be 0% in order to improve various properties of the steel in a stable manner is preferably 0.002%, more preferably 0.005%.
[0048]
　[Ti: 0.1% or less]
　Ti is mechanical properties, use performance, an element for improving the production stability, the steel material may contain, if necessary Ti. On the other hand, because it may impair the耐発rust resistance when the steel material is excessively containing Ti, it is preferable that 0.1% or the upper limit of the Ti content. Ti content is more preferably 0.03% or less. Ti content of the lower limit need not be particularly defined, but may be 0% in order to stably improve the properties of the steel is preferably 0.005%, more preferably 0.01%.
[0049]
　[Mg: 0.01% or less]
　Mg is mechanical properties, use performance, an element for improving the production stability, the steel material may contain, if necessary Mg. On the other hand, because it may impair the耐発rust resistance when the steel material is excessively containing Mg, the upper limit of the Mg content preferably set to 0.01%. Mg content is more preferably 0.002% or less. Mg content lower limit need not be particularly defined, but may be 0% in order to improve various properties of the steel in a stable manner is preferably 0.0001%, more preferably 0.0005%.
[0050]
　[Zr: 0.05% or less]
　Zr, the mechanical properties, use performance, an element for improving the production stability, the steel material may contain, if necessary Zr. On the other hand, because it may impair the耐発rust resistance when the steel material is excessively contain Zr, it is preferable to 0.05% and the upper limit of the amount of Zr. Zr content is more preferably 0.02% or less. Zr amount of the lower limit need not be particularly defined, but may be 0% in order to improve various properties of the steel in a stable manner is preferably 0.003%, more preferably 0.005%.
[0051]
　[B: 0.0050% or less]
　B is, mechanical properties, use performance, is an element to improve the production stability, the steel may contain as needed B. On the other hand, because it may impair the耐発rust resistance when the steel material is excessively containing B, it is preferable that the upper limit of B content as 0.0050%. B content is more preferably 0.002% or less. The lower limit of the B content does not need to be particularly specified, but may be 0% in order to improve various properties of the steel in a stable manner is preferably 0.0002%, more preferably from 0.0005%.
[0052]
　[Ca: 0.02% or less]
　Ca has mechanical properties, use performance, an element for improving the production stability, the steel material may contain, if necessary Ca. On the other hand, because it may impair the耐発rust resistance when the steel material is excessively contains Ca, is preferably set to 0.02% the upper limit of the Ca content. Ca content is more preferably at most 0.003%. Ca content lower limit need not be particularly defined, but may be 0% in order to improve various properties of the steel in a stable manner is preferably 0.0002%, more preferably from 0.0005%.
[0053]
　[REM: 0.02% or
　less] REM, the mechanical properties, use performance, an element for improving the production stability, the steel material may contain, if necessary REM. REM is representative of rare earth metals (Rare Earth Metals), from La atomic number 57 up to atomic number 71, corresponding to the so-called lanthanide elements. In this embodiment, steel, it may be contained alone or a compound of one kind of element belonging to REM, may contain a mixture containing plural kinds of REM. Such mixtures can include Ce, La, misch metal mainly composed of Nd and the like.
[0054]
　On the other hand, because it may impair the 耐発 rust resistance when the steel material is excessively contained REM, it is preferable to 0.02% and the upper limit of the REM content. REM content is more preferably 0.01% or less. REM amount of the lower limit need not be particularly defined, but may be 0% in order to improve various properties of the steel in a stable manner is preferably 0.0002%, more preferably from 0.0005%.
[0055]
　The content of the above-described optional elements (Al, Cu, Ni, Mo, W, Sn, Sb, V, Nb, Ti, Mg, Zr, B, Ca and REM) is 1.5% or less in the sum and it is more preferable to be, further preferably 1.0% or less, 0.8% or less, may be 0.6% or less or 0.4% or less.
[0056]
　In the steel material used in the present invention, the balance other than the above elements is Fe and unavoidable impurities. Such unavoidable impurities, for example, P, S, may be mentioned N, etc., it is acceptable so long as this does not compromise the improvement of 耐発 rust resistance of the steel.
[0057]
　: [P 0.03% or less]
　amount P, when it exceeds 0.03%, since there are cases where toughness and ductility is lowered, so the upper limit is preferably made 0.03%. A more preferable upper limit of the P content is 0.02% or 0.01%. On the other hand, it is not necessary to particularly defined the lower limit of the P content, but the lower limit of the P content may be 0%, since the manufacturing cost to reduce the P content to less than 0.001% increases, the P content 0.001 % or more is preferable.
[0058]
　[S: 0.01% or less]
　S amount exceeds 0.01%, since there are cases where toughness and ductility or impair lowered, the hot workability, the upper limit is made 0.01% it is preferred. A more preferable upper limit of the S content is 0.006%, or 0.003%. On the other hand, it is not necessary to specifically defined the lower limit of the S content, may also be, but as a 0% lower limit of the S content, since the manufacturing cost to reduce the S content to less than 0.0001% is increased, the amount of S 0.0001 % or more is preferable.
[0059]
　: [N 0.02% or less]
　amount N, when it exceeds 0.02%, since there are cases where toughness and ductility is lowered, so the upper limit is preferably made 0.02%. A more preferable upper limit of the N content is 0.01%, more preferably 0.006%. On the other hand, it is not necessary to particularly defined the lower limit of the N content, the lower limit of the N content may be 0%, but since the manufacturing cost to reduce the N content to less than 0.001% increases, the amount of N is 0.001 % or more is preferable.
[0060]
　Incidentally, C, Si, Mn, the total content of elements other than Cr and Fe, may be limited to 2.0% or less. If necessary, the total of 1.6% or less, 1.2% or less, 0.9% or less, may be 0.6% or less or 0.4% or less. It is not particularly necessary to define the lower limit of the total, may be the lower limit is 0%.
[0061]
　Steel used in the present invention, the general manufacturing process (e.g., casting, heat-rolling, cold-rolling, and, as required heat treatment) is manufactured through the. That is, in the present invention, a steel slab by casting the molten steel, then hot rolling, such as alms cold rolling, heat treatment as needed, the steel sheet, strip, shaped steel, steel pipe, steel bar, steel wire in the form of an equal, it is possible to use a steel material is produced through a conventional general steel process. In the present invention, it can be used for welded structures and steel structures constructed using such steel. The thickness of the steel material is not particularly limited, but is usually 3 ~ 50mm. Preferable lower limit is 6 mm, more preferably 10 mm, the preferred upper limit is 40 mm, and more preferably 30 mm.
[0062]
　Strength steel sheet used for ballast tanks (tensile strength) is generally have 650MPa or less of the steel sheet used above 400 MPa, may be used steel sheets of the intensity. Method of manufacturing the steel plate of the strength, as stipulated in the rules of each classification societies such as NK, ABS and LR, while rolling, by TMCP (Thermo-Mechanical Control Process) or normalizing heat treatment (Normalizing) There is a general. The treated steel sheet back quenching or quenching grilled are not used almost. Therefore, the steel material used in the present invention, while rolling, the steel sheet produced by normalizing TMCP or tempered, may be limited.
[0063]
　[Coating]
　coating constituting the anticorrosive steel of the present invention is formed by curing the alkali silicate inorganic zinc-coating composition containing an alkali silicate and zinc particles. Hereinafter, containing components of the alkali silicate-based inorganic zinc coating composition, it will be described in detail.
[0064]
　<-Containing component of the coating composition>
　"alkali silicates"
　alkali silicates for use in the present invention, M 1 2 O · NSiO 2 in [formula, M 1 is an alkali metal or an amine component or ammonium component, n represents be positive , usually from 1 to 100, preferably 1 to 70. A compound represented by the general formula of.
[0065]
　When alkali silicates containing alkali metals as M1, the alkali metal silicates are exemplified consisting of an alkali metal silicate, as such compounds, for example, lithium silicate (Li 2 O · SiO 2 , etc.), sodium silicate ( Na 2 O · SiO 2 , Na 2 O · 2SiO 2 , Na 2 O · 4SiO 2 , etc.), potassium silicate (K 2 O · SiO 2 may be mentioned silicate compounds such as etc.).
[0066]
　When alkali silicates containing amine component or ammonium component as M1, primary amine, ammonium and a second amine or a tertiary amine silicate silicates, quaternary consisting of a quaternary ammonium silicate and an ammonium silicate. Amine component and ammonium components derived from ammonium silicate, remains in the coating film without some volatilize during film formation, can contribute to corrosion protection as the alkaline component.
[0067]
　Primary amine, secondary amine, the tertiary amine component, for example, NR 3 ... amine component represented by the formula (1). Formula (1), R are each independently a hydrogen atom, substituted hydrocarbon group having 1 to 4 carbon atoms, or said one or more hydrogen atoms having a hydrocarbon group having a substituent such as a hydroxyl it is made based on. However never all R are hydrogen atoms at the same time, two R may form a cyclic group bonded to each other. R are each preferably independently a hydrogen atom, an alkyl group or hydroxyalkyl group.
[0068]
　As the quaternary ammonium component, for example, NR 4 Tasu and ammonium cation represented by Equation (2). In the formula (2), R each independently represent a hydrocarbon group having 1 to 4 carbon atoms or 1 or 2 or more made by replacing a substituent such as a hydroxyl group of a hydrogen atom with the said hydrocarbon group, is there. However, two R may form a cyclic group bonded to each other. R is preferably independently an alkyl group or hydroxyalkyl group.
[0069]
　In the above formula (1) and (2), the carbon number of the alkyl group is usually 1-4, preferably 1-2. The number of carbon atoms of the hydroxyalkyl group is usually 1-4, preferably 1-2.
[0070]
　Specific examples of the amine component and ammonium components are, for example, tetramethylammonium, tetraethylammonium, tetrapropylammonium, methyl triethanolammonium, ethyl triethanol ammonium, methyl tri-propanol ammonium, isopropyl triethanolammonium, dimethyl diethanol ammonium, tetra ethanol quaternary ammonium component such as ammonium; methylamine, ethylamine, ethanolamine, diethanolamine, and a first, second and third amine component, such as triethanolamine. Among them, tertiary amine component, a quaternary ammonium ingredient is preferably a quaternary ammonium ingredient is more preferable.
[0071]
　Among the alkali silicate containing amine component or ammonium component, the remaining of the coating film at the time of film formation, and the like odor surface of the paint, ammonium silicates and quaternary ammonium silicates with tertiary amine component is preferably , quaternary ammonium silicate is more preferable.
[0072]
　Alkali silicates containing amine component or ammonium components are, for example, from Nissan Chemical QAS-25 (SiO 2 solid content: 25 wt%) and QAS-40 (SiO 2 : under the tradename solid content: 40 wt%), or Japan chemical industry ammonium silicate 17804 (SiO 2 solid content: 40 wt%) and ammonium silicate 88J3 (SiO 2 : commercially available under the trade name solid content of 20 wt%).
[0073]
　Alkali silicate is a compound which functions as a binder component, also the alkaline component for anticorrosive effect expression by interaction with the Cr contained in steel, a source of alkali metal and amine components or ammonium component Become.
[0074]
　Alkali silicates may be used alone, or in combination of two or more.
[0075]
　"Silicic anhydride"
　silicic anhydride, in the inorganic zinc coating composition can be used in order to obtain good self-curing. Moreover, silicic acid anhydride, as described below, may be used to adjust atomic molar ratio (Si / M).
[0076]
　When using anhydrous silicic acid, it can be incorporated into the coating composition as an aqueous sol. (Hereinafter also referred to as "aqueous silica sol".) The aqueous sol of anhydrous silicic acid, and water as a dispersion medium, a colloidal solution prepared by dispersing ultrafine particles in water anhydrous silicic acid, typically such as an aqueous colloidal silica and the like. Inorganic Zinc coating composition when containing aqueous silica sol, by dehydration condensation reaction of aqueous silica sol, self-curing of the coating proceeds.
[0077]
　"Zinc particles"
　zinc particles, in order to obtain the sacrificial anti-corrosion effect on steel is incorporated in an alkaline silicate-based inorganic zinc-coating composition. Such zinc particles, for example, it is possible to use zinc powder, zinc alloy powder, or mixtures thereof. The zinc alloy includes, for example, an alloy of aluminum or tin and zinc.
[0078]
　The average particle diameter of the zinc particles is preferably, for example, 2 ~ 20μm. The average particle size of such zinc particles using a Blaine air permeability apparatus, can be measured by determining the specific surface area of ​​the particles.
[0079]
　"Acid component and bicarbonate"
　alkali silicate inorganic zinc-coating composition is self-curable composition. Specifically, sodium or potassium carbonate by the coating composition will absorb the carbon dioxide and moisture in the air, lithium carbonate, to precipitate the alkali generating salt comprising carbonate such as ammonium carbonate, a composition for curing, curing speed is also fast.

The scope of the claims
[Claim 1]
　And a steel,
　a coating film thickness of 10μm or more formed on the surface of the steel material
be corrosion steel comprising;
　said steel material containing, by
　mass%, C:
　0.001% ~ 0.20% Si: 0.01
　～ 3.0 Pasento Pasento
　Mn: 0.1 Pasento ～ 3.0 Pasento Cr: 0.1 Pasento ～ 9.99 Pasento
the containing respectively;
　the coating film is, to cure the alkali silicate-based inorganic zinc coating composition is formed, said in the coating film, and a silicon atom, contains at least one kind of atoms selected from alkali metal atom and a nitrogen atom, {the mole number of silicon atoms Si in the coating} / {the molar ratio represented by the total number of moles of alkali metal atoms and nitrogen atoms in the coating film} is located at 2.0 to 125;
　wherein the inorganic zinc coating composition contains an alkali silicate and zinc particles, " the quality represented by mass "of a solid mass / zinc particles of the binder component Ratio is 0.01 to 0.35
anticorrosive steel, characterized in that.
[Claim 2]
　A Cr content in said steel material, the coating film the molar ratio in the satisfies the following conditional expression (1), anticorrosive steel according to claim 1.
　Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material (μm)) × a / b
in [condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 7, b is 6. ]
[Claim 3]
　A Cr content in said steel material, the coating film the molar ratio in the satisfies the following conditional expression (1), anticorrosive steel according to claim 1.
　Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material (μm)) × a / b
in [condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 17, b is 6. ]
[Claim 4]
　Said in the coating film include a silicon atom and an alkali metal atom, anticorrosive steel according to any one of claims 1 to 3.
[Claim 5]
　Said in the coating film include a silicon atom and a nitrogen atom, anticorrosive steel according to any one of claims 1-4.
[6.]
　The alkali silicate, M1 2 O · NSiO 2 [in the formula, M1 is an alkali metal or an amine component or ammonium component, n is a positive number. Is a compound represented by, anticorrosive steel according to any one of claims 1 to 5.
[7.]
　The alkali silicate comprises at least one selected from lithium silicate, sodium silicate and potassium silicate, anticorrosive steel according to any one of claims 1-6.
[8.]
　The alkali silicate is at least selected from primary amine, secondary amine or ammonium silicate consisting of a tertiary amine and silicic acid, and quaternary ammonium silicates consisting of a quaternary ammonium silicate 1 including species, anticorrosive steel according to any one of claims 1 to 7.
[9.]
　The alkali silicate comprises a quaternary ammonium silicate consisting of a quaternary ammonium silicate, anticorrosive steel according to any one of claims 1-8.
[10.]
　The inorganic zinc-coating composition, substantially free of alkyl silicate-based binder and an organic solvent
anticorrosive steel according to any one of claims 1 to 9, characterized in that.
[11.]
　The thickness of the coating film is 200μm or less
anticorrosive steel according to any one of claims 1 to 10, characterized in that.
[12.]
　Wherein said steel material consists of a coating, the coating does not comprise a top coating film on the film,
　which is used for ballast tanks
anticorrosive steel according to any one of claims 1 to 11, characterized in that.
[13.]
　The steel material contains, by mass%
　Cr: 0.3% ~ 3.0%
anticorrosive steel according to any one of claims 1 to 12, characterized in that it contains.
[14.]
　In the steel, C, Si, other Mn and Cr, in the mass Pasento
　Al: 2.0 Pasento following
　Cu: 1.0% or less
　Ni: 2.0% or less
　Mo: 0.5% or less
　W: 0.5 % or less
　Sn: 0.5% or less
　Sb: 0.5% or less
　V: 0.2% or less
　Nb: 0.08% or less
　Ti: 0.1% or less
　Mg: 0.01% or less
　Zr: 0.05% hereinafter
　Bs: 0.0050% or less
　Ca: 0.02% or less
　REM: 0.02% or less
　P: 0.03% or less
　S: 0.01% or less
　N: 0.02% or less
　balance: iron and unavoidable impurities
anticorrosive steel according to any one of claims 1 to 13, characterized in that.
[15.]
　Ballast tanks constructed with corrosion steel according to any one of claims 1 to 14.
[16.]
　In mass
　Pasento,
　C:
　0.001 Pasento ～ 0.20 Pasento Si: 0.01 Pasento ～ 3.0 Pasento
　Mn: 0.1 Pasento ～ 3.0 Pasento Cr: 0.1 Pasento ～ 9.99 Pasento
each the surface of the steel material containing,
　by containing an alkali silicate and zinc particles, alkaline silicate weight ratio, represented by "weight of solid content / zinc particles of the binder component" is from 0.01 to 0.35 the system inorganic zinc coating composition, thickness of the coating after curing was applied so that the above 10 .mu.m,
　contains a silicon atom, and at least one atom selected from an alkali metal atom and a nitrogen atom and, {mole number of silicon atoms Si in the coating} / mole ratio represented by {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film} is, a coating film is 2.0 to 125 forming
manufacturing method of anticorrosive steel material characterized in that it comprises a.
[17.]
　A Cr content in said steel material, the coating film the molar ratio in the satisfies the following conditional expression (1), the manufacturing method of anticorrosive steel according to claim 16.
　Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material (μm)) × a / b
in [condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 7, b is 6. ]
[18.]
　The inorganic zinc coating composition to be to self-cure method of manufacturing a corrosion steel according to claim 16 or 17, characterized in that forming a coating film on the surface of the steel material.
[19.]
　In mass
　Pasento,
　C:
　0.001 Pasento ～ 0.20 Pasento Si: 0.01 Pasento ～ 3.0 Pasento
　Mn: 0.1 Pasento ～ 3.0 Pasento Cr: 0.1 Pasento ～ 9.99 Pasento
each the surface of the steel material containing,
　by containing an alkali silicate and zinc particles, alkaline silicate weight ratio, represented by "weight of solid content / zinc particles of the binder component" is from 0.01 to 0.35 the system inorganic zinc coating composition, thickness of the coating after curing was applied so that the above 10 .mu.m,
　contains a silicon atom, and at least one atom selected from an alkali metal atom and a nitrogen atom and, {mole number of silicon atoms Si in the coating} / mole ratio represented by {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film} is, a coating film is 2.0 to 125 forming
corrosion method of steel which comprises a.
[20.]
　A Cr content in said steel material, the coating film the molar ratio in the satisfies the following conditional expression (1), corrosion prevention method of steel according to claim 19.
　Condition (1): [Cr] ≧ {0.25 × ln ( molar ratio (Si / M)) + 0.5 } × 20 (μm) / ( thickness of the coating film formed on the surface of the steel material (μm)) × a / b
in [condition (1), [Cr] is an Cr content in said steel material (% by weight); the molar ratio (Si / M) is {in the coating film expressed in moles of silicon atoms Si} / {the total number of moles of alkali metal atoms and nitrogen atoms in the coating film}; a is. 7, b is 6. ]
[21.]
　The inorganic zinc coating composition to be to self-cure, corrosion protection method for steel according to claim 19 or 20, characterized in that forming a coating film on the surface of the steel material.