JP2001342576A - Method for manufacturing weather resistant steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing weather-resistant steel in which by forming a rust layer for corrosion prevention is formed on a surface of the steel for a short time to prevent a flow rust. SOLUTION: The method includes repeating treatments of feeding a solution including Fe ion of 0.010-2.0 mol/L on the surface of the steel on which surface layer the rust layer is formed, feeding an alkali solution having OH- concentration equivalent to the Fe ion concentration or more, and drying the surface of the steel, preferably for several times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a weather-resistant steel material, and more particularly to a method for producing a weather-resistant steel material capable of forming a corrosion-resistant rust layer on the surface of a steel material at an early stage and preventing the occurrence of flow rust. About. In addition, in the steel material in the present invention,
It includes thick steel plates, thin steel plates, steel bars, and steel bars.

[0002]

2. Description of the Related Art Weather-resistant steel in which alloying elements such as P, Cu, Cr, and Ni are added to steel to improve corrosion resistance in the atmosphere,
A rust layer called stable rust, which is hard to penetrate oxygen and water, which is the cause of corrosion in an exposed environment, is formed in several years, and the corrosion of ground iron is suppressed. In addition, since the stable rust is dark brown in harmony with the landscape as compared with ordinary steel, it has recently been increasingly used for building exterior materials and steel structures such as bridges. Weather-resistant steel does not require the application of a rust-preventive paint, and is an inexpensive and highly corrosion-resistant material that can be used barely.

[0003] However, when used in the countryside, conventional weather-resistant steel takes several years to form stable rust, during which time flow rust called rust juice is generated. there were. Further, the weather-resistant steel has a problem in that stable rust is hardly formed due to the action of sea salt particles flying in the coastal zone, and the suppression of corrosion is not recognized.

[0004] To deal with such problems, various treatment methods have been studied for steel materials. First, it is widely practiced to form a coating film on the surface of a steel sheet to shut off the surface of the steel sheet from a corrosive environment. However, in the method of forming a coating film on the weather-resistant steel surface, it takes a long period of several tens of years before a stable rust layer is formed because the coating film has high corrosion resistance, and during that period, the deterioration of the coating film In some cases, peeling occurred and the appearance became unsightly. Further, when the deterioration is particularly severe due to the environment, it is necessary to apply a recoating film, and there is a problem that the advantage of the weather-resistant steel material, which can be used without maintenance, is not necessarily utilized. Furthermore, there is a problem that color unevenness occurs due to the difference in the degree of progress of corrosion under the coating film.

Japanese Patent Application Laid-Open No. 49-11739 discloses a weather-resistant rust-layer-forming steel material in which water, a corrosive liquid or both are applied to the surface of a steel sheet to form rust, and then a semipermeable coating is formed. Is disclosed. On the other hand, as a method without using a coating film,
A method of forming a rust layer having anticorrosion performance in advance and preventing flowing rust has also been proposed. For example, JP-A-1-42088
Japanese Patent Publication No. 7-37672 discloses a method for treating the surface of a weather-resistant steel, which comprises forming a phosphate film after treating the surface of the steel sheet with an acidic solution. A rust-resistant weathering steel sheet treated with a rust-treating solution having the composition described in Japanese Patent No. 2765425 is disclosed in Japanese Patent No. 2765425.
Rust layer of 00 nm or less or α-
Each steel material covered with FeOOH is disclosed.

[0006]

The steel material with a weather-resistant rust layer disclosed in Japanese Patent Application Laid-Open No. 49-11739 is manufactured by coating a steel material with a semi-permeable membrane. Rust is generated on the surface of the steel material, and the effect of suppressing flow rust and peeling rust is enhanced. However, as shown in FIG. 2 of JP-A-49-11739, the anticorrosion effect of the rust layer itself is insufficient, and two treatments, namely, a rust accelerating treatment and a semipermeable film forming treatment are performed. , The process becomes complicated.

On the other hand, in the techniques described in Japanese Patent Application Laid-Open No. 1-142088, Japanese Patent Publication No. 7-37672 and Japanese Patent No. 2765425, a rust layer having anticorrosion performance is formed in advance, and the paint is applied. It is to suppress the generation of flowing rust without using it. In these techniques, a method of forming a rust layer or a corrosion treatment liquid has been studied with a focus on forming a rust layer having weather resistance.

However, in the technique described in Japanese Patent Application Laid-Open No. 1-142088, an acidic corrosive solution having a pH of 2.3 or less is applied once and dried to form a rust layer, and then a phosphate film is formed. It is mandatory. However, the phosphate coating is known as a simple rust preventive treatment (rust preventive primer treatment), and has two problems of rusting and rust preventive treatment, so that the process is complicated.

According to the technique described in Japanese Patent Publication No. 7-37672, the concentration of ions contained in the corrosion treatment solution is reduced to reproduce the corrosion close to the actual exposure environment, thereby forming a weather-resistant rust layer. It was done. However, even in this method, as shown in FIG. 1 of Japanese Patent Publication No. 7-37672, the effect of inhibiting corrosion at an early stage after exposure is not always sufficient.
During this time, there was a problem that rust was generated.
Another problem is that the rusting process requires a long period of several days.

A rust layer having an average crystal grain size of 200 nm or less or an average crystal grain size of 200 nm or less disclosed in Japanese Patent No. 2765425.
In order to obtain a steel material covered with α-FeOOH of nm or less, a chromium sulfate solution may be applied and exposed, or a chromium sulfate solution may be applied on rust generated by the exposure. However, simply applying the solution and exposing it is not sufficient because the chromium sulfate is washed away by rainfall in some places, and the effect is not enough.In the same building or bridge, the progress of rust etc. may be uneven depending on the place and it is unsightly There was a problem.

As related to this technology, Japanese Patent No.
No. 66673 discloses a paint containing a substance effective in stabilizing rust such as chromium sulfate in the paint, but as described above, a stable rust layer is formed due to the high anticorrosion properties of the coating film. There is a problem that it takes a long time to do so. As described above, it has been studied to form a corrosion-resistant rust layer on a weather-resistant steel sheet in advance to reduce the flow rust caused by subsequent exposure, but the effect was not always sufficient.

Accordingly, an object of the present invention is to propose a method for producing a weather-resistant steel material capable of forming a corrosion-resistant rust layer on the surface of a steel material in a short time and reducing flow rust.

[0013]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have intensively studied the generation of stable rust. As a result, they came to the conclusion that the rust layer leading to stable rust had many defective portions, corrosion proceeded from the defective portions, and flow rust was generated. Then, after forming a rust layer on the surface of the steel material in advance, the present inventors supply a solution containing Fe ions to the surface, and further supply and dry an alkaline solution to form a rust, FeOOH Have been found to precipitate and adhere to the defective portion inside the rust layer, reduce the defective portion, improve the blocking of corrosion factors in the rust layer, and prevent the occurrence of flow rust.

The present invention has been completed based on the above findings and further studies. That is, the present invention provides an iron ion supply process of supplying a solution containing 0.01 to 2 mol / l of Fe ions to the surface of a steel material in which a rust layer is formed on a surface layer in advance, and an Fe ion concentration of the solution on the surface of the steel material. And a hydroxide ion supply process for supplying an alkali solution having an OH ^- concentration equal to or higher than the equivalent, and then performing a drying process for drying the surface of the steel material. Further, in the present invention, it is preferable to repeat the above-mentioned step a plurality of times, and in the present invention, the rust layer is formed by coating the steel surface with a solution having a pH of 2.5 or more and less than 7.0, more preferably 0.05% Fe ^{+ 2} . 0.10-5mg / cm containing ~ 2.5g / l
^It is preferably formed by repeating the process of wet and dry in ² and drying.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a rust layer is previously formed on a surface layer of a steel material. The rust layer previously formed on the surface layer may be artificially formed or may be formed by exposure under a corrosive environment. An iron ion supply process for supplying a solution containing Fe ions and a hydroxide ion supply process for supplying an alkali solution are performed on the surface of a steel material having a rust layer formed on the surface layer in advance.

When an iron ion supply process for supplying a solution containing Fe ions to the surface of a steel material is performed, Fe ions (Fe ²⁺ , Fe ³⁺ ) penetrate into defective portions of the rust layer. Next, OH ^- solution containing Doing hydroxide ion supplying process for supplying the (alkaline solution), the defect portion of the rust ^{layer, Fe 2+ + 2OH - → Fe} (OH) 2 Fe 3+ + 3OH ^- → Fe (OH) ₃ ... (1) The following reaction proceeds, and a precipitate of iron hydroxide is formed. Further, when a drying treatment for drying the surface of the steel sheet is performed, the reaction of Fe (OH) ₂ + 1 / 4O ₂ → FeOOH + 1 / 2H ₂ O Fe (OH) ₃ → FeOOH + H ₂ O (2) proceeds, FeOOH is artificially precipitated and fixed as rust on the defect in the rust layer. Thereby, both the size and the number of the defective portions in the rust layer are reduced, the blocking property of the corrosion factor in the rust layer is improved, and the generation of flowing rust is suppressed.

In the above, the example in which the solution containing Fe ions is first supplied to the surface of the steel sheet has been described. However, even if the alkaline solution is supplied first, there is essentially no change. Solution and iron ion supply step of supplying a containing Fe ions, OH ^- no problem in either the earlier order of steps and the hydroxide ion supply step of supplying a. The solution used in the iron ion supply treatment of the present invention is a solution containing 0.01 to 2 mol / l of Fe ions. Fe ion concentration
If it is less than 0.01 mol / l, the amount of iron penetrating into the inside of the rust layer is small, and as a result, the amount of rust precipitate becomes insufficient, and the effect of reducing the size of the defective portion is small. On the other hand, when the Fe ion concentration exceeds 2 mol / l, the corrosiveness of the solution is strong and the base iron is significantly dissolved. For this reason, the Fe ion concentration of the solution used in the iron ion supply treatment was limited to 0.01 to 2 mol / l.

As the form of Fe ions in the solution, there are generally Fe ²⁺ and Fe ³⁺ , and either of them can be used in the present invention. As a specific method for adjusting the solution containing Fe ions, a method in which a predetermined amount of iron chloride (II), iron chloride (III), iron sulfate (II), iron sulfate (III), or the like is dissolved in a predetermined amount is preferable. It used a hydroxide ion supply process of the present invention, OH ^- solution (alkaline solution) containing the equivalent or more of OH of Fe ion concentration in the solution containing Fe ions ^- and an alkaline solution having a concentration. Fe ²⁺ , Fe
^3+, but the Fe ²⁺ concentration of the solution containing Fe ions is Xmol / l
When the Fe ³⁺ concentration is Ymol / l, the OH ⁻ concentration of the solution containing OH ⁻ (alkali solution) should be equal to or more than the equivalent of the Fe ion concentration, that is, (2X + 3Y) mol / l or more. preferable. OH ^- OH solution (alkaline solution) containing ^- concentration,
It is sufficient that the concentration is equal to or more than the equivalent of Fe ion, and it is economically disadvantageous to make the concentration too high.

[0019] OH ^- solution containing the (alkaline solution),
(1) As shown in equation necessary and sufficient OH to produce iron hydroxide in combination with iron ^- amount, i.e. have a density that can supply more equivalents of hydroxide ions Fe ions Just do it. If the OH ^- concentration is less than the equivalent of Fe ions, unreacted Fe ²⁺ or Fe ³⁺ remains. If exposed in a corrosive environment as it is, corrosion is accelerated and flow rust is generated.

The OH ^- concentration of the alkaline solution is practically up to three times the equivalent of Fe ions. As a specific method of adjusting the alkali solution, a method of dissolving a predetermined amount of sodium hydroxide, potassium hydroxide, or the like in water is preferable. In addition, it is inexpensive to use sodium hydroxide industrially. After performing the iron ion supply treatment and the hydroxide ion supply treatment, a drying treatment for drying the surface of the steel material is performed. By performing the drying treatment, iron rust and FeOOH are fixed to the defective portion in the rust layer by the reaction shown in equation (2). Thereby, the defective part in the rust layer is repaired, and the defective part is reduced.

After the drying treatment, the surface of the steel sheet is preferably cleaned. This is to wash off chlorides and sulfates generated at the same time that iron hydroxide is generated by the reaction between Fe ions and alkali, and to remove iron rust that does not adhere.
After performing the iron ion supply treatment and the hydroxide ion supply treatment on the steel material, the degree of repair of the defective portion in the rust layer is increased by repeating the process of performing the drying treatment a plurality of times instead of once. The blocking of corrosion factors in the rust layer is further improved.

In the present invention, the rust layer previously formed on the surface layer of the steel material may be artificially formed or may be formed by exposure in a corrosive environment. Preferably, the steel sheet is subjected to a treatment in which the surface of the steel sheet is repeatedly wetted with an acidic solution and then dried. The acidic solution is a solution having a pH of 2.5 or more and less than 7, and is preferably an aqueous solution. However, in a strongly acidic solution having a pH of less than 2.5, although the dissolution of the base iron proceeds at a sufficient rate, it is difficult to form a rust layer having high adhesion. As the solution having a pH of 2.5 or more and less than 7, an aqueous solution obtained by diluting sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, or the like with water is preferable because the pH can be easily adjusted. To further increase the corrosion protection of the rust layer, add 0.05% Fe ²⁺ to the solution.
Preferably, the content is up to 2.5 g / l. Although the principle is not clear, Fe ²⁺ has the effect of accelerating corrosion, accelerating the formation of a rust layer, and improving the corrosion resistance of the rust layer. This effect is remarkable at 0.05 g / l or more. However, at more than 2.5 g / l, the corrosiveness is too strong to form an adhesive rust layer.

In order to prepare an Fe ²⁺ -containing solution, one or more iron salts such as iron sulfate, iron chloride, and iron nitrate are added to a predetermined Fe
^It may be dissolved in water so as to have a ²⁺ concentration. 0.05-2.5g / l
As a further third component to Fe ²⁺ containing solution, Fe ^3+, Cu ^2+, Ni
One or more of ²⁺ , Co ²⁺ , Cr ³⁺ , and PO ₄ ^3- may be used in combination. As a result, the rust becomes finer, and a rust layer having better corrosion resistance is formed.

The amount of the liquid for making the surface of the steel material wet is 0.10 to 5 mg / cm ² (0.10 to 5 mg / cm ² per 1 cm ^{2 of the} steel material surface).
5 mg). When the concentration is less than 0.10 mg / cm ² , the progress of the corrosion is slowed down due to a shortage of the liquid, and the control of the liquid amount is substantially difficult, and the liquid tends to evaporate immediately, which tends to cause unevenness. On the other hand, if the liquid amount is more than 5 mg / cm ² , the supply of oxygen to the iron base interface becomes insufficient,
Fe ₃ O ₄ is generated and a weather-resistant rust layer is not easily formed.

In the cycle of repeated wet and dry,
The retention time of the wet state per cycle is preferably 5 to 60 minutes. The number of repetitions of the wet and dry cycles (the number of dry and wet cycles) is 2 or more, preferably 10 or more. By increasing the thickness of the rust layer by increasing the number of dry and wet cycles and treating it 10 times or more, there is an effect of preventing flow rust in an exposed environment. However, even if the number of drying and wet cycles is excessively increased, the anticorrosion property of the rust layer tends to be saturated, which is time-consuming and is not economically preferable.

In the present invention, as the steel material forming the rust layer on the surface layer, any weather-resistant hot-rolled steel material for a welded structure specified in JIS G 3114 can be suitably used. In addition, particularly when used in coastal areas, for example,
C: 0.001 to 0.025%, Si: 0.60% or less, Mn: 0.10 to 3.
00%, P: 0.005 to 0.030%, S: 0.01% or less, Al: 0.
10% or less, Cu: 0.1-1.5%, Ni: 0.1-6.0%, B:
0.0001 to 0.0050%, or Mo: 0.005 to
0.5% and / or Nb: 0.005 to 0.20%, V: 0.00
5 to 0.20%, Ti: 0.005 to 0.20%, REM: 0.02% or less, and contains the following formula (1): (11P + 4.0Cu + 3.1Ni + 2.6Mo) ) / (1−0.1 (10000 B) ^0.35 ) ≧ 1 + 13X (1) (where, P, Cu, Ni, Mo, B: content (% by mass) of each element, X: by gauze method) Measured incoming salt (mg / dm ² / da
y))), a high-shore weather-resistant steel material which satisfies (i)) and comprises the balance of Fe and inevitable impurities is preferred.

According to the present invention, a rust layer having a high anticorrosion property can be formed on the surface of a weather-resistant steel in a short period of time, thereby greatly reducing the generation of flowing rust when unpainted and used, and causing a problem of landscape or environmental pollution. In addition to this, this effect is also exerted in coastal areas where stable rust is hardly formed, and the occurrence of flowing rust of weather-resistant steel is significantly reduced even in areas near the coast.

[0028]

EXAMPLES Two types of steel materials A and B having the compositions shown in Table 1 are shown.
A test piece having a size of 100 × 50 × 10 mm ³ was sampled from the sample, the surface was shot blasted, and then subjected to a test. Steel material A
Is a weather-resistant steel sheet specified in JIS G 3114, and steel material B is a high shore weather-resistant steel sheet having improved shore weather resistance.

First, a test piece (steel material) S was placed in a test tank 1 as shown in FIG. 1, and the following rust accelerating treatment was performed to form a rust layer on the surface of the test piece (steel material) S. The rust acceleration treatment was performed as follows. A plurality of test pieces (steel materials) S are placed in the tank 1 and a spray-type nozzle 4 installed on the upper part of the tank 1 is used to apply a rust-promoting treatment solution to the surface of the test piece (steel materials) S at 4.0 mg / cm
^{2 was} supplied to make the surface of the test piece S wet. The arrangement of the nozzles 4 was set such that the same amount was supplied to each test piece.
The solution for rust accelerating treatment stored in the solution tank 2 was fed to the nozzle 4 by the pump 3. The amount of the solution on the surface of the test piece (steel material) S was adjusted by changing the spray time. After supplying the rust-promoting solution, the inside of the tank 1 was kept in a high-humidity atmosphere (80% or more humidity) using the humidifier 5 to prevent the solution from evaporating and escaping on the surface of the test piece (steel material) S. After keeping this wet state for a predetermined holding time (10 min), air dried by the drying blower 6 was introduced into the tank 1 to forcibly dry the surface of the test piece (steel material) S. Next, the surface of the test piece (steel material) S was washed with a large amount of washing water, and forcedly dried again. This wet (wet state) -dry cycle was repeated a predetermined number of times (100 cycles).

As a solution for rust acceleration treatment, Fe ²⁺ concentration 1.5 g /
l, pH 3.8 (pH adjusted with hydrochloric acid) solution was used. By the above-mentioned process, about 30μm thick on the surface layer of test piece (steel material) S
A rust layer was uniformly formed. In addition, some test pieces were subjected to rust acceleration treatment for comparison. The test piece (steel material) having the rust layer formed on the surface layer by the above-mentioned rust acceleration treatment was subjected to an iron ion supply treatment in the same tank shown in FIG. 1 and then to a hydroxide ion supply treatment. In addition,
Table 2 shows both iron ion supply processing and hydroxide ion supply processing.
Under the conditions shown in (1), an aqueous solution in which the type of iron salt (additive) to be added and the Fe ion concentration were changed was used. For comparison, under some conditions, neither the iron ion supply treatment nor the hydroxide ion supply treatment was performed (condition No. 16).

In the iron ion supply process, the types shown in Table 2
Solution a containing Fe ions at a high concentration is applied to the surface of the test piece (steel).
5 mg / cm ^{2 was} supplied. In the hydroxide ion supply treatment, an alkali solution b having an OH ^- concentration shown in Table 2 was supplied to the surface of the test piece (steel material) at 5 mg / cm ² . After performing these treatments, a drying treatment for drying the surface of the test piece (steel material) by introducing air was performed. In addition, about some samples, the process which consists of iron ion supply processing, hydroxide ion supply processing, and drying processing was repeated several times. Finally, the surface of the test piece (steel material) was washed with a large amount of water and dried again to complete the treatment.

After the treatment, the test piece (steel material) was taken out of the tank, and the steel material A was exposed for 3 months in the countryside and the coastal zone, and the steel material B was exposed for 3 months in the coastal zone, and the generation of flowing rust was examined. The occurrence of flow rust is indicated by the test piece (steel)
The rainwater flowing on the surface was collected in a polyethylene bottle and collected every month, and the amount of rust and iron ions in the solution were quantified,
The total amount of iron effluent (mg) for the three months was totaled to evaluate the occurrence of flow rust.

Table 2 shows the results.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

Hereinafter, steel materials A and B treated under the condition No. i
Are referred to as test Nos. Ai and No. Bi. Test No.
A15 and No. B15 were subjected to an exposure test with the rust accelerating treatment performed for comparison. No. A16, No.
B16 is the one subjected to an exposure test without any rust accelerating treatment without any treatment (bare exposed material). No. A16 generated much flow rust in the countryside and even more in the coastal area. In No. B16, the flow rust in the coastal area was reduced compared to No. A16, but it was generated to the same extent as in No. A16 in the rural area. On the other hand, No. A15, N
o. For B15, the amount of run-through rust is reduced compared to bare exposed materials (No. A16, No. B16).

Test No. A1 to No. A5, No. B1 to No.
B5 is an example of the present invention in which iron ion supply treatment was performed using a solution containing iron ions using iron (II) chloride as an additive. Since the concentration of the solution containing iron ions and the concentration of the alkaline solution are appropriate, the amount of flowing rust is lower than that of No. A15 and No. B15 which have only been subjected to the rust accelerating treatment.
No. A11, No. A12, No. B11, and No. B12 are obtained by repeating the process of the present invention a plurality of times, and further have an effect of reducing flowing rust.

Test No. A13, No. A14, No. B13, No.
B14 is an example of the present invention in which iron ion supply treatment was performed using a solution containing iron ions using iron (II) sulfate as an additive. In all of these, flowing rust is reduced because the processing conditions are appropriate. On the other hand, Test Nos. A6 to No. A, which were treated under the condition that the Fe ion concentration was out of the range of the present invention, were used.
8, No. B6 to No. B8, and No. A treated with an alkaline solution having an OH ^- concentration outside the range of the present invention.
No. 9, No. A10, No. B9 and No. B10 did not have the effect of reducing the flowing rust as compared with No. A15 and No. B15 which are the comparative examples using only the rust accelerating treatment.

Test No. A17 to No. A22, No. B17 to No.
B22 is an example of the present invention in which iron ion supply treatment was performed using a solution containing iron ions using iron (III) chloride as an additive. Since the concentration of the solution containing iron ions and the concentration of the alkaline solution were appropriate within the range of the present invention, the amount of flowing rust was lower than that of No. A15 and No. Has been reduced. No. A28, No. A29, N
o. B28 and No. B29 are obtained by repeating the process of the present invention a plurality of times, and further have an effect of reducing flowing rust.

Test No. A30 to No. A32, No. B30 to No.
B32 is an example of the present invention in which iron ion supply treatment was performed using a solution containing iron ions using iron (III) sulfate as an additive. In all of these, flowing rust is reduced because the processing conditions are appropriate. On the other hand, Test Nos. A23 to A2, which were treated under the condition that the Fe ion concentration was out of the range of the present invention, were used.
5, No. B23 to No. B25, and No. A2 treated with an alkaline solution having an OH ^- concentration outside the range of the present invention.
6, No. A27, No. B26, and No. B27 did not have the effect of reducing the flowing rust as compared with No. A15 and No. B15, which are comparative examples using only the rust accelerating treatment.

Test No. A33 to No. A38, No. B33 to No.
B38 is an example of the present invention in which an iron ion supply treatment was performed using a solution containing iron ions using both iron (II) chloride and iron (III) chloride as additives. These are all Fe ion concentration and OH ^-. Since the concentration is appropriate, the amount of flow rust as compared to No. A15, No B15 is a comparative example of a rust-promoting treatment only is reduced. No. A43, No. A44, No. B43, N
o. B44 is obtained by repeating the process of the present invention a plurality of times, and has an effect of reducing flow rust.

Test Nos. A45 and B45 are examples of the present invention in which iron ion supply treatment was performed using a solution containing iron ions using iron (II) sulfate and iron (III) chloride as additives. No. A46, No. A47, No. B46 and No. B47 use iron (II) sulfate and iron (III) chloride as additives. In all of these, flowing rust is reduced because the processing conditions are appropriate.

On the other hand, No. A39, No. A40, No. B39, No. B40 whose Fe ion concentration is out of the range of the present invention, and No. A41 and No. A4 whose OH ^- concentration is out of the range of the present invention. A
No. 42, No. B41 and No. B42 did not have the effect of reducing the flowing rust as compared with No. A15 and No. B15 which were the comparative examples only with the rust accelerating treatment.

[0046]

According to the present invention, it is possible to form a corrosion-resistant rust layer on the surface of a steel material such as a weather-resistant steel material or a high shore weather-resistant steel material used without painting in a rural area or a coastal area in a short time. It is possible to improve the productivity of weather-resistant steel materials that can reduce the occurrence of flow rust when unpainted is used, and achieve a remarkable industrial effect. In addition, the generation of run-off rust can be reduced,
Excellent effect can be expected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a test apparatus suitable for carrying out the present invention.

[Explanation of symbols]

 Reference Signs List 1 tank 2 solution tank 3 pump 4 nozzle 5 humidifier 6 drying blower S test piece (steel material)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Akio Omori 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Kawasaki Steel Corporation Mizushima Works (72) Inventor Kenichi Amano 1-chome (without address) Mizushima Kawasaki-dori Kurashiki-shi, Okayama Prefecture Kawasaki Steel Corporation Mizushima Works (72) Inventor Uki Kogyo 1F Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in the Technical Research Institute, Kawasaki Steel Co., Ltd. 4K026 AA02 BA08 BB08 BB10 CA13 CA16 CA32 CA33 CA34 CA36 DA06 DA11 DA15 EA06 EA10

Claims (3)

[Claims] 1. A steel material having a rust layer formed on its surface is coated with Fe
Iron ion supply processing for supplying a solution containing ions in an amount of 0.010 to 2.0 mol / l, and hydroxide ion supply for supplying an alkaline solution having an OH ^- concentration equal to or higher than the Fe ion concentration of the solution to the surface of the steel material And performing a drying process of drying the surface of the steel material after the heat treatment. 2. The method according to claim 1, wherein the step is repeated a plurality of times. 3. The steel sheet according to claim 3, wherein the rust layer has a pH of 2.5 or more on the steel surface.
The method for producing a weather-resistant steel material according to claim 1 or 2, characterized by being formed by repeating a process of wetting with a solution of less than 0 and 0.15 to 5 mg / cm ² and then drying.