JP2001226778A - Rust stabilizing treating method for steel, steel subjected to same rust stabilizing treatment and steel structure constructed by same steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rust stabilizing treating method for steel by which flowing rust is prevented in a region high in the content of flied salt, also, the permeation of corrosive anions, e.g. of flied salt is suppressed, and stable rest can efficiently be formed without damaging its appearance, to provide steel subjected to the same rust stabilizing treatment and to provide a steel structure constructed by the same steel. SOLUTION: The surface of weather resistant steel in which Cr is not substantially contained, and also, Ni is added is coated with a rust stabilizing treating agent containing tervalent chromium ions and resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stabilizing rust of steel used in an area having a high amount of flying salt, such as a coastal zone. More specifically, in areas where the amount of flying salt is high, rust having high anticorrosion performance on the surface of weathering steel, that is, stable rust is efficiently formed, and furthermore, the steel material which does not impair the appearance due to flowing rust in the stable rust forming process. The present invention relates to a rust stabilization treatment method, a steel material subjected to the rust stabilization treatment, and a steel structure constructed from the steel material.

[0002]

2. Description of the Related Art Weathering steels are made of Cu, Ni, Cr, P, M.
When it is a low alloy steel containing elements such as o and is exposed to the atmosphere without painting, rust excellent in anticorrosion properties, that is, stable rust is naturally formed in the process of corroding and rusting. After the stable rust is formed, the corrosion of the steel material hardly progresses. Unlike weathering steel, weather-resistant steel does not require repair and is maintenance-free, so it is applied to various steels such as shaped steel, steel plates, steel pipes, etc., and has a wide range of uses as structures such as bridges and steel towers.

However, in areas where the amount of incoming salt is large, such as coastal areas and areas where salt is melted, stable rust is unlikely to be formed on the weather-resistant steel. Therefore, the area where the weather-resistant steel can be applied is an area where the amount of incoming salt is low. Has been restricted to.

In order to solve this problem, weather-resistant steels containing Ni as a main additive element and having sufficient corrosion resistance without coating even in an environment where the amount of flying salt is large are disclosed in JP-A-9-165647 and JP-A-3-158436. Etc.

[0005]

However, even in the case of weather-resistant steel containing Ni as a main additive element, it takes a long period of five years or more before stable rust is formed. During the period until stable rust is formed, in particular, flowing rust and floating rust in the early stage of use, the appearance of steel materials and structures may be lost, and furthermore, there may be a problem of surrounding environmental pollution.

Accordingly, an object of the present invention is to provide an area having a high amount of incoming salt (specifically, an amount of incoming salt ≧ 0.05 mdd).
(Mdd = 1 mg / dm ² / day)), it is possible to efficiently form stable rust without impairing the appearance by preventing flow rust and suppressing permeation of corrosive anions such as flying salt. Another object of the present invention is to provide a rust stabilization method for a steel material, a steel material subjected to the rust stabilization process, and a steel structure constructed from the steel material.

[0007]

According to the first aspect of the present invention,
The present invention is characterized in that a rust stabilizing agent containing trivalent chromium ions and a resin is applied to the surface of a weather-resistant steel material which does not substantially contain Cr and to which Ni is added.

According to a second aspect of the present invention, the amount of the trivalent chromium ion applied to the weathering steel is 1 to 200 μm.
ol / cm ² .

A third aspect of the present invention is characterized in that the resin contains at least one salt composed of an anion having a trapping and depositing action on iron ions and a counter cation. is there.

The invention according to claim 4 is characterized in that it comprises a resin having a negative fixed charge.

The invention according to claim 5 is characterized in that the surface of the weather-resistant steel material which does not substantially contain Cr and to which Ni is added,
It is characterized in that a first treatment agent containing trivalent chromium ions is applied, and then a second treatment agent containing a resin is applied.

According to a sixth aspect of the present invention, the amount of the trivalent chromium ion of the first treating agent applied to the steel material is 1 to 20.
It is characterized by being within the range of 0 μmol / cm ² .

According to a seventh aspect of the present invention, the resin of the second treatment agent contains at least one salt composed of an anion having a trapping and depositing action on iron ions and a counter cation. It has features.

The invention according to claim 8 is characterized in that the resin of the second treatment agent contains a resin having a negative fixed charge.

A ninth aspect of the present invention is characterized in that the addition amount of Ni is in a range of 0.4 to 5.0% by mass.

According to a tenth aspect of the present invention, there is provided a steel material which has been subjected to a rust stabilizing treatment by any one of the first to ninth aspects.

The invention according to claim 11 is the invention according to claim 10.
The present invention has a feature in a steel structure constructed from the described steel material.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for stabilizing rust of steel according to the present invention will be described.

(Steel) In the present invention, the range of Ni and Cr is particularly important from the viewpoint of weather resistance in a region where the amount of flying salt is high, among the combined elements of the base steel. The other elements are not particularly limited. The treated surface is preferably in a state where scale and rust on the surface have been removed by blasting or the like, but this is not always necessary.

Ni Ni has the effect of forming rust with excellent anticorrosion properties in an environment where the amount of flying salt is large. Add the necessary amount for that. However, if the Ni content is less than 0.4% by mass,
The effects described above are not exhibited. On the other hand, when the amount of Ni added is 5.
If it exceeds 0% by mass, it is disadvantageous in terms of economy, and
A bainite structure is likely to occur, and mechanical properties, especially,
The toughness deteriorates. Therefore, the amount of Ni added is 0.4 to 5.
It is preferable that the content be limited to the range of 0% by mass.

Cr Cr is an element that promotes the occurrence of perforated corrosion in an environment where the amount of flying salt is large. In the case of perforated corrosion, corrosive anions such as chloride ions are concentrated to inhibit the generation of stable rust. In addition, the amount of flow rust increases due to perforated corrosion.
Therefore, Cr was not substantially contained in the steel material. Here, substantially not containing means that 0.1% by mass or less may be contained.

(Rust stabilizing agent) In the present invention, the rust stabilizing agent is a treating agent having a function of stabilizing the rust of the underlying steel material by being applied to the surface of the steel material. Contains a trivalent chromium ion and a resin. By containing the trivalent chromium ion and the resin, the functions required for the rust stabilizing agent such as the flow rust prevention function and the corrosive anion permeation suppression function can be maintained for a long time.

In addition to the above-described one-layer coating rust stabilizing agent, a two-layer coating comprising a first processing agent having trivalent chromium ions and a second processing agent containing a resin. It is also possible to use a treating agent.

Hereinafter, the composition of the treating agent in the case of one-layer coating will be described.

Resin The resin used here is a liquid in the state of a processing liquid,
By drying after the treatment, any type can be used as long as it can form a film, for example, epoxy resin, phenol resin, polyester resin, acrylic resin, polyurethane resin, fluorine resin, butyral resin,
Resins used as general coating resins, such as vinyl resins and alkyd resins, are preferred. Further, the rust stabilizing agent of the present invention may contain a solvent, water, a pigment, various additives, and the like, in addition to the resin.

Trivalent Chromium Ions Trivalent chromium ions have the effect of penetrating rust defects and pores and densifying rust to form stable rust. Such a trivalent chromium ion is added by dissolving a salt composed of a trivalent chromium ion and a counter anion, and examples thereof include chromium acetate, chromium formate, chromium hydroxide, chromium nitrate, chromium phosphate, and chromium sulfate. However, the present invention is not limited to these. In order to contribute to the densification of rust, 3
The amount of chromium ions applied is the steel material unit area (cm ² )
Per μmol / cm ² or more. on the other hand,
The amount of trivalent chromium ion applied is steel unit area (cm ² )
Even if the amount exceeds 200 μmol / m, the effect is saturated. Therefore, the coating amount of trivalent chromium ions is 1 to 20.
It was limited to the range of 0 μmol / cm ² .

Salt In the present invention, the salt comprising an anion having a trapping and depositing action on iron ions contained in the cured film and a counter cation reacts with iron ions generated by a corrosion reaction,
A salt consisting of an anion and a counter cation that can form a deposited film under certain conditions.

Examples of such anions include phosphate ion, chromate ion, beryllate ion, silicate ion, titanate ion, vanadate ion, manganate ion, selenate ion, zirconate ion, molybdate ion, Tungstate ions and the like.

Among these, a cured film in which a salt having phosphate ions and / or molybdate ions as anions is combined effectively prevents deterioration in appearance due to flowing rust and the like in the rust stabilization process, and This is preferable because stable rust can be efficiently generated under the coating film.

Specific examples include zinc phosphate, aluminum phosphate, ammonium phosphate, calcium monohydrogen phosphate, cadmium phosphate, potassium phosphate, calcium phosphate, silver phosphate, chromium phosphate, cobalt phosphate,
Mercury phosphate, sodium ammonium hydrogen phosphate, uranyl hydrogen phosphate, strontium hydrogen phosphate, diammonium hydrogen phosphate, dipotassium hydrogen phosphate, disilver hydrogen phosphate, disodium hydrogen phosphate, barium hydrogen phosphate,
Magnesium hydrogen phosphate, manganese hydrogen phosphate, cerium phosphate, thallium phosphate, iron phosphate, copper phosphate, thorium phosphate, sodium phosphate, lead phosphate, zinc dihydrogen phosphate, cadmium dihydrogen phosphate, Ammonium dihydrogen phosphate, potassium dihydrogen phosphate, calcium dihydrogen phosphate, sodium dihydrogen phosphate, barium dihydrogen phosphate,
Manganese dihydrogen phosphate, lithium dihydrogen phosphate, nickel phosphate, barium phosphate, bismuth phosphate, magnesium phosphate, magnesium ammonium phosphate, manganese phosphate, lithium phosphate, sodium phosphotungstate, sodium phosphomolybdate , Aluminum phosphomolybdate, ammonium phosphomolybdate, aluminum dihydrogen tripolyphosphate, sodium molybdate, zinc molybdate, ammonium molybdate, potassium molybdate, calcium molybdate, lead molybdate and the like.

In addition to these, other salts capable of capturing and depositing iron ions, such as chromate, vanadate and tungstate, may be added.

The concentration of the salt is preferably 1 to 10 parts by mass based on 100 parts by mass of the solid content of the treating agent. The reason is that if it is less than 1 part by mass, the effect of preventing flow rust is insufficient, while if it exceeds 10 parts by mass, the strength of the film is lowered and the appearance is rather deteriorated.

Resin having a negative fixed charge The resin having a negative fixed charge in the present invention is:
Resin, pigments and other actions, refers to the resin negative fixed charge in the rust stabilizing agent, specifically as a functional group in the molecule of the resin component in the rust stabilizing agent,
It is a resin having a carboxyl group, a sulfone group, a phosphoric acid group, a phenolic hydroxyl group and the like.

When the resin has a negative fixed charge, permeation of corrosive anions such as flying salt to the surface of the steel material is suppressed, and stable rust can be efficiently formed without impairing the appearance.

As long as it is a resin having these functional groups and capable of forming a cured film of a rust stabilizing agent, any type of base resin can be used. Examples of the base resin include epoxy resin and phenol. Resin, polyester resin, acrylic resin, polyurethane resin, fluororesin, butyral resin, vinyl resin, alkyd resin, polysulfone humic acid, tannic acid, cation exchange resin, etc. Obtained by using

Among them, particularly, an acid value of 10 having a free anionic functional group such as a carboxyl group and a sulfone group.
A treating agent containing a resin of from 100 to 100 is preferable because it has good resistance to flying salt. Here, the reason why the acid value is limited to the range of 10 to 100 is that if the acid value is less than 10, the flying salt resistance is poor, while if the acid value exceeds 100, the stable rust forming performance is poor. is there.

The content of the resin having a free anionic functional group based on 100 parts by mass of the solid content in the rust stabilizing agent is determined from the viewpoint of the balance between the strength of the coating film and the function of maintaining the appearance during the deterioration process of the coating film. 20 to 50 parts by mass are preferred. As the type of the resin having a free anionic functional group, a reaction product of a fatty acid-modified epoxy resin and a carboxylic anhydride is preferable because it is most excellent in appearance retention performance and stable rust forming function.

Next, the case of two-layer coating will be described.

The rust stabilizing agent of the first layer is an aqueous solution or a resin composition containing trivalent chromium ions as an essential component. The type of trivalent chromium ions is the same as that in the case of one-layer coating, and the coating amount is 1 to 200 μmol / cm.
It is within the range of ² .

The rust stabilizing agent of the second layer is a resin composition containing at least one salt composed of an anion having a trapping and depositing action on iron ions and a counter cation. 1 to 10 parts by mass per 100 parts by mass of resin, 2
It is preferably from 0 to 50 parts by mass.

Other preferable conditions such as the composition of the salt and the resin are the same as those in the case of one-layer coating.

(Treatment method) The treatment can be performed by a known coating method, that is, air spray, airless spray, brush coating, or the like, and the treatment method is not particularly limited. Also, in particular, since processing such as heating and baking is unnecessary,
Both factory construction and on-site construction are available.

(Effect of Combination of Steel and Rust Stabilizing Agent) Both Ni and Cr have an effect of densifying rust and improving rust corrosion prevention performance. The rate at which these elements concentrate in the rust layer is different, and Cr
i thickens over time. For this reason, it is possible to stabilize rust early by supplying Cr from the rust stabilizing agent. Further, as described above, when Cr is contained in a steel material, it promotes the occurrence of perforated corrosion and increases the amount of flowing rust. From this point, it is desirable that Cr is supplied from a rust stabilizing agent.

On the other hand, when Ni is supplied from the treating agent, the effect is reduced due to weathering of the rust stabilizing agent before the Ni is concentrated in the steel. Therefore, it is preferable that Ni is added to the steel material and is slowly concentrated in the steel.

From the above, a dense rust layer in which Cr and Ni are concentrated can be obtained by a combination of applying a Ni-free and Cr-added rust stabilizing agent to a Ni-added and Cr-free steel material. It is possible to form a rust layer excellent in anticorrosion performance by this.

Another function of the rust stabilizing agent is to prevent the occurrence of flowing rust due to the above-described trapping and depositing action on iron ions and to suppress the permeation of corrosive anions by negative fixed charges. When elaborate,
Anions in the rust stabilizing agent are also adsorbed in the rust particles. This anion is considered to concentrate particularly at the corrosion active site at the interface between the rust and the steel material, and to block the chloride ion from reaching the corrosion active site by an electrical reaction.

However, once perforated corrosion occurs on the steel material surface, the supply of anions cannot catch up,
This allows the chloride ions to enter the perforated corrosion zone. In other words, when perforated corrosion occurs in the steel material, the effect of the rust stabilizing agent is reduced. In order to prevent this, it is necessary to use a steel material excellent in perforation corrosion resistance. As in the present invention, by combining a steel material substantially free of Cr with the above-mentioned rust stabilizing agent. For the first time, it is possible to form a rust layer having excellent anticorrosion performance.

As described above, according to the present invention, a steel material having excellent corrosion resistance to pitting is used, densification of rust by trivalent chromium ions, and prevention of generation of flow rust by capture and deposition of iron ions. By applying a rust stabilizing agent that also suppresses permeation of corrosive anions by negative fixed charges, it is possible to efficiently form stable rust that does not impair the appearance even in an environment with a flying salt content of 0.05 mdd or more. Can be.

[0049]

Next, the present invention will be further described with reference to examples.

First, a steel material having a chemical composition as shown in Table 1 was prepared. In Table 1, A is a steel material of an example of the present invention, and B, C, and D are comparative steel materials. Each steel material was cut into a size of 150 mm × 70 mm × 6 mm, and the surface was shot blasted.

[0051]

[Table 1]

The steel materials A, B, C,
D was coated with a single-layer or two-layer rust stabilizing agent shown in Tables 2 and 3 to a predetermined thickness, and dried to obtain various rust-stabilized steel materials. The trivalent chromium ion is 3
Chromium sulfate. Tables 2 and 3 show the evaluation results of these rust stabilizing steels.

[0053]

[Table 2]

[0054]

[Table 3]

A resin having a carboxyl group is blended with the base resin, and a reaction product of a castor oil-modified epoxy resin and a hexahydrophthalic acid is used. The acid ratio was adjusted by variously changing the ratio. As the color pigment, a mixture of red iron oxide and iron black at a weight ratio of 1: 3 was used.

As a component other than those described in Tables 2 and 3, cobalt naphthenate was used as a hardening accelerator in an amount of 0.1%.
1 part by mass, 0.1 part by mass of lead naphthenate, and other additives for adjusting physical properties as a rust stabilizing agent were appropriately added. The parts by mass in Tables 2 and 3 are parts by mass in the cured coating film.

Then, the flow rust resistance and the quality of rust stabilization formation of the weathering steel coated with the rust stabilizing agent shown in Tables 2 and 3 were evaluated by the following methods. (1) Exposure to coastal areas (3 years, exposure to 30 ° on the south side, average flying salt during the exposure period is about 0.4 mdd). (2) Presence or absence of flowing rust by accelerated test (salt spray test specified in JIS K-5400, one month).

The evaluation criteria were as follows.

Flowing rust: A white paint was applied to the lower end of the sample, and the contamination of the white paint by the flowing rust was evaluated as follows.
It was evaluated on a scale.

A: No contamination is observed.

：: Almost no contamination was observed.

Δ: Some contamination is observed.

X: Contamination is remarkably observed.

Stable rust formation: The coating film was peeled off, and the state of rust under the coating film was examined.

A: The rust is dense, has few defects, and is formed continuously.

○: The rust is dense, but partly defective and discontinuous.

Δ: Rust formation is not uniform, and powdery rust is easily formed.

×: Layered rust that easily peels off is formed.

Coating Peelability: Ferroxil test and Cellotape (registered trademark) peel test were performed on rust under the coating film.

The ferroxyl test evaluates the stability of rust. A filter paper immersed in a test solution (a mixed aqueous solution of potassium ferrocyanide, potassium ferricyanide, and sodium chloride) is stuck on the test surface to determine the corrosion active point. hand,
It examines blue spots appearing on filter paper. The number density of spots was counted and evaluated according to the following four grades.

A: The number of coloring points is less than 50 / dm ² .

：: The number of coloring points is 50 / dm ² or more and 100
Pcs / dm ² .

Δ: The number of coloring points is 100 / dm ² or more and 20
It is less than 0 pieces / dm ² .

×: The number of coloring points is 200 / dm ² or more.

The cellophane tape peeling test evaluates the amount of floating rust. The cellophane tape is adhered to the rust surface (test area is 2500 mm ² ), peeled off, and the number density and size of rust particles attached to the cellophane tape are examined. It is. The same location was repeated three times, and the total amount of floating rust was evaluated on the following three levels.

○: The amount of floating rust is less than 10 mg.

Δ: The amount of floating rust is 10 mg or more and less than 50 mg.

×: The amount of floating rust is 50 mg or more.

Table 2 also shows the results of these evaluations.

As is clear from Table 2, the invention example has a good appearance maintaining function and a stable rust forming function in an environment with a large amount of salt, and is also excellent in an accelerated test simulating a severe environment. Rust prevention function. In particular, it was confirmed that trivalent chromium ions densified rust early. Regarding the base steel material, it was confirmed that the rust was densified and the flow rust was reduced by adding Ni, and the rust was continuously formed by lowering the Cr content. In addition, with regard to the rust stabilizing agent, it was confirmed that flowing rust was reduced by anions having a trapping action of iron ions, and continuous formation of rust was caused by a resin having a negative fixed charge.

Further, by combining the steel material of the present invention and the rust stabilizing agent, an effect of improving the peelability of the coating film was obtained. This is presumed to be due to the following mechanism. (1) Pitting corrosion occurs in Cr-added steel, and as a result, locally large rust portions are formed. (2) Local rust thickness growth presses the coating film, and as a result,
Peeling occurs in the coating film. (3) Even if Cr is not added, if Ni is not added, densification of the rust is insufficient, so that the rust layer becomes thick and the irregularities become large, resulting in uneven appearance.

According to the coastal area exposure test of Invention Example 11,
Although it does not contain a salt having a Fe ²⁺ trapping function, permeation of chloride ions is suppressed by the anionic functional group of the resin,
Further, it was found that since the steel material was within the scope of the present invention and the concentration of trivalent chromium ions was high, the densification of rust was promoted and the flow rust resistance was excellent. In addition, since the steel material had sufficient weather resistance and a high trivalent chromium ion concentration, it was excellent in stable rust formation. In the accelerated test of Invention Example 11, the poor flow rust resistance was due to the absence of a salt having a Fe ²⁺ trapping function.

According to the coastal zone exposure test of Invention Example 12,
Since it contains a salt having an Fe ²⁺ trapping function, it has excellent flow rust resistance. In addition, since the steel material was within the scope of the present invention and the concentration of trivalent chromium ions was high, it was excellent in stable rust formation. In the accelerated test of Inventive Example 12, the inferior in flow rust resistance is that it does not contain an anionic functional group, so the amount of chloride ion penetration increases and the amount of corrosion increases. As a result, the salt Fe ^{2 + Because} it exceeded the limit of the capture function.

According to the coastal zone exposure test of Comparative Example 13,
Although the resin is within the scope of the present invention, since it does not contain trivalent chromium ions, the flow rust resistance was inferior to the invention examples. In addition, since trivalent chromium ions were not included, a discontinuous portion was partially formed in the rust layer, and stable rust formation was inferior to that of the invention. Comparative Example 1
According to the accelerated test of No. 3, the salt and the resin are within the scope of the present invention, but because they do not contain trivalent chromium ions, the densification of rust is not promoted and the flow rust resistance is poor. Was.

According to the coastal zone exposure test of Comparative Example 14,
Although the salt and the resin were within the scope of the present invention, they did not contain trivalent chromium ions, so that the flow rust resistance was inferior to that of the invention. In addition, since trivalent chromium ions are not contained, a discontinuous portion is partially generated in the rust layer,
The stable rust formation was inferior to the invention examples. According to the accelerated test of Comparative Example 14, the salt and the resin are within the scope of the present invention, but since trivalent chromium ions are not contained, the densification of rust is not promoted, The sex was inferior.

According to the coastal zone exposure test of Comparative Example 15,
Although the steel material is within the scope of the present invention and the concentration of trivalent chromium ions is high, since the rust stabilizing agent does not contain both salts and anionic functional groups, the flow rust resistance is inferior to the invention examples. I was However, since the steel material was within the scope of the present invention and the concentration of trivalent chromium ions was high, it was excellent in stable rust formation. Further, according to the accelerated test of Comparative Example 15, since neither the salt having the Fe ²⁺ trapping function nor the anionic functional group was contained, the flow rust resistance was poor.

According to the coastal zone exposure test of Comparative Example 16,
Salts and resins are within the scope of this invention, but the C
Because of the high r content, the flow rust resistance was inferior to the invention examples. Moreover, since the steel material has a high Cr content, stable rust formation was inferior to that of the invention. Comparative Example 1
According to the accelerated test No. 6, the salt and the resin were within the scope of the present invention, but were inferior in flow rust resistance because the steel material had a large Cr content.

According to the coastal zone exposure test of Comparative Example 17,
Salts and resins are within the scope of this invention, but the C
Since the r content was large, the flow rust resistance was poor. In addition, since the steel material has a high Cr content and a low trivalent chromium ion concentration, stable rust formation was inferior to the invention examples. According to the accelerated test of Comparative Example 17, the resin was within the range of the present invention, but was inferior in flow rust resistance because the steel material had a large Cr content.

According to the coastal zone exposure test of Comparative Example 18,
Since neither a salt having an Fe ²⁺ trapping function nor an anionic functional group was contained, the rust resistance was poor. Moreover, C of steel material
Since the r content was large, the flow rust resistance was poor. Also,
According to the accelerated test of Comparative Example 18, since neither the salt having the Fe ²⁺ trapping function nor the anionic functional group was contained, the flow rust resistance was poor.

According to the coastal zone exposure test of Comparative Example 19,
Although the rust stabilizing agent is within the scope of the present invention, the steel material has a low Ni content and a high Cr content, so that the flow rust resistance was inferior to the invention examples. Moreover, since the Ni content of the steel material is low and the Cr content is high,
Poor stable rust formation. Further, according to the accelerated test of Comparative Example 19, the Ni content of the steel material was low and the Cr content was high, so that the corrosion amount increased, and the steel exceeded the Fe ²⁺ trapping function of the salt. It was inferior in rust property.

According to the coastal zone exposure test of Comparative Example 20,
Although the rust stabilizing agent is within the scope of the present invention, the flow rust resistance was inferior to that of the inventive example because the Ni content of the steel material was small. Moreover, since the Ni content of the steel material was small, the formation of stable rust was inferior. Further, according to the accelerated test of Comparative Example 20, since the Ni content of the steel material was small, the corrosion amount increased, exceeding the limit of the Fe ²⁺ trapping function of the salt, and the flow rust resistance was poor. .

In each of Comparative Examples 13 to 20, the peelability of the coating film was inferior to that of the inventive examples. This is because the combination of the steel material and the treatment agent and the composition of the treatment agent are out of the range of the present invention, so that the local peeling of the coating film due to the occurrence of pitting corrosion in the steel material or the densification of the rust layer is insufficient. This is because peeling of the coating film occurred due to the following.

As is clear from Table 3, the same result was obtained in the case of the two-layer coating as in the case of the one-layer coating.

That is, all of the invention examples showed good results in both the flow rust resistance and the stable rust formation, and the coating film peelability was also excellent. On the other hand, in Comparative Example 1, 3
Since no chromium ions having a high valency were contained, both the flow rust resistance and the peelability of the coating film were inferior to those of the invention examples. In Comparative Examples 2 and 3, since the composition of the steel material was out of the range of the present invention, none of the characteristics was sufficient.

[0095]

As described above, the rust-stabilized steel material according to the present invention has both a flow rust prevention performance and an efficient stable rust formation performance in an environment with a large amount of flying salt.
It was found that even in a very severe accelerated test, it had sufficient flow rust prevention performance. By using the rust-stabilized steel material of the present invention for steel structures, it is possible to maintain a good appearance and maintain maintenance-free steel structures even in an environment with a large amount of flying salt, and to replace the conventional paint. Useful effects are brought about, such as eliminating the need for such expenses.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shigeru Takano 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. (reference) 4K026 AA02 BA03 BA06 BB08 CA19 CA23 CA24 CA29 CA30 CA31 CA32 CA33 CA39 DA02

Claims (11)

[Claims] A rust stabilizing agent containing trivalent chromium ions and a resin is applied to the surface of a weather-resistant steel material substantially free of Cr and to which Ni is added. , Steel material rust stabilization treatment method. 2. The rust stabilization of a steel material according to claim 1, wherein the amount of the trivalent chromium ion applied to the weather-resistant steel material is in a range of 1 to 200 μmol / cm ² . Processing method. 3. The resin according to claim 1, wherein the resin contains at least one salt composed of an anion having a trapping and depositing action on iron ions and a counter cation. , Steel material rust stabilization treatment method. 4. The method for stabilizing rust of a steel material according to claim 1, wherein the method comprises a resin containing a resin having a negative fixed charge. 5. A first treatment agent containing trivalent chromium ions is applied to the surface of a weather-resistant steel material substantially free of Cr and to which Ni is added, and then contains a resin. A rust stabilization treatment method for steel materials, which comprises applying a second treatment agent. 6. The steel material according to claim 5, wherein the amount of the trivalent chromium ion of the first treating agent applied to the steel material is in the range of 1 to 200 μmol / cm ² . Rust stabilization treatment method. 7. The resin of the second treating agent comprises one or more salts composed of an anion having a trapping and depositing action on iron ions and a counter cation. 7. The method for stabilizing rust of a steel material according to 5 or 6. 8. The steel material according to claim 5, wherein the resin of the second treatment agent contains a resin having a negative fixed charge. Rust stabilization treatment method. 9. The method according to claim 1, wherein the addition amount of Ni is in a range of 0.4 to 5.0% by mass.
The rust stabilizing method for steel material according to any one of the above. 10. A steel material which has been subjected to a rust stabilization treatment by any one of the above-mentioned methods. 11. A steel structure constructed from the steel material according to claim 10.