JP3336942B2 - Rust stabilization surface treatment method for steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for promoting the formation of stable rust on steel in the anticorrosion surface treatment of steel used for bridges, steel towers, buildings, marine structures and the like. With the addition of alloy elements such as Mo, mainly so-called weather-resistant steel, when steel is used without painting, the weather-resistant stable rust layer having an anticorrosive protective action on the surface of the steel is promptly promoted and generated, The present invention relates to a rust stabilizing surface treatment method for a steel material, which does not involve a stable rust forming process and loss of aesthetic appearance after the formation.

[0002]

2. Description of the Related Art Steel materials used for bridges, steel towers, buildings, marine structures, etc., as they are, cause red rust, yellow-brown floating rust, flow rust due to corrosion, and not only impair the scenery, but also cause the wall thickness due to corrosion. Since the decrease causes the strength of the structure to decrease, some anticorrosion measures are required. Conventionally, as a method of preventing corrosion of these structures, painting methods are generally used, and heavy-duty anti-corrosion coatings with long-term durability are also known.However, the coating cost is high, the service life is limited, and regular repainting is required. However, there is a problem that the maintenance cost is high because of the necessity.

On the other hand, by adding a small amount of an element such as P, Cu, Cr, or Ni to steel, rust (stable rust) having a protective property against corrosion is formed in the air in several years. Weather-resistant steel is known as a steel material having an extremely low corrosion rate. The weather-resistant steel is a so-called maintenance-free steel that has a permanent anticorrosion effect without being painted after stable rust is formed. In recent years, it has been increasingly used for structures such as bridges and steel towers.

However, since it takes several years for stable rust to be formed, floating rust such as red rust and yellow rust and flowing rust occur during that period, which is not only unfavorable in appearance, but also unfavorable in the surrounding environment. May cause contamination. Further, there is a problem that stable rust is hardly formed in a sea salt particle flying environment and a snow melting salt spraying area in a coastal area, so that an available area is limited.

To solve these problems, for example, Japanese Patent Publication No. 56-33991 discloses a resin layer containing a stable rust component as a lower layer and a resin layer having excellent weather resistance and corrosion resistance as an upper layer. A surface treatment method by two-layer coating is disclosed.

Further, Japanese Patent Publication No. 53-22530 discloses a method for forming stable rust without flowing rust by applying a resin film containing a stable rust forming component. Further, Japanese Patent No. 2,666,673 discloses a steel material coated with an organic resin having a stable rust formation promoting action.

[0007]

However, among the above-mentioned prior arts, the method disclosed in Japanese Patent Publication No. 56-33991 is capable of preventing flow rust, but has a high anticorrosion property, so that the rust generation speed is low and the stability is low. There is a problem that it takes time to form rust. The method disclosed in Japanese Patent Publication No. 53-22530 has a problem in that flow rust is not sufficiently prevented in a highly corrosive environment, particularly in an environment where salt comes in. Patent 26
No. 66673 also has a disadvantage that the ability to form stable rust is inferior in a highly corrosive environment, particularly in an environment where salt comes in. In addition, these publications do not solve the problem of poor appearance such as cracking or peeling of the coating due to deterioration of the resin coating in the process of forming stable rust.

The present invention has been made in order to solve the above-mentioned problems. In particular, even in a highly corrosive environment, the surface of weather-resistant steel, ordinary steel, or the like or the surface of the rust layer thereof has red rust or the like. The present invention provides a rust-stabilizing surface treatment method for steel materials that forms stable rust early without causing floating rust or flowing rust, and does not impair the appearance of the stable rust during and after the formation process. .

[0009]

Means for Solving the Problems (1) On the surface of a steel material or the surface of a rust layer of a steel material, 2-50% of a resin having a chelate-forming group as a solid content is added, and Cu, Ni, Cr, Al,
At least one compound selected from Mo and P compounds is coated with 0.02 to 10% by weight in terms of metal, and a treating agent containing a pigment and a coating agent in a dry film thickness of 1 to 100 μm. Rust stabilizing surface treatment method.

(2) At least one of molybdic acid or molybdate is added to the surface of the steel material or the surface of the rust layer of the steel material.
0.01-5% by weight in terms of o, phosphoric acid or phosphate,
0.01-5% by weight of one or more polyphosphates in terms of P
And a resin having a chelate-forming group as a solid content of 2-5.
0% and a treating agent containing a pigment and a paint preparation agent is 1-1.
A rust stabilizing surface treatment method for a steel material applied with a dry film thickness of 00 μm.

(3) Cu, Ni,
(2) The rust stabilizing surface treatment method for steel according to (2), wherein at least one selected from the compounds of Cr and Al contains 0.05 to 5% by weight in terms of metal.

(4) The rust stabilizing surface treatment method for steel according to (1) to (3), wherein the pH of the treating agent is 1-6. (5) The steel material is P: 0.03 to 0.1 by weight%.
5%, Ni: 0.4-4%, Mo: 0.1-1.5%, S: 0.02% or less, Cr: 0.1% or less. ) To (4).

[0013]

Embodiments of the present invention will be described below in detail. (Applicable Steel Materials) In the present invention, applicable steel materials are not particularly limited. Although the effect is also observed for ordinary steel, it is particularly effective for low alloy steel such as weathering steel containing a small amount of elements such as P, Ni, and Mo. The treated surface is preferably in a state where the scale and rust on the surface have been removed by blasting or the like, but this is not always necessary, and the effect can be seen even if the surface of the rust layer is treated.

The reason for adding the components and the reason for limiting the range of addition of the weather-resistant steel suitable as the steel material of the present invention will be described below. P: P is an important element in the present invention, and has an effect of promoting the formation of stable rust and further improving the corrosion resistance of steel after the formation of stable rust. Therefore, the necessary amount is added. If the addition is less than 0.03%, there is no effect on the improvement of the corrosion resistance, and if the addition exceeds 0.15%, the weldability deteriorates. Therefore, the addition is made 0.03 to 0.15%.

S: Since S is an element harmful to corrosion resistance,
0.02% or less. Cr: Cr has an effect of inhibiting the formation of stable rust and promoting perforated corrosion in an environment with a large amount of salt. Therefore, 0.1% or less is added.

Ni: Ni is an essential element in the present invention. Co-existence with Mo promotes the formation of stable rust even in an environment with a large amount of salt, and further improves the corrosion resistance of steel after the formation of stable rust. effective. Addition of less than 0.4% has no effect, but addition of more than 4% is disadvantageous in terms of economy, and also tends to cause a bainite structure and deteriorate mechanical properties, particularly toughness. 0.4 ~
4%.

Mo: Mo is an essential element in the present invention, and promotes the formation of stable rust even in an environment with a large amount of salt due to the coexistence with Ni, and further improves the corrosion resistance of steel after the formation of stable rust. Has the effect of causing Addition of less than 0.1% has no effect, but addition of more than 1.5% is disadvantageous in terms of economy, and tends to form a bainite structure, deteriorating mechanical properties, particularly toughness. So, 0.
1% to 1.5%.

Specific steel materials are exemplified by P, Ni, M
The contents of o, S, and Cr are limited to the above-mentioned ranges. In addition, C: 0.15% or less, Si: 0.7% or less, Mn: 0.2% to 1.5%, Al : 0.01-0.
1%, Cu: 0.2 to 0.4%, and if necessary, Ca: 20 to 100 ppm, Ti: 0.005% to
0.1%, V: 0.005 to 0.1%, Nb: 0.00
A steel material containing one or more selected from 5 to 0.1% and B: 0.0003 to 0.001%, with the balance being Fe and unavoidable impurities. In this steel material, the reason for adding each additive element and the reason for limiting the range of addition are as follows.

C: C is added in order to secure a predetermined strength, but if it exceeds 0.15%, the weldability and toughness deteriorate, so the upper limit is made 0.15%.

Si: Si is added as a deoxidizing agent and a strength improving element at the time of steel making, but if added excessively, the toughness is remarkably reduced.

Mn: Mn is added in an amount of 0.2% or more to secure a predetermined strength. However, if added in excess, a bainite structure is likely to occur, and mechanical properties, particularly toughness, are degraded.

Al: Al is used as a deoxidizing agent in steelmaking at 0.0
Although 1% or more is added, if it is added excessively, inclusions that become corrosion starting points are easily generated.

Cu: Cu has an effect of maintaining rust in a stable state after stable rust is formed.
% Or more. Addition exceeding 0.4% saturates the effect and is disadvantageous in terms of economy, so it is set to 0.4% or less. (Treatment Agent 1) (1) The treatment agent applied to the surface of the steel material or the surface of the rust layer of the steel material includes a resin having a chelate-forming group, Cu, Ni,
It contains compounds of Cr, Al, Mo, and P, a pigment, and a paint conditioner.

(Resin Having Chelate-Forming Group) In the present invention, a resin component having a chelate-forming group in the basic skeleton of the resin is used. It is presumed that the resin having a chelate-forming group according to the present invention fixes and concentrates steel-eluting ions at the interface to form a uniform stable rust layer. Suitable chelating groups include amino acid groups, carboxyl groups, dithiocarbamic acid groups, polyamino groups, thiol groups, thioureido groups,
It is at least one or two or more selected from dithioic acid groups, β-diketone groups, hydroxam oxime groups, and salts thereof.

As specific examples, the resin component having a chelate-forming group in the basic skeleton of the resin includes an iminodiacetic acid group, an amino acid group, an oxime group, an amidoxime group, an oxine group, a glucamine group, an aminophosphate group and a dithiocarbamic acid group. Thiourea groups, β-diketones, polyamines, cryptands, crown ethers and other functional groups and skeletons that can form chelates alone, Schiff bases and hydroxyl groups, azo bonds and hydroxyl groups, azo bonds and carboxylic acids, amines and phosphoric acids,
Amine and thiocarboxylic acid, amine and thiocarbonyl group,
A site capable of forming a chelate by a plurality of functional groups such as a carbonyl group and a hydroxyl group is a styrene-divinylbenzene copolymer, an acrylonitrile-divinylbenzene copolymer, an ethyleneimine polycondensate, a phenol resin, an epoxy resin, a butyral resin, A resin component introduced into a base resin such as a vinyl resin, a urethane resin, a polyester resin, an acrylic resin, and an alkyd resin.

The proportion of the organic resin component having a chelate-forming group to the treating agent is preferably 2 to 50% by weight. If it is less than this range, the effect of preventing flow rust is inferior, and if it exceeds this range, the effect does not change. (Compound of Cu, Ni, Cr, Al, Mo, P)
In the present invention, Cu, Ni, Cr, A
1, one or more compounds of Mo, P
It contains 2 to 10% by weight. This further enhances the effect of promoting stable rust formation. This is presumably because they have an effect of transforming iron ions into stable rust and a fine effect of stable rust particles. Their content is 0.
If the amount is less than 02% by weight, the effect of promoting the formation of a stable rust layer becomes insufficient, and the effect does not change even if added over 10% by weight. The supply form of these metal ions or compounds may be any form as long as it does not form an insoluble salt and does not contain chloride ions that inhibit stable rust formation.

(Pigment, Paint Conditioning Agent) In addition to the above components, it is preferable to add other organic resin components, various pigments, paint conditioners and the like to the treating agent of the present invention. The organic resin component is not particularly limited, but a resin capable of forming a coating film at room temperature is preferable, and specifically, a butyral resin,
Epoxy resin, vinyl resin, urethane resin, polyester resin, acrylic resin, alkyd resin and the like can be applied.
Resins that require effects, molding, fusion, and the like by heating are not preferred in terms of construction.

Examples of various pigments and paint modifiers include dispersants for suppressing sedimentation and separation of solids, thickeners for preventing sagging of coated surfaces, inorganic pigments such as red iron oxide, talc and silica, condensed polycyclic, phthalocyanine An organic pigment such as a system can be appropriately added.

When the above resin is formed into a coating, not only an organic solvent but also a water-based coating such as a water-soluble coating or an emulsion coating may be used as a solvent. (PH of treatment agent) In the present invention, the treatment agent has a pH of 1
It is preferably set to 6 to 6. If the pH exceeds 6, the effect of promoting stable rust is not sufficient, and if the pH is less than 1, the surface of the steel material or the surface of the rust layer of the steel is excessively dissolved to form a stable rust as a layer. What is used for adjusting the pH can be used without any particular limitation as long as it does not generate chlorine ions.
Inorganic acids such as nitric acid and phosphoric acid are preferably used. There is no problem even if alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonia coexist for pH adjustment.

(Thickness of Treated Film) The dry film thickness of the treated film is preferably 1 to 100 μm. If it is less than this range, the effect of preventing chlorine ions and flowing rust is inferior. If it exceeds this range, the protective effect on the underlying steel material becomes excessive, and it takes time to form stable rust.

The treated film of the present invention has a dry film thickness of 1 to 10
By forming a coating having a thickness of 0 μm, the resin having a chelate-forming group fixes and concentrates steel-eluting ions at the interface, forms a uniform stable rust layer, and forms Cu, Ni, Cr, Al, Mo, P
Since the compound and the pH 1-6 increase the rate of stable rust generation, even in a severe corrosive environment such as an environment where sea salt particles fly, almost no flow rust or floating rust is generated, and an extremely excellent appearance is exhibited.

(Treatment method) In the treatment method of the present invention, 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. In addition, since processing such as heating and baking is not particularly required, both factory construction and on-site construction are possible. (Treatment agent 2) (2) The treatment agent applied to the surface of the steel material or the surface of the steel rust layer has molybdate, molybdate, phosphoric acid, phosphate, polyphosphate, and a chelate-forming group. It contains a resin, a compound of Cu, Ni, Cr, and Al, a pigment, and a paint conditioner, which are added as necessary.

(Molybdic acid or molybdate and at least one of phosphoric acid or phosphate and polyphosphate) Molybdic acid or molybdate and at least one of phosphoric acid or phosphate and polyphosphate Addition contributes to uniform stable rust formation. By adding these, it is quite unexpected that stable rust with a remarkably small number of defects is formed at an early stage.However, such an effect is obtained by first using a predetermined acidic solution. Thus, corrosion of the steel material is promoted and iron ions are eluted, but it is presumed that the presence of molybdate and phosphate ions fixes the iron ions and promotes the formation of fine and uniform stable rust.

One or more of molybdic acid and molybdate contains 0.01 to 5% by weight in terms of Mo, and one or more of phosphoric acid, phosphate and polyphosphate contains 0.01 to 5% by weight in terms of P. . If the Mo content is less than 0.01% by weight, the formation of stable rust is not promoted, and the effect does not change even if added over 5% by weight. As the supply form of molybdenum,
It is not particularly limited as long as it is soluble in a solution having a pH of 1 to 6, and examples thereof include sodium molybdate, potassium molybdate, and molybdophosphate.

When the P content is less than 0.01% by weight,
The formation of stable rust is insufficient, and the effect does not change even if it is added in excess of 5% by weight. As a supply form of P, polyphosphoric acid such as orthophosphoric acid, metaphosphoric acid, or pyrophosphoric acid, and salts or phosphates thereof are used.

Further, this treating agent contains a resin having a chelate forming group in a solid content of 2 to 50%, and the balance is composed of a pigment and a paint conditioner, and has a preferable pH of 1 to 6.
About these points, since it is the same as the above-mentioned "the processing agent which consists of the resin which has a chelate forming group, the compound of Cu, Ni, Cr, Al, Mo, and P, and the rest pigment and a paint modifier," Description is omitted.

(Compound of Cu, Ni, Cr, Al) In the present invention, Cu, Ni, C
r, one or more compounds of Al, 0.05 to
By containing 5% by weight, the effect of promoting stable rust generation is further improved. This is presumably because these ions have an effect of transforming iron ions into stable rust and a fine effect of stable rust particles. When their content is less than 0.05% by weight, the effect of promoting the formation of a stable rust layer becomes insufficient, and the effect remains unchanged even when added in an amount exceeding 5% by weight. The supply form of these metal ions or compounds is
Any form may be used as long as it does not form an insoluble salt and does not contain chloride ions that inhibit stable rust formation.

(Thickness of Treated Film) The dry film thickness of the treated film is preferably 1 to 100 μm. If it is less than this range, the effect of preventing chlorine ions and flowing rust is inferior. If it exceeds this range, the protective effect on the underlying steel material becomes excessive, and it takes time to form stable rust.

The treated film of the present invention has a dry film thickness of 1 to 10
By applying 0μm, the resin with chelating group fixes and elutes steel-eluting ions at the interface to form a uniform stable rust layer, and the combination of molybdate and polyphosphate has a dramatic effect. And Cu, Ni, Cr, A
The addition of 1 and pH 1-6 enhances the rate of stable rust generation, so even in severely corrosive environments such as sea salt particle flying environments,
Almost no flowing rust or floating rust is generated, and it has an extremely excellent appearance effect.

[0040]

Next, the present invention will be described based on embodiments. Table 1 shows the chemical components of the test steels used in the examples of the present invention.
In Table 1, A indicates ordinary steel, and B indicates weather-resistant steel. Table 2 shows the base resin, which is a main component of the organic resin paint, and the resin having a chelate-forming group.

The test steel was 150 mm × 70 m.
It is mx 6 mm and the surface is blasted. Tables 3-1 to 3-5 show preparation conditions and test results of each test piece.

The treating agent was applied by brush, and the organic resin coating was applied by airless spray. This test piece was exposed for one year at an exposure test site in Tsu City, Mie Prefecture. The exposure site is about 200m from the coast.

After the exposure for one year, the presence or absence of flowing rust and the state of the coating were confirmed by appearance observation. Further, the number of defects in the rust layer was measured by a ferroxyl test, and the amount of floating rust was measured by a tape peeling test. Tape peel test is 5
Using a tape of 0 mm × 50 mm, the same amount of the peeled floating rust was repeated three times at the same position of the test piece. Further, the remaining treated film and rust were removed by using caustic soda, and the decrease in corrosion weight was measured. It should be noted that the ferro-hexyl test results, less than the color number 100 / dm ² as "○", the 100 / dm ² or more and less than 200 cells / dm ² "△", "×" the 200 / dm ² or more, The tape peeling test results were less than 0.01 g for "O", 0.0
1 g or more and less than 0.05 g were evaluated as “Δ”, and 0.05 g or more as “x”.

In the examples of the present invention, despite the exposure to severe corrosive environments near the coast, according to the ferroxyl test, the defects in the rust layer are small, the corrosion weight loss is small,
In addition, from the result of the tape peeling test, almost no floating rust was observed, so that it was confirmed that stable rust was being formed under the coating, and there was no generation of flowing rust, cracking of the coating, peeling, etc., and it was extremely good. Appearance. In particular, Mo, P
It has been confirmed that the addition of both (corresponding to the invention of claim 2) has particularly excellent effects.

In the treatment method of the present invention, the treatment performed on a weather-resistant steel (No. 20.21) is highly effective.
o.22-23), it was confirmed that a sufficient effect was observed.
On the other hand, as shown in the comparative examples, those having a dry film thickness too thin and out of the range of the present invention (No. 24) have flow rust, have a large amount of corrosion loss, and have good results in the ferroxyl test and the tape test. It can not be said. If it is too thick and is out of the range of the present invention (No. 25), the results of the ferroxyl test and the tape test cannot be said to be good. In addition, those in which Cu, Ni, Cr, Al, etc. were not added (No. 26, No. 30), and those in which the added amount was small and which were out of the range of the present invention (No. 27, No. 30) .28) had run-off rust, a large amount of corrosion loss, and poor results in the ferroxyl test and tape test. The organic resin film containing no resin having a chelate-forming group in the organic resin film (No. 29) shows run-through rust, a large amount of corrosion loss, and the results of the ferroxyl test and the tape test are not satisfactory.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

[Table 5]

[0051]

[Table 6]

[0052]

[Table 7]

[0053]

The treated film of the present invention has a dry film thickness of 1 to 1
By coating with a thickness of 00 μm, even in a severe corrosive environment such as an environment in which sea salt particles fly, almost no flowing rust or floating rust is generated, and an extremely excellent appearance is exhibited.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahito Kaneko 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Ken-ichi Tanaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan (56) References JP-A-62-260866 (JP, A) JP-A-10-1789 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22 / 00-22/86 B05D 7/14 C23F 11/00

Claims (5)

(57) [Claims] Claims: 1. On the surface of a steel material or the surface of a rust layer of a steel material,
2-50% of resin having chelating group as solid content
And at least one selected from compounds of Cu, Ni, Cr, Al, Mo, and P in terms of metal
A rust-stabilizing surface treatment method for steel, wherein a treatment agent containing 0% by weight, a pigment, and a paint preparation agent is applied in a dry film thickness of 1 to 100 μm. 2. The method according to claim 1, wherein the surface of the steel material or the surface of the rust layer of the steel material is
One or more molybdates or molybdates in terms of Mo, 0.01-5% by weight, and one or more types of phosphoric acid or phosphates, polyphosphates, 0.01-5% by weight in terms of P, 2-50% of resin having chelating group as solid content
, A treating agent containing a pigment and a paint preparation agent,
A rust-stabilizing surface treatment method for steel materials, which is applied with a dry film thickness of 0 μm. 3. The treatment agent further comprises Cu, Ni, Cr,
The rust stabilizing surface treatment method for steel according to claim 2, wherein the steel contains at least one selected from Al compounds in an amount of 0.05 to 5% by weight in terms of metal. 4. The rust stabilizing surface treatment method for steel according to claim 1, wherein the pH of the treatment agent is 1-6. 5. The steel material has a P content of 0.03% by weight.
0.15%, Ni: 0.4-4%, Mo: 0.1-1.
5%, S: 0.02% or less, Cr: 0.1
%. The rust stabilizing surface treatment method for steel materials according to claim 1, wherein the rust stabilizing surface treatment method is limited to not more than%.