JPH06143490A - Coated steel material high in coating durability in high concentration chloride ion atmospheric environment - Google Patents

Abstract

PURPOSE:To provide a steel material greatly enhanced in coating durability as the steel used in the seashore or the bridge of a road over which chloride is spread. CONSTITUTION:A film is formed on the surface of a steel material containing 1-10% of Ni by coating the surface of the steel material with a mixed treatment soln. consisting of 1-50% of Fe2O3+Fe3O4, 0.01-5% of phosphoric acid, 0.01-10% Pb or a compd. thereof, 3-30% of a butyral resin and the remainder of a solvent and a coating film is formed on the formed film. Since the coating durability is extended in environment wherein the concn. of a chloride ion is high and coating is most easily deteriorated, the maintenance cost of repainting can greatly be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material used for bridges, constructions, etc. installed in an atmospheric environment in which the concentration of chlorides sprayed to prevent freezing of roads and roads is high, and more specifically, A steel material containing 1 to 10% of Ni in the steel is used as a steel material, and a coating base film and a coating film having an effect of increasing the coating durability are formed on the surface of the steel material. It concerns high coated steel.

[0002]

2. Description of the Related Art Steel materials used for bridges, buildings, etc. are generally coated and used for ensuring corrosion resistance and landscape. After steel is usually processed into parts,
It is blasted and then painted (primer, middle coat, topcoat). This coating, especially from the viewpoint of corrosion resistance, swelling of the coating film,
The important point is the degree of coating durability such as peeling, and it has been attempted to improve the coating durability in terms of coating technology, such as changing or improving the coating resin or the contained rust preventive pigment. . That is, for example, there are various topcoat paints such as long-oil phthalic acid resin, silicon alkyd resin, chlorinated rubber, polyurethane resin, and fluororesin.

[0003]

In the above-mentioned painted bridges, buildings, etc., for example, if the bridges are taken as an example, the current standard paint durability is about 4 years on the coast and about 8 years in the mountains. It is said that it is a year, and the coast where repainting is done after this is due to the high chloride concentration, but even in the mountainous areas, chloride spraying to prevent road freezing has recently caused atmospheric environment. Since the chloride ion concentration in the product became high, the corrosiveness increased and the coating durability deteriorated.

On the other hand, since the painting work is not always performed in a clean environment, a shortage of painters is common, and it is becoming difficult to repaint the paint, which poses a serious social and economic problem.

An object of the present invention is to achieve a high concentration of chloride which can greatly extend the coating durability of steel materials in such an environment where the concentration of chloride ions is high and solve the above problems all at once. It is to provide a coated steel material that has high coating durability in the atmospheric environment.

[0006]

Means for Solving the Problems The gist of the present invention for solving the above problems is that Fe ₂ O ₃ + Fe ₃ O ₄ 1 to 50% is added to the surface of a steel material containing 1 to 10% Ni in steel. ,
Phosphoric acid 0.01-5%, Pb, Cu, P, Zn, Cr
0.01 to 10% of one or more simple substances or compounds,
A film formed by applying a butyral resin alone or a mixed treatment liquid consisting of a butyral resin and a resin compatible with butyral resin 3 to 30% with a main component, the balance solvent and a paint additive, and a film formed thereon. It is a coated steel having high coating durability in a high concentration chloride ion atmospheric environment, characterized by having a coating film formed by the applied coating.

The present invention will be described in more detail below.

[0008]

The present inventors have found that the durability of the coating film on the steel material in the high-concentration chloride ion atmosphere environment, that is, the coating durability,
As a result of diligent research on the type of steel material and the coating base coating, it was found that the coating durability in this environment is greatly affected by these. That is, the coating durability is affected by trace corrosion occurring at the interface between the steel and the coating in the sound coating area and the corrosion resistance of the steel itself in the coating scratch area, except that the coating itself deteriorates due to ultraviolet rays. It depends a lot. In particular, it was revealed that the durability of the coating in the scratched portion of the coating film occupies a large specific gravity in the high-concentration chloride ion atmosphere environment.

More specifically, the corrosion of the steel material at the interface between the steel material and the coating film, which influences the coating durability of the coating film in a healthy part, is caused by the corrosion of water, oxygen, chloride ions, etc. which have permeated the coating film. Caused by ionic ions, a part of the steel material surface becomes a minute anode and elutes, forming minute blisters,
It is known that after that, peeling occurs in the peripheral cathode region, resulting in a full-scale blister of the coating film and deterioration of the coating durability. Therefore, if the anode reaction can be suppressed, the coating durability will be improved.

The present inventors used a steel material containing 1 to 10% of Ni in the steel, and Fe ₂ O ₃ + Fe ₃ O _{4 on the} surface of the steel material.
1 to 50%, phosphoric acid 0.01 to 5%, Pb, Cu,
One or more of P, Zn, Cr and the like, or one or more compounds, may be used.
01-10%, butyral resin alone or resin 3 compatible with butyral resin and butyral resin
When a coating undercoat is formed by applying a mixed treatment liquid consisting of 30% as the main component and the balance solvent and paint additives, an ultrathin film (the complex phosphate is considered to be the lowest layer of this film, that is, the surface of the steel material. It was found that the Ni-containing steel material on which this ultrathin film was formed had a large anodic polarization even in an environment containing a high concentration of chloride, and suppressed the anodic reaction. I found it. Therefore, in this case, since the generation of the minute anode under the coating film is suppressed, the generation of minute swelling does not occur.

Further, as for the coating durability in the scratched portion of the coating film, since the surface of the steel sheet is exposed, the corrosion results from the anodic dissolution of this exposed surface. Therefore, it is considered that the effect is large if the steel material suppresses the anode reaction in the high-concentration chloride ion atmosphere environment. As a result of measurement, it was found that the steel material containing 1 to 10% Ni in the steel largely suppressed the anode reaction.

Further, even if the anodic dissolution reaction occurs in the sound coating portion and the scratched portion of the coating film, the cathodic reaction of the paired reaction occurs around these,
If a large amount of iron oxide is contained in the undercoating film that is in contact with the steel plate, the cathode current is consumed for its own reduction, so that the OH ions that cause large blisters to the interface The movement is suppressed, and the cathode blisters are less likely to occur.

The reasons for limiting the scope of the claims of the present invention invented based on such a principle will be described below.

First, the steel material is limited to the steel material containing 1 to 10% Ni in the steel, because the blisters in the coating film scratches, which control the coating durability in the high-concentration chloride ion atmospheric environment, are the scratches. This is because it depends on the anodic reactivity of Al and that the anodic reaction is significantly suppressed by Ni. In this case, if less than 1%, the effect is small and 10%.
This is because if it exceeds the above value, the weakest point of the scratched portion will largely corrode like pitting like the passive state of stainless steel, and there will be a problem in terms of the durability of the entire coated steel material. Ultra-thin film on the steel surface (complex phosphate) that controls the coating durability in the healthy part of the coating film
The formation of Ni is not hindered by the fact that Ni is contained. Rather, when it is contained in an amount of 1% or more, Ni is contained in the thin film constituent material.
Since Ni is contained to enhance the effect of suppressing the anode reaction, Ni in the steel is set to 1 to 10% also from this point.

Phosphoric acid and Pb, Cu, P, Zn, Cr
The reason for adding one or more of simple substances or compounds such as is that phosphoric acid reacts with these simple substances or compounds and components in the steel to form an extremely thin film of a complex phosphate. If the content of phosphoric acid is 0.01% or less, it has no effect on the formation of an extremely thin film, and if it exceeds 5%, the coating becomes sticky.
This is because a film cannot be formed by drying at room temperature. Furthermore P
The content of simple substance or compound such as b, Ni, Cu, P, Zn, Cr is 0.01 to 10% means 0.01%
This is because it is difficult to form an ultrathin film below, and if it exceeds 10%, a stable coating operation of the treatment liquid is hindered, and the treatment film is easily peeled off.

Fe ₂ O ₃ + Fe ₃ O ₄ is added in order to consume and suppress the cathode current by its own reduction when the minute anode swells and the cathode is formed in the periphery as described above. However, the content is set to 1 to 50% because if it is less than 1%, the distribution in the coating is small, the chance of contact with the steel surface is small, and it is not possible to receive a sufficient cathode current. 50%
If it exceeds, the effect is great, but the coating becomes brittle and easily scratched, which is not suitable for practical use.

Further, as the resin for curing the undercoat, the butyral resin alone or the resin compatible with the butyral resin and the butyral resin is limited, because these resins easily mix with other processing liquid components, and When the treatment of the present invention is performed on a steel material, the reason is that spray coating or brush coating can be easily performed, the drying time is short, and the adhesion with the coating film to be coated on this treated film is good. The amount added is 3 to 30%. When the amount added is less than 3%, the coating becomes brittle and easily scratched, and when it exceeds 30%, the viscosity of the treatment liquid increases and workability deteriorates and the coating is dried. This is because it takes time.

In order to maintain the stability of the treatment liquid, usual paint additives such as a pigment dispersant that suppresses sedimentation and separation of solids, which are usually added in small amounts to the paint, are added to the treatment liquid. With regard to the above, it is possible to appropriately select and use one that is suitable for the blending of the treatment liquid, if necessary.

Next, it is a coating film formed on the undercoating film, but this is not particularly limited, and a normal coating film suitable for applications such as bridges or constructions may be formed. Long oil phthalate resin as paint,
The coating film may be formed of silicon alkyd resin, chlorinated rubber, polyurethane resin, fluororesin or the like. In addition, undercoating such as zinc-rich primer and cyanamide lead rust preventive paint is applied in normal painting, but this undercoating can be omitted in the present invention.

[0020]

EXAMPLES The present invention will be specifically described below based on examples.

Test pieces of the Ni-containing steel of the present invention shown in Table 1 and ordinary steel as a comparative material (thickness 6 mm, size 30)
(0 × 300 mm) was completely scale-removed by shot blasting, and then the coating film shown in Table 2 was formed.

For forming the coating film, first, a treatment solution for forming a base coating film was applied by spraying to a film thickness of about 15 μm, and naturally dried for 3 hours to form a coating film. A normal coating material as a comparative material was subjected to undercoating, intermediate coating and topcoating after shot blasting.

Scratches reaching the surface of the steel material were put into these test pieces with a cutter knife (scratches), and an atmospheric exposure test was conducted for 3 years in the coastal zone (500 m from the coast) to judge the coating durability.

The results are shown in Table 3, in which the base film and the coating film were formed by using the steel material containing 1 to 10% of Ni according to the present invention. No swelling was observed, whereas rust and swelling were observed in some of the ordinary steel materials treated in the same manner, and many rusts and swelling were observed in the comparatively painted ones. occured.

Furthermore, what should be noted is the scratched portion of the coating film, but in the case of the present invention, the rust in the scratched portion became a dense and stable rust, and no swelling of the coating film in the periphery was observed. On the other hand, in the case of the ordinary coating material, many red rusts were generated in the scratches, and the coating film was severely damaged due to rust swelling around.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

EFFECTS OF THE INVENTION As is clear from the above examples, the coated steel material of the present invention can be applied to bridges, constructions, etc. in high-concentration chloride ion atmospheric environments such as coasts, mountainous areas where chloride is sprayed to prevent road freezing. When applied, not only repainting every few years when using the conventional painting method is not necessary to greatly improve the painting durability, so not only can maintenance costs be greatly reduced,
It has an extremely high industrial value effect that will greatly help to preserve social capital in the social trend of labor shortage for painting.

Claims (1)

[Claims] 1. Fe ₂ O ₃ + Fe ₃ O ₄ 1-50%, phosphoric acid on the surface of a steel material containing 1-10% Ni in the steel.
0.01 to 5%, one or more of Pb, Cu, P, Zn, Cr, etc., or one or more compounds, 0.01 to 10%, butyral resin alone, or butyral resin and resin 3 compatible with butyral resin 3 to A high-concentration chloride ion coated steel material having high coating durability in an atmospheric environment, which comprises a coating film composed of 30% and a coating additive, and a coating film thereon.