JP3065191B2 - Highly concentrated chloride ion Painted steel with high coating durability in atmospheric environment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to steel materials used for bridges, buildings, etc., which are installed in an atmospheric environment where the concentration of chlorides sprayed to prevent coastal and road freezing is high. As a steel material, a steel material containing 1 to 10% of Ni in steel is used, and a coating undercoat and a coating film having an effect of enhancing coating durability are formed on the surface of the steel material. It concerns high painted steel.

[0002]

2. Description of the Related Art In general, steel materials used for bridges, buildings, and the like are used after being painted to secure corrosion resistance and landscape. Normally, steel material is processed into members,
It is cleaned and then painted (undercoat, middle coat, top coat). This coating, especially in terms of corrosion resistance, blistering of the coating,
The importance of the coating durability such as peeling is an important point, and painting durability has been improved in terms of coating technology such as changing and improving the coating resin or the contained rust preventive pigment. . That is, for example, there are various types of topcoat paints such as long-oil phthalic resin, silicone alkyd resin, chlorinated rubber, polyurethane resin, and fluororesin.

[0003]

The above-mentioned painted bridges, buildings, etc. are, for example, in the case of a bridge, for example, the paint durability, which is currently the standard, is about 4 years on the coast and about 8 in the mountains. It is said that the coast where repainting is performed is short after this, because the chloride concentration is high, but even in mountainous areas in recent years the atmospheric environment has been reduced by spraying chloride to prevent road freezing. Due to the high chloride ion concentration, the corrosion resistance is increased and the coating durability is further degraded.

[0004] On the other hand, since the painting work is not always performed in a clean environment, a shortage of painting work has become common and there has been a large social and economic problem that it has become difficult to change the paint.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-concentration chloride capable of greatly extending the coating durability of steel and solving the above-mentioned problems at once in an environment where the chloride ion concentration is high. It is an object of the present invention to provide a coated steel material having high coating durability in an atmospheric environment.

[0006]

Means for Solving the Problems The gist of the present invention to solve such problems, a steel material surface containing 1 to 10% Ni in the _{steel, Fe 2 O 3 + Fe 3} O 4 1~50% ,
Phosphoric acid 0.01-5%, Pb, Cu, P, Zn, Cr
One or more compounds such as 0.01 to 10%,
A film formed by applying a mixture of a butyral resin alone or a mixture of a butyral resin and a resin compatible with the butyral resin in an amount of 3 to 30% and a solvent and a paint additive, and a film formed thereon. A coated steel having high coating durability in a high-concentration chloride ion atmosphere environment, characterized by having a coating film formed by the applied coating.

Hereinafter, the present invention will be described in more detail.

[0008]

The present inventors have investigated the durability of a coating film on steel in a high concentration chloride ion air environment, that is, the coating durability.
As a result of earnest research on the type of steel and the coating undercoat, it has been found that the coating durability in this environment is greatly affected by these. In other words, except for the fact that the coating film itself is deteriorated by ultraviolet light, etc., the coating durability is affected by the slight corrosion that occurs at the interface between the steel material and the coating film in the healthy coating film portion, and the corrosion resistance of the steel material itself in the scratched coating film portion It depends greatly. In particular, it was found that the coating durability at the scratched portion of the coating occupies a large specific gravity in the high chloride ion air environment.

More specifically, the corrosion of the steel at the interface between the steel and the coating, which affects the coating durability of the healthy part of the coating, is caused by the corrosion of moisture, oxygen, chloride ions, etc. which have permeated the coating. Caused by ionic ions, a part of the steel surface elutes as a minute anode, forming minute blisters,
Thereafter, it is known that peeling occurs in a peripheral cathode region to form a full-fledged coating film, thereby deteriorating coating durability. Therefore, it is considered that if this anode reaction can be suppressed, coating durability will be improved.

The present inventors used a steel material containing 1 to 10% of Ni in the steel, and provided Fe ₂ O ₃ + Fe ₃ O _{4 on the} surface of the steel material.
1-50%, phosphoric acid 0.01-5%, Pb, Cu,
At least one element or compound of P, Zn, Cr, etc.
01 to 10%, butyral resin alone or butyral resin and resin 3 to 3 having compatibility with butyral resin
When an undercoating film is formed by applying a mixed treatment solution containing 30% as a main component and a balance of a solvent and a coating additive, an extremely thin film (considered as a complex phosphate) is formed on the lowermost layer of the film, that is, on the surface of the steel material. ) Is formed, and further electrochemical measurements are made. As a result, the anodic polarization is large even in an environment in which the Ni-containing steel material on which this ultrathin film is formed contains a high concentration of chloride, and the anodic reaction is suppressed. I found it. Therefore, in this case, the generation of minute anodes under the coating film is suppressed, and the occurrence of minute blisters does not occur.

[0011] Furthermore, the coating durability at the scratched portion of the coating film is such that corrosion is caused by dissolution of the anode on the exposed surface since the steel plate surface is exposed. Therefore, a steel material that suppresses the anodic reaction in a high-concentration chloride ion atmospheric environment is considered to be highly effective. As a result of the measurement, it was found that a steel material containing 1 to 10% of Ni in the steel greatly suppressed the anodic reaction.

[0012] Further, even if an anodic dissolution reaction occurs in the healthy portion of the coating film and the scratched portion of the coating film, the cathode reaction of the paired reaction occurs around these components.
Here, if a large amount of iron oxide is contained in the undercoat film in contact with the steel sheet, the cathode current is consumed for its own reduction, so that the OH ions at the interface of the Movement is suppressed, and cathode blistering is 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 reason why the steel material is limited to the steel material containing 1 to 10% of Ni in the steel is that the blister at the coating film flaw which governs the coating durability in the atmosphere of high concentration chloride ions is caused by the flaw. Because the anode reactivity is greatly affected by Ni. In this case, if less than 1%, the effect is small and 10%
In the case of super, the weakest point of the flaw is greatly corroded like a pit like the passive state of stainless steel, and there is a problem in the durability of the coated steel material as a whole. Ultra-thin film (complex phosphate) on the steel surface that controls coating durability in healthy coatings
Is not hindered by the inclusion of Ni. Rather, if more than 1% is contained, Ni is contained in the thin film constituent material.
Is contained to enhance the effect of suppressing the anodic reaction. Therefore, Ni in the steel is set to 1 to 10% from this point as well.

Phosphoric acid and Pb, Cu, P, Zn, Cr
The reason for adding one or more of such simple substances or compounds is that phosphoric acid reacts with these simple substances or compounds and components in steel to form an extremely thin film that is a complex phosphate. Phosphoric acid has no effect on the formation of an extremely thin film at 0.01% or less, and the coating becomes sticky at more than 5%,
This is because a film cannot be formed by drying at room temperature. Further P
The content of a simple substance or a compound such as b, Ni, Cu, P, Zn, and Cr is set to 0.01 to 10% by 0.01%.
In the following, it is difficult to form an extremely thin film, and if it exceeds 10%, it will hinder the stable application of the treatment liquid, and the treated film will be 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 minute anode bulges and a cathode is formed in the periphery as described above. However, the content is set to 1 to 50%. When the content is less than 1%, the distribution in the coating is small and the chance of contact with the steel surface is reduced, so that the cathode current cannot be sufficiently received. 50%
If the ratio exceeds 1, the effect is large, but the coating becomes brittle and easily scratched, which is not practically suitable.

Furthermore, the reason for limiting the butyral resin alone or the butyral resin and the resin compatible with the butyral resin as the resin for curing the undercoat film is that these resins are easily mixed with other processing liquid components, and When applying the treatment of the present invention to steel, it is because spray coating or brush coating can be easily performed, drying time is short, and adhesion to a coating film applied on the treated film is good. The reason why the addition amount is 3 to 30% is that if the content is less than 3%, the coating becomes brittle and easily scratched, and if it exceeds 30%, the viscosity of the treatment liquid increases, the workability becomes poor, and the drying of the coating is carried out. This takes time.

In order to maintain the stability of the treatment liquid, a usual paint additive such as a pigment dispersant which suppresses sedimentation and separation of solids is added to the treatment liquid. As for the method, a material suitable for the composition of the processing solution may be appropriately selected and used as needed.

Next, the coating film formed on the undercoat film is not particularly limited, and a normal coating film suitable for a bridge or building application may be formed. Long-oil phthalic acid resin as paint,
The coating film may be formed with a silicon alkyd resin, a chlorinated rubber, a polyurethane resin, a fluororesin, or the like. In the usual coating, an undercoat such as a zinc-rich primer or a cyanamide lead rust preventive paint is applied, but in the present invention, this undercoat can be omitted.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

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

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

The test pieces were scratched with a cutter knife to the surface of the steel material (scratch portion), and an atmospheric exposure test was performed for 3 years in a coastal zone (500 m from the coast) to determine the coating durability.

The results are shown in Table 3. As shown in Table 3, when the undercoating film and the coating film were formed by using the steel material containing 1 to 10% of Ni according to the present invention, not only rust was generated but also the coating film in the healthy portion of the coating film. No blistering occurred, whereas the same treatment of ordinary steel resulted in rust and blistering in some parts. occured.

Further, it should be noted that the coating film is flawed. In the case of the present invention, the rust on the flaw was turned into dense and stabilized rust, and no blistering of the surrounding coating film was observed. On the other hand, in the case of a normal coating material, red rust was often generated at the scratched portion, and the coating film was severely damaged by rust bulging around.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

As is apparent from the above examples, the coated steel material of the present invention can be applied to bridges, buildings, etc. in the high-concentration chloride ion atmospheric environment such as coastal areas and mountainous areas where chloride is sprayed to prevent road freezing. When applied, the maintenance cost can be significantly reduced, since repainting every few years in the case of the conventional coating method is not required to greatly improve the coating durability,
It has an extremely high industrial value, which greatly contributes to the maintenance of social capital in the social trend of a shortage of paint labor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 15/08 B05D 7/14 C23F 11/00

Claims (1)

(57) [Claims] 1. A steel material containing 1 to 10% of Ni in steel, 1 to 50% of Fe ₂ O ₃ + Fe ₃ O ₄ and phosphoric acid
0.01 to 5%, one or more of Pb, Cu, P, Zn, Cr, etc., alone or in a compound of 0.01 to 10%, butyral resin alone or butyral resin and resin 3 to 3 compatible with butyral resin A coated steel material having high coating durability in a high concentration chloride ion atmosphere environment, characterized by having a coating comprising 30% and a coating additive and a coating film thereon.