JP3056372B2 - Super-painting durable steel and its painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of painting and using steel materials such as bridges and various buildings, and more particularly to a coated steel material having extremely excellent coating durability and a coating method therefor.

[0002]

2. Description of the Related Art The use of steel as a material for supporting a structure at a low cost and high reliability has greatly increased with the development of economy. There are many types of usage, for example,
The amount of steel used in the atmosphere, such as bridges and various buildings, is extremely large. These are the most common methods used by applying a coating for ensuring durability and aesthetics. Usually, a steel material is processed into a member, polished and then painted (undercoat, intermediate coat, topcoat). This painting is
From the viewpoint of durability, it is important that two types of properties be excellent. The first is corrosion resistance after painting. Related to this are swelling, peeling, and cracking of the coating film caused by corrosion of the steel material interface. For these, from the viewpoint of the coating technology, improvements have been made by approaches such as changing and improving the coating resin or the contained rust preventive pigment. Second is the weather resistance of the coating. It is well known that an organic coating film is oxidatively decomposed from the surface of the coating film by light energy, and gradually loses its initial properties due to a decrease in gloss and chalking accompanying the decomposition of the resin. On the other hand, for resin, for example, a resin that has a large binding energy and is chemically stable, that is, a resin that has a binding energy level that can overcome the excitation energy of ultraviolet light, is used to improve the performance from the viewpoint of coating technology. Has been planned.

[0003]

The above-mentioned painted bridges and various buildings are, for example, bridges.
After about 4 years on the shore and about 8 years on the mountainous area, it is necessary to repaint the coating from the viewpoint of corrosion resistance and weather resistance. The repainting operation is costly and the lack of a painter is serious, which poses a major social and economical problem that paint repainting is becoming difficult.

[0004] It is an object of the present invention to provide a coated steel material and a coating method capable of solving the above problems by greatly improving the coating durability of the steel material and extending the repainting period.

[0005]

The gist of the present invention for solving such a problem is as follows. First, the first layer is formed on the surface of the weather-resistant steel from the surface side of the steel upward. A coating consisting mainly of phosphates of Fe, Cr and Zn to a thickness of 0.0
5 to 2 μm, a second layer mainly composed of a complex of polyvinyl butyral resin and chromium / phosphoric acid, Fe ₂ O ₃ + Fe ₃ O
₄ , Pb, Ni, Cu, P, Zn, Cr, etc. One or more of compounds such as zinc phosphate and butyral resin with a thickness of 5 to 50 μm. Consisting of pigment and resin for paint, pigment volume concentration (PVC) is 50% of critical pigment volume concentration (CPVC)
A super-coating durable steel material having a thickness of 15 to 200 [mu] m, wherein the coating has an elongation percentage of 4% or more after the completion of hardening. Second, the surface of the steel material is made of weather-resistant steel. the _{Fe 2 O 3 + Fe 3 O} 4 1~50 mass%, phosphoric acid 0.01~5 mass%, Pb, Ni, Cu, P,
Simple substance or compound of Zn, Cr, etc.
% To 10% by mass , butyral resin alone or butyral resin and resin 3 having compatibility with butyral resin
30% by mass as a main component, a coating base treatment film is formed by applying a mixed treatment liquid consisting of a residual solvent and a paint additive, and thereafter, the pigment is mainly composed of a paint pigment and a paint resin, and is a finished pigment. A super-coating durable steel material characterized by applying a treatment liquid having a volume concentration (PVC) of 50% or more of the critical pigment volume concentration (CPVC) and an elongation of a film after curing is 4% or more. It is a painting method.

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

[0007]

The present inventors have investigated the durability of the coated steel material as a whole, that is, the coating durability, the alloy elements contained in the steel, the steel material and the coating film and the coating film necessary for the interface between them, which have not been studied so far. As a result of diligent research into the relationship between the above, it was found that the coating durability greatly depends on these.

First, the first characteristic, corrosion resistance after painting, will be described. As a result of the study of the present inventors, it has been found that the corrosion resistance after painting is affected by the minute corrosion occurring at the interface between the steel material and the coating film.

More specifically, the corrosion of the steel at the interface between the steel and the coating is caused by corrosive ions such as moisture, oxygen, and chloride which have passed through the coating. A part of the surface of the steel material elutes as a minute anode, so that a minute swelling is formed.
It is known that H 2 ^- ions are generated, and the coating film is peeled off by the ions to generate corrosion products, resulting in full-scale swelling of the coating film, resulting in deterioration of durability after coating. Therefore, it is considered that if this anode reaction can be suppressed, coating durability will be improved.

The present inventors have used various weather-resistant steels as coating steel materials as coating base steel materials, and formed a coating mainly formed of a phosphate of Fe, Cr, Zn on the surface thereof by a method described later. As a result of electrochemical measurement, it was found that the anodic polarization was large and the anodic reaction was suppressed. In this case, the generation of the minute anode under the coating film is suppressed, so that the minute swelling does not occur.

Further, if iron oxide is contained in the second layer coating in contact with the steel sheet in the peripheral cathode reaction region that is paired with the anode reaction, even if micro-swelling occurs, the iron oxide is removed. Cathode current is consumed in the reduction (harmless cathode reaction), and there is an effect that the generation of OH ^- ions, which causes the adhesion of the coating film to be reduced and causes swelling, is suppressed, and the cathode swelling is hardly caused. However, in order to produce a harmless cathodic reaction in the area sufficiently adjacent to the accidental anode reaction zone under the coating,
It is necessary to arrange the iron oxide finely and homogeneously at the interface of the second layer coating and to supply a necessary and sufficient moisture to form a fine and uniform harmless cathode.

Next, the second characteristic, that is, the weather resistance of the coating film will be described. Conventionally, research has been conducted on the weather resistance of coated steel materials, mainly on the deterioration of the coating film itself due to damage mainly by light. However, as described above, as a result of intensive studies on the relationship between alloying elements contained in steel, which had not been studied hitherto, steel materials, coatings, and the coatings necessary for these interfaces, the weather resistance of the coatings is also affected by these. I found something. That is, it has been found that the weather resistance of the coating film in the coated steel material system depends on the amount of corrosion under the coating film at the same time as the conventionally known light from above the coating film.

More specifically, a coated steel material (150 ×
70) A sample with a cross-cut at the bottom is subjected to a weathering corrosion test (one that allows salt water spraying to be performed at an arbitrary ratio within the water spraying time during the sunshine carbon arc lamp-type duty cycle weathering test). The sample was prepared by changing the salt spray time. The gloss at the top of the crosscut was measured for the samples with the same light irradiation and moisture irradiation times and different amounts of undercoat corrosion, and the result was that the greater the amount of undercoat corrosion, the greater the decrease in gloss. Was. Further observation of the cross section of these samples,
When the distribution of Fe concentration in the coating film was examined by EPMA,
Although the Fe concentration gradually decreased from the interface with the steel material toward the coating film surface, the result was that the higher the corrosion, the higher the Fe concentration in the coating film. Although the mechanism of the amount of corrosion under the coating film or the effect of Fe distributed after corrosion in the coating film on the weather resistance of the coating film is not clearly understood, from the results described above, the weather resistance of the coating film of the coated steel material was determined. In order to improve the corrosion, the corrosion under the coating film is suppressed, and the Fe
It can be said that it is an effective method to suppress the transfer to the surface layer of the coating film.

The reasons for limiting the scope of the claims of the present invention, which have been invented on the basis of such an idea relating to the improvement of the corrosion resistance after coating and the weather resistance of the coating film, will be described below.

First, the reason why the steel material is weather-resistant steel is that the above-mentioned ultrathin film on the steel surface is formed only when the steel contains Cu. Further, within the scope of the claims, the effects of the steel components on the overall coating durability are excellent in the following order.

Large Cu 0.2-0.7 mass % P
0.03 to 0.15 mass %> Cu 0.2 to
1.1 mass % P 0.03 to 0.15 mass %
(Excluding range)> Cu 0.2-0.7 mass %
> Cu 0.2-1.1 mass % (excluding range)
>> SS41 Weatherproof steel other than >> SS41 First, a coating mainly composed of a phosphate of Fe, Cr, Zn is formed on the surface of the small steel material in a thickness of 0.05 to 2 μm, and this coating is combined with the steel material. This has the effect of suppressing the anodic reaction, but the effect is small when the thickness is less than 0.05 μm, and when the thickness exceeds 2 μm, the coating becomes brittle and the mechanical properties deteriorate.

The next film, a complex of polyvinyl butyral resin and chromium / phosphoric acid, Fe ₂ O ₃ + Fe ₃ O ₄ ,
A film composed of zinc phosphate and butyral resin of at least one of simple substances or compounds such as Pb, Ni, Cu, P, Zn, and Cr is formed to a thickness of 5 to 30 μm. This coating has the function of securing the adhesion between the lower phosphate coating and the upper coating, and the function of suppressing the cathode reaction after the formation of micro blisters due to the self-reduction of the iron oxide contained. If it is less than 5 μm, the effect of suppressing the cathode reaction is particularly small due to its iron oxide, and if it exceeds 50 μm, the coating itself becomes brittle and the adhesion to the upper coating film is impaired.
５０50 μm.

Next, the final layer is mainly composed of a pigment for paint and a resin for paint, the pigment volume concentration (PVC) is 50% or more of the critical pigment volume concentration (CPVC), and the elongation of the film after curing is completed. 4% or more of the coating, thickness 15 ~
Although the film is formed to have a thickness of 200 μm, this film is a so-called coating film, and the components of the coating film are not particularly limited, and the components of a normal coating film suitable for applications such as a bridge or a building may be applied. For example, in the case of a bridge, the resin may be a long-oil phthalic acid resin, a silicon alkyd resin, a chlorinated rubber resin, a polyurethane resin, a fluororesin, an acrylic resin, or the like. The elongation of the coating film is determined by the glass transition point and crosslink density of the resin used, the pigment volume concentration in the coating composition, and the resin that is compatible with the resin to be used and has a plasticizing effect (an example of an epoxy resin). For example, a certain kind of polyamide resin) can be appropriately selected. In both cases, the corrosion resistance after coating and the weather resistance of the coating film are both excellent. Additives such as color pigments and volume pigments can be appropriately included while satisfying the necessary range of the pigment volume concentration. The reason why the pigment volume concentration (PVC) is set to 50% or more of the critical pigment volume concentration (CPVC) is 50%
%, The corrosion resistance after coating and the weather resistance of the coating film are both reduced. The reason why the elongation percentage of the coating is 4% or more is that if it is less than 4%, both the corrosion resistance after painting and the weather resistance of the coating film are lowered. The reasons for the claims of the pigment volume concentration and the hardness are as described above, but the mechanism for expressing the effect is as described above. It is presumed that it is most suitable for suppressing the amount of corrosion under the coating film in combination with other layers and for suppressing the upward diffusion of Fe, but it is not clear at this point.

When the thickness of the coating is less than 15 μm, both the corrosion resistance after coating and the weather resistance of the coating cannot usually exceed the durability of the coating of 8 years, so that it is not practical. In this case, the corrosion resistance after coating and the weather resistance of the coating film are rather deteriorated.

Next, these coating methods will be described. The first layer phosphate film and the second layer film can be formed very easily by applying the following treatment liquid to the steel material surface. That is, Fe ₂ O ₃ + Fe ₃ O ₄ 1
~ 50%, phosphoric acid 0.01 ~ 5%, Pb, Ni, Cu,
At least one element or compound of P, Zn, Cr, etc.
01 to 10%, butyral resin alone or butyral resin and a resin having compatibility with butyral resin 3 to 3
The method is to apply a mixed treatment liquid containing 0% as a main component and a balance of a solvent and a paint additive.

In this case, since the formation of the phosphate thin film of the first layer and the second layer is performed with the same processing solution, it is considered that it is particularly difficult to control the thickness of the first layer. Since it is formed by reacting with the steel material surface, it can be controlled and formed relatively easily.

Here, phosphoric acid and Pb, Ni, Cu,
The addition of at least one element or compound of P, Zn, Cr, etc. is for the purpose of forming an extremely thin film made of complex phosphate by reacting the element or compound with phosphoric acid. Content of 0.01 to 5 mass %
The reason is that if it is 0.01 mass % or less, there is no effect in forming an extremely thin film, and if it exceeds 5 mass %, the coating becomes sticky,
This is because a film cannot be formed by drying at room temperature. Further P
The reason why 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 mass % is as follows.
When the content is less than 0.01 mass %, it is difficult to form an extremely thin film.
If it exceeds 0% by mass, it may hinder the stable application of the processing solution, and the processing film may be easily peeled off.
Fe ₂ O ₃ + Fe ₃ O ₄ is added to consume and suppress the cathode current by its own reduction when a minute anode swelling occurs and a cathode is formed in the periphery as described above. Its content is 1-50mas
was a s% has no effect because it can not receive a sufficient cathode current contact opportunity is decreased with less steel surface distribution in the coating is less than 1 mass%, 50 m
If it exceeds ass %, the effect is large, but the coating is brittle and easily scratched, which is not suitable for practical use. Furthermore, the butyral resin alone or limited to butyral resin and a resin having compatibility with the butyral resin, these resins are easily mixed with other processing liquid components, and the treatment of the present invention is performed on weathering steel. This is because spray coating or brush coating can be easily performed, drying time is short, and adhesion to a coating film applied thereon is good. If the addition amount is less than 3 mass %, the coating is brittle and easily scratched, and if it exceeds 30 mass %, the viscosity of the treatment liquid increases, the workability deteriorates, and it takes time to dry the coating. As for the other additives, those having various necessary blends may be appropriately selected and used.

For the formation of the third layer coating film, a conventional method for forming a coating film of a top coat can be used. As the resin, a long-oil phthalic acid resin, a silicon alkyd resin, a chlorinated rubber resin, a polyurethane resin, a fluororesin, an acrylic resin, or the like is used. (PVC) is adjusted to 50% or more of the critical pigment volume concentration (CPVC) and the elongation of the film after curing is adjusted to 4% or more.
By coating so as to have a thickness of 0 μm, a predetermined film can be easily formed.

[0024]

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

A test piece (sheet thickness: 6 mm, size: 300 mm) of a weathering steel according to the present invention and a standard steel as a comparative material shown in Table 1
× 300 mm) was completely removed by shot blasting, and then a film was formed with the treatment liquid shown in Table 2. Here, Λ is the volume concentration of the reduced pigment represented by the following formula.

Λ = Pigment Volume Concentration (PVC) / Critical Pigment Volume Concentration (CPVC) (1) In the film forming treatment, first, the first and second layer forming treatment liquids are applied by spraying, and then naturally dried for 6 hours and then applied. Thus, a third layer was formed.

The test pieces were scratched with a cutter knife down to the surface of the steel material, and exposed to the air in a semi-industrial zone (Sagamihara City, Kanagawa Prefecture) for 4 years to determine the coating durability. As an evaluation method, a visual inspection method was used for the corrosion resistance after coating according to the following criteria.

The weather resistance was evaluated by a gloss meter using a gloss retention (60-degree gloss retention after water washing).

：: No rust, no swelling Δ: Partially rusted, partially swelled X: Rusted, swelled As shown in Table 3, the steel material according to the present invention had a predetermined thickness and coating. In the case where no rust was generated, no swelling of the coating film was caused as well as in the case where rust was generated, rusting and swelling occurred. The thing produced a lot of rust and blistering. Further, the weather resistance of the coating film evaluated at the 60-degree gloss retention was within the range of the present invention, but the deterioration was small.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

As is apparent from the above examples, when the coating method of the super-painting durable steel material and the super-painting durable coating steel material of the present invention is applied to a bridge, a building, and the like, the corrosion resistance and the weather resistance after the coating are improved. Repainting every few years in the case of the conventional painting method is greatly extended in order to significantly improve the maintenance cost. Has an extremely high industrial value that greatly contributes to the retention of

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kanda 3 6-10-73 Minamitsukaguchi-cho, Amagasaki-shi, Hyogo Inside Shinto Paint Co., Ltd. (72) Inventor Shigeaki Maeda 6, Minamitsukaguchi-cho, Amagasaki-shi, Hyogo No. 10 No. 73 Inside Shinto Paint Co., Ltd. (56) References JP-A-55-97477 (JP, A) JP-A-5-220449 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) B05D 1/00-7/26 B32B 15/08 B32B 15/08 102

Claims (10)

(57) [Claims] 1. A coating mainly composed of a phosphate of Fe, Cr, or Zn having a thickness of 0.05 to 2 μm on a steel material surface of a weather-resistant steel. In the second layer, a complex of mainly polyvinyl butyral resin and chromium / phosphoric acid, Fe ₂ O ₃ + Fe ₃ O ₄ , Pb, Ni, C
u, P, Zn, among simple or compound such as Cr 1
Species above, the thickness of 5~50μm a coating of zinc phosphate and butyral resin, mainly the third layer consists of a coating pigment and coating resin, pigment volume concentration (PVC) is the critical pigment volume concentration (CPVC )) And a coating having an elongation of 4% or more after curing is completed,
A super-painting durable steel material having a thickness of 200 μm. 2. The weathering steel has a Cu content of 0.2 to 1.1 mas.
The super-painting durable steel material according to claim 1, which contains s %. 3. The weathering steel contains Cu in an amount of 0.2 to 0.7 mas.
The super-painting durable steel material according to claim 1, which contains s %. 4. The weathering steel further increases P by 0.03 to 0.1.
The superpainting durable steel material according to claim 2 or 3, wherein the steel material contains 5 mass %. 5. The coating resin according to claim 1, wherein the third coating resin is mainly an acrylic resin.
Super painted durable steel material as described. 6. A weather-resistant steel having a surface of Fe ₂ O
_{3 + Fe 3 O 4 1~50 mass} %, phosphoric acid 0.01
５5 mass %, at least one kind of a simple substance or a compound of Pb, Ni, Cu, P, Zn, Cr, etc., in a range of 0.01 to 10 mas
s %, butyral resin alone or a mixed treatment solution containing butyral resin and a resin having a compatibility with butyral resin of 3 to 30% as a main component, and a balance of a solvent and a paint additive to form a base coat for coating. After that, it is mainly composed of a paint pigment and a paint resin, and the finished pigment volume concentration (PVC) is the critical pigment volume concentration (CPV).
C) is 50% or more, and the elongation of the film after the completion of curing is 4
%. A coating method for a super-painting durable steel material, characterized by applying a treatment liquid having a concentration of not less than 10%. 7. The weathering steel contains Cu in an amount of 0.2 to 1.1 mas.
The method for coating a super-painting durable steel material according to claim 6, wherein the coating material contains s %. 8. The weathering steel comprises Cu of 0.2 to 0.7 mas.
The method for coating a super-painting durable steel material according to claim 6, wherein the coating material contains s %. 9. The weathering steel further increases P by 0.03 to 0.1.
9. The method for coating a super-painting durable steel material according to claim 7, wherein the coating material contains 5 mass %. 10. The method for coating a super-painting durable steel material according to claim 6, wherein the third-layer coating resin is mainly an acrylic resin.