JP2002020876A - Organic resin coating material and surface treated steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic resin coating material capable of generating weather resistant stable rust at an early stage while preventing flowing rust and floating rust, sufficiently exhibiting those effects even in the case fly salt is large and excellent in application performance and cost effectiveness and to provide surface treated steel using the same organic resin coating material. SOLUTION: An organic resin coating material containing, by mass, 1 to 65% chromium sulfate, and in which the total concentration of the chromium sulfate and pigment lies in ±5% of the critical pigment weight concentration is applied to the surface of steel or on a rust layer of the steel so as to control the dry film thickness to 5 to 150 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic resin paint and a surface-treated steel material, and more particularly to a rust layer (so-called weatherable stable rust) having a protective action against an atmospheric corrosion environment.
The present invention relates to a steel material excellent in weather resistance which can be formed at an early stage without loss of appearance due to flowing rust or the like, and an organic resin paint suitably used for the steel material.

[0002]

2. Description of the Related Art As is generally known, P, C
By adding elements such as u, Cr, and Ni, corrosion resistance in the atmosphere can be improved. These low-alloy steels are called weather-resistant steels, which form rust (stable rust) that protects against corrosion in a few years outdoors, so-called maintenance-free that eliminates the need for corrosion-resistant work such as painting. It is steel.

However, since it takes several years to form weather-resistant rust, floating rust such as red rust and yellow rust and flowing rust occur during the period, which is not only unfavorable in appearance, but also However, there is also a problem that causes pollution of the surrounding environment. In particular, there is a problem that weather-resistant rust is not formed in a salt flying environment.

To solve this problem, for example, Japanese Patent Laid-Open Publication No. 1-1
As disclosed in Japanese Patent No. 42088, a surface treatment method for forming a phosphate film is disclosed. Also,
Japanese Patent No. 22530 discloses a method of forming a stable rust by applying a resin film without causing flow rust. Furthermore, in Japanese Patent Publication No. 56-33991,
A surface treatment method by two-layer coating is disclosed.

[0005]

However, among the above-mentioned prior arts, the method disclosed in Japanese Patent Application Laid-Open No. 1-142088 requires that a proper pre-treatment be performed before the formation of phosphates. However, when welding of a steel material is required, it is not easy to apply a treatment to the welded portion, and there is a problem that application to a building structure is difficult.
Furthermore, the salt resistance was not improved.

On the other hand, the method disclosed in Japanese Patent Publication No. 53-22530 not only does not sufficiently prevent flow rust in a severely corrosive environment, but also has a poor ability to promote stable rust formation. Furthermore, in the method disclosed in Japanese Patent Publication No. 56-33991, it is possible to prevent run-off rust, but there is a problem that it takes more than several years to form stable rust because of high anti-corrosion property and the workability is poor. .

Therefore, the present inventors have solved these problems by the method disclosed in Japanese Patent No. 2,666,673.

However, in a mild environment with a small amount of flying salt, there is a problem that formation of stable rust takes time.

Therefore, a main object of the present invention is to provide an excellent workability and economical surface treatment on the surface or surface rust layer of a steel material such as weathering steel or ordinary steel, and even in a severe salt flying environment. To obtain an organic resin paint and a surface-treated steel material that can form weathering stable rust early even in a mild environment with little flying salt without generating floating rust such as red rust or yellow rust or running rust after treatment. It is in.

[0010]

<Invention according to claim 1>
An organic resin paint containing 1 to 65% by mass of chromium sulfate, and the total concentration of the chromium sulfate and the pigment is within ± 5% of the critical pigment weight concentration.

<Invention of claim 2>
An organic resin paint containing 65% by mass and having a total concentration of the chromium sulfate and the pigment within ± 5% of the critical pigment weight concentration is applied on the steel surface or the rust layer of the steel material to a dry film thickness of 5 to 150 μm.
A surface-treated steel material characterized by being coated so as to have a thickness of m.

<Invention according to claim 3>
An organic resin paint containing 65% by mass is coated on a steel material surface or a rust layer on the steel material surface with a dry film thickness of 5 to 150 μm and a water permeability of 1
A surface-treated steel material coated so as to be 0 to 1000 ml / cm ² / year.

[0013]

Embodiments of the present invention will be described below. The present invention mainly has two configurations: a configuration in which the pigment is adjusted in concentration and added (inventions described in claims 1 and 2), and a configuration in which the water permeability of the coating is adjusted (invention described in claim 3). In the following, an embodiment having both of these configurations will be described. (Chromium Sulfate) The organic resin paint in the present embodiment contains 1 to 65% by mass of chromium sulfate. this is,
For the following reasons. If the structure of the rust is dense, it is easy to physically block the atmospheric corrosion environment, and the elution of iron ions, which is a fundamental cause of floating rust and flowing rust, is reduced. However, if there are cracks or pores in the rust, it becomes a supply path for water or oxygen, and the corrosion protection of the rust is reduced. Therefore, it is necessary to form a dense and continuous rust layer. At this point, when moisture permeates into the resin coating, the chromium sulfate becomes chromium ions and sulfate ions, and reaches the interface between the coating and steel. Sulfate ions and moisture corrode steel to form iron ions. Chromium ions and sulfate ions catalytically accelerate the transformation of iron ions into α-FeOOH, which is the main component of weatherable stable rust. Further, some of the chromium ions are α-Fe
OOH is taken into the crystal grains, and the crystal grains have a fine and dense structure, thereby improving the anticorrosion performance of the weather-resistant stable rust layer. Further, it is considered that sulfate ions are involved not only in the acceleration of the initial iron ion generation but also in the fineness and densification of the weather-resistant stable rust layer. Therefore, in order to obtain such an effect, at least 1% by mass or more of chromium sulfate is contained in the coating.

On the other hand, the reason why the amount of chromium sulfate is set to 65% by mass or less is that if it exceeds 65% by mass, the coating becomes brittle due to a shortage of the organic resin which plays a role in binding these inorganic substances, This is because through-holes reaching the surface are formed and flow rust is generated.

(Pigment) The organic resin paint according to the present invention includes:
In addition to the chromium sulfate described above, it is preferable to include a pigment such that the total concentration of the pigment and chromium sulfate is within ± 5% of the critical pigment weight concentration. This is for the following reason.
First, the reason why the concentration of the critical pigment is set to -5% or more is that at such a concentration, the permeability of water and oxygen is increased, and appropriate moisture and oxygen are supplied to the steel surface to form weather-resistant stable rust. It is because it can promote. On the other hand, the critical pigment weight concentration of +5
The reason why the content is not more than% is that if the concentration exceeds the above range, the coating becomes too porous and not only the occurrence of flow rust increases, but also the binder property is inferior, the coating strength is reduced, and the adhesion is reduced. is there.

The organic resin paint is mainly composed of an organic resin component and a pigment in a dry film state.
As the ratio of the pigment to the organic resin increases, the resin connecting the pigment becomes insufficient, resulting in a porous structure. The critical concentration at this time is the critical pigment weight concentration (CPW
C), and although there are some differences depending on the type of resin, the type of pigment, and the particle size of pigment, approximately 60 to 80%
It has become. The critical pigment weight concentration (CPWC) can be determined by preparing an isolated coating in which the pigment content is changed, and measuring the gas permeability, water vapor permeability, water absorption, and the like of the coating. These values are the critical pigment weight concentration (CPWC)
In the vicinity, it will rise sharply.

In the present invention, the pigment weight concentration is adjusted in addition to chromium sulfate which is an essential component,
It can be carried out with a coloring pigment such as titanium dioxide, carbon black, phthalocyanine blue or the like, or an extender pigment such as talc, silica, mica, barium sulfate or calcium carbonate.

The pigment that can be used in the present invention is not limited to the above, but in an environment with a lot of flying salt, it is preferable to add a rust-preventive pigment in a range of 10% by mass or less. The reason why the content of the rust preventive pigment is within 10% by mass is that if it exceeds this, the rust preventive effect becomes too strong and the generation of weather-resistant stable rust is delayed.

As the rust-preventive pigment, chromium-based rust-preventive pigments represented by zinc chromate, and phosphorus-based rust-preventive pigments such as zinc phosphate, aluminum tripolyphosphate, and aluminum phosphomolybdate can be used. However, the present invention is not limited to these, and two or more of these may be contained.

The concentration of the additive in the resin coating described above indicates the concentration after drying and solidification. The coating composition before coating is adjusted to a viscosity suitable for a coating operation with an appropriate amount of a solvent or water, and the solvent or moisture evaporates by natural drying after coating.

(Organic resin) As the organic resin which can be used in the present invention, epoxy resin, urethane resin, vinyl resin,
Examples thereof include a polyester resin, an acrylic resin, an alkyd resin, a butyral resin, and a phthalic acid resin, but are not limited thereto. However, phenolic resins (excluding those cured at room temperature), which require heating for curing, or resins which need to be heated and melted when bonding, such as polyethylene resin, A resin that does not require heating for curing and bonding is preferred because of poor performance and economic efficiency.

The organic resin coating may contain conventional additives such as a thixotropic agent, a dispersant and an antioxidant. In this case, it is preferable to add a coloring pigment to the organic resin so that the organic resin coating is brown or chocolate in the same color as the weather-resistant stable rust so that the appearance is not impaired even if the organic resin coating is worn or peeled in the future.

(Formation of Coating) First, the organic resin coating in the present embodiment has a water permeability of 10 to 1000 ml / cm.
² / year. This is for the following reason.
As described above, when moisture permeates into the resin coating,
The chromium sulfate becomes chromium ions and sulfate ions, and reaches the interface between the coating and the steel. Sulfate ions and moisture corrode steel to form iron ions. Chromium ions and sulfate ions catalytically accelerate the transformation of iron ions into α-FeOOH, which is a main component of weatherable stable rust. Therefore, the water permeability of the coating is an important factor in producing weatherable stable rust. If the water permeability is less than 10 ml / cm ² / year, the formation of weather-resistant stable rust will be delayed, while if it exceeds 1000 ml / cm ² / year, iron ions eluted from the inside of the coating will Red rust or run-off rust occurs on the surface. Further, when the water permeability exceeds 1000 ml / cm ² / year in an environment with a high amount of flying salt, there is also a problem that the formation of weather-resistant stable rust is hindered by permeation of chloride ions.

The water permeability is measured by the method specified in JIS K5400. Since the water permeability is inversely proportional to the film thickness, in the case of a coating composition having a low water permeability, a thin film is used, and in the case of a coating composition having a high water permeability, a thick film is used to obtain a coating having a predetermined water permeability. Can be. The water permeability varies depending on the type of resin and the composition of the pigment, but particularly increases when the concentration is higher than the critical pigment weight concentration (CPWC) or higher. Further, when the film thickness is 15 μm or less, defects tend to occur in the coating, and increase to a value that is inversely proportional to the film thickness.

Next, the organic resin coating in the present embodiment has a dry film thickness of 5 to 150 μm. The dry film thickness of not less than 5 μm is that a coating thickness of less than 5 μm has a low barrier effect and a water permeability of 1000 ml / cm.
² / year or less, the amount of chromium sulfate that promotes the formation of weather-resistant stable rust, which cannot completely prevent the leaching of iron ions generated by corrosion of steel materials and causes flow rust. Is likely to be insufficient. Further, if the coating thickness is less than 5 μm, there is a problem that excessive corrosion occurs due to permeation of chloride ions in an environment with a large amount of flying salt, and continuous generation of weather-resistant stable rust is hindered.

On the other hand, the organic resin coating is dried at a dry film thickness of 150
The reason why the thickness is not more than μm is that when the coating thickness exceeds 150 μm, not only is the economy inferior, but also the barrier effect becomes too high, and it takes a long time to form weather-resistant stable rust.

Even if an upper coating having a water permeability of 1000 ml / cm ² / year is provided on the surface-treated steel material of the present invention, the reaction by-product (iron sulfate) generated at the initial stage can be suppressed.

In forming the coating, the organic resin may be used as a solvent-based paint or a water-based paint. Also,
The organic resin coating can be applied by any method such as air spraying, airless spraying, or brush coating, in the same manner as a normal coating method. Therefore, the construction can be carried out regardless of the place, and since the effect is obtained by one coating operation, the economy is excellent. Furthermore, since on-site painting is possible, it is possible to respond quickly even after processing such as cutting and welding of steel materials on-site.

The steel material used in the present invention is not particularly limited in steel type, and may be ordinary steel as well as weather-resistant steel. This is because chromium sulfate and phosphorus-based rust-preventive pigments in the resin coating transform the rust into chemically stable and dense weather-resistant stable rust even if it is ordinary steel in an environment with a lot of flying salt. , Because the protective action can be exerted.

However, when some external force acts on the weather-resistant stable rust layer thus generated and cracks or peeling occurs,
Since ordinary steel is inferior in self-healing ability to generate weather-resistant stable rust again at the damaged portion, it is desirable to use weather-resistant steel as the steel material. As for the weather-resistant steel, not only conventionally used JIS-specified weather-resistant steel but also a recently developed Ni-based weather-resistant steel (seashore weather-resistant steel) can be used.

[0031]

Embodiments of the present invention will be described below in detail. Table 1 shows the chemical components of the test steels used in the examples of the present invention. Also,
Table 2 shows the pretreatment method of the steel material, and Table 3 shows the resin system used for the coating material. The dimensions of the test steel are 150 × 70 × 3.2
mm, and the surface before the treatment was removed by shot blasting.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

The type using a curing agent is a two-pack type in which the main agent (base resin + additive) and the curing agent are mixed immediately before coating.

Tables 4 and 5 show the preparation conditions and test results of the samples. Table 4 shows the case where the pigment concentration is adjusted and added (the invention according to claims 1 and 2; hereinafter simply referred to as the concentration structure). Table 5 shows the structure where the water permeability of the coating is adjusted (claims). The invention described in No. 3 (hereinafter simply referred to as water permeability configuration) is shown.

Tables 4 and 5 were used when preparing the samples.
A coating material having a viscosity (measured by a B-type viscometer) of 200 to 1000 CPS was prepared by adding an appropriate amount of a solvent to the coating material composition shown in (1), and coated by air spray coating. This test steel was used in Amagasaki City, Hyogo Prefecture (flying salt amount: 0.01 ml
1 / day / dm ² ) for 2 years, and the coverage of the weather-resistant stable rust (the weather-resistant stable rust portion was quenched) was measured by cross-sectional observation of the exposed sample with a polarizing microscope. This coverage was measured as 100% when the weather-resistant stable rust covers the entire steel surface, and 0% when there was no weather-resistant stable rust (including when it was not rusted).

[0038]

[Table 4]

[0039]

[Table 5]

As a result, in both the concentration configuration and the water permeability configuration, as shown in Test Nos. 1 to 11 in Tables 4 and 5, weather-resistant stable rust was generated so as to cover the entire surface of the steel material.

However, first, when the total concentration of chromium sulfate and the pigment was not set within ± 5% of the critical pigment weight concentration, as shown in Test Nos. 12 and 13 in Table 4, the formation of weather-resistant stable rust was observed. Was only partial. In addition, the total concentration of chromium sulfate and pigment is set to ± 5% of the critical pigment weight concentration.
If the coating thickness exceeds 150 μm,
As indicated by the test number 14 in Table 4, the formation of weather-resistant stable rust was only partial. On the other hand, the permeability of the coating is 1
When the amount was less than 0 ml / cm ² / year, as shown in Test No. 12 in Table 5, although red rust did not occur, generation of weather-resistant stable rust was only partial. When the water permeability of the coating is set to exceed 1000 ml / cm ² / year,
As shown by test number 13 in Table 5, red rust occurred. Further, even when the water permeability of the coating was 10 to 1000 ml / cm ² / year, when the amount of chromium sulfate added was less than 1% by mass, the formation of weather-resistant stable rust was only partial.

Incidentally, in Comparative Example 15 of Tables 4 and 5, all of the coatings were very brittle and were peeled off from the steel material, so that they could not be exposed.

[0043]

According to the organic resin coating material of the present invention and the surface-treated steel material using the organic resin coating material, it is possible to generate weatherable stable rust at an early stage while preventing the occurrence of flowing rust and floating rust. Even if the amount of flying salt is large, these effects are sufficiently exhibited, and the workability and economic efficiency are excellent.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 201/00 C09D 201/00 C23C 22/30 C23C 22/30 C23F 11/00 C23F 11/00 A (72 Inventor Hideaki Yuki 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (72) Inventor Takayuki Uemura 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (72) Inventor Seishi Kawanishi 6-10-73 Minamitsukaguchi-cho, Amagasaki City, Hyogo Prefecture Inside Shinto Paint Co., Ltd. (72) Inventor Masafumi Ueda 6-10-73 Minamitsukaguchi-cho, Amagasaki City, Hyogo Prefecture Shinto Paint Co., Ltd. In-company F term (reference) 4D075 BB92Z CA32 CA33 CA37 DB02 DC01 DC05 EA06 EA07 EB15 EB19 EB20 EB22 EB33 EB35 EB36 EB38 EC01 EC11 EC13 EC54 4F100 AA07B AA07H AB03A BA02 CA13B CA13H CC01B GB07 JB02 JL09 4J038 CE071 CF101 CG141 DB001 DD001 DD121 DG001 EA011 HA376 HA416 KA08 NA03 PC02 4K026 AA02 BA01 BA08 BA11 BB01 BB08 BB10 CA16 CA18 CA19 CA20 CA23 CA29 CA33 CA41 DA15 DA16 EA04 4K062 AA01 BA01 FA08

Claims (3)

[Claims] 1. A chromium sulfate containing 1 to 65% by mass of chromium sulfate, and the total concentration of the chromium sulfate and the pigment is ± 5% of the critical pigment weight concentration.
%, Characterized in that the content is within%. 2. A chromium sulfate content of 1 to 65% by mass, and the total concentration of the chromium sulfate and the pigment is ± 5% of the critical pigment weight concentration.
% Of the organic resin paint on the steel surface or the rust layer of the steel material with a dry film thickness of 5 to 150%.
A surface-treated steel material coated to a thickness of μm. 3. An organic resin paint containing 1 to 65% by mass of chromium sulfate is applied to a steel material surface or a rust layer on the steel material surface to a dry film thickness of 5-1.
A surface-treated steel material coated so as to have a thickness of 50 μm and a water permeability of 10 to 1000 ml / cm ² / year.