JPH05237450A - Material for roof/exterior - Google Patents

Abstract

PURPOSE:To obtain a roof/exterior material excellent in weatherability and design effect by providing a galvanized layer colored so as to form a hue having a specific brightness index and a specific chromaticness index on a stainess steel plate and applying clear painting to the surface of the galvanized layer. CONSTITUTION:A galvanized layer colored so as to form a hue which has a brightness index L-value of 45-52, a chromaticness index a-value of 0-0.4 and a chromaticness index b-value of 1.3-4.4 is provided on a stainless steel plate and clear painting is applied to the surface of the galvanized layer. At this time, the galvanized layer is formed by hot dip zinc coating and the basis wt. of zinc is set to 200g/m<2> or more per a single surface and coloration due to chemical forming treatment is performed by phosphate treatment and the basis wt. of a phosphate film is set to 4.0-5.0g/m<2>. The thickness of clear painting is set to 5-20mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-plated stainless material for roof / exterior which is excellent in weather resistance and design.

[0002]

2. Description of the Related Art Conventionally, as a metal roof / exterior material,
Copper plate, aluminum plate, stainless steel plate, zinc alloy plate,
Hot-dip galvanized steel sheets and coated steel sheets are used.

Copper forms the basic salt patina on its surface in the atmosphere. This patina has been used since ancient times in shrines, temples, etc. to add a sense of flavor to the building. A problem when using copper as a roof / exterior material is galvanic corrosion with other metals. For example, it enhances the corrosion of aluminum, iron, and zinc, which are base metals less than copper. There is also a problem that the plants are killed by the copper ions that flow by the rain. Among metals, copper belongs to the soft category, so its use is restricted in areas where strength is a problem. Therefore, although there is a material plated with copper on the steel sheet, the above-mentioned galvanic corrosion is feared.

Aluminum is a very base metal,
Corrosion resistance is maintained by the film formed on the surface layer. Therefore, in a severe corrosive environment in which the coating is destroyed, deep pitting occurs. Corrosion of aluminum in the atmosphere begins with the adhesion of dust, iron powder, and chloride ions, so it is necessary to clean it for a while in coastal areas and heavily soiled areas.

Zinc is a base metal, and the metal itself is highly corrosive, but keeps the weather resistance due to the basic corrosion product formed on the surface. Zinc has been conventionally plated on ordinary steel plates because it has a function of sacrificially protecting other metals by being corroded by itself. Corrosion protection by galvanizing has a problem of white rust flow. Zinc has a large coefficient of thermal expansion as compared with other metals, which limits its use in environments where the temperature difference between day and night and summer and winter is large. In addition, zinc is a very soft metal, and its use is restricted in a region where strength is a problem. For this purpose, alloy elements are added to zinc to increase the strength, or steel sheets are plated to be used. This galvanized steel sheet also does not have sufficient corrosion resistance in the use environment, and there is a problem of perforation due to corrosion and red rust flow from the end surface.

The stainless steel sheet has excellent corrosion resistance due to the passivation film on the surface. However, there is a problem that local corrosion occurs due to pitting corrosion and crevice corrosion, and the red rust flow from the corroded portion deteriorates the appearance of the structure. In addition, since the gloss of stainless steel does not match the natural environment, surface treatment such as coloring may be performed.

Conventionally, these steel sheets have been used unpainted, but colors and designs tend to be required in places easily accessible to the public such as public buildings. Therefore, coated steel sheets with high weather resistance coating are used. Has been done. However, coated steel sheets also have problems such as fading due to deterioration of the coating film, swelling of the coating film due to corrosion under the coating film, and rust flow from the end surface. Especially 2
In order to guarantee a high weather resistance of 0 years or more, it is necessary to improve the quality of the paint, which is disadvantageous in terms of cost due to, for example, a fluorine-based paint.

The present inventors have examined the corrosion when galvanizing stainless steel, and as a result, not only the sacrificial anticorrosion effect by the sacrificial dissolution of zinc but also the corrosion inhibition effect by the adhesion of zinc corrosion products. And found that
132792, JP-A-2-4996, JP-A-3-2
No. 26583. Here, the corrosion inhibition effect by the corrosion product of zinc is an action by which the corrosion product of zinc adhering to the surface of the stainless steel sheet suppresses the oxygen reduction reaction which is a cathode reaction in the corrosion process, and the pH buffering action by dissociation. This effect was observed when a stainless steel plate was used as the plating base plate, and was not observed when ordinary steel was used. Particularly, in JP-A-3-226583, a material obtained by galvanizing stainless steel is subjected to a coloring treatment by a chemical conversion treatment so that the color tone is 45 to 5 in terms of a chromaticness index and an L value.
2. A roof / exterior material made of a stainless steel plate having a galvanized layer having a chemical conversion treatment, which has a color tone of a value of 0.0 to 0.4 and b value of 1.3 to 4.4, is disclosed.

The requirements to be met as a material for a metal roof / exterior are, in general, (1) sufficient weather resistance in the use environment and changes in surface appearance (for example, fading of painted steel sheets, reduction of gloss, corrosion). ) Is small. (2) It has sufficient strength as a roof / exterior material. (3) The coefficient of thermal expansion is small. (4) Having a color tone that is in harmony with the natural environment. However, the material of JP-A-3-226583 substantially satisfied this requirement, but was unsatisfactory in that the life of the colored layer was limited. The present invention solves this point.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, zinc colored on a stainless steel plate has a lightness index L value of 45 to 52, a chromaticness index a value of 0 to 0.4, and a b value of 1.3 to 4.4. A roof / exterior material comprising a galvanized stainless steel sheet having a plating layer and having a clear coating on the surface layer. In the present invention, preferably, the galvanized layer is hot dip galvanized, and the basis weight of zinc is 200 g / m ² or more per side. In the present invention, the coloring is preferably a phosphate treatment, and the basis weight of the phosphate film is 4.0 to 5.0 g / m 2.
^{Is 2} . In the present invention, the thickness of the clear coating is preferably 5 to 20 μm.

In the present invention, stainless steel is preferably galvanized at 200 g / m ² or more per side. This is for improving the corrosion resistance of stainless steel and for the coloring treatment described later. The coating weight of zinc plating should be determined by predicting the service life according to the amount of zinc consumed in the environment used as the roof / exterior material. 20 in a relatively mild corrosive environment such as in the mountains
Even with a basis weight of 0 g / m ² , a life expectancy of about 40 years is predicted. However, in relatively severe corrosive environments such as beach areas, the annual consumption of zinc is said to be 20 g / m ² or more. A galvanized layer of 200 g / m ² or more seems necessary. Further, the life can be extended by increasing the basis weight. It is well known that the hot dipping method is more cost effective than the electroplating method for galvanizing 200 g / m ² or more per side.

After galvanizing, the surface is colored, preferably by a phosphate treatment. This is because the galvanized surface has a metallic luster, and when used as a roof / exterior material, it does not match the natural color tone. Further, if galvanized as it is, the metallic luster is lost due to the formation of a basic corrosion product formed on the surface, and the color changes with time to white and black gray. This is also a problem when galvanized steel sheets are used as roof / exterior materials. From these viewpoints, the galvanized surface is colored.

The basis weight of the phosphate coating is 4.0-5.0 g /
By setting m ² , the color tone is that of zinc corrosion products, that is, the lightness index L value according to JIS Z 8729 is 45 to 52, and the chromaticity index a value is 0 to 0.
It has a color tone of 1.4 to 1.4 and a color tone of 1.3 to 4.4. When the basis weight of the phosphate film is less than 4.0 g / m ² , the color becomes white unlike the color tone of the corrosion product of zinc. Further, when the basis weight is more than 5.0 g / m ² , although the color tone of the corrosion product of zinc is similar, the phosphate film is easily peeled off, the workability is poor, and the treatment time is long. It becomes economically disadvantageous that the length becomes longer. Therefore, the basis weight of the phosphate film formed by the phosphate treatment is preferably 4.0 to 5.0 g / m ² .

Here, as long as the finish of coloring by the chemical conversion treatment has a predetermined color tone, it is not limited to the phosphate treatment, and other treatments are possible. For example, in order to improve corrosion resistance, chromate treatment may be performed on the phosphate film. Further, the weight per unit area may be suitable for each process. Moreover, since the dissolution of the plating layer is suppressed by forming the phosphate coating on the zinc plating layer, it is expected that the corrosion resistance is improved and the life of the plating layer is extended.

In the present invention, clear coating is applied to the zinc-plated surface layer after the phosphate treatment. This is to improve corrosion resistance and prevent scratches during processing. Until the clear coating is deteriorated by applying the clear coating, the galvanized layer does not come into contact with the atmosphere, so that the corrosion reaction is less likely to occur. Therefore, the consumption rate of the galvanized layer is reduced,
Depending on the life of the clear coating, it is possible to have a long-term function as a roof / exterior material. Further, since the phosphate film and the plating layer are soft, they are likely to be flawed during processing. When the plating layer has a flaw that reaches the material, the galvanic action accelerates the dissolution rate of zinc around the flaw, causing white rust flow and impairing the aesthetic appearance, and partially shortening the life of the zinc plating layer. Will be made. Therefore, by applying clear coating, it becomes difficult for defects to enter during processing, and local dissolution of zinc can be prevented.

When the thickness of the clear coating is less than 5 μm, the clear coating is destroyed when a strong force is applied from the outside,
Defects are likely to occur in the plating layer. Further, deterioration due to solar heat is fast, and as a result, corrosion of the galvanized layer is accelerated. When the film thickness of the clear coating is more than 20 μm, although the scratch resistance and the life of the coating film are excellent, the swelling of the coating film due to corrosion under the coating film is noticeable and the appearance is impaired. In addition, the deteriorated clear paint becomes dusty and may get stuck in a gutter.
Therefore, in the present invention, the film thickness of clear coating is 5 to
It was set to 20 μm. In this range, the color tone is similar to that of zinc corrosion products, but outside this range, the color changes extremely. In the present invention, acrylic clear coating is preferably applied, but the type of paint is not limited as long as it is a paint that can maintain the color tone of the phosphate film. Also,
By changing the film thickness of the clear coating within the range of 5 to 20 μm, it is possible to finely adjust the color, and it is possible to provide a black gray tone according to the environment.

[0017]

[Detailed Disclosure of the Invention]

Example Commercially available SUS430 steel strip (nitric acid hydrofluoric acid pickling finish, 0.4 mm
(Thickness) was subjected to galvanization by a hot dip coating method, and colored by the phosphate treatment with the phosphate treatment liquid shown in Table 1.

[Table 1]

[Table 2]

The color tone after coloring is measured in accordance with JIS Z8721, and is based on JIS Z8727 L,
The a and b values are L value = 48.7, a = 0.08, b = 3.0.
It was 3. This plate was coated with an acrylic clear coating (trade name: Aklion (produced by Kubo Ken Paint)) by the roll coater method, and the thickness of the clear coating was 5, 10, 2
Four kinds of materials of 0,30 μm were obtained. These materials were subjected to an accelerated corrosion test of 80 cycles and 200 cycles under the conditions shown in Table 2 to examine the corrosion resistance and the change in color tone. The results are shown in Table 3. The phosphate-treated material (A) which was not subjected to clear coating showed good corrosion resistance after the 80-cycle test, but white rust was generated on the entire surface after the 200-cycle test. In addition, even when the clear coating is applied, the clear coating film thickness of more than 20 μm (E) causes swelling of the coating film after the 200-cycle test, white rust flow from the swelling part is recognized, and The color tone also became dark due to the low L value, which was different from the color tone of the zinc corrosion product. On the other hand, the material (B, C, D) of the present invention, which was subjected to clear coating so as to have a coating film thickness of 5 to 20 μm, showed no coating swelling or white rust even after the 200-cycle test. It has been found that the corrosion of the galvanized layer is protected, excellent corrosion resistance is exhibited, and the color tone can be maintained.

[0019]

[Table 3]

[0020]

[Effect] As described above, in the method of the present invention, the stainless steel is galvanized at 200 g / m ² or more per side, and the surface is subjected to clear coating. Shows extremely excellent weather resistance. Since the color of the corrosion product of zinc is previously colored by the phosphate treatment, the color tone does not change with time even if the corrosion of the plating layer progresses. Also, since it is a black gray color similar to the Japanese roof tile, it creates a profound and calm atmosphere. further,
Since the plating base is stainless steel, it has sufficient strength as a roofing material, has a smaller coefficient of thermal expansion than zinc sheets, and can be applied to long roofs. The material of the present invention is a roof / exterior material having semi-permanent weather resistance and designability even in a severe corrosive environment, as compared with conventional metal materials.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location C23C 22/00 Z 28/00 A E04F 13/12 A 7806-2E // B32B 15/08 G 7148-4F ( 72) Inventor Shuji Ohashi 3-4-1, Marunouchi, Chiyoda-ku, Tokyo Nisshin Steel Co., Ltd.

Claims (4)

[Claims] 1. A color tone of a lightness index L on a stainless steel plate.
The value is 45 to 52, and the chromaticness index a value is 0 to 0.
4. A roof / exterior material made of a zinc-plated stainless steel sheet having a zinc coating layer having a b value of 1.3 to 4.4 and a clear coating on the surface layer. 2. The roof according to claim 1, wherein the galvanized layer is formed by hot dip galvanizing, and the basis weight of zinc is 200 g / m ² or more per side.
Exterior materials. 3. The material according to claim 1, wherein the coloring method by chemical conversion treatment is phosphate treatment, and the basis weight of the phosphate coating is 4.0 to 5.0 g / m ^2. Characteristic roof / exterior material. 4. The roof according to claim 1, wherein the clear coating has a thickness of 5 to 20 μm.
Exterior materials.