JP2782121B2 - Lead roofing material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roof material having excellent corrosion resistance and aesthetic appearance using a lead substrate.

2. Description of the Related Art Lead is extremely stable in the atmosphere and has a calm color tone, and has long been loved as a roofing material in Europe and the United States. On the other hand, in Japan, lead has hardly been used as a roofing material until now, but in recent years, interest in roofing materials has been increasing with the upgrading of buildings. Lead is said to be extremely stable in the atmosphere, but when used as a roofing material, when exposed to wind and rain, corrosion produces a white lead compound powder on the surface, which flows out due to rain, etc., and causes white stripes. There is a problem that the shape becomes a pattern and the appearance is significantly impaired. The generation of this white lead compound is 1-2.
Years later, it gradually subsides into a dark gray chemically stable protective coating.
It is necessary to prevent the generation of such an initial white compound and to stabilize the color tone. In order to prevent the formation of white initial corrosion products by the chemical conversion treatment of the lead substrate surface, the coating formed by the chemical conversion treatment has low solubility in water, is chemically stable, and causes cracks and peeling. It is necessary to have a color tone that matches the building. Here, since the solubility of lead phosphate in water is extremely low, first studying the formation of a lead phosphate coating shows that the coating formed by immersing a lead substrate in a phosphoric acid solution is not chemically stable. It is a film of lead hydrogen phosphate which is not suitable, or a film which is easily peeled off when rubbed, and a satisfactory film cannot be obtained. Next, based on the report that the composition of a stable protective coating after the initial white corrosion of conventional lead roofing material has subsided is mainly lead sulfate and lead sulfite, lead sulfate-based coating or lead sulfite-based coating When a pure lead plate was immersed in sulfuric acid solutions of various concentrations, a white lead sulfate film was formed. However, when this film was rubbed, the film was easily peeled off into a powdery form and could not be used as a protective film. The coating obtained by subjecting this lead sulfate coating to high-temperature sulfuric acid vapor treatment at 250 to 270 ° C. also produces white corrosion products when exposed to a salt water environment for a long time.

[0002]

Means for Solving the Problems: The present inventors have made an alkali metal permanganate solution such as a KMnO ₄ solution, a NaMnO ₄ solution.
It has been found that by treating a lead substrate with a solution or the like, a stable coating layer is easily formed on the surface of the lead substrate, and the white compound hardly occurs, thereby overcoming the conventional technical problems. The present invention is based on the above findings,
According to the present invention, there is provided a lead roofing material characterized in that an underlayer of lead oxide and an amorphous surface layer are provided on the surface of a lead substrate using a permanganate solution of an alkali metal. As a preferred example, a lead substrate is immersed in a potassium permanganate solution, and an underlayer of lead oxide, K, Mn,
There is provided a lead roofing material characterized by forming an amorphous surface layer containing Pb and O 2.

Hereinafter, the present invention will be described by taking as an example a case where a potassium permanganate (KMnO ₄ ) solution is used. When the lead plate is immersed in the KMnO ₄ solution according to the processing conditions shown in Table 1, a smooth, extremely dense, glossy brass or blue-black coating is formed as shown. The color tone of the film varies depending on the film thickness, and as the film thickness increases, the color becomes brass-purple-blue-black-
Turns black. This coating is chemically very stable, and as an example, the sample of test No. 1 contains 3% saline and 50%
No corrosion product is produced without any change when immersed in sulfuric acid solution at pH 4 and pH 4 for 24 hours. Furthermore, a sulfuric acid solution of pH 4 and 35 ° C,
It shows a glossy blue-black color without any apparent change in the spray test for 30 days. In addition, the coatings of Test Nos. 12 to 15 have apparently cracks even when the sample is bent, and have excellent mechanical strength.

[0004] Here, for the coating of sample No. 1, the S
The EM photograph is shown in FIG. This coating is 2 as shown in FIG.
According to EPMA, the underlayer 1 (about 1
μm), Pb and O are found, and the surface layer 2 (about 5 μm)
In m), K, Mn, Pb, and O are found. When the surface layer was peeled off and analyzed by X-ray diffraction, it was amorphous without any diffraction lines as shown in FIG. On the other hand, Pb and PbO diffraction lines are obtained from the underlayer. From the above results, about 5 μm from the surface of the lead substrate 3 is an amorphous surface layer containing K, Mn, Pb, and O, and an underlayer made of PbO with a thickness of about 1 μm is formed below it. It is thought that it is.

[0005]

[Table 1]

[0006]

The lead roofing material of the present invention has excellent corrosion resistance because it has a two-layer coating layer consisting of an underlayer in contact with a lead substrate and an amorphous surface layer thereabove. It does not produce such white initial corrosives. For this reason, an excellent appearance can be maintained for a long time. Also, the mechanical strength is large and cracks hardly occur. Further, since the color tone can be adjusted by controlling the thickness of the coating, it is easy to achieve harmony with the building.

[Brief description of the drawings]

FIG. 1 is a photomicrograph showing a crystal structure of a cross section of a coating of a roofing material according to the present invention.

FIG. 2 is an X-ray diffraction diagram of a coating surface layer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 22/00-22/86 E04D 1/18 E04D 1/28

Claims (2)

(57) [Claims] 1. A lead roofing material wherein a lead oxide underlayer and an amorphous surface layer are provided on a lead substrate surface with an alkali metal permanganate solution. 2. A lead substrate is immersed in a potassium permanganate solution, and an underlayer of lead oxide, K, Mn,
2. The lead roofing material according to claim 1, wherein an amorphous surface layer containing Pb and O is formed.