JPH07173639A - Corrosion resistant copper tube and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a corrosion resistant copper tube which is used for the pipings of the water or hot water supply system in a building or the like and whose inner surface is tin-plated, and its manufacturing method thereof. CONSTITUTION:In the inner film structure of a copper tube for supplying water or hot water, after the tin-plated film consisting of the tin particles laminated to the thickness of <=3mum is formed on the copper which is the base metal, the tin-plated film consisting of the tin particles laminated to the thickness of <=3mum through the substitution plating or chemical reduction plating is formed on the corrosion resistant copper tube for supplying water or hot water and the copper which is the base metal of the inner surface of the copper tube which are characterized in that the number of pin holes (fine pores) in the plated film is set to <=0.1/cm<2> on the average through the frictional working. Then, the solid substance is inserted in the tube, and the number of the pinholes (fine pores) in the plated film is reduced to <=0.1/cm<2> on the average through the friction working. This constitution greatly improves the corrosion resistance even under the severe water quality environment, and prevents the plated film from cracking and there is no fear of the deformation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner surface tin-plated copper pipe used for a fresh water pipe system, that is, a water supply / hot water supply system for a building or the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a water supply pipe material for water supply,
Copper pipes, steel pipes, stainless steel pipes, resin pipes, etc. are used. Among them, copper pipes can be rolled up in a coil shape even if they are long to facilitate transportation, and are widely used because they have good workability in construction and good corrosion resistance against hot and cold water. It is used.

[0003]

However, even a phosphorus-deoxidized copper pipe having excellent corrosion resistance and workability causes pitting corrosion depending on the water quality (for example, water such that HCO ₃ ⁻ / SO ₄ ² <1). Sometimes. Furthermore, at the joint between the copper pipe and the copper pipe joint, erosion due to significant disturbance of the water flow may occur inside, leading to water leakage.

In order to solve these problems, copper pipes or copper alloy pipes having improved corrosion resistance have been proposed (for example, JP-A-60-200954 and JP-A-60-200975).
JP-A-62-61717, JP-A-62-61717
61718). Further, a method for producing these copper pipes or copper alloy pipes has been proposed (for example, JP-A-62-617).
16 publication). Further, the present inventors have proposed a copper pipe or a copper alloy pipe having improved corrosion resistance and a method for producing the same (Japanese Patent Laid-Open Nos. 4-45282 and 4-99180,
JP-A-4-131384).

All of the above-mentioned techniques can provide a considerable amount of performance, but for example, JP-A-60-20
It is a work that requires a high level of skill and skill to uniformly coat the inner surface of the copper pipe with the plated metal powder and the flux and form a film by heating as shown in Japanese Patent Publication No. 0954. It has been difficult to always provide products of constant quality.

Even with the inner surface tin-plated copper pipe previously proposed by the present inventors, pinholes (micropores) in the plating film are present in a severe water quality environment (for example, in a highly oxidizing environment).
It was found that corrosion started from the point of.

It is known that the pinholes existing in the tin-plated film formed by displacement plating or chemical reduction plating can be reduced by reflow treatment (heat treatment here), but the plated film becomes brittle depending on the treatment temperature and time. It has been found from a number of experiments that the tin-copper intermetallic compound, which has poor ductility, may crack the plating film due to severe deformation.

The present invention solves the above-mentioned problems in the prior art and is used for a fresh water piping system which has high corrosion resistance and does not have a risk of cracking of the plating film against severe deformation, that is, piping for water supply / hot water supply systems such as buildings. It is an object of the present invention to provide an inner surface tinned copper pipe and a method for manufacturing the same.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted diligent research and, as a result, carried out displacement plating or chemical treatment on the inner surface of a copper pipe used for water supply / hot water supply system piping. The inventors have found that high corrosion resistance and easy workability can be realized by reducing the number of pinholes (micropores) existing in the tin-plated film formed by reduction plating to a certain number or less, and completed the present invention.

That is, the present invention based on the above findings is
In the inner surface coating structure of a copper pipe for water supply / hot water supply, a tin plating film composed of tin crystal grains laminated to a thickness of 3 μm or less is formed on copper as a base material, and a pinhole of the plating film (small The main point is a corrosion-resistant copper pipe for water supply / hot water supply, characterized in that the average number of holes is 0.1 / cm ² or less. After forming a tin-plated film consisting of tin crystal grains laminated to a thickness of 3 μm or less, insert a solid substance into the tube, and friction-process the average number of pinholes (micropores) of the plated film to 0.1. The gist is a method of manufacturing a corrosion-resistant copper pipe for water supply and hot water supply, which is characterized in that the water content is reduced to / cm ² or less.

[0011]

The structure and operation of the present invention will be described. The water supply / hot water supply copper pipe of the present invention has excellent corrosion resistance even in a severe water environment,
Moreover, in order to provide a corrosion-resistant copper tube inexpensively and easily, a tin-plated film which is very thin (thickness of 3 μm or less) and has few pinholes (micropores) is formed on the inner surface of the copper tube.

When a tin-plated film is formed by displacement plating or chemical reduction plating, there is a 3
Since the formation of a thick plated film having a thickness of more than μm is costly, it is desirable that the film thickness be 3 μm or less. In the present invention, the reason why the plating film forming means is the displacement plating or the chemical reduction plating is that it is necessary to insert the counter electrode inside the copper tube according to the electroplating means, and this becomes difficult in the case of a thin tube. . According to the displacement plating means or the chemical reduction plating means, the plating film is formed only by passing the chemical solution into the tube, and the operation is easier than the electroplating means. Further, the molten metal plating means cannot circulate the molten tin in the copper tube having a small inner diameter due to the surface tension of the plating bath, and cannot control the plating film thickness to be thin.

It is presumed that the tin-plated film formed on the copper surface by displacement plating or chemical reduction plating maintains the corrosion resistance due to the sacrificial anode effect even if there are pinholes (micropores). No. 45282), pinholes (micropores) must be avoided because corrosion occurs in a portion where copper is exposed under a severe water quality environment. The average number of pinholes (micropores) present in the plating film is 0.
It has been found from many experiments that if the number is reduced to 1 / cm ² or less, the corrosion resistance is significantly improved even in a severe water quality environment.

In the present invention, as a means for reducing the number of pinholes (micropores) in the plating film, the inner surface of the copper tube on which the tin plating film is formed by displacement plating or chemical reduction plating is used.
By inserting a solid substance (resin or metal plug) and frictionally processing (for example, drawing or drawing) the surface of the tin-plated film, the number of pinholes (fine holes) in the plated film is reduced.

A typical method for reducing pinholes (micropores) is reflow treatment, but friction processing does not tend to cause cracks in the plated film as a tin-copper intermetallic compound. Since the pure tin layer having processability remains on the surface of the plated film, there is no risk of the plated film cracking even under severe deformation.

[0016]

EXAMPLES The present invention will be specifically described with reference to Examples.
The present invention is not limited thereby. Example 1 Outer diameter 22.22 mm x wall thickness 0.81 mm x length 100 m
A tin-plated film having a film thickness of 0.6 to 2.0 μm was formed on the inner surface of a copper pipe of m, and the plated film was rubbed using a metal plug to produce a prototype. With respect to these samples, the number of pinholes was examined by a porosity test, and the corrosion resistance of the coating was evaluated by a potentiostatic electrolysis test.

The test method is as follows. Porosity test (immersion method) Test liquid: 30 vol% ammonia water, 15 mass% ammonium persulfate Immersion time: 60 minutes Liquid temperature: room temperature potentiostatic electrolysis test Test liquid: Tokyo tap water Potential: 200 mV vs. SCE period: 3 days The results of the test are shown in Table 1 and the metallographic micrograph of the plated film surface after the porosity test in FIG.

[0018]

[Table 1] * 1: Average * 2: ◎: No corrosion ○: General corrosion (no pitting corrosion) ×:
Pitting corrosion occurred

Example 2 The same sample as in Example 1 was used to measure the amount of copper ions eluted in the water supply system and the hot water supply system. The test solution used was Nagoya City tap water (normal temperature) as a water supply system, and Nagoya City tap water (60 ° C.) as a hot water supply system. The above two types of sample water,
After being filled in a sample copper tube and left at room temperature for 24 hours, the copper ion concentration in each sample water was measured by an atomic absorption method. The test results are shown in Table 2.

[0020]

[Table 2] In Table 2, Nos. 2 to 4 are examples satisfying the conditions of the present invention, and all have excellent copper ion elution resistance.

[0021]

Since the present invention is configured as described above, it is suitable for fresh water piping systems, that is, piping for water supply / hot water supply systems for buildings, etc., and the corrosion resistance is greatly improved even under severe water quality environment. At the same time, there is an effect that the plating film is not likely to be cracked even when it is deformed, which is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a photomicrograph showing a metal structure of a copper tube of the present invention after a plating surface porosity test.

Claims (2)

[Claims] 1. An inner surface coating structure of a copper pipe for water supply / hot water supply, wherein a tin plating film composed of tin crystal grains laminated to a thickness of 3 μm or less is formed on copper as a base material, and Corrosion resistant copper pipe for water and hot water supply, characterized in that the average number of pinholes (micro holes) is 0.1 / cm ² or less. 2. A tin plating film made of tin crystal grains laminated to a thickness of 3 μm or less is formed on copper, which is a base material of the inner surface of a copper pipe for supplying water and hot water, and then a solid substance is placed in the pipe. A method for producing a corrosion-resistant copper pipe for water supply / hot water supply, which comprises inserting and rubbing to reduce the number of pinholes (micropores) in the plating film to an average of 0.1 / cm ² or less.