JP2544678B2 - Inner Sn plated copper pipe for water / hot water supply and method for manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inner surface Sn-plated copper pipe used for a fresh water pipe system, that is, a pipe for a water supply / hot water supply system of a building and the like, and a manufacturing method thereof.

[Prior Art] Copper pipes, steel pipes, stainless steel pipes, vinyl chloride pipes, etc. are used as water supply piping materials. Among them, copper pipes can be rolled up in a coil shape even if they are long to facilitate transportation, and are widely used due to their workability in construction and good corrosion resistance to water and hot water. It is widely used, especially in piping for construction. However, under special water quality conditions (for example, tap water with a relatively low pH), copper ions may elute from the inner surface of the copper pipe, and the copper ion concentration in water may exceed 1 ppm, which is the tap water quality standard of the Ministry of Health and Welfare. is there. Even if the amount of copper ions is 1 ppm or less, it may be colored blue depending on the type of detergent, and it is desirable that the amount of copper ions in water is small. As a method of reducing the elution of copper ions, Cu-Mg alloys have been developed or chemicals have been added to the water supply. However, in the alloy system, manufacturing methods such as melting, casting, and processing are complicated and expensive. In addition, it was necessary to replenish the chemicals and install a new injection facility when the chemicals were injected into the water supply.

In order to solve these problems, the inner surface of a copper pipe is coated with a metal or alloy having a low melting point and a flux, and then the alloy is coated by heating to improve the corrosion resistance (JP-A-60-2).
00954, JP60-200975, JP62-61717
JP-A-62-61718), a copper tube having a Cu-Sn alloy layer formed on its inner surface (JP-A-61-221359), and a floating plug of molten plated metal in the copper tube. There has been proposed a method of plating by using (Japanese Patent Laid-Open No. 62-61716).

[Problems to be Solved by the Invention] Although the above-mentioned conventional techniques are capable of attaining comparable performance to some extent, the plated metal powder and the flux are uniformly applied to the inner surface of the copper pipe and heated. It is a work that requires a high level of skill and skill to form a film by carrying out, and it has been difficult to always provide a product of constant quality. In addition, such plating means can be applied to pipes whose length is shorter than the diameter of the pipe, but pipes whose length is longer than the pipe diameter (usually an inner diameter of 15.88m
m, length 4m or more) was not applicable.

Further, it is known to coat the copper surface with Sn in order to avoid elution of copper ions from the copper surface. Moreover, Yurick's book states, "Water pollution by copper ions is caused by coating the inner surface of the copper tube with Sn (tinned coppe
r) Can be avoided. The presence of pores in this coating causes Sn or Cu-Sn intermetallics to become a cathode for Cu and promote corrosion of exposed Cu, so pores should be avoided. " HH Yulic "Corrosion reaction and its control-Principle and application-CORROSION AND CO
RROSION CONTROR ”industry book (1968) p275), it was disliked.

However, it is presumed that copper ions do not elute in the film formed by the displacement plating or the chemical reduction plating because of the high hydrogen overvoltage of Sn or the sacrificial anode effect even if the film has micropores.

Therefore, an object of the present invention is to coat the inner surface of a copper pipe with a Sn plating layer having a thickness of 3 μm or less to 0.1 μm or more by a displacement plating method or a chemical reduction plating method which has not been considered so far, and copper ions from tap water are provided. Another object of the present invention is to provide an inner surface-treated copper pipe which is less expensive and easy to handle.

[Means for Solving the Problems] As a result of intensive studies conducted by the present inventors in order to achieve the above object, an extremely thin film formed by displacement plating or chemical reduction plating is a film having minute holes. However, they have found that they have a sufficient effect of preventing the elution of copper ions, and have completed the present invention.

That is, the gist of the present invention is that the inner surface of a copper tube is subjected to displacement plating or chemical reduction plating, and displacement plating or chemical reaction comprising Sn crystal grains laminated to a thickness of 3 μm or less to 0.1 μm or more on copper as a base material. Formed by reduction plating
An inner surface Sn-plated copper pipe for water supply / hot water supply having a Sn-plated film is defined as the first invention, and a plating pretreatment liquid is circulated from the end opening of the coiled copper pipe to the inside of the pipe to wash the inside of the pipe, Sn
By converting 1 g / l to 20 g / l of the displacement plating solution or the chemical reduction plating solution continuously for 10 to 60 minutes, a Sn plating film having a thickness of 3 μm or less is formed on the inner surface of the copper tube.
A second invention is a method of manufacturing an inner surface Sn-plated copper pipe for supplying water and hot water.

[Operation] The present invention is characterized in that the thickness of the coating is very thin, and even if micropores are present, it has an Sn plating coating in which Sn crystal grains are laminated on the inner surface of the copper tube.

Stacking of crystal grains In displacement plating of Sn, precipitation proceeds due to the substitution reaction of copper and tin. From the scanning electron microscope photograph shown in FIG. 2, the deposition pattern of plating is such that crystal grains are laminated at each time in the state as shown in (a) to (e). This film forming process is schematically shown in FIGS. 1 (a) to (c). In chemical reduction plating, a film is laminated due to the catalytic activity of the surface.

Thickness of plating film The thickness of the plating film is preferably 0.1 μm or more in order to prevent the elution of copper ions. Further, in the case of displacement plating, since the precipitation proceeds due to the substitution reaction of copper and tin, the maximum is 3 μm. In the chemical reduction plating, the reaction is slow, the deposition takes a long time, and the effect of preventing the elution of copper ions is saturated even when the thickness is 3 μm or more, and therefore the thickness is preferably 3 μm or less.

In order to prevent the elution of copper ions, it is most preferable that the copper is not exposed. For example, he was disliked, as Euric wrote in his book, "Pores should be avoided because they accelerate corrosion in exposed copper." However, it is presumed that the copper ion does not elute in the coating formed by displacement plating or chemical reduction plating if the coverage is 50% or more because the hydrogen overvoltage of Sn becomes high or due to the sacrificial anode effect. . The present invention is to prevent the elution of copper ions by the Sn plating method even if copper is exposed. However, if the coverage is less than 50%, this effect cannot be obtained.

Next, a manufacturing method will be described.

Continuously circulating the treatment liquid inside the pipe Continuously circulating the treatment liquid inside the pipe does not require the invention to perform treatment on the inner surface of the pipe. It is effective for such a long length with respect to the diameter. Further, the use of displacement plating or chemical reduction plating as the treatment liquid has an effect of uniformly forming a thin film on the inner surface of the copper tube because the plating film deposition rate is slow.

Sn concentration in the plating solution The Sn concentration has the greatest effect on the plating thickness.If it is less than 1 g / l, the film formation rate is low and it takes a long time even if the temperature is raised, which is industrially disadvantageous. is there. If it exceeds 20 g / l, depending on the type of plating solution, the solution will be saturated and the solution cannot be manufactured.

Treatment time In displacement plating, the precipitation proceeds due to the substitution reaction of copper and tin. Therefore, if the exposed copper portion is reduced, the precipitation will decrease, so it is necessary to adjust the treatment time to control the film thickness. preferable. Also, with chemical reduction plating, a thick plating thickness can be obtained by newly updating the plating solution, but in order to control the film thickness, the deposition rate is about 1 μm / hr, so the treatment time should be adjusted. Is preferred.

The temperature affects the plating thickness, and the higher the temperature is, the faster the plating speed becomes, which is preferable, but if the temperature is 80 ° C. or higher, the plating solution is decomposed, which is not preferable.

[Examples] Examples of the present invention will be described.

Example 1 A deoxidized copper plate having a side length of 100 mm was prepared, the displacement plating solution and the chemical reduction plating solution shown in Table 1 were used in the following steps, the solution temperature was 60 ° C., and the treatment time was Plating with various changes was performed to obtain test materials with various changes in plating thickness.

Alkaline degreasing → Washing → Pickling (high-concentration acidic solution) → Washing →
Neutralization (dilute acidic solution) → plating → washing with water → washing with hot water → drying A part of the obtained test material was dissolved in a hydrochloric acid solution, the plating thickness was calculated from the weight reduction amount, and a test material having a plating thickness as shown in Table 2 was obtained. These test materials were immersed in tap water for 24 hours, and the amount of copper ions eluted in the tap water was measured by atomic absorption spectrophotometry. The results are shown in Table 2.

From these, the invention examples No. 1 to 10 have a plating film thickness of 0.1.
Since it is present in an amount of μm or more, the elution amount of copper ions is 0.08 ppm or less, which is good. On the other hand, No. 11 of the comparative example is
Since the plating film thickness is 4 μm, the elution amount of copper ions is as good as 0.01 ppm or less, but this is obtained by the hot dipping method of the plate material, and it is difficult to plate the inner surface of a long pipe material. .

No. 12 and 16 have thick plating thickness, so
The elution amount of copper ions is as good as 0.01 ppm or less, but it is obtained by the flux heating method and the electroplating method, and it is difficult to perform the inner surface plating of a long pipe material.

No. 13 and 14 are displacement plating and chemical reduction plating, but since the plating thickness is as thin as 0.01 μm, the elution amount of copper ions is 0.36 ppm and 0.20 ppm, which exceeds the standard value (0.1 ppm) of the present invention. ing.

No.15 is chemical reduction plating and the plating film thickness is 4 μm.
Although it was formed, the copper ion elution amount is 0.01 ppm or less and it is good, but the rate of chemical reduction plating is low,
Frequent renewal of the liquid and long processing time are not preferable.

No. 17 is a copper plate material that has not been plated, and the amount of copper ions eluted is as high as 1.24 ppm.

Example 2 Using various displacement plating solutions, tests in which Sn concentration, treatment time and treatment temperature were changed were conducted in the same manner as in Example 1,
The results are shown in Table 3.

No. 18 to 27, in which the Sn concentration of the plating solution, the treatment time and the treatment temperature are within the scope of the invention, have a plating thickness of 0.08 μm.
The above is obtained, the copper ion elution amount is 0.08 ppm or less,
It is good.

On the other hand, No. 28 has a high Sn concentration of 20 g / l, but the treatment time is as short as 5 minutes and the plating thickness is as thin as 0.08 μm.
The elution amount of copper ions was 0.10 ppm.

In Nos. 29, 30 and 31, since the Sn concentration of the displacement plating solution was as low as 0.5 g / l, the treatment time and the treatment temperature were set to the upper limits of the range of the invention, but the plating thickness became 0.05 to 0.07 μm, The elution amount of copper ions was as high as 0.15 to 0.18 ppm.

Example 3 A test was conducted by using the displacement plating solution and the chemical reduction plating solution and changing the treatment time and the treatment temperature in the same manner as in Example 1, and the results are shown in Table 4.

No. 32 to 4 whose processing time and temperature are within the scope of the invention
In No. 5, the plating thickness is 0.25 μm or more, and the amount of copper ions eluted is 0.04 ppm or less, which is good.

On the other hand, in Comparative Examples Nos. 46 to 51, since the treatment time was short at 5 minutes, the plating thickness was 0.04 μm or less, and the copper ion elution amount was 0.19 ppm or more.

Example 4 A coil of a deoxidized copper pipe having an outer diameter of 15.88 mm, a wall thickness of 0.71 mm and a length of 50 m was prepared, and the treatment liquid was circulated from the pipe end of the coil in the treatment process shown in the first embodiment to perform plating treatment. Was done. For the obtained copper tube, length from both ends and the center of the coil
A test material of 500 mm was cut out and subjected to a plating film thickness and a copper ion elution test.

The thickness of the plating film was measured by filling a copper tube with a hydrochloric acid solution to dissolve the Sn layer, and calculating the plating thickness from the weight reduction amount.

In the copper ion elution test, tap water is filled in a 500 mm copper pipe.
After sealing and 24 hours later, the elution amount of copper ions was measured by atomic absorption spectrophotometry. The results are shown in Table 5.

No.52 with processing time and processing temperature within the scope of the invention
Nos. 54 to 54 have a plating thickness of 0.33 μm or more, and the elution amount of copper ions is 0.01 ppm or less, which is good. On the other hand, in Comparative Examples Nos. 55 and 56, since the treatment time was as short as 5 minutes, the plating thickness was 0.02 μm or less, and the elution amount of copper ions was 0.31 ppm or more.

EFFECT OF THE INVENTION Since the present invention is configured as described above,
It is possible to easily form a thin Sn plating film on the inner surface of a copper pipe, prevent the elution of copper ions, and have the effect that the conventional joint parts can be used as they are, which is extremely useful industrially.

[Brief description of drawings]

FIGS. 1 (a), (b) and (c) are schematic views showing a situation in which Sn crystals are stacked. Figure 2 (a) after 1 minute, Figure 2 (b) after 5 minutes, Figure 2 (c) after 10 minutes, Figure 2 (d) after 30 minutes, Figure 2 (e).
FIG. 6 is a scanning micrograph showing a state in which Sn crystals are laminated by displacement plating after 60 minutes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kozo Kono, Kochi Kono, Aichi Prefecture, Nagoya City, 3-1, 12th, 1000, Minen-ku, Sumitomo Light Metal Industries, Ltd. (56) Reference JP-A-63-109179 (JP, A) ) Japanese Patent Publication Sho 55-34862 (JP, B2)

Claims (2)

(57) [Claims] 1. In an internal surface film structure of a copper pipe for water supply / hot water supply, a thickness of 3 μm to 0.1 μm is formed on copper as a base material.
An inner surface Sn-plated copper pipe for water / hot water supply, comprising an Sn plating film formed by displacement plating or chemical reduction plating composed of the above-mentioned Sn crystal grains. 2. A pretreatment liquid for plating is circulated from the end opening of the coiled copper pipe into the pipe to wash the inside of the pipe, and then a substitution plating liquid of 1 g / l to 20 g / l in terms of Sn or Manufacture of Sn-plated copper pipe for water supply / hot water supply, characterized in that a chemical reduction plating solution is continuously circulated for 10 to 60 minutes to form a Sn plating film having a thickness of 3 μm or less to 0.1 μm or more on the inner surface of the copper pipe. Method.