JPH0823072B2 - Inner-composite coated 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 composite coated copper pipe used for a fresh water piping system, that is, a water supply / hot water supply system for a building and the like, and particularly to a copper manufacturing method. The present invention relates to an inner surface Sn-plated composite-coated copper tube having excellent ion elution prevention and excellent peeling resistance of a plating layer, and a method for producing the same.

[Prior Art] Copper pipes, steel pipes, stainless steel pipes, vinyl chloride pipes and the like are used as piping materials for supplying tap water. Among them, copper pipes are widely used because they can be rolled up in a coil shape to facilitate transportation even if they are long, and because of their workability in construction and good corrosion resistance to water and hot water. It is widely used for construction piping.

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 concentration in water may exceed 1 ppm, which is the water quality standard for tap water of the Ministry of Health and Welfare. 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 the water column is small. As a method for 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 tube 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-60-20).
0954, JP-A-60-200975, JP-A-62-6171
No. 7, JP-A-62-61718), a copper tube having a Cu-Sn alloy layer formed on its inner surface (JP-A-61-221359), and a molten plating metal floating in the copper tube. A method of plating using a plug (Japanese Patent Laid-Open No. 62-61716) is known.

Further, the present inventors have previously proposed an inner surface Sn-plated copper pipe for water supply / hot water supply having an Sn plating film made of Sn crystal grains laminated to the inner surface of the copper pipe to a thickness of 3 μm or less (Japanese Patent Application No. 2- 15
No. 2844).

[Problems to be Solved by the Invention] Although the above-mentioned conventional technique can obtain a performance comparable to that of the conventional technique, the plated metal powder and the flux are uniformly applied to the inner surface of the copper pipe. Forming a coating by heating requires a high level of skill and skill, and it has been difficult to always provide products of constant quality.

In addition, such plating means can be applied to pipes with a length shorter than the diameter of the pipe, but pipes with a length longer than the diameter of the pipe (usually an inner diameter of 15.88mm) 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. In addition, Yurick's book states that "contamination of water by copper ions is caused by coating the inner surface of the conduit with Sn (so-called tinned cop).
per) can be avoided. The presence of pores in this coating should be avoided because Sn or Cu-Sn intermetallic compounds become the cathode for Cu and promote corrosion of exposed Cu. "Corrosion reaction and its control" -Principle and application-CORROSION AND CORROSION CONTROL HH by Yurick Sangyo Tosho (1968) p275.

However, the present inventors have found that the coating formed by displacement plating or chemical reduction plating in Japanese Patent Application No. 2-152844 has a high hydrogen overvoltage of Sn even if it has micropores, or because of the sacrificial anode effect. After confirming that copper ions do not elute, we proposed an inner surface Sn-plated copper pipe for water supply / hot water supply, which has an Sn plating film made of Sn crystal grains laminated to a thickness of 3 μm or less on the inner surface of the copper pipe. However, elution of copper ions was sometimes detected after long-term use. This is because the conditions such as the speed of the liquid flowing through the inner surface of the pipe change, and the cause is that the Sn plating layer wears and peels off due to erosion, and the coverage of the Sn plating layer is 50% or less. all right.

Therefore, an object of the present invention is to cover the inner surface of a copper pipe with a Sn plating layer having a thickness of 3 μm or less by a substitutional plating method or a chemical reduction plating method, which has not been conventionally considered, or even for long-term use. Reduces the elution of copper ions from tap water,
Moreover, it is an object of the present invention to provide an inner surface treated copper pipe which is inexpensive and easy to handle, and a manufacturing method thereof.

[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, having a sufficient effect to prevent the elution of copper ions, and
The inventors have found that the presence of an oxide film formed by the oxidation treatment on the surface of the Sn plating layer improves wear resistance and peeling resistance, and have completed the present invention.

That is, the present invention provides (1) an inner surface coating structure of a copper pipe for water supply / hot water supply,
A Sn layer in which Sn crystal grains are deposited by Sn displacement plating or Sn chemical reduction plating on copper as a base material, and an Sn oxide film formed by oxidation treatment on the Sn layer or Sn by each plating. Formed by oxidation of Sn layer with stacked crystal grains
Water supply characterized by having only Sn oxide film and having a sum of thickness of Sn layer and thickness of Sn oxide film of 3 μm or less to 0.1 μm or more and Sn oxide film thickness of 0.1 μm or more
Inner surface composite coated copper pipe for hot water supply.

(2) A plating pretreatment liquid is circulated from the end opening of the coiled copper pipe into the pipe to wash the interior of the pipe, and then a displacement plating liquid or a chemical reduction plating liquid is circulated to obtain a thickness of 3 μm or less to 0.1 μm or less. A Sn plating film having a thickness of μm or more is formed on the inner surface of the copper pipe, and then the plating film surface is oxidized with warm water or steam at 80 to 120 ° C. for 10 to 100 minutes to form an oxide film on Sn. Manufacturing method of inner surface composite coated copper pipe for water and hot water supply.

Is the gist.

[Operation] The configuration and operation of the present invention will be described.

The present invention is very thin, even if micropores are present,
The Sn plating film in which Sn crystal grains are laminated and the Sn oxide film formed by oxidation treatment on the Sn plating film are characterized by being present 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 the plating is such that crystal grains are laminated at each time in the states shown in (a) to (e). This film forming process is schematically shown in FIGS. 1 (a) to (e). 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, it takes a long time to deposit, and the effect of preventing the elution of copper ions is saturated even if the thickness exceeds 3 μm, so 3 μm or less is preferable.

In order to prevent the elution of copper ions, it is most preferable that 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. . A feature of the present invention is that even if copper is exposed, elution can be prevented by performing Sn plating by displacement plating or chemical reduction plating. However, if the coverage is 50% or less, this effect cannot be obtained.

Sn oxide film thickness 0.1 generated by hot water or steam of 80-120 ℃
The Sn oxide film with a thickness of μm or more improves the peeling resistance of the plating film when it is used for water supply / hot water supply piping. An oxide film is formed by washing with water after plating, but only washing with water does not improve the peeling resistance because the oxide film is thin. It is considered that the Sn oxide film formed by hot water or steam is improved in peeling resistance because the activated Sn surface is forcibly formed by hot water in a thick and stable film.

Continuously circulating the treatment liquid inside the pipe Continuously circulating the treatment liquid inside the pipe does not require the invention to perform the treatment on the inner surface of the pipe.
This is effective for long diameter pipes such as copper pipes for hot water supply. 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 Plating Solution The Sn concentration has the greatest effect on the plating thickness, and if it is 1 g / g or less, the film formation rate is low, and the temperature is raised and it takes a long time, which is industrially disadvantageous. If it exceeds 20g /, the dissolution will be saturated depending on the type of plating solution and the solution will not be manufactured.

Treatment time In displacement plating, the precipitation proceeds due to the substitution reaction between copper and tin, so 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.

Hot Water or Steam Treatment Hot water or steam treatment is performed by circulating hot water or steam through the inner surface of the plated copper pipe. When the treatment temperature is 80 ° C or lower, it takes time to form an oxide film, which is not industrial. In addition, the oxide film formed on the plated surface at 120 ° C or higher will be removed by erosion, and as a result, the oxide film will be less generated and the protective effect will be lost.

[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 Various platings were performed to obtain test materials with various plating thicknesses.

Alkaline degreasing → Washing → Pickling (high-concentration acidic solution) → Washing → Neutralization (dilute acidic solution) → Plating → Washing → Washing → Drying Some of the test materials obtained were dissolved in hydrochloric acid solution to reduce the weight. The plating thickness was calculated from the amount, and a test material having a plating thickness as shown in Table 2 was obtained. Further, a part of the obtained test material was immersed in warm water at 100 ° C. for 48 hours to apply a Sn oxide film, and then the following various tests were conducted. Note that Sn
The thickness of the oxide film was analyzed with SnO by using an Auger analyzer while sputtering from the surface in the depth direction.
The depth at which was not detected was measured.

These test materials were immersed in tap water for 24 hours, and the amount of copper ions eluted in tap water was measured by atomic absorption spectrophotometry.

For the peeling resistance test, use a hot water load tester (Fig. 3) with a hot water tank (15) and a cold water tank (15), insert a Sn-plated copper plate (test piece), and put the Sn-plated side into the hot water tank. Exposed
The hot water loading cycle was performed 42 times. In the hot water load cycle, raise the temperature to 80 ° C in about 120 minutes, hold for 20 minutes, and then
It takes about 90 minutes to cool to room temperature. The liquid in the tank was constantly stirred by a magnetic stirrer and kept in a fluid state.

The peeling rate was determined by taking a photograph of the surface of the test piece and then applying the photograph to an image diffraction apparatus. The test material subjected to the hot water load test was immersed in tap water for 24 hours, and the amount of copper ions eluted in the tap water was measured by an atomic absorption spectrophotometric method.

The results are shown in Table 2 above. The plating thickness in the table is the sum of the thickness of the Sn layer and the thickness of the Sn oxide film.

From these, in Nos. 1 to 7 of the present invention examples, since the Sn plating film having the Sn oxide film has a thickness of 0.1 μm or more, the elution amount of copper ions is 0.08 ppm or less, and the peeling test of the plating film is performed. The amount of copper ions eluted after carrying out the step is almost the same as that before the peeling test, which is good.

On the other hand, in Comparative Examples No. 8 to 11, the plating film thickness is
Since the thickness was as thin as 0.05 and 0.01 μm, the elution amount of copper ions after the peeling test increased to 0.1 to 0.4 ppm. Nos. 12 to 17 had no Sn oxide film, and thus the elution amount of copper ions after the peeling test was as large as 0.1 to 0.4 ppm.

Example 2 A coil of a deoxidized copper tube 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 displacement plating solution and the chemical reduction plating solution shown in Table 1 were circulated inside the copper tube for treatment. The time and the treatment temperature were variously changed to obtain inner surface plated copper tubes having different plating thicknesses.

With respect to the obtained copper tube, a test material having a length of 500 mm was cut out from both ends and the central part of the coil, and the thickness of the plating film and the copper ion elution test were conducted.

The thickness of the plating coating 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 3.

The peel resistance was tested by alternately circulating hot water and tap water inside the copper tube for 168 hours, and the results are also shown in Table 3. The plating thickness in the table is the sum of the thickness of the Sn layer and the thickness of the Sn oxide film.

No. 18 with processing time and processing temperature within the scope of the invention
Nos. 28 to 28 have a plating thickness of 0.6 μm or more, of which an oxide film thickness of 0.1 μm is obtained, and the copper ion elution amount is 0.05 ppm or less even after the peeling test, which is good.

On the other hand, in Comparative Examples Nos. 29 and 33, the oxidation treatment temperature was as low as 66 ° C, and the proportion of the oxide film in the plating film was as thin as 3% and 0.7%. Was as high as 0.21 and 0.35 ppm.

In No. 30 to No. 32 and No. 34, the oxidation treatment time was as short as 5 minutes, so the ratio of the oxide film was 5% or less, and the elution amount of copper ions after the peeling test was 0.06 ppm or more. .

[Effects of the Invention] Since the present invention is configured as described above, it becomes possible to easily form a Sn plating film having a thin oxide film on the inner surface of a copper tube, and to prevent elution of copper ions,
Moreover, the effect that the conventional joint parts can be used as they are is extremely useful industrially.

[Brief description of drawings]

FIGS. 1 (a), (b) and (c) are schematic diagrams showing a process of forming a film according to the present invention, showing a situation in which Sn crystals are laminated, and FIGS. Inventive displacement plating
FIG. 2 is a scanning micrograph showing a structure in which Sn metal crystals are laminated, wherein FIG. 2 (a) shows 1 minute later, FIG. 2 (b) shows 5 minutes later, and FIG. 2 (c) shows 10 minutes later. After that, FIG. 2 (d) shows the state after 30 minutes, FIG. 2 (e) shows the state after 60 minutes, and FIG. 3 is a schematic view of the hot water load test apparatus for which the peeling test of the film was performed.

Continuation of the front page (72) Kozo Kono, 3-12-12, Chiennen, Minato-ku, Nagoya, Aichi Prefecture, Sumitomo Light Metal Industry Co., Ltd. Research Laboratory (56)

Claims (2)

[Claims] 1. An Sn layer in which Sn crystal grains are deposited by Sn displacement plating or Sn chemical reduction plating on copper, which is a base material in the internal surface coating structure of a water supply / hot water supply copper pipe, and the Sn layer. Sn oxide film formed by oxidation treatment, or having a Sn oxide film formed by oxidation treatment of the Sn layer in which Sn crystal grains are laminated by each plating, and the thickness of the Sn layer and the Sn oxide film If the sum of the thickness and the thickness is 3 μm or less or 0.1 μm or more, Sn
An inner surface composite coated copper pipe for water supply and hot water supply, characterized by an oxide film thickness of 0.1 μm or more. 2. A plating pretreatment liquid is circulated from the end opening of the coiled copper pipe into the inside of the pipe to wash the inside of the pipe, and then a displacement plating liquid or a chemical reduction plating liquid is circulated to obtain a thickness of 3 μm.
After forming a Sn plating film of m or less to 0.1 μm or more on the inner surface of the copper tube, warm water or steam at 80 to 120 ° C for 10
~ 100 minutes oxidation treatment on the surface of the plating film to a thickness of 0.1μ
Water supply characterized by forming Sn oxide film of m or more
A method of manufacturing an inner surface composite coated copper pipe for hot water supply.