JPH0445282A - Internally tinned copper pipe for feeding water and hot water and production thereof - Google Patents

Abstract

PURPOSE:To obtain a low-cost internally tinned Cu pipe suppressing the leaching of Cu ions in tap water and easy to handle by coating the inside of a Cu pipe with an Sn layer by substitution tinning or chemical reduction tinning. CONSTITUTION:When the inside of a Cu pipe is coated with an Sn layer consisting of Sn grains by substitution tinning or chemical reduction tinning to produce an internally tinned Cu pipe for feeding water and hot water, a pretreating soln. for tinning and 1-20g/l (expressed in terms of Sn) tinning soln. for substitution tinning or chemical reduction tinning are continuously circulated in the coil-shaped Cu pipe from an open end for 10-60min to form an Sn layer of <=3mum thickness on the inside of the Cu pipe. An internally tinned Cu pipe preventing the leaching of Cu ions can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an internal Sn-plated copper pipe used for freshwater piping systems, that is, piping for water supply and hot water supply systems for buildings, etc., and a method for manufacturing the same.

[Prior Art] Copper pipes, copper pipes, stainless copper pipes, vinyl chloride pipes, etc. are used as piping materials for water supply of waterworks. Among these, copper pipes are widely used because even long pipes can be rolled up into coils and transported easily, and are easy to construct and have good corrosion resistance of 1 or higher against water and hot water. It is often used for architectural piping in temples. However, under special water quality conditions (for example, tap water with a relatively low pH), copper ions are eluted from the inner surface of copper pipes, and the concentration of copper ions in the water can exceed the IPPM water quality standard set by the Ministry of Health and Welfare. be. Further, even if the amount of copper ions is 1 ppm or less, the water may be colored blue depending on the type of detergent, so it is desirable that the amount of copper ions in the water be small.

As a method to reduce the elution of copper ions, Cu-M
G-based alloys have been developed or chemicals have been introduced into the water supply. However, in the case of alloy-based materials, manufacturing methods such as melting, casting, and processing are complicated and expensive. In addition, injecting chemicals into the water supply required replenishing the chemicals and installing new dosing equipment.

In order to solve these problems, the inner surface of the copper tube was coated with a low melting point metal or alloy and flux, and then heated to coat the alloy and improve corrosion resistance (Japanese Patent Application Laid-Open No. 1986-1999-1).
200954, JP 60-200975, JP 62-61717, JP 62-617
18), a copper tube with a Cu-5n alloy layer formed on the inner surface (Japanese Unexamined Patent Publication No. 61-221359), a method of plating molten plating metal inside a copper tube using a floating plug (Special 62-61716) etc. have been proposed.

[Problems to be Solved by the Invention] All of the above-mentioned conventional techniques can achieve a certain level of performance, but they do not require that plating metal powder and flux be uniformly applied to the inner surface of the copper tube and then heated. Forming a film by doing this is work that requires advanced technology and skill, and it has been difficult to always provide products of constant quality. In addition, such plating means can be applied to pipe materials that are short in length relative to the pipe diameter, but are applicable to pipe materials that are long relative to the pipe diameter (usually inner diameter 15.88 mm), such as water and hot water supply piping.
mm, length of 4 m or more) could not be applied.

Furthermore, in order to prevent copper ions from eluting from the copper surface, it is known to coat the copper surface with Sn-. Moreover, according to Neelik's book, ``Water contamination by copper ions is
By coating the inner surface of the copper tube with Sn (tinne
d copper) can be avoided. If there are pores in this coating, Sn or Cu-8n
Pores must be avoided because the intermetallic compounds act as cathodes for Cu, accelerating corrosion of exposed Cu areas. -CORRO8ION AND
C0RRO8IONCONTRORJ Industrial Book (19
68) p275), it was hated.

However, in a film formed by displacement plating or chemical reduction plating, even if there are micropores, copper ions are presumed not to be eluted due to the high Sn hydrogenation voltage or the sacrificial anode effect.

Therefore, the purpose of the present invention is to coat the inner surface of a copper pipe with a Sn plating layer with a thickness of 3 μm or less using a displacement plating method or a chemical reduction plating method, which has not been thought of in the past, to reduce the elution of copper ions by tap water. However, it is an object of the present invention to provide an internally treated copper tube that is inexpensive and easy to handle.

[Means for Solving the Problems] In order to achieve the above object, the present inventors have conducted intensive research and found that extremely thin films formed by displacement plating or chemical reduction plating, even if they have minute pores, However, the present inventors have found that the present invention is sufficiently effective in preventing the elution of copper ions.

That is, the gist of the present invention is to coat the inner surface of a copper tube with a thickness of 3.
The first invention is an internal Sn-plated copper pipe for water supply and hot water supply having a Sn-plated film consisting of Sn crystal grains laminated to a size of less than μm. Liquid and Sn equivalent amount 1 g/l ~ 20
g/l displacement plating solution or chemical reduction plating solution,
Flowed continuously for 10 to 60 minutes, S with a thickness of 3 μm or less
The second invention is a method for manufacturing a Sn-plated copper pipe for water supply and hot water supply by forming an n-plated film on the inner surface of the copper pipe.

[Operations] The present invention is capable of producing a Sn plating film in which Sn crystal grains are laminated, even if the film is very thin and has micropores.
It is characterized by having it on the inner surface of the copper tube.

In displacement plating of Sn, in which crystal grains are stacked, precipitation progresses due to a displacement reaction between copper and tin. From the scanning electron microscope photograph shown in FIG. 2, the precipitation form of the plating is as shown in (a) to e), with crystal grains stacked at each time point. This film forming process is schematically shown in FIGS. 1(a) to 1(c). In chemical reduction plating, a film is deposited due to the catalytic activity of the surface.

Thickness of the plating film The thickness of the plating film is preferably 0.1 μm or more in order to prevent elution of copper ions. In addition, in the case of displacement plating, since precipitation proceeds due to the fi exchange reaction between copper and tin, the thickness is at most 3 μm. In chemical reduction plating, the reaction is slow and it takes a long time to adhere, and even if the thickness is 3 μm or more, the effect of preventing elution of copper ions is saturated, so the thickness is preferably 3 μm or less.

To prevent elution of copper ions, it is most preferable that copper is not exposed. For example, it was frowned upon in Neelik's book: ``Pores should be avoided as they promote corrosion on exposed copper.'' However, if the coating formed by displacement plating or chemical reduction plating has a coverage of 50% or more, it is estimated that copper ions will not be eluted due to the high hydrogenation voltage of Sn or the sacrificial anode effect. Ru. The present invention resides in that even if copper is exposed, elution can be prevented by the sn Menke method. However, this effect cannot be obtained if the coverage is less than 50%.

Next, the manufacturing method will be explained.

Continuously flowing the treatment liquid inside the pipe Although it does not require special inventiveness to treat the inner surface of the pipe, it is possible to continuously flow the treatment liquid inside the pipe. It is effective for objects that have a long length relative to their diameter.

Furthermore, the use of displacement plating or chemical reduction plating as the treatment liquid has the effect of uniformly forming a thin film on the inner surface of the copper tube because the deposition rate of the plating film is slow.

Sn concentration in the plating solution The Sn concentration has the greatest effect on the plating thickness, and is 1 g/I! Below this, the film formation rate is low and a long time is required even if the temperature is raised, which is industrially disadvantageous. 2
If it exceeds 0 g/l, depending on the type of plating solution, the dissolution will reach saturation, making it impossible to produce the solution.

Processing time In displacement plating, precipitation progresses due to a substitution reaction between copper and tin, so the less copper is exposed, the less precipitation occurs, so adjusting the processing time is the best way to control the film thickness. preferable. In addition, with chemical reduction plating, a thick plating thickness can be obtained by renewing the plating solution, but in order to control the film thickness, the deposition rate is about 1 μm/hr, so the processing time must be adjusted. is preferable.

Temperature affects the plating thickness, and higher temperatures are preferable because the plating speed becomes faster, while temperatures higher than 80° C. are not preferable because the plating solution decomposes.

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

Example 1 A deoxidized copper plate with a side length of 100 mm was prepared and treated in the steps shown below using the displacement plating solution and chemical reduction plating solution shown in Table 1 at a solution temperature of 60°C. Plating was performed at various times to obtain test materials with various plating thicknesses.

Alkali degreasing → water washing → pickling (highly concentrated acidic solution) → water washing → neutralization (dilute acidic solution) → cleaning → water washing → hot water washing → drying Table 1: Part of the obtained test material was washed with hydrochloric acid solution. The plating thickness was determined by calculation from the amount of weight loss after melting, and test materials having the plating thickness shown in Table 2 were obtained. These test materials were immersed in tap water for 24 hours, and the amount of copper ions eluted into the tap water was measured by atomic absorption spectrometry. The results are shown in Table 2.

Use a 100 x 100 mm copper plate.

From these, invention examples No. 1 to 10 have a plating film thickness of 0.1 μm or more, so the amount of copper ion elution is o, o
sppm or less, which is good. On the other hand, Comparative Example No. 11 has a plating film thickness of 4 μm, so the copper ion elution amount is less than O,lll ppm, which is good, but this was obtained by hot-dipping the plate material. However, it is difficult to plate the inner surface of long tubes.

No. 12 and No. 16 all have thick coatings, so the copper ion elution amount is 0.01 ppm or less, or they are obtained by flux heating method and electroplating method, and are suitable for inner plating of long pipe materials. is difficult to do.

Nos. 13 and 14 are displacement plating and chemical reduction plating, but because the plating thickness is as thin as 0.01 μm,
Elution amount of copper ions is 0.36 ppm and 0.20 ppm
m, which exceeds the standard value (0.1 ppm) of the present invention.

No. 15 has a plating film thickness of 4μ by chemical reduction plating.
whether the copper ion elution amount is 0.01
ppm or less, which is good, but it is not preferable because the speed of chemical reduction plating is low, the solution must be refreshed frequently, and these treatments require a long time.

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 A test was conducted in the same manner as in Example 1 using various displacement plating solutions and varying the Sn concentration, treatment time, and treatment temperature.
The results are shown in Table 3.

Table 3 Displacement plating solutions ■■■ had the compositions shown in Table 1 with varying amounts of Sn compounds.

For N0118 to 27, the Sn concentration of the plating solution, treatment time, and treatment temperature are within the range of the invention, the plating thickness is 0.
．． 0.08 μm or more was obtained, and the amount of copper ion elution was 0.08 μm or more. O8p
pm or less, which is good.

On the other hand, No. 28 has a high Sn concentration of 20 g/l, a short processing time of 5 minutes, and a plating thickness of 0.08μ.
The copper ion elution amount was 0.10 ppm.

For Nos. 29, 30, and 31, the Sn concentration of the displacement plating solution was as low as 0.5 g/I, so the treatment time and treatment temperature were set at the upper limit of the range of the invention, but the plating thickness was 0.05 g/I.
~0.07μm, and the amount of copper ion elution is 0.15~0.
．． It was as high as 18 ppm.

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

Table 4 No. 3 where the treatment time and treatment temperature are within the range of the invention
For Nos. 2 to 45, a plating thickness of 0.25 μm or more was obtained, and the amount of copper ion elution was also 0. O4 ppm or less, which is good.

On the other hand, in Comparative Examples Nos. 46 to 51, the processing time was as short as 5 minutes, so the plating thickness was 0.04 μm.
m or less, and the amount of copper ion elution was also 0.19 ppm or more.

Example 4 Outer diameter 15.88 mm, wall thickness 0.71 mm, length 5
A coil of 0 m long deoxidized copper tube was prepared, and a plating treatment was performed in the treatment process shown in Example 1 by flowing a treatment liquid from the tube end of the coil. Regarding the obtained copper tube, test pieces having a length of 500 mm were cut from both ends and the center of the coil, and the thickness of the plating film and the copper ion elution test were conducted.

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 amount of weight loss.

In the copper ion elution test, a 500 mm copper tube was filled with tap water and sealed, and the amount of copper ion elution after 24 hours was measured by atomic absorption spectrometry. Those results in the fifth
Shown in the table.

Table 5 Processing time and processing temperature are within the range of the invention No. 5
Samples Nos. 2 to 54 are good, with a plating thickness of 0.33 μm or more and a copper ion elution amount of 0.01 pprn or less. On the other hand, in Comparative Examples No. 55 and 56, the processing time was as short as 5 minutes, so the plating thickness was 0.02 μm or less, and the amount of copper ions eluted was 0.31 μm.
It became more than ppm.

[Effects 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 also prevent coupling parts. It has the effect that conventional products can be used as is, and is extremely useful industrially.

[Brief explanation of drawings]

FIGS. 1(a), 1(b), and 1(c) are schematic diagrams showing how Sn crystals are stacked. Figure 2 (a) l;! After 1 minute, Figure 2(b) after 5 minutes, Figure 2(c) after 10 minutes, Figure 2(d) after 30 minutes,
Figure (e) is a scanning micrograph showing the state in which Sn crystals were stacked after 60 minutes of displacement plating. Agent Noboru Hoshino-4F1Fl-

Claims (2)

[Claims] (1) In the internal surface coating structure of copper pipes for water supply and hot water supply,
Sn layered to a thickness of 3 μm or less on the copper base material
An internal Sn-plated copper pipe for water supply and hot water supply, characterized by having a Sn-plated film consisting of crystal grains. (2) Apply plating pretreatment solution and displacement plating solution or chemical reduction plating solution in an Sn equivalent amount of 1 g/l to 20 g/l continuously from the end opening of the coiled copper tube to the inside of the tube for 10 to 60 minutes. 1. A method for manufacturing a Sn-plated internal copper pipe for water supply and hot water supply, characterized by forming an Sn-plated film with a thickness of 3 μm or less on the internal surface of the copper pipe.