JPH09279354A - Internally coated copper or copper alloy tube and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance of a copper or copper alloy tube having tin-plated internal surface. SOLUTION: The surface roughness Ra (center line average height) of a tin plating layer is regulated to <=0.8μm, or the ratio between the surface roughness Ra (center line average height, the same applies to the following) of the plating layer and the thickness of the plating layer, Ra/(thickness of plating layer), is regulated to <=1.5. This internally coated copper or copper alloy tube can be produced by using a copper or copper alloy tube having <=0.8μm inner surface roughness Ra and allowing an electroless tin plating bath to flow from the end of the tube at <=80 deg.C at a rate of (0.05 to 2.5)m/s to perform plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner surface tinned copper or copper alloy tube used as a water supply / hot water supply construction pipe or an air conditioning pipe such as a fan coil unit, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a phosphorous deoxidized copper pipe (JIS H3300 C1220T) has been used as a pipe for supplying water and hot water or a pipe for air conditioning because of its workability and brazing property. However, in the phosphorous deoxidized copper pipe, copper ions are eluted into water for the purpose of water supply and hot water supply pipes. Therefore, from the viewpoint of suppressing copper ions, a technique of coating the inner surface with tin was devised (Japanese Patent Laid-Open No. 4-45282). See the bulletin). Since this technology performs plating by circulating an electroless tin plating solution on the inner surface of the copper pipe, it can be applied to long pipes with respect to the pipe diameter, and is extremely effective in preventing copper ion elution. It can be said that this is a meaningful technique.

However, this technique has a problem with respect to the corrosion resistance of tin as a coating layer, and the tin layer may be corroded in running water and the background of the pipe may be exposed. To cope with this, a technique of further forming an oxide film on the tin-plated surface (JP-A-4-99180)
Although a technique for alloying a tin layer (Japanese Patent Laid-Open No. 4-131384) was devised, and some improvements were made,
The effect was not sufficient.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and an object thereof is to further improve the corrosion resistance of the tin plating layer on the inner surface of the copper or copper alloy tube.

[0005]

As a result of various researches conducted by the present inventors along with the above problems, the corrosion resistance of the tin-plated layer coated on the inner surface of the copper or copper alloy pipe is determined by the surface roughness of the tin-plated layer or the We have found that the surface roughness and film thickness are highly dependent on each other, and by controlling the surface roughness and film thickness of the tin plating layer, we have developed an inner surface tin-plated copper or copper alloy tube with significantly improved corrosion resistance. I got it.

That is, the inner surface-coated copper or copper alloy tube according to the present invention is a copper or copper alloy tube having a tin plating layer as a coating layer on the inner surface, and the surface roughness of the plating layer is Ra.
(Center line average roughness) ≦ 0.8 μm. Alternatively, the ratio of the surface roughness Ra of the plating layer to the plating layer thickness (Ra / plating layer thickness) is 1.5 or less. In the present invention, the definition of the center line average roughness Ra is in accordance with JISB0601.

The corrosion resistance of the tin-plated layer is due to the stable oxide film formed on its surface, Ra ≦ 0.8 μ
When the ratio of m or Ra to the plating layer thickness (Ra / plating layer thickness) is 1.5 or less, a stable tin oxide film is uniformly formed. Conversely, if Ra> 0.8 μm and (Ra
If the (plating layer thickness) exceeds 1.5, a stable tin oxide film cannot be formed uniformly. Incidentally, the above-mentioned JP-A-4-4528.
No. 2, the tin plating layer formed by electroless tin plating is inferior in corrosion resistance because the roughness of the plating surface is not controlled and Ra> 0.8 μm and the ratio of Ra to film thickness (Ra / plating). There are places where the layer thickness) exceeds 1.5,
It is considered that the tin plating layer was corroded at that portion.

The method for producing an inner surface coated copper or copper alloy tube according to the present invention is for obtaining a copper or copper alloy tube having the above-mentioned requirements, and a tin plating solution is applied from the end of the copper or copper alloy tube. In the method for producing an inner surface-coated copper or copper alloy tube, the inner surface roughness is Ra ≦ 0.8 μm.
0.05m of copper or copper alloy tube with plating solution below 80 ℃
The method is characterized in that plating is performed by circulating at a speed of up to 2.5 m / s.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Electroless Sn plating is particularly preferably applied to the method of the present invention. Further, in the present invention, electroless plating means both chemical plating and displacement plating. The thickness of the tin plating can be controlled by controlling the temperature of the plating solution and the plating time. However, in order to control the Ra of the tin plating layer, the inner surface roughness Ra of the base material (copper or copper alloy tube itself), the plating temperature, It is important to control the flow rate of the plating solution. In order to set Ra to 0.8 μm or less, or to set the ratio of Ra to film thickness (Ra / plating layer thickness) to 1.5 or less, the inner surface roughness of the base material must be Ra ≦ 0.8 μm. The plating temperature must be 80 ° C. or lower, and the plating solution flow rate must be 0.05 to 2.5 m / s.

Ra tends to increase when plating is performed at a plating temperature higher than 80 ° C. or when the plating solution flow rate exceeds 2.5 m / s. Therefore, Ra is 0.8 μm or less or the ratio of Ra to the film thickness ( It is difficult to control Ra / plating layer thickness) to 1.5 or less. Therefore, it is essential that the plating temperature be 80 ° C. or lower and the flow rate be 2.5 m / s or lower. However, the higher the temperature is, the faster the plating rate is, so from an industrial viewpoint, plating at 30 ° C. or higher is desirable. On the other hand, when the flow rate is less than 0.05 m / s, the supply amount of Sn becomes small and uneven plating may occur, so plating at 0.05 m / s or more is essential.

[0011]

Example: Phosphorus deoxidized copper tube (JIS H3300 C12
20T, outer diameter 15.88 mm, wall thickness 0.71 mm, length 4000 mm) with different inner surface Ra, the electroless plating solutions shown in Table 1 were circulated to prepare test materials. Table 2 shows Ra, plating conditions and post-plating properties of each test material.

[0012]

[Table 1]

[0013]

[Table 2]

A jet test and a water flow test were conducted using these test materials. The evaluation methods of the jet test and the water flow test are shown below. <Jet test> A half-divided tube having a length of 60 mm was cut out from the test material shown in Table 2 to obtain a test material. To this test material, tap water of Kitakyushu City, Fukuoka Prefecture, which was added with 80 ppm of Cl ⁻ at 60 ° C., was jetted with the same water for 180 days perpendicularly to the plating surface with a diameter of 2 mm and a flow rate of 10 m / s. The state of occurrence of corrosion (erosion) was investigated. <Water Flow Test> A tube having a length of 500 mm was cut out from the materials shown in Table 2 to obtain a test tube. Connect these tubes in series, Cl in Kitakyushu, Fukuoka Prefecture of tap water in the tube ^- 50
Water added with ppm was continuously flowed for 300 days at a flow rate of 1.0 m / s. After the test, each test tube was halved and the peeling rate was examined by an image analyzer in order to observe the situation in which the Sn coating was corroded and peeled off to expose the base material.

Table 3 shows the appearance, the jet test result and the water flow test result after plating.

[0016]

[Table 3]

As shown in Table 3, Ra after plating was 0.
8 μm or less or ratio of Ra to film thickness (Ra / plating layer thickness)
Is 1.5 or less, and in Examples 1 to 6 which are uniformly plated,
No corrosion was observed in the jet test, and no Sn layer was corroded and separated in the water flow test. On the other hand, in each of Comparative Examples 7, 8 and 10 in which the Ra of the base material, the flow rate, and the plating temperature are not predetermined conditions, the Ra after plating exceeds 0.8 and the ratio of Ra to the film thickness (Ra / plating layer thickness). ) Is more than 1.5, the corrosion of the base metal is progressing after the Sn layer is peeled off in the jet test, and the Sn coating is peeled off due to the corrosion of Sn in the water flow test. Further, in Comparative Example 9, since the flow velocity is slower than the predetermined condition, uneven plating occurs, and corrosion or peeling occurs at the uneven plating portion.

[0018]

INDUSTRIAL APPLICABILITY According to the present invention, an inner surface-coated copper or copper alloy tube having excellent corrosion resistance can be obtained by controlling the roughness and film thickness of the tin-plated surface layer of the inner surface-coated copper or copper alloy tube. Therefore, the reliability and life of the inner surface coated copper or copper alloy tube can be significantly improved.

Claims (3)

[Claims] 1. A copper or copper alloy tube having a tin plating layer as a coating layer on the inner surface thereof, wherein the surface roughness of the plating layer is R.
a (center line average roughness, the same applies hereinafter) ≦ 0.8 μm, an inner surface-coated copper or copper alloy tube. 2. A copper or copper alloy tube having a tin plating layer as a coating layer on its inner surface, wherein the surface roughness Ra of the plating layer is
And the plating layer thickness ratio (Ra / plating layer thickness) is 1.5 or less, an inner surface-coated copper or copper alloy tube. 3. A method for producing an inner surface-coated copper or copper alloy tube by carrying out plating by passing a tin plating solution from the end portion of the copper or copper alloy tube, wherein copper having an inner surface roughness of Ra ≦ 0.8 μm or The copper alloy tube is coated with the plating solution at a temperature of 80 ° C. or lower at 0.05-2.
A method for producing an inner surface-coated copper or copper alloy tube, which comprises plating by circulating at a speed of 5 m / s.