JP3005469B2 - Manufacturing method of long copper tube with inner tin plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a corrosion-resistant inner tin-plated copper pipe used for water supply, hot water supply pipes, heat exchanger pipes, etc., and in particular, to form a tin-plated coating having no coating defects and excellent corrosion resistance. The present invention relates to a method for producing an internal tin-plated long copper tube that can be used.

[0002]

2. Description of the Related Art A tin plating film is formed on the inner surface of a copper tube to improve the corrosion resistance of the inner surface of the copper tube used for water supply, hot water supply piping, heat exchanger piping and the like and to prevent elution of copper ions. As a method for forming a tin plating film on the inner surface of a long coiled copper tube, a plating method of flowing a substitution type electroless tin plating solution inside the copper tube has been proposed. ing. (Japanese Patent Laid-Open No. 4-4
No. 5282)

[0003] The above method is a simple and extremely efficient method for plating a coil-shaped long copper tube, and a thin tin plating film having excellent adhesion is formed. It has been experienced that elution of copper ions is detected due to abrasion and peeling of a tin plating film. To further improve corrosion resistance, after forming a tin plating film, oxidize with hot water or steam. Methods have also been proposed. (Japanese Patent Application Laid-Open No. 4-99180) However, the tin plating film formed by this method may cause pitting corrosion when the use environment becomes severe, and generally, when a long copper tube is plated, Since there is a tendency that a uniform plating film is not formed on the whole and the corrosion resistance tends to be insufficient, further improvement of the corrosion resistance is desired.

When a copper material is tin-plated by immersing a copper plate in a plating bath or circulating a plating solution inside a short copper tube having a length of several meters or less, tin ions in the plating bath and copper A method is proposed in which the ion concentration ratio and the value of (copper ion concentration / tin ion concentration) are controlled within a range of 0.7 or less to form a uniform plating film without defects and further improve pitting corrosion resistance and the like. Have been. In this method, when the plating solution is out of the above-mentioned control range, the plating solution is renewed or replenished with a chemical such as tin salt so that the performance of the plating solution falls within the control range. By holding, a uniform plating film is formed.

[0005] However, when plating treatment is performed by flowing a plating solution through a coil-shaped long copper tube having a length of about 1,000 meters to several hundreds of meters, it takes a long time for the plating solution to flow in the tube. After the plating solution is introduced from one end of the tube, until the plating solution flows out from the other end,
The properties of the plating solution flowing inside the tube cannot be changed. While the plating solution is flowing inside the copper tube, Sn ²⁺
+ 2Cu = Sn + 2Cu ⁺ as a result of the plating reaction,
Since tin ions are consumed and copper ions gradually accumulate,
The quality of the plating film tends to deteriorate inside the copper tube on the side where the plating solution flows out, and this tendency becomes more remarkable as the copper tube to be treated becomes longer. Therefore, in the tin plating of long copper tubes,
It is necessary to control the plating solution within a predetermined performance range from a viewpoint different from the tin plating treatment method for the short copper tube.

[0006] In the case of performing substitution type electroless tin plating on the inner surface of a long copper tube, a plating solution containing stannous sulfate or the like is circulated.
It is performed at a high temperature of 70 ° C. This is because, for example, when the plating treatment is performed at a low temperature such as 40 ° C. or less, it is difficult to form a thick film because the deposition rate of the plating film is low, and the size of tin particles to be deposited varies, so that the number of pinholes increases, This is because a uniform plating film having corrosion resistance cannot be obtained.
However, when a long copper tube is subjected to tin plating at a high temperature, the deposition rate of the plating film is high, so that the consumption of tin ions and the accumulation of copper ions are promoted, and the plating of the inner surface of the copper tube on the side where the plating solution flows out. At present, the film thickness of the film is reduced, the number of pinholes is increased, and the adhesion is liable to be reduced. At present, it is possible to treat only a copper pipe having a length of about 200 m (9 m ² ).

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems in the inner surface tin plating of a long copper tube by replacing a long copper tube with a substitution type electroless electroless plating tube. In the tin plating process, for copper tubes of various lengths, the relationship between the properties of the plating solution introduced into the tube and the plating solution flowing out of the tube end, the relationship between the plating conditions and the deposition of the tin plating film on the inside of the tube is multilaterally examined. The purpose of this study is to provide an inner tin plating film with an inner tin plating film that has no defects such as pinholes, has excellent adhesion, and has good corrosion resistance such as erosion resistance and pitting corrosion resistance. An object of the present invention is to provide a method for manufacturing a shaku copper tube.

[0008]

Means for Solving the Problems In order to achieve the above-mentioned object, a method for producing a long copper tube having an inner tin-plated surface according to the present invention is characterized by flowing a substitution type electroless tin plating solution inside a copper tube. In the method of forming a tin plating film on the inner surface of a copper rod, the value obtained by dividing the total copper ion concentration in the plating solution immediately after flowing through the copper tube by the divalent tin ion concentration after flowing through the copper tube is 0. A first plating treatment step of plating by adjusting the deposition rate of the tin plating film so as to be not more than .8 and a first plating treatment step.
Plating solution or plating distributed in the first plating process
A second plating treatment step of performing plating treatment by using another plating solution having the same composition as the solution and setting the temperature of the plating solution to a temperature higher than the temperature of the plating solution in the first plating treatment. Features above.

In the above plating process, the temperature of the plating solution in the first plating process is 20 ° C. or more and 60 ° C.
, The temperature of the plating solution in the second plating process is 60
The present invention is to perform the first plating process and the second plating process by continuously raising the temperature of the plating solution without stopping the flow of the plating solution inside the copper tube without stopping the flow of the plating solution inside the copper tube. The above is the second and third features.

The plated copper tube to be plated according to the present invention is:
Usually, it is a phosphorus deoxidized copper pipe (JIS H3300 C1220) generally used as a pipe material for water supply and hot water supply. However, a deoxidized copper pipe using B, Mg, Si or the like as a deoxidizing agent other than P is also used. The present invention can be applied without any hindrance to the effects. In addition, low copper alloy pipes to which various elements such as Sn, Al, Zn, Mn, and Mg are added in small amounts for the purpose of improving corrosion resistance, as long as the copper content is 96% by weight or more, can be used as a phosphorus deoxidized copper pipe. Similarly, the present invention can be applied without any hindrance to the effects.

In the present invention, first, a value obtained by dividing the total copper ion concentration in the plating solution immediately after flowing out of the copper tube after flowing through the inside of the copper tube by the divalent tin ion concentration (total Cu ion concentration / 2) The first plating process is performed by adjusting the deposition rate of the tin plating film so that the (valent Sn ion concentration) becomes 0.8 or less. When a plating solution is introduced from one end of a long copper tube and the plating solution is allowed to flow out from the other end to cause a plating reaction inside the tube and form a plating film on the inner surface of the tube, the flowing plating solution is The value of (total Cu ion concentration / divalent Sn ion concentration) in the plating solution reaches the maximum value when it reaches the outlet end of the tube. During the plating reaction, the above-mentioned concentration ratio is maintained at 0.8 or less over the entire length of the treated copper tube, and a uniform and good plating film is formed over the entire length of the treated copper tube. The value of (total Cu ion concentration / divalent Sn ion concentration) is preferably low, more preferably 0.6 or less.

In the present invention, in the first plating process of the substitution type electroless tin plating process of the coiled long copper tube, the total copper ion concentration in the plating solution flowing out of the copper tube is reduced to the divalent tin ion concentration. It is not necessary to always adjust the value divided by 0.8 or less, at the start of the plating process, a plating solution is introduced from one end of the long copper tube, and the plating solution flowing through the inside of the tube is removed. When flowing out from the end, the value obtained by dividing the total copper ion concentration in the plating solution by the divalent tin ion concentration is 0.8 or less, preferably 0.1 mm. It is only necessary to satisfy 6 or less.

In the initial stage of the plating process, it is important to form a tin plating film with a plating solution in which the value of total Cu ion concentration / divalent Sn ion concentration is 0.8 or less. The good initial film becomes the core of the plating film growing thereon, and a high quality plating film is obtained. If the value obtained by dividing the total copper ion concentration in the plating solution by the divalent tin ion concentration exceeds 0.8, the deposited plating film contains a large amount of Cu-Sn intermetallic compound, and thus has poor adhesion. As a result, the quality of the coating deteriorates. Particularly, in the initial stage of the plating process, if a plating film is formed with a plating solution having a concentration ratio of more than 0.8, the plating film having good quality can be treated with a plating solution having a concentration ratio of 0.8 or less. It is difficult to form a film.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out the present invention, a coil-shaped long copper tube to be subjected to inner plating is degreased and washed in a conventional manner, and if necessary, lightly etched in an acid solution. After sufficiently washing with water and drying, a first plating treatment is performed by introducing a substitution type electroless tin plating solution containing a stannous salt from one end of the copper tube and flowing through the inside of the tube.

After flowing through the inside of the tube, the plating film is adjusted so that the value obtained by dividing the total Cu ion concentration in the plating solution immediately after flowing out from the other end of the copper tube by the divalent Sn ion concentration is 0.8 or less. In order to adjust the deposition rate, the plating treatment is performed at a relatively low temperature of the plating solution, preferably 20 ° C. or more and less than 60 ° C., more preferably 20 to 40 ° C. By performing the plating treatment by lowering the temperature of the plating solution, the plating reaction is suppressed, the precipitation of Sn ions and the elution of Cu ions in the flowing plating solution are suppressed to the outflow side of the plating solution, and a good initial A plating film is formed.

The lower the temperature of the plating solution in the first plating process, the lower the total Cu
The ratio of the concentration of ions to the concentration of divalent Sn ions can be reduced, but if the temperature is lower than 20 ° C., precipitation tends to occur in the plating solution. If the temperature exceeds 60 ° C., an initial film having good adhesion is not formed. The temperature of the plating solution in the first plating process is adjusted by the length of the copper tube to be plated. For example, at a plating solution temperature of 20 to 40 ° C., an outer diameter of 15.88 mm, a wall thickness of 0.71 mm, and a length of It is possible to form a good initial tin plating film by treating a copper tube having a length of about 2000 m.

If the flow of the plating solution at a low temperature with a low deposition rate of Sn is continued, the growth of the plating film is extremely slow, not only it takes a long time to obtain a plating film of a desired film thickness, but also the Sn particles to be deposited There is variation in the size of
Since pinholes are easily generated, formation of a plating film having excellent corrosion resistance cannot be expected. In order to solve such a problem, in the present invention, a first plating process in which plating is performed with the plating solution at a relatively low temperature, and a temperature of the plating solution in the first plating process is reduced. A higher plating solution is circulated to combine the second plating process step in which the Sn deposition rate is increased, and a plating film is grown on the initial film formed in the first plating process.

The temperature of the plating solution in the second plating treatment is preferably in the range of 60 ° C. or more and 80 ° C. or less, more preferably 60 to 70 ° C. As a method of heating the plating solution, there are a method of heating the plating solution in the plating bath by an appropriate means, a method of heating the copper tube and increasing the temperature of the flowing plating solution, and the like. Since the heating means may increase the size of the heating equipment, a method of heating in a plating bath is more convenient. Note that if washing and drying are performed after the first plating treatment, the surface of tin deposited in the first plating treatment step is oxidized, and the growth of the plating film is easily reduced. It is preferable to perform the second plating process without performing the above process.

In the present invention, as a mode of shifting from the first plating process to the second plating process, first, after performing the first plating process for a predetermined time, the temperature of the plating solution in the plating bath is increased. When the temperature reaches a predetermined value, the second
After performing the first plating process for a predetermined time, without stopping the flow of the plating solution,
While increasing the temperature of the plating solution in the plating bath, the circulation is further continued, and when the temperature of the plating solution reaches a predetermined temperature, the heating of the plating solution is stopped, and the plating solution is circulated for a predetermined time to perform the second plating process. A method for performing the first plating process and the second plating process by continuously increasing the temperature of the plating solution in the plating bath at the start of the plating process or at some point after the start without stopping the flow of the plating solution inside the copper tube. A plating bath in which the temperature of the plating solution is raised to a predetermined temperature in advance, and after the completion of the first plating process, the plating solution in the plating bath is allowed to flow to perform the second plating process. There are ways to do that.

[0020]

EXAMPLES Hereinafter, examples will be described in comparison with comparative examples. Example 1, Comparative Example 1 A phosphor-deoxidized copper plate having a thickness of 0.5 mm, a width of 20 mm and a length of 80 mm was used as a material to be plated, and washed with a chromic sulfuric acid solution (10% chromic anhydride, 1% sulfuric acid). Washed thoroughly and dried. Then, a commercially available substitution type electroless tin plating solution (stannous salt 0.1 mol / l) organic sulfur compound 1 mol /
l, organic carboxylate 0.1 mol / l, sulfuric acid 0.5 m
ol / l, aromatic sulfonate 0.2 mol / l, nonionic surfactant 1 g / l), and adding copper ion (copper sulfate) to the plating solution to obtain a total Cu ion concentration / divalent Sn ion. The concentration ratio was adjusted as shown in Table 1, and the copper plate was immersed in these plating solutions.
The first plating process was performed under the processing conditions of n, and then the plating solution was heated to perform the second plating process under the processing conditions of 70 ° C. × 60 min to form a tin plating film.

With respect to the obtained test materials, the adhesion and the corrosion resistance of the plating film were evaluated by the following methods. (1) Evaluation of adhesion: A peeling test was performed using a tape (Nitto No. 31B) to peel off the plating film, and the presence or absence of peeling was visually observed. (2) Evaluation of corrosion resistance: A jet stream of Nagoya city water, whose pH was adjusted to 6, was continuously applied to the surface of the plating film of the test material for 5 days, and the occurrence of corrosion was observed. In addition, the diameter of the jet hole of the jet stream was 1.5 mm, and the distance between the jet hole and the surface of the plating film was 2 mm.

As shown in Table 1, the evaluation results are as shown in Table 1. All of the samples Nos. 1 to 5 had excellent adhesion and formed a plating film having a maximum corrosion depth of less than 0.05 mm and good corrosion resistance. On the other hand, the ratio of total Cu ion concentration / divalent Sn ion concentration in the plating solution (ion concentration ratio in the table)
The test material No. of which 0.8 exceeds 0.8 The tin plated films of Nos. 6 to 8 had poor adhesion and had a corrosion with a maximum corrosion depth of 0.05 mm or more.

[0023]

[Table 1]

Example 2 Outer diameter 15.88 mm, wall thickness 0.71 mm, length 1000
m of coil-shaped phosphorous deoxidized copper tube was used as a material to be plated, and the inner surface thereof was coated with a commercially available degreasing agent (amine compound 10%, hydrochloric acid 9).
%, Nonionic surfactant 5%) and sulfuric acid 13
% And nitric acid 4%, and then soft-etched, washed thoroughly with water and dried. Then, a commercially available substitution type electroless tin plating solution (stannous salt 0.1 mol / l, organic sulfur compound 1 mol / l, organic carboxylate 0.1 mol / l)
1, sulfuric acid 0.5 mol / l, aromatic sulfonate 0.2
mm / l, a nonionic surfactant 1 g / l) was passed through the inside of the copper tube to be plated, and the first plating treatment and the second plating treatment were performed under the conditions shown in Table 2. After the first plating treatment, the plating solution in the plating bath was heated up to a temperature of 70 ° C. at a heating rate of 1 ° C./min without stopping the flow of the plating solution in the tube, and then heated. The time until the processing was completed was set as the processing time of the second plating processing.

[0025]

[Table 2]

The inner surface of the copper tube after the formation of the plating film is washed with water and dried, and a test material is sampled from a position 1 m from each of the end of the tube for introducing the flowing plating solution and the end of the tube from which the plating solution flows out. The following plating film thickness and pinhole density were measured, and the adhesion and corrosion resistance of the plating film were evaluated. (1) Plating film thickness measurement: Measured using an electrolytic plating film thickness measuring device TH-10P manufactured by Chuo Seisakusho Co., Ltd. (2) Pinhole density measurement: 30% ammonia water 270
ml, pure water 630 ml and ammonium persulfate 135
g is mixed with a plated test material (length 10 mm).
cm), left for 1 hour at room temperature, washed with water, dried,
The plating film was peeled off with a tape (Nitto No. 31B), the point-like exposed portions of copper were pinholes, counted by microscopic observation, and the counted value was obtained by dividing the counted value by the inspection area.

(3) Evaluation of adhesion: the test material was halved,
The plating film was peeled off with a tape (Nitto No. 31B), and the presence or absence of peeling was visually observed. (4) Corrosion resistance evaluation: The test material was cut to a length of 10 cm,
This was split in half, and the surface of the plating film was continuously exposed to a jet stream of Nagoya City water, whose pH was adjusted to 6, for 5 days.
The occurrence of copper corrosion was observed. In addition, the diameter of the jet hole of the jet stream was 1.5 mm, and the distance between the jet hole and the surface of the plating film was 2 mm.

[0028]

[Table 3]

As shown in Table 3, the results show that, for each test material, both the plating solution introduction side and the plating solution outflow side were used.
No or little pinholes were formed, and a tin plating film having excellent adhesion was formed. No corrosion was observed in these plating films, and the corrosion resistance of the plating films was extremely excellent.

Comparative Example 2 Phosphorus-deoxidized copper tubes having the same dimensions and the same material as in Example 2 were pretreated in the same manner as in Example 2, and the treatments shown in Table 4 were performed using the same plating solution as in Example 2. After plating under the conditions,
In the same manner as in Example 2, the plating film thickness and the pinhole density were measured, and the adhesion and corrosion resistance of the plating film were evaluated. Table 5 shows the results.

[0031]

[Table 4]

[0032]

[Table 5]

As shown in Table 5, the test material No. 12
Nos. 14 to 14 are obtained by performing a single-step plating process using a relatively high-temperature plating solution, and particularly at the end of the copper tube on the plating solution outflow side, many pinholes are generated in the plating film. The adhesion was reduced and the corrosion resistance was poor, and erosion occurred in the corrosion test.

Example 3 Outer diameter 22.22 mm, wall thickness 0.81 mm, length 1100
m was used as a material to be plated, and the inner surface was washed in advance with a mixed solution of 1% sulfuric acid and 5% chromic anhydride, sufficiently washed with water, and dried. Then, stannous sulfate 0.
2 mol / l, thiourea 1 mol / l, sodium hypophosphite 0.2 mol / l, sulfuric acid 1 mol / l, alkanolsulfonic acid 0.2 mol / l) Substitution type electroless containing 1 g / l nonionic surfactant The plating treatment was performed under the conditions shown in Table 6 using a tin plating solution.

[0035]

[Table 6]

After the plating treatment, the inner surface of the copper tube was washed with water and dried, and a test material was sampled from a position 1 m from the outflow end of the plating solution, and the plating film thickness and the pinhole density were measured in the same manner as in Example 2. The measurement and the adhesion evaluation were performed. Furthermore, after cutting the test material to 10 cm, halving, the exposed portion of the copper on the outer surface was masked with an enamel resin,
A constant potential electrolysis was performed at 200 mV vs SCE for 3 days, the presence or absence of copper corrosion was observed, and the corrosion resistance was evaluated. Table 7 shows the results. As can be seen in Table 7, the test material No.
All of the tin plated films of Nos. 15 to 16 had almost no pinholes and were excellent in corrosion resistance.

[0037]

[Table 7]

Comparative Example 3 A phosphorous deoxidized copper tube having the same material and dimensions as those used in Example 3 was pretreated in the same manner as in Example 3, and the same tin plating solution as in Example 3 was used. After the substitutional electroless tin plating treatment under the treatment conditions shown in 8, the plating film thickness and pinhole density were measured in the same manner as in Example 3, and the adhesion and corrosion resistance of the plating film were evaluated. Table 9 shows the results.

[0039]

[Table 8]

[0040]

[Table 9]

As shown in Table 9, the plating solution was cooled to a low temperature.
The test material No. The tin plating films formed on Nos. 17 and 18 had many pinholes and were poor in adhesion. Pitting occurred in the corrosion test.

[0042]

As described above, according to the present invention, there is little variation in the film thickness on the inner surface of a long copper tube, there is no pinhole, the adhesion is excellent, and the corrosion resistance is good without erosion or pitting. A tin plating film can be formed stably.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 18/00-18/54

Claims (3)

(57) [Claims] 1. A method for forming a tin plating film on the inner surface of a long copper tube by flowing a substitution type electroless tin plating solution inside the copper tube, and then flowing from the copper tube after flowing through the inside of the copper tube. A first plating treatment step of performing plating treatment by adjusting a deposition rate of a tin plating film so that a value obtained by dividing a total copper ion concentration in the plating solution by a divalent tin ion concentration is 0.8 or less, Flow in the first plating process
Through the plating solution or the first plating process
Use another plating solution with the same composition as the plating solution
And a second plating step of performing plating by setting the temperature of the plating solution to be higher than the temperature of the plating solution in the first plating process. . 2. The temperature of the plating solution in the first plating process is set to 20 ° C. or more and less than 60 ° C., and the temperature of the plating solution in the second plating process is set to 60 ° C. or more and 80 ° C. or less. A method for producing a long copper tube with inner tin plating as described in the above. 3. A without stopping the flow of copper tube inside the plating solution, raising the temperature of the plating solution continuously claim 1 or, characterized in that performing a first plating and the second plating process 3. The method for producing an internal tin-plated long copper tube according to item 2 .