JP5072059B2 - Cleaning method for inner surface of copper tube or copper alloy tube - Google Patents

Description

  The present invention relates to a method for cleaning an inner surface of a copper tube or a copper alloy tube, particularly a copper tube suitable for obtaining a uniform surface by removing a carbon film formed on the inner surface of a long copper tube or copper alloy tube coil. The present invention relates to a method for cleaning the inner surface of a copper alloy tube.

  A copper pipe or a copper alloy pipe uses a lubricating oil at the time of drawing, but the lubricating oil remaining in the pipe becomes an inorganic carbonaceous film (hereinafter referred to as a carbon film) by heating during annealing and remains on the inner surface of the pipe. When a copper pipe with a lot of carbon film is used as piping for water supply or hot water supply, corrosion may occur depending on the environment used, and through corrosion may occur in the copper pipe, leading to a leakage accident.

  As a countermeasure against corrosion of such copper pipes, a method of forming a tin plating film on the inner surface of the copper pipe is known. In particular, since a tin plating film is formed on the inner surface of a coiled long copper pipe, a substitution type electroless There has been proposed a plating method in which a tin plating solution is passed through a copper tube (for example, Patent Document 1).

  In order to form a tin plating film with excellent adhesion in order to obtain good corrosion resistance, it is important to remove the carbon film in the tube before plating. A method of performing heat treatment by distribution (for example, Patent Document 2) has been proposed, but this method is not always sufficient for obtaining a tin plating film having excellent adhesion, and combined with chemical treatment with a chemical solution. Has also been considered.

  Since the carbon film is firmly attached to the inner surface of the tube and is inorganic, it cannot be removed with an organic cleaning agent or surfactant. Therefore, there is no method other than dissolving the inner surface of the tube and removing it together with copper. Since copper and copper alloys have a higher natural potential than hydrogen and cannot be dissolved with acids such as sulfuric acid and hydrochloric acid, use an acid that has an oxidizing property, for example, a mixed acid obtained by adding hydrogen peroxide to nitric acid or sulfuric acid. Attempts have been made to obtain a metal active surface by removing the carbon film and activating the inner surface of the tube.

  However, since these acids generate harmful gases in the copper dissolution reaction, when they are passed through a long coil of several hundred meters, the generated gas increases the pressure in the tube and allows the cleaning liquid to pass. There is a concern that the liquid supply pipes (hose etc.) attached to both ends of the long coil may come off, and there is a problem with the safety of the work. Therefore, no gas is generated by the reaction with copper in cleaning the long coil inner surface. It was necessary to use a cleaning solution having a composition.

On the other hand, a cleaning solution composed of sulfuric acid and chromic anhydride is known as a cleaning solution for copper, and no gas is generated in the reaction with copper, and the cleaning property (removal of carbon film, surface uniformity) is excellent. Since hydrogen ions are required for the reaction with copper, the components of the cleaning solution cannot be replenished in the long coil where the reaction proceeds in a sealed state, and the reaction ends in the middle of the long coil. For this reason, there is a limit to the length of the long coil that can be cleaned, and this reaction is an exothermic reaction, and the temperature of the cleaning liquid rises with the circulation of the cleaning liquid. There is also a drawback that the entire length cannot be cleaned uniformly. Therefore, when using a cleaning solution made of sulfuric acid or chromic anhydride, it is not practical because the length of the coil is shortened or the flow direction of the cleaning solution is reversed and equipment for suppressing the temperature rise of the coil is required. .
Japanese Patent Laid-Open No. 4-45282 JP-A-8-81780

  The present invention has been made to solve the above-mentioned conventional problems in removing the carbon film formed on the inner surface of a copper tube or a copper alloy tube, and the purpose thereof is to use no special equipment. To reduce the carbon film on the inner surface of a copper tube or copper alloy tube, especially to remove the carbon film formed on the inner surface of a long copper tube or copper alloy tube coil to obtain a uniform metal active surface An object of the present invention is to provide a method for cleaning the inner surface of a suitable copper tube or copper alloy tube. The cleaning method is also effective as a pretreatment for electroless tin plating on the inner surface of a copper tube or a copper alloy tube.

The method for cleaning the inner surface of a copper tube or a copper alloy tube according to claim 1 for achieving the above object is characterized in that a cleaning solution containing sulfuric acid and ferric sulfate as an oxidizing agent is used in a coiled long copper tube or copper alloy tube. It is characterized in that the inner surface of the pipe is washed by letting it pass through.

According to a second aspect of the present invention, there is provided a method for cleaning an inner surface of a copper tube or a copper alloy tube by passing a cleaning solution containing sulfuric acid and sodium peroxodisulfate as an oxidizing agent through a coiled long copper tube or copper alloy tube. It is characterized by washing.

  According to a third aspect of the present invention, there is provided a method for cleaning an inner surface of a copper pipe or a copper alloy pipe according to the first or second aspect, wherein a surfactant is added to the cleaning liquid.

A method for cleaning an inner surface of a copper tube or a copper alloy tube according to claim 4 is a pretreatment for electroless tin plating on the inner surface of a copper tube or a copper alloy tube according to any one of claims 1 to 3. .

  According to the present invention, the carbon film on the inner surface of a copper tube or a copper alloy tube can be reduced without using special equipment, and in particular, the carbon formed on the inner surface of a long copper tube or copper alloy tube coil A method for cleaning the inner surface of a copper tube or copper alloy tube suitable for removing the coating to obtain a uniform metal active surface is provided. The cleaning method is also effective as a pretreatment for electroless tin plating on the inner surface of a copper tube or a copper alloy tube.

Examples of the ferric salt include ferric sulfate, ferric chloride, and ferric hydroxide. When the present invention is applied as a pretreatment for electroless tin plating on the inner surface of a copper tube or a copper alloy tube, a plating solution for electroless substitution tin plating that is carried out following the cleaning step that is the pretreatment is provided. Since it is usually sulfuric acid acid, it is desirable to use ferric sulfate in combination with the plating solution.

  Examples of peroxodisulfate include sodium peroxodisulfate, potassium peroxodisulfate, and ammonium peroxodisulfate. However, potassium peroxodisulfate has low solubility in water, and ammonium peroxodisulfate is an ammonium salt. Therefore, it is more preferable to use sodium peroxodisulfate because the nitrogen source increases and the wastewater treatment load increases.

Since the concentration range of ferric sulfate and sodium peroxodisulfate varies depending on the length of the pipe, the pipe diameter, the flow rate based on the flow pump capacity, and the like, a range suitable for the pipe to be cleaned and the cleaning equipment is appropriately selected. Moreover, in order to improve the dissolving ability of each oxidizing agent and dissolved copper, it is desirable to add the above oxidizing agent to an acidic solution to which sulfuric acid has been added.

  As the surfactant, an anionic surfactant, a cationic surfactant, and a nonionic surfactant, which is stably present even in an acidic solution, and a general-purpose nonionic surfactant is used. The concentration range is preferably 0.1 to 10 g / L. In view of empirically applied concentration during metal cleaning, use at a concentration of about 1 g / L is most appropriate.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects. In addition, these Examples show one embodiment of this invention, and this invention is not limited to these.

Example 1, Comparative Example 1
A phosphorus deoxidized copper plate with a thickness of 0.5mm, width 20mm, and length 80mm is used as the material to be cleaned, and immersed in each cleaning solution shown in Table 1 (liquid temperature: 30 ° C) for 100 minutes to check for gas generation from the copper plate surface. confirmed. The results are shown in Table 1.

  As shown in Table 1, in Test Nos. 1 and 2 according to the present invention, no gas generation was observed. On the other hand, gas was generated in test No. 3 using a cleaning liquid consisting of sulfuric acid and hydrogen peroxide, and in test No. 4 using a cleaning liquid consisting of sulfuric acid and nitric acid.

Example 2
6 pipes connected in series with coiled phosphorous deoxidized copper tubes with an outer diameter of 15.88mm, wall thickness of 0.71mm, and length of 100m, from which an inert gas was circulated and subjected to heat treatment. As the material to be treated, the temperature of the cleaning solution consisting of 98% sulfuric acid: 15 g / L, 41% ferric sulfate solution: 200 g / L, and surfactant: 1 g / L is adjusted to 20 ° C from the end of one tube of the material to be treated. Then, circulation was performed for 50 minutes. Thereafter, it was sufficiently washed with water, and the washing water in the pipe was discharged by air blow.

  Subsequently, a commercially available substitutional electroless tin plating solution (for example, stannous salt: 0.1 mol / L, organic sulfur compound: 1 mol / L, organic carbonate: 0.1 mol / L, sulfuric acid: 0.5 mol / L, aroma Group sulfonate: 0.2 mol / L, non-surfactant: 1 g / L), followed by the first plating process for 30 minutes at a liquid temperature of 30 ° C, followed by 100 minutes at a liquid temperature of 70 ° C. A tin plating film was formed by performing a second plating process for plating. After the completion of the second plating treatment, it was sufficiently washed with water and air blow dried.

  During the flow of the cleaning liquid, measure the temperature of the cleaning liquid at the cleaning liquid outflow side of the long coil.After the cleaning is completed, the water is washed, and after the flushing water in the pipe is discharged by air blow, 0m from the coil introduction side of the cleaning liquid Pipes were removed from 300m, 400m, 500m, and 600m (corresponding to the washing liquid outflow side), and the adhesion of the carbon film on the inner surface of the copper pipe was compared with the same position before washing.

The carbon film was adhered by the following method. That is, the sample at each position was cut to 1 m, the inner surface of the tube was dissolved with a mixed acid composed of hydrochloric acid and nitric acid, the carbon film was removed, and this was collected and the amount of carbon was measured by an infrared absorption method. The adhesion state of the carbon film after the cleaning was confirmed by a residual ratio in which the carbon amount after the cleaning was gradually reduced by the carbon amount before the cleaning. In addition, the adhesion amount of the carbon film at each position of the long coil before cleaning was ² to 4 mg / m ² .

  After tin plating, extrude from 0m, 300m, 400m, 500m, 600m (equivalent to the outlet side) from the plating solution introduction side of the long coil, and measure the thickness of tin plating film and the number of pinholes by the following methods The tin plating film characteristics were evaluated. The results are shown in Table 2.

Measurement of tin plating film thickness: It was measured using an electrolytic plating film thickness measuring instrument TH-10P manufactured by Chuo Seisakusho.
Pinhole number measurement: A solution consisting of 270 mL / L of 28% ammonia water and 135 g / L of ammonium peroxodisulfate was filled in a tin-plated test material (length: 10 cm), left at room temperature for 1 hour, washed with water and dried. . After the test material was halved in the longitudinal direction, the tin plating film was peeled off with tape (Nitto No. 31B), and the copper spot-like exposed part was observed with a microscope as a pinhole, and the maximum occurrence per cm ² Numbers were counted.

  As shown in Table 2, the cleaning solution temperature on the outflow side of the long coil is 24 ° C., and considering the outside air temperature (22 ° C.) and the heat generation of the pump for feeding liquid, there is almost no heat generation due to cleaning. The degree of carbon film removal at each position of the long coil after cleaning was 40% or less before the cleaning over the entire length of the long coil, which was sufficiently removed when tin plating was performed. The number of pinholes in the tin plating film after tin plating was completely absent from the plating solution introduction side to the outflow side, and a tin plating film having excellent adhesion was formed.

  In addition, instead of the 41% ferric sulfate solution as the main component of the cleaning solution, sodium peroxodisulfate: 100 g / L was used, and after washing under the same conditions as in Example 2, tin plating was performed. Similarly, good results were obtained for both cleaning properties (temperature rise during cleaning, carbon film removal status) and plating properties (thin plating film thickness, number of pinholes).

Comparative Example 2
A coiled phosphorous deoxidized copper tube with an outer diameter of 15.88 mm, a wall thickness of 0.71 mm, and a length of 600 m manufactured under the same conditions as in Example 2 was washed with a cleaning solution consisting of 98% sulfuric acid 15 g / L and chromic anhydride 50 g / L. The liquid was circulated under the same conditions as in Example 2. After cleaning, after performing tin plating treatment with the same plating solution and conditions as in Example 2, the cleaning solution temperature on the outflow side of the long coil cleaning solution during cleaning, removal of the carbon film after cleaning, in the same manner as in Example 2 The situation was confirmed, and after plating, the thickness of the tin film and the number of pinholes were measured. The results are shown in Table 3.

As shown in Table 3, during the cleaning, the cleaning solution generated heat due to the copper dissolution reaction, and a temperature increase of 10 ° C. was observed on the cleaning solution outflow side. In addition, since the copper dissolution reaction of the carbon film was terminated by the consumption of hydrogen ions, the remaining ratio of the carbon film increased after the center of the long coil. The number of pinholes was 20 / cm ² after the center of the long coil where the carbon film was not sufficiently removed by washing, and a tin plating film with poor adhesion was formed.

Claims (4)

Cleaning the inner surface of a copper tube or copper alloy tube, characterized by passing a cleaning solution containing sulfuric acid and ferric sulfate as an oxidizing agent through a coiled long copper tube or copper alloy tube to clean the inner surface of the tube Method. Cleaning of the inner surface of a copper tube or copper alloy tube characterized by passing a cleaning solution containing sulfuric acid and sodium peroxodisulfate as an oxidizing agent through a coiled long copper tube or copper alloy tube to clean the inner surface of the tube Method. The method for cleaning an inner surface of a copper tube or a copper alloy tube according to claim 1, wherein a surfactant is added to the cleaning solution. The method for cleaning an inner surface of a copper tube or a copper alloy tube according to any one of claims 1 to 3 , wherein the inner surface of the copper tube or the copper alloy tube is a pretreatment for an electroless tin plating process.