JP2010209450A - Surface treatment method and surface treatment apparatus of metal wire or metal line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment method and a surface treatment apparatus of metal wire or metal line, capable of suppressing the generation of VOC to suppress an influence on the environment, improving removing power of attached substance from metal surface, suppressing the oxidation of the metal surface and reducing the cost. <P>SOLUTION: This invention relates to the surface treatment method in which a metal wire or metal line 10 is brought into contact with gas-liquid mixed phase fluid to perform surface treatment, wherein the liquid constituting the gas-liquid mixed phase fluid is like droplet having a diameter of 1-100 μm. The metal wire or metal line 10 is a copper wire or a copper line. The liquid constituting the gas-liquid mixed phase fluid consists essentially of water. An average temperature of the gas-liquid mixed phase fluid falls into the range of 40°C to the boiling point. A molar fraction of oxygen contained in the gas-liquid mixed phase fluid is 1% or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface treatment method and a surface treatment apparatus for a metal wire or a metal strip.

  In the production of a metal wire or a metal strip, for example, a copper wire or a copper strip, after the raw copper wire is processed into a predetermined cross-sectional shape by cold rolling, the surface of the copper wire or the surface of the copper strip is removed by washing or the like Processing is in progress. Examples of the deposit on the surface include lubricating oil used for rolling and copper powder generated during rolling.

  As a conventional method for removing deposits, for example, as disclosed in Non-Patent Document 1, a technique (prior art 1) for dissolving and removing lubricating oil by immersing in an organic solvent is known. Further, as disclosed in Non-Patent Document 2, a technique (prior art 2) is known in which fine particles are removed by irradiating an object to be cleaned with ultrasonic waves in a liquid. These techniques are used in combination as necessary.

  FIG. 6 is a diagram schematically showing a conventional copper strip cleaning apparatus, and FIG. 7 is a diagram schematically showing the main part of FIG. In FIG. 6, 11 is an uncoiler (feeding device) for feeding a copper strip 10 from a copper strip reel 1 before cleaning (the copper strip wound before winding is wound around the reel), and 12 is a copper strip reel (after feeding) This is a recoiler (winding device) for forming a copper strip after cleaning on a reel. Between the uncoiler 11 and the recoiler 12, a feed roller 15 for feeding the copper strip 1 and a cleaning processing chamber (surface processing chamber) constituting a cleaning processing device (surface processing device) for cleaning the copper strip 1 (surface treatment) ) 21 and a drying processing chamber 22 constituting a drying processing apparatus for drying the cleaned copper strip.

  As shown in FIG. 7, a cleaning liquid tank 213 containing a cleaning liquid is provided in the cleaning processing chamber 21, and an introduction port 211 for introducing a copper strip into the cleaning processing chamber 21 and a discharge port 212 for discharging the copper strip 10. And a guide roller 214 disposed so as to guide the copper strip 10 into the cleaning liquid tank 213. In the cleaning processing chamber 21, a cleaning process using the organic solvent (conventional technique 1) or a cleaning process using ultrasonic irradiation in a liquid (conventional technique 2) is performed.

Ready-to-use cleaning technology (Industry Research Committee, 2001), p. 262 Ready-to-use cleaning technology (Industry Research Committee, 2001), p. 138

  However, the problem with the prior art 1 is that it may cause pollution of the working environment and the atmosphere as the organic solvent volatilizes. According to the Air Pollution Control Law revised in 2005, the amount of volatile organic compounds (hereinafter referred to as VOC) generated by 2010 is required to be reduced by 30% from the 2000 level.

  Copper strips and copper wires have a long overall length, and even when wound on a reel or the like, the diameter and width of the reel are large, making it difficult to store the entire material in a sealed device. Therefore, in general, the uncoiler 11 and the recoiler 12 are installed outside the apparatus, and after the copper strip or the copper wire is introduced into the cleaning processing chamber 21 from the inlet 211 and processed, the cleaning processing chamber 21 is discharged from the discharge port 212. And is wound around a new reel by a recoiler 12 installed outside.

  That is, the cleaning chamber 21 communicates with the external atmosphere through at least two openings, namely the inlet 211 and the outlet 212, and is difficult to seal. Therefore, in order to recover the organic solvent, it is necessary to introduce equipment for sucking in a large air volume so that the organic solvent does not leak from the opening of the cleaning processing chamber 21, and further, a processing operation of the recovered organic solvent occurs. A new problem arises.

  As a countermeasure, water may be used without using an organic solvent. In this case, a new problem arises that the metal surface is oxidized. When the surface of a metal material such as copper is oxidized, there are problems such as a decrease in adhesion between the resin and the metal in the subsequent resin coating process, or formation of holes called pits in the plating process, for example. appear.

  On the other hand, the problem with the prior art 2 is that the removal power is not necessarily high enough. If the ultrasonic output is increased for the purpose of improving the removal force, there is a high possibility that the ultrasonic transducer is damaged, and there is a new problem that the device management is costly.

  Therefore, the object of the present invention is to solve the above-mentioned problems, suppress the occurrence of VOC and suppress the influence on the environment, improve the removal power of deposits on the metal surface, and suppress the oxidation of the metal surface. Another object of the present invention is to provide a surface treatment method and a surface treatment apparatus for metal wires or strips that can reduce costs.

  In order to achieve the above object, a first invention of the present invention is a surface treatment method for performing surface treatment by bringing a metal wire or a metal strip into contact with a gas-liquid mixed phase fluid, wherein the gas-liquid mixed phase fluid is The constituent liquid is a droplet having a diameter of 1 micrometer or more and 100 micrometers or less.

  The metal wire or metal strip may be, for example, a copper wire or a copper strip. The liquid constituting the gas-liquid mixed phase fluid preferably contains water as a main component. The average temperature of the gas-liquid mixed phase fluid is preferably 40 ° C. or higher and the boiling point or lower. The mole fraction of oxygen contained in the gas-liquid mixed phase fluid is preferably 1 percent or less.

  The second invention includes a fluid generation step for generating a liquid constituting the gas-liquid mixed phase fluid, a surface treatment step for bringing a metal wire or a metal strip into contact with the gas-liquid mixed phase fluid and performing a surface treatment, and the surface treatment after the surface treatment. A liquid discharging step for discarding the gas-liquid mixed phase fluid, wherein the liquid constituting the gas-liquid mixed phase fluid is a droplet having a diameter of 1 micrometer or more and 100 micrometers or less, and the fluid generating step is mainly water. Including a step of electrolyzing a liquid as a component, in which liquid generated in the vicinity of one of the anodes or cathodes selected in the electrolysis is liquid A, and liquid generated in the vicinity of the other electrode is liquid B In the fluid generating step, a gas-liquid mixed phase fluid is generated using the liquid A, and the draining step includes a mixing step of mixing the gas-liquid mixed phase fluid and the liquid B after the surface treatment.

  The third invention comprises a metal wire or metal strip inlet, a gas-liquid mixed phase fluid generator, a surface treatment chamber for performing a surface treatment by bringing the gas-liquid mixed phase fluid into contact with the metal wire or metal strip, The liquid constituting the gas-liquid mixed phase fluid is a droplet having a diameter of 1 micrometer or more and 100 micrometers or less.

  It is preferable to provide a temperature control device that controls the temperature of the gas-liquid mixed phase fluid to 40 ° C. or higher and the boiling point or lower. A nitrogen gas generating device that generates nitrogen gas having a molar fraction concentration of oxygen of 1 percent or less by atmospheric distillation; and a gas-liquid mixed phase fluid generating device that generates the gas-liquid mixed phase fluid using the nitrogen gas. It is preferable. An electrolysis chamber for electrolyzing a liquid containing water as a main component, and a liquid generated in the vicinity of one electrode selected from the anode or cathode of the electrolysis chamber by electrolysis is liquid A and in the vicinity of the other electrode. When the generated liquid is liquid B, a gas-liquid mixed phase fluid generating device that generates the gas-liquid mixed phase fluid using the liquid A, and a mixing device that mixes the gas-liquid mixed phase fluid after the surface treatment with the liquid B. Are preferably provided.

  According to the present invention, the occurrence of VOC can be suppressed, and the influence on the working environment and the atmospheric environment can be suppressed. In addition, the ability to remove deposits on the metal surface is improved, oxidation of the metal surface can be suppressed, no recovery treatment like an organic solvent is required, and the cost can be reduced.

It is a figure which shows the surface treatment apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the effect of the surface treatment apparatus which concerns on 1st Embodiment. It is a figure which shows the surface treatment apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the effect of the surface treatment apparatus which concerns on 2nd Embodiment. FIG. 5 is a view showing a surface treatment apparatus according to a third embodiment of the present invention. It is a figure which shows the conventional copper surface treatment apparatus roughly. It is a figure which shows the principal part of FIG. 6 schematically.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is explained in full detail based on an accompanying drawing.

  A first embodiment of a cleaning treatment method (surface treatment method) and a washing treatment apparatus (surface treatment apparatus) for a metal strip, such as a copper strip, according to the present invention will be described with reference to FIG.

  The copper strip 10 wound around the copper strip reel 1 before cleaning is fed from the uncoiler 11 by the feed roller 15 and cleaned from the inlet 211 of the cleaning processing chamber (surface processing chamber) 21 constituting the cleaning processing device 210. Enters the inside of the chamber 21 and exits the cleaning processing chamber 21 through the discharge port 212. An introduction port 211 is formed in the front wall portion of the cleaning treatment chamber 21, and a discharge port 212 is formed in the rear wall portion. A guide roller 215 for horizontally guiding the copper strip 10 from the introduction port 211 toward the discharge port 212 is provided in the cleaning processing chamber 21.

  A gas-liquid mixed-phase fluid generating nozzle 101 which is a gas-liquid mixed-phase fluid generator or a gas-liquid mixed-phase fluid generator is disposed in the cleaning processing chamber 21, and two pipes connected to the gas-liquid mixed-phase fluid generating nozzle 101. One pipe (liquid pipe) 110 is connected to the liquid tank 114 via a flow rate adjustment valve 111, a flow meter 112 and a pump 113, and the other pipe (gas pipe) 120 is a flow rate adjustment valve 121 and a flow meter 122. And a gas cylinder 124 through a pressure regulator 123. The gas-liquid mixed phase fluid generating nozzle 101 is arranged above the copper strip 10 in a state of facing downward, and discharges the gas-liquid mixed phase fluid toward the copper strip 10 in a mist form. A waste liquid receiving portion 216 that receives the cleaning waste liquid is formed below the cleaning processing chamber 21 and is discharged from the waste liquid receiving portion 216 to the outside of the cleaning processing chamber 21 through a waste liquid pipe (not shown).

  Here, by setting the pump 113, the pressure regulator 123, and the flow rate adjusting valves 111 and 121 to appropriate values, liquid and gas (gas) are supplied to the gas-liquid mixed phase fluid generating nozzle 101, and the gas-liquid mixed phase fluid is supplied. By bringing the gas-liquid mixed phase fluid discharged from the generating nozzle 101 into contact with the surface of the copper strip 10, the surface of the copper strip 10 is cleaned.

  The mechanism by which the contamination is removed is as follows as a result of the study by the present inventors. That is, the metal powder and the processing lubricant oil that are adhering matter receive kinetic energy from the colliding liquid droplets, and desorb from the metal surface when the magnitude is larger than the adhering energy with the metal surface. In addition, when oil-insoluble contamination that is insoluble in water such as processing lubricating oil is brought into contact with a gas-liquid mixed phase fluid mainly composed of water, the oily contamination cannot be dissolved in the droplets constituting the gas-liquid mixed phase fluid. Collect at the gas interface. However, since the metal surface is covered with a liquid film having a certain thickness, oily contamination that could not be collected at the interface between the droplet and the gas reattaches to the metal surface with a certain probability.

  Accordingly, the larger the area of the gas-liquid interface that the gas-liquid mixed phase fluid has, the higher the cleaning capability. If the amount of liquid forming the gas-liquid mixed phase fluid is the same, the smaller the droplet diameter, the higher the cleaning capability. According to the study by the present inventors, the upper limit of a suitable droplet diameter is 100 μm. On the other hand, the lower limit of the droplet diameter is determined by the evaporation rate of the droplet. That is, even if a droplet is formed at the tip of the nozzle, it does not contribute to cleaning if it evaporates before reaching the surface of the metal to be cleaned. As a result of the study by the present inventors, if the droplet diameter is 1 μm or more, the cleaning process can be performed before the droplets evaporate by appropriately maintaining the distance between the nozzle and the surface of the metal to be cleaned.

  Furthermore, the higher the temperature, the lower the viscosity of the oily contamination and the smooth movement of the droplet from the metal surface to the gas-liquid interface. As a result of the study by the present inventors, when the temperature of the gas-liquid mixed phase fluid is 40 ° C. or higher, the efficiency of cleaning and removing by the gas-liquid mixed phase fluid is improved. It was confirmed that the viscosity coincided with the drastic decrease in viscosity above the temperature.

  Furthermore, it was confirmed that the lower the concentration of oxygen contained in the gas-liquid mixed phase fluid, the more the oxidation of the metal surface can be suppressed, and it is more desirable that it be 1% or less.

  As an example, the copper strip 10 after completion of the rolling process as a metal strip, an air cylinder as the gas cylinder 124, and a water tank filled with pure water as the liquid tank 114 are used, respectively. The removability was evaluated. As a comparative example, using the cleaning apparatus of FIG. 7, the copper strip was immersed in each of an organic solvent, pure water, and microbubble water, and the removability of the rolling lubricant on the copper strip surface was evaluated. The organic solvent listed in the comparative example is decane heated to 35 ° C., and the microbubble water is microbubble water generated by the method described in Patent Document 1 (Japanese Patent Laid-Open No. 2003-154205). , Respectively.

  The results are shown in FIG. Compared with pure water immersion and microbubble water immersion, residual contamination concentration can be reduced in a shorter time by using gas-liquid mixed phase fluid cleaning.

  FIG. 3 shows a cleaning processing apparatus according to the second embodiment of the present invention. A gas-liquid mixed phase fluid having a boiling point of 40 ° C. or higher and a boiling point or lower was generated using the cleaning processing device 210, and the copper strip surface was cleaned as in the first embodiment. The reason why the gas-liquid mixed phase fluid is made below the boiling point (less than) is to prevent the vapor of the gas-liquid mixed phase fluid from evaporating. As shown in FIG. 3, one pipe (liquid pipe) 110 is provided with a heater (liquid heater) 115 for heating a liquid, and the other pipe (gas pipe) 120 is a heater (gas heater) for heating a gas. 125 is provided. The heaters 115 and 125 constitute part of a temperature control device that controls the temperature of the gas-liquid mixed phase fluid to 40 ° C. or more and the boiling point or less. The results are shown in FIG. Compared with pure water immersion, microbubble water immersion, and gas-liquid mixed-phase fluid cleaning near room temperature, high-temperature gas-liquid mixed-phase fluid cleaning is superior, and cleaning performance almost equivalent to that of organic solvent immersion is obtained.

Here, as a result of examining a more preferable temperature range, the results shown in Table 1 were obtained. That is, it can be seen that the residual contamination concentration satisfies the target (5 mg / m ² or less) when a liquid of 40 ° C. or higher is used. In Table 1, the cleaning agent water represents a gas-liquid mixed phase fluid using water. The cleaning time is 5 seconds. Comparative Example 1 and Reference Example 1 in Table 1 correspond to the evaluation described in the first embodiment. Examples 1 to 3 in Table 1 are examples when the temperature of the gas-liquid mixed phase fluid is set to 70 ° C, 60 ° C, and 40 ° C, and Reference Example 1 is the temperature of the gas-liquid mixed phase fluid of 20 ° C. Is the case. It can be seen that the residual contamination concentration decreases as the temperature of the gas-liquid mixed phase fluid increases, and the cleaning power depends on the temperature.

  A cleaning apparatus according to a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a copper strip after completion of the rolling process is used as the metal strip, a nitrogen cylinder to which a certain amount of oxygen is added as the gas cylinder 124, and a tank filled with pure water as the water tank 114, respectively. The gas-liquid mixed phase fluid was generated, and the oxide film thickness on the surface of the copper strip surface after removing the rolling lubricant was evaluated. The results are shown in Table 2. As is apparent from this result, when the oxygen concentration is 1.0% or less, the thickness of the oxide film becomes 10 nm or less, and the oxidation of the copper strip surface can be suppressed. In addition, Reference Examples 2 and 3 in Table 2 are cases where the oxygen concentration is 2.0% and 20%, and Examples 4 to 6 have an oxygen concentration of 0.1%, 0.5%, and 1.0%. %.

  A cleaning apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. As the liquid constituting the gas-liquid mixed phase fluid, it is preferable to use an alkaline liquid having a pH (pH is a hydrogen ion index) of 9 or more and 14 or less in order to further improve the deposit removing ability. The alkaline liquid can be generated by electrolyzing a liquid containing water as a main component. In the present embodiment, anodic water and cathodic water are generated by water electrolysis, a gas-liquid mixed phase fluid is generated using them, and the copper strip surface is cleaned similarly to the first embodiment.

  In FIG. 5, the copper strip 10 sent out from the uncoiler 11 enters the inside of the cleaning processing chamber 21 through the introduction port 211 of the cleaning processing chamber 21, and goes out of the cleaning processing chamber 21 through the discharge port 212. A gas-liquid mixed phase fluid generating nozzle 101 is disposed in the cleaning processing chamber 21, and one of the two pipes 110 connected to the gas-liquid mixed phase fluid generating nozzle 101 is connected to the flow meter 112 and the pump 113. The other piping 120 is connected to a nitrogen cylinder 124 via a flow meter 122 and a pressure regulator 123, respectively. Furthermore, the electrolytic cell 51 is separated into two chambers, an A-pole chamber 52 in which the electrode A521 is disposed and a B-pole chamber 53 in which the electrode B531 is disposed, by a partition wall 54 that does not hinder the movement of ions. By performing electrolysis using one of the A-pole chamber 52 and the B-pole chamber 53 as an anode and the other as a cathode, electrolyzed water can be supplied to the gas-liquid mixed phase fluid generating nozzle 101.

  By setting the pump 113, the pressure regulator 123, and the flow rate regulating valves 111 and 121 to appropriate values, electrolytic water and gas are supplied to the gas-liquid mixed phase fluid generation nozzle 101, and the gas-liquid mixed phase discharged from the nozzle 101. By bringing the fluid into contact with the surface of the copper strip, the surface of the copper strip is cleaned. The gas-liquid mixed phase fluid discharged to the surface of the copper strip is discharged out of the cleaning processing chamber 21 from the waste liquid receiving portion 216 through the waste liquid pipe 172 as cleaning waste liquid.

  The electrolyzed water generated in the B electrode chamber 53 of the electrolytic cell 51 is transported by the pipe 170 via the pump 171 and mixed with the cleaning waste liquid discharged by the waste liquid pipe 172 in the external mixing unit (mixing device) 71. It is discharged as final waste liquid. The electrolyzed water generated in the B electrode chamber 53 of the electrolytic cell 51 is transported by the pipe 170 via the pump 171, mixed with the cleaning waste liquid at the waste liquid receiving portion 216 in the cleaning processing chamber 21, and discharged as the final waste liquid. You may come to be.

  Using the above cleaning apparatus, the electrolytic bath 51 is filled with a 0.1 mol / L potassium sulfate aqueous solution, electrolysis of water is performed using the electrode A521 as a cathode, and the copper strip surface is cleaned in the same manner as in the first embodiment. And the hydrogen ion index of the final waste liquid was evaluated. As Comparative Example 3, using the apparatus shown in FIG. 3, using a nitrogen cylinder as a gas cylinder, filling a water tank with a 0.01 mol / L potassium hydroxide aqueous solution, the surface of the copper strip as in the third embodiment. A washing treatment was performed.

  The results are shown in Table 3. In this Example 7, the hydrogen ion index of the final waste liquid is 7.2, and can be discarded into the sewage or discharged into the river after oil-water separation treatment, but the hydrogen ion index in Comparative Example 3 is as high as 12, In addition to the oil / water separation treatment, a neutralization treatment is required.

  In this example, the water electrolysis tank was filled with a 0.1 mo1 / L potassium sulfate aqueous solution, but an aqueous solution of an appropriate concentration and electrolyte can be used without being limited thereto. In this embodiment, the electrode A is a cathode. However, the present invention is not limited to this, and the electrode A may be used as an anode according to the type of contaminant to be removed by cleaning. For example, when the contamination to be removed is mainly composed of a rolling lubricating oil containing an ester, the ester is hydrolyzed by using an alkaline aqueous solution generated in the A electrode chamber 52 by using the electrode A521 as a cathode. Can be removed more efficiently. At this time, an acidic solution is generated in the B pole chamber 53.

  Further, for example, when the contamination to be removed is mainly composed of a salt made of a metal ion called carboxylic acid and a carboxylic acid, an acidic aqueous solution generated in the A electrode chamber 52 by using the electrode A521 as an anode, It can be efficiently removed by dissolving the metal soap. At this time, an alkaline aqueous solution is generated in the B pole chamber 53. In any case, since the cleaning waste liquid is neutralized by mixing the electrolyzed water generated in the B electrode chamber 53 with the cleaning waste liquid, no further neutralization treatment is required.

  As mentioned above, although embodiment of this invention has been explained in full detail with drawing, this invention is not limited to the said embodiment, The various design change in the range which does not deviate from the summary of this invention is possible.

DESCRIPTION OF SYMBOLS 1 Copper strip reel before washing | cleaning 2 Copper strip reel after washing | cleaning 10 Copper strip 11 Uncoiler 12 Recoiler 15 Feeding roller 21 Cleaning processing chamber 22 Drying processing chamber 51 Electrolytic tank (electrolytic processing chamber)
52 A pole chamber 53 B pole chamber 54 Bulkhead 55 DC power supply 71 Mixing unit (mixing device)
DESCRIPTION OF SYMBOLS 101 Gas-liquid mixed phase fluid production | generation nozzle 111,121 Flow control valve 112,122 Flowmeter 113 Pump 123 Pressure regulator 124 Gas cylinder 125 Heater 171 Liquid pump 172 Waste liquid pipe 211 Inlet 212 Outlet 213 Cleaning liquid tank 214 Guide roller 215 Guide roller 216 Waste liquid receiver 521 Electrode A
531 Electrode B

Claims (10)

  A surface treatment method for performing a surface treatment by bringing a metal wire or a metal strip into contact with a gas-liquid mixed phase fluid, wherein the liquid constituting the gas-liquid mixed phase fluid is a droplet having a diameter of 1 micrometer or more and 100 micrometers or less. A surface treatment method for a metal wire or a metal strip, characterized in that it exists.   The surface treatment method for a metal wire or a metal strip according to claim 1, wherein the metal wire or the metal strip is a copper wire or a copper strip.   3. The metal wire or metal strip surface treatment method according to claim 1, wherein the liquid constituting the gas-liquid mixed phase fluid contains water as a main component.   4. The surface treatment method for a metal wire or metal strip according to claim 1, wherein an average temperature of the gas-liquid mixed phase fluid is 40 ° C. or more and a boiling point or less.   5. The surface treatment method for a metal wire or metal strip according to claim 1, wherein the molar fraction of oxygen contained in the gas-liquid mixed phase fluid is 1 percent or less.   A fluid generation step for generating a liquid constituting the gas-liquid mixed phase fluid, a surface treatment step for bringing a metal wire or a metal strip into contact with the gas-liquid mixed phase fluid for surface treatment, and the gas-liquid mixed phase fluid after the surface treatment are discarded. A liquid constituting the gas-liquid mixed phase fluid is a liquid droplet having a diameter of 1 micrometer or more and 100 micrometers or less, and the fluid generation process uses a liquid mainly composed of water. Including the step of decomposing, wherein the liquid generated in the vicinity of one electrode selected from the anode and the cathode in the electrolysis is liquid A, and the liquid generated in the vicinity of the other electrode is liquid B, A surface of a metal wire or metal strip, wherein a gas-liquid mixed phase fluid is generated using liquid A, and the draining step includes a mixing step of mixing the gas-liquid mixed phase fluid and liquid B after surface treatment. How to process .   A metal wire or metal strip inlet, a gas-liquid mixed phase fluid generator, a surface treatment chamber for performing a surface treatment by bringing the gas-liquid mixed phase fluid into contact with the metal wire or metal strip, and a metal wire or metal strip The surface treatment apparatus for a metal wire or metal strip, characterized in that the liquid constituting the gas-liquid mixed phase fluid is a droplet having a diameter of 1 micrometer or more and 100 micrometers or less.   The surface treatment apparatus for a metal wire or metal strip according to claim 7, further comprising a temperature control device that controls a temperature of the gas-liquid mixed phase fluid to 40 ° C. or more and a boiling point or less.   A nitrogen gas generating device that generates nitrogen gas having a molar fraction concentration of oxygen of 1 percent or less by atmospheric distillation; and a gas-liquid mixed phase fluid generating device that generates the gas-liquid mixed phase fluid using the nitrogen gas. The surface treatment apparatus for metal wires or strips according to claim 7 or 8.   An electrolysis chamber for electrolyzing a liquid containing water as a main component, and a liquid generated in the vicinity of one electrode selected from the anode or cathode of the electrolysis chamber by electrolysis is liquid A and in the vicinity of the other electrode. When the generated liquid is liquid B, a gas-liquid mixed phase fluid generating device that generates the gas-liquid mixed phase fluid using the liquid A, and a mixing device that mixes the gas-liquid mixed phase fluid after the surface treatment with the liquid B. The surface treatment apparatus for a metal wire or metal strip according to any one of claims 7 to 9.

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