Flux solution for hot dipping and hot dipping method

Abstract

To provide a flux solution for hot dipping which does not contain hydrochloric acid as a main acid and in which metal plating for coating the surface of a plating object has high wettability, and to provide a hot dipping method capable of satisfactorily coating the surface of the plating object with metal plating while suppressing or preventing hydrogen chloride from vaporizing and remaining in a surrounding atmosphere.SOLUTION: The hot dipping method includes: a flux step S1 in which the surfaces of the wire rod are flux-treated using a flux solution for hot dipping; and a hot dipping step S2 in which the wire rod after the flux step S1 is immersed in a plating tank and then pulled up from the plating tank, and the surfaces of the wire rod are coated with metal plating. The flux solution for hot dipping used in the flux step S1 contains carboxylic acid, a surfactant, and at least one of zinc chloride and ammonium chloride.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to a flux liquid for fusion plating and a fusion plating method.

Background Art

[0002] Conventionally, as a method for coating the surface of an object to be plated, such as a wire, with a metal plating, a fusion plating method is known. In the fusion plating method, an object to be plated (for example, a wire) is immersed in a plating bath in which molten metal is stored. Then, by pulling up the object to be plated from the plating bath, the surface of the object to be plated is coated with a metal plating.

[0003] In the fusion plating method, as shown in Patent Document 1 below, in order to perform a good coating with a metal plating, prior to immersing the object to be plated in the plating bath, the surface of the object to be plated may be flux-treated using a flux liquid for fusion plating. As the flux liquid for fusion plating, various flux liquids can be employed. In Patent Document 2 below, azonil is disclosed as a flux liquid. Azonil is a strong acid containing hydrochloric acid, and in addition to hydrochloric acid, it contains ammonium chloride and zinc chloride.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using azonil as a flux solution for hot-dip plating, there are the following problems. That is, the flux solution for hot-dip plating adheres to the surface of the object to be plated immersed in the molten metal. When immersed in the molten metal, the flux solution for hot-dip plating vaporizes due to the high-temperature molten metal. Since azonil contains hydrochloric acid as the main acid, when using azonil as the flux solution for hot-dip plating, hydrogen chloride (HCl) may remain in the surrounding atmosphere. If hydrogen chloride (HCl) remains in the surrounding atmosphere, it may cause oxidation and chlorination of the equipment structure (i.e., rust generation), and / or deterioration of the production environment.

[0006] Therefore, a new flux treatment solution for hot-dip plating to replace azonil is desired. This flux treatment solution is required not only to not contain hydrochloric acid as the main acid, but also to have high wettability for the metal to plate the object to be plated.

[0007] Thus, one object of the present invention is to provide a flux solution for hot-dip plating that does not contain hydrochloric acid as the main acid and has high wettability for the metal plating covering the surface of the object to be plated.

[0008] Another object of the present invention is to provide a hot-dip plating method that can well coat the surface of the object to be plated with metal plating while suppressing or preventing hydrogen chloride from vaporizing and remaining in the surrounding atmosphere.

Means for Solving the Problems

[0009] One embodiment of the present invention provides a flux solution for hot-dip plating having the following characteristics.

[0010] 1. A flux solution for hot-dip plating containing a carboxylic acid, a surfactant, and at least one of zinc chloride and ammonium chloride.

[0011] According to the present invention, it is possible to provide a flux solution for fusion plating that does not contain hydrochloric acid as a main acid and has high wettability for metal plating that coats the surface of an object to be plated.

[0012] 2. The flux solution for fusion plating according to item 1, wherein the carboxylic acid contains a hydroxy acid.

[0013] 3. The flux solution for fusion plating according to item 2, wherein the hydroxy acid contains at least one of malic acid and citric acid.

[0014] 4. The flux solution for fusion plating according to any one of items 1 to 3, wherein the carboxylic acid contains at least one of acetic acid, malonic acid, maleic acid, butyric acid, and propanoic acid.

[0015] 5. The flux solution for fusion plating according to any one of items 1 to 4, wherein the carboxylic acid contains a plurality of carboxylic acids of different types from each other.

[0016] 6. The flux solution for fusion plating according to any one of items 1 to 5, wherein the surfactant contains an acetylene-based nonionic surfactant.

[0017] 7. A flux step of performing a flux treatment on the surface of an object to be plated using a flux solution for fusion plating, and a fusion plating step of immersing the object to be plated after the flux step in a plating bath and then pulling it out from the plating bath to coat the surface of the object to be plated with metal plating, wherein the flux solution for fusion plating used in the flux step contains a carboxylic acid, a surfactant, and at least one of zinc chloride and ammonium chloride, a fusion plating method.

[0018] According to the present invention, since the flux liquid for fusion plating does not contain hydrochloric acid as the main acid, it is possible to suppress or prevent the generation of hydrogen chloride (HCl) in the surrounding atmosphere during the fusion plating process. Therefore, the influence associated with the vaporization and residue of hydrogen chloride in the surrounding atmosphere can be reduced or eliminated.

[0019] In addition, since the surface of the object to be plated is flux-treated using the flux liquid for fusion plating, the metal plating that coats the surface of the object to be plated has high wettability. As a result, the surface of the object to be plated can be well coated with the metal plating.

[0020] Therefore, it is possible to provide a fusion plating method capable of well coating the surface of the object to be plated with metal plating while suppressing or preventing the vaporization and residue of hydrogen chloride in the surrounding atmosphere.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0022] Hereinafter, with reference to the drawings, a molten plating method according to an embodiment of the present invention will be described in detail. In addition, together therewith, a flux solution 1 for molten plating according to an embodiment of the present invention will be described in detail.

[0023] FIG. 1 is a schematic diagram for explaining a molten plating apparatus 2 according to an embodiment of the present invention. FIG. 2 is a flowchart showing the flow of a molten plating method according to an embodiment of the present invention.

[0024] The molten plating apparatus 2 performs a fluxing step S1 and a molten plating step S2 on a wire 3 as an example of an object to be plated. The molten plating apparatus 2 includes a wire supply unit 4, a flux tank 5, a plating tank 6, a wire recovery unit 7, and a plurality of guide rollers 8. In the molten plating apparatus 2, the molten plating method shown in FIG. 2 is executed.

[0025] The wire supply unit 4 includes a supply bobbin 9. The wire 3 is wound around the supply bobbin 9. The wire 3 is a round wire having a circular cross section. In this embodiment, the wire 3 is a copper wire. The wire 3 may be an iron wire (steel wire). The wire 3 wound around the supply bobbin 9 is a wire after wire drawing treatment. The wire diameter (diameter) of the wire 3 is preferably 0.05 mm or more and 2.0 mm or less. The wire diameter is more preferably 0.1 mm or more and 1.0 mm or less.

[0026] The flux tank 5 stores a flux solution 1 for molten plating. The flux solution 1 for molten plating has a cleaning action, an antioxidant action, and a surface tension reducing action. The cleaning action is an action of removing foreign matter and an oxide film from the wire 3. The antioxidant action is an action of preventing oxidation of the surface of the wire 3. The surface tension reducing action is an action of improving the wettability of the surface of the wire 3 and making it easier for the wetting to spread. The temperature of the flux solution stored in the flux tank 5 is not particularly limited. The temperature of the flux solution may be normal temperature (25°C).

[0027] In the plating bath 6, molten metal is stored. In this form, the molten metal is tin (Sn). That is, molten tin is stored in the plating bath 6. In other words, the plating bath 6 receives a tin plating bath. The temperature of the stored molten tin is 230°C or higher and 300°C or lower.

[0028] The wire recovery unit 7 includes a take-up bobbin 10. A wire 3 (i.e., a tin-plated wire) with its surface coated by tin plating is wound around the take-up bobbin 10.

[0029] The plurality of guide rollers 8 includes a sinker roller 11 and a lifting roller 12. The sinker roller 11 is disposed in the molten tin in the plating bath 6. The sinker roller 11 guides the wire 3 passing through the molten tin in the plating bath 6. The lifting roller 12 is disposed above the sinker roller 11. The lifting roller 12 is disposed at a predetermined interval above the liquid level (surface of the molten tin) of the molten tin in the plating bath 6.

[0030] With reference to FIGS. 1 and 2, a molten plating method using the molten plating apparatus 2 will be described. The wire 3 pulled out from the supply bobbin 9 of the wire supply unit 4 is sent to the flux bath 5. The wire 3 passes through the molten plating flux liquid 1 stored in the flux bath 5.

[0031] Specifically, the wire 3 is immersed in the molten plating flux liquid 1 and then pulled up. Thereby, the surface of the wire 3 is flux-treated (S1 in FIG. 2: flux process). By the flux treatment, foreign matters and oxide films are removed from the wire 3 (cleaning), oxidation of the surface of the wire 3 is prevented (oxidation prevention), and the wettability of the surface of the wire 3 is improved (reduction of surface tension).

[0032] In the flux process S1, the wire speed of the wire 3 is preferably 10 m / min or higher and 800 m / min or lower. More preferably, the wire speed of the wire 3 is 50 m / min or higher and 100 m / min or lower.

[0033] The wire 3 that has passed through the flux liquid 1 for molten plating is sent to the plating bath 6 by the guide roller 8. The wire 3 is immersed in molten tin and then pulled up. The wire 3 pulled up from the molten tin is air-cooled until it is wound around the pulling-up roller 12. Thereby, a plating layer is formed on the surface of the wire 3 (S2 in FIG. 2: molten plating process). In other words, the surface of the wire 3 is coated with tin plating (metal plating). Thereby, a tinned wire is manufactured.

[0034] In the molten plating process S2, the wire speed of the wire 3 is preferably 10 m / min or more and 800 m / min or less. The wire speed of the wire 3 is preferably 50 m / min or more and 100 m / min or less.

[0035] The manufactured tinned wire is wound around the winding bobbin 10 and recovered in the wire recovery section 7.

[0036] The flux liquid 1 for molten plating stored in the flux bath 5 contains a carboxylic acid, a surfactant, and at least one of zinc chloride (ZnCl2) and ammonium chloride (NH4Cl). In this form, both zinc chloride and ammonium chloride are contained in the flux liquid 1 for molten plating. Only one of zinc chloride and ammonium chloride may be contained in the flux liquid 1 for molten plating.

[0037] The carboxylic acid includes hydroxy acids. The hydroxy acid may be malic acid (C4H6O5). The hydroxy acid may be citric acid (C6H8O7).

[0038] The flux solution 1 for hot dip plating may contain carboxylic acids other than hydroxy acids as carboxylic acids. Specifically, the carboxylic acid may be acetic acid (C2H4O2, glacial acetic acid). The carboxylic acid may be malonic acid (C3H4O4). The carboxylic acid may be maleic acid (C4H4O4). The carboxylic acid may be butyric acid (C4H8O2). The carboxylic acid may be propanoic acid (C3H6O2). The flux solution 1 for hot dip plating may contain carboxylic acids other than the above-described carboxylic acids.

[0039] When the flux solution 1 for hot dip plating contains a carboxylic acid, the flux solution 1 for hot dip plating has a high cleaning effect. As a result, the flux solution 1 for hot dip plating exhibits high wettability. Thereby, it is possible to provide a flux solution 1 for hot dip plating that does not contain hydrochloric acid as a main acid and has high wettability for the tin plating covering the surface of the wire 3.

[0040] The flux solution 1 for hot dip plating may contain a plurality of types of carboxylic acids. Specifically, the flux solution 1 for hot dip plating may contain at least two acids (carboxylic acids) among malic acid, citric acid, tartaric acid (C4H6O6), acetic acid, malonic acid, maleic acid, butyric acid, and propanoic acid.

[0041] When the flux solution 1 for hot dip plating contains a plurality of types of carboxylic acids, it exhibits even higher wettability. Therefore, it is possible to provide a flux solution 1 for hot dip plating that does not contain hydrochloric acid as a main acid and has high wettability for the tin plating covering the surface of the wire 3.

[0042] The flux solution 1 for hot dip plating may contain a plurality of different types of hydroxy acids. Specifically, the flux solution 1 for hot dip plating may contain both malic acid and citric acid. The flux solution 1 for hot dip plating may contain both malic acid and tartaric acid. The flux solution 1 for hot dip plating may contain both citric acid and tartaric acid.

[0043] The concentration of the carboxylic acid in the molten plating flux liquid 1 is preferably 0.10 (mol / liter) or more, and more preferably 0.20 (mol / liter) or more.

[0044] The surfactant is not particularly limited, and any surfactant can be used, but it is preferable to use at least one of a nonionic surfactant and a cationic surfactant. Among them, the nonionic surfactant is less affected by electrolytes and has less foaming, so it is superior to the cationic surfactant. Therefore, it is preferable to use a nonionic surfactant as the surfactant.

[0045] Examples of the nonionic surfactant include acetylene glycol-based surfactants, polyoxyalkylene alkyl ether type surfactants, fatty acid alkanolamides, polyhydric alcohol type surfactants, silicone-based nonionic surfactants, and fluorine-based nonionic surfactants. Among these, one or more selected from the group consisting of acetylene glycol-based surfactants and polyoxyalkylene alkyl ether type surfactants are preferable.

[0046] Examples of commercially available products of nonionic surfactants include the "Surfinol" series manufactured by Nissin Chemical Industry Co., Ltd. and Air Products & Chemicals, the "Acetylenol" series manufactured by Kawaken Fine Chemical Co., Ltd., and the "Emulgen" series manufactured by Kao Corporation. The "Surfinol" series is an example of an acetylene glycol-based surfactant and contains acetylene glycol.

[0047] The concentration of zinc chloride contained in the molten plating flux liquid 1 is preferably 0.1 (mol / liter) or more, and more preferably 0.2 (mol / liter) or more.

[0048] The concentration of ammonium chloride in the flux solution 1 for fusion plating is preferably 0.3 (mol / liter) or more, and more preferably 0.6 (mol / liter) or more.

[0049] The molar ratio of zinc chloride to ammonium chloride in the flux solution 1 for fusion plating is not particularly limited, but is preferably 1:1 to 1:4, and more preferably 1:2 to 1:3.

[0050] The solvent contained in the flux solution 1 for fusion plating is not particularly limited, but may usually be water (H2O). In other words, the flux solution 1 for fusion plating may be an aqueous solution containing a carboxylic acid, a surfactant (nonionic surfactant), and at least one of zinc chloride and ammonium chloride.

[0051] It is preferable that both zinc chloride and ammonium chloride are contained in the flux solution 1 for fusion plating. In the flux solution 1 for fusion plating, one of zinc chloride and ammonium chloride may be omitted. In particular, when the carboxylic acid contained in the flux solution 1 for fusion plating is malic acid, one of zinc chloride and ammonium chloride may be omitted. Also, when the carboxylic acid contained in the flux solution 1 for fusion plating is citric acid, zinc chloride may be omitted.

[0052] Specifically, the flux solution 1 for fusion plating may contain malic acid, a surfactant (nonionic surfactant), and zinc chloride. In this case, the flux solution 1 for fusion plating may not contain ammonium chloride.

[0053] Also, the flux solution 1 for fusion plating may contain malic acid, a surfactant (nonionic surfactant), and ammonium chloride. In this case, the flux solution 1 for fusion plating may not contain zinc chloride.

[0054] Incidentally, zinc chloride is generally produced by adding hydrochloric acid to zinc or zinc oxide. Zinc chloride is distributed in the form of an aqueous zinc chloride solution (zinc chloride solution). The aqueous zinc chloride solution may contain a small amount of hydrochloric acid.

[0055] That is, the flux solution 1 for fusion plating may further contain hydrochloric acid. In this case, it is desirable that the concentration of hydrochloric acid in the flux solution 1 for fusion plating is sufficiently low. For example, the concentration of hydrochloric acid in the flux solution 1 for fusion plating is preferably 0.1 (mol / liter) or less. More preferably, the concentration of hydrochloric acid in the flux solution 1 for fusion plating is 0.02 (mol / liter) or less. Of course, the flux solution 1 for fusion plating may not contain hydrochloric acid.

[0056] The value of the pH (hydrogen ion exponent) of the flux solution 1 for fusion plating is preferably less than 3.0, and more preferably 2.3 or less. If the value of the pH of the flux solution 1 for fusion plating is 2.3 or more, the cleaning effect may decrease, and there is a risk that oxides and the like cannot be sufficiently removed from the surface of the wire 3. As a result, the wettability may decrease.

[0057] The lower the value of the pH of the flux solution 1 for fusion plating, the higher the cleaning effect. Therefore, the lower limit of the pH is not particularly defined, but if the pH is too low, it becomes difficult to handle the flux solution. Therefore, it may be 0.8 or more, and more preferably 1.2 or more.

[0058] The method for adjusting the pH is not particularly limited, but it can be adjusted by changing the type of carboxylic acid and the content ratio of the carboxylic acid and hydrochloric acid.

[0059] As described above, according to this embodiment, since the flux solution 1 for fusion plating does not contain hydrochloric acid as the main acid, it is possible to suppress or prevent hydrogen chloride (HCl) from being generated in the surrounding atmosphere during the fusion plating step S2. Therefore, the influence associated with the vaporization and residue of hydrogen chloride in the surrounding atmosphere can be reduced or eliminated.

[0060] Also, since the surface of the wire 3 is flux-treated using the flux solution 1 for molten plating, the tin plating that coats the surface of the wire 3 has high wettability. As a result, the surface of the wire 3 can be satisfactorily coated with tin plating.

[0061] Therefore, the surface of the wire 3 can be satisfactorily coated with tin plating while suppressing or preventing hydrogen chloride from vaporizing and remaining in the surrounding atmosphere.

[0062] Although tin has been described as an example of the metal (molten metal) used as metal plating in the molten plating method, zinc, zinc alloy, aluminum, aluminum alloy, tin alloy, etc. may also be used.

[0063] The object to be plated is not limited to the wire 3. The object to be plated may be a plate material or the like.

[0064] As described above, one embodiment of the present invention has been described, but it is merely an example showing one embodiment of the present invention, and various modifications can be made within the scope of the claims.

Example

[0065] The molten plating method of the present invention will be described based on examples. The present invention is not limited to the following examples only.

[0066] Wettability tests were conducted on the examples and comparative examples of the present invention. Specifically, a wire as the wire to be plated was flux-treated using the flux solution for molten plating, and then tin plating was applied to the wire (tin coating was performed), and the wettability of tin in that case was evaluated.

[0067] In the wettability test, a copper wire with a circular cross-section and a wire diameter of 0.6 mm was used as the wire to be plated. The copper wire was flux-treated using the flux solution for molten plating. As the flux solution for molten plating, an aqueous solution containing a carboxylic acid, a nonionic surfactant, an aqueous zinc chloride solution, ammonium chloride, and water (solvent) was used.

[0068] Then, the wettability test was carried out by varying the type of carboxylic acid and the like contained in the flux liquid used for the flux treatment.

[0069] As the carboxylic acid contained in the flux liquid for fusion plating, one or two of malic acid (0.28 (mol / liter (L))), citric acid (0.20 (mol / liter)), tartaric acid (0.25 (mol / liter)), acetic acid (glacial acetic acid, 0.63 (mol / liter)), malonic acid (0.37 (mol / liter)), maleic acid (0.33 (mol / liter)), butyric acid (0.43 (mol / liter)), and propanoic acid (0.51 (mol / liter)) were used. The values in parentheses are the concentrations of the carboxylic acid in the flux liquid for fusion plating.

[0070] As the nonionic surfactant, a mixed Surfynol prepared based on the "Surfynol" series manufactured by Nissin Chemical Industry Co., Ltd. and Air Products & Chemicals, Inc. was adopted. This mixed Surfynol is obtained by mixing Methyloxirane polymer with oxirane, ether with 2,4,7,9-tetramethyl-5-decyne-4,7-diol (2:1) (CAS No. 182211-02-5) and 2,4,7,9-TETRAMETHYL-5-DECYNE-4,7-DIOL ETHOXYLATE (CAS No. 9014-85-1) in a ratio of 1:1. Specifically, the amount of the nonionic surfactant is 0.5 milliliter with respect to 100 milliliters of the flux liquid for fusion plating.

[0071] In the inventive examples of test number T13, test number T23, and test number T26, the amount of the nonionic surfactant contained in the flux liquid for fusion plating (100 milliliters (mL)) is 0.06 milliliter (mL).

[0072] In the inventive examples of test number T14, test number T24, and test number T27, the amount of non-ionic surfactant contained in the flux solution for hot dip plating (100 milliliters) is 2.0 milliliters.

[0073] The zinc chloride aqueous solution contained in the flux solution for hot dip plating contains zinc chloride (70.02 wt%), hydrochloric acid (1.1 wt%), and water (28.7 wt%). The values in parentheses are the content ratios (wt%) of each component in the zinc chloride aqueous solution.

[0074] The mass of the zinc chloride aqueous solution contained in the flux solution for hot dip plating (100 milliliters) is 4.4 g. Since the proportion of zinc chloride in the zinc chloride aqueous solution is 70.02 wt%, at this time, the concentration of zinc chloride in the flux solution for hot dip plating is 0.226 (mol / liter). Since the proportion of hydrochloric acid in the zinc chloride aqueous solution is 1.1 wt%, the concentration of hydrochloric acid in the flux solution for hot dip plating is 0.0133 (mol / liter).

[0075] In the test of test number T30, the mass of the zinc chloride aqueous solution contained in the flux solution for hot dip plating (100 milliliters) is 1.0 g. Since the proportion of zinc chloride in the zinc chloride aqueous solution is 70.02 wt%, the concentration of zinc chloride in the flux solution for hot dip plating is 0.051 (mol / liter). Since the proportion of hydrochloric acid in the zinc chloride aqueous solution is 1.1 wt%, the concentration of hydrochloric acid in the flux solution for hot dip plating is 0.0030 (mol / liter).

[0076] In the tests of test number T31 and test number T32, the mass of the zinc chloride aqueous solution contained in the flux solution for hot dip plating (100 milliliters) is 2.2 g. Since the proportion of zinc chloride in the zinc chloride aqueous solution is 70.02 wt%, the concentration of zinc chloride in the flux solution for hot dip plating is 0.113 (mol / liter). Since the proportion of hydrochloric acid in the zinc chloride aqueous solution is 1.1 wt%, the concentration of hydrochloric acid in the flux solution for hot dip plating is 0.0066 (mol / liter).

[0077] The ammonium chloride contained in the flux solution for fusion plating is solid (powder form). The mass of ammonium chloride contained in the flux solution for fusion plating (100 milliliters) is 3.0 g. At this time, the concentration of ammonium chloride in the flux solution for fusion plating is 0.56 (mol / liter (mL)).

[0078] Only in the test of test number T30, the mass of ammonium chloride contained in the flux solution for fusion plating (100 milliliters) is 1.0 g. At this time, the concentration of ammonium chloride in the flux solution for fusion plating is 0.19 (mol / liter (mL)).

[0079] The type of carboxylic acid contained in the flux solution for fusion plating and the pH of the flux solution for fusion plating are shown in FIGS. 3 to 5. The temperature of the flux solution in the flux treatment was 25°C (room temperature).

[0080] In each wettability test, the wire as the wire to be plated was passed through the flux solution stored in the flux tank, and then immersed in the molten tin stored in the plating tank. The temperature of the molten tin was 250°C, the immersion speed was 4 mm / second, the immersion depth was 2 mm, and the immersion time was 5 seconds. After the elapse of the immersion time, the wire was pulled up at a pulling-up speed of 4 mm / second and dried to obtain a tin-plated wire. Then, the wettability of tin with respect to the wire at the time of pulling up was evaluated.

[0081] FIG. 6 is a graph showing the test results of the wettability test for the example of the present invention (test number T12). FIG. 7 is a graph showing the test results of the wettability test for the comparative example (test number T0). As shown in FIGS. 6 and 7, the meniscograph method was used for the evaluation of the wettability of tin. The higher the wettability of tin, the shorter the zero crossing time ZT and the greater the maximum wetting force FF.

[0082] Referring to FIGS. 3 and 7, among the comparative examples, Test No. T0 is an example in which Azonil (specifically, Azonil No. 1 (trade name, manufactured by Yakka Pharmaceutical Co., Ltd.)) is used as the flux solution for molten plating. For Test No. T0, the zero-crossing time ZT is 0.65 seconds, and the maximum wetting force FF is 0.53 mN.

[0083] Specifically, Azonil No. 1 contains hydrochloric acid (HCl), zinc chloride (ZnCl2), ammonium chloride (NH4Cl), and water (solvent, H2O). The content ratio (by mass) of hydrochloric acid is 0.2 wt% or more and 9.7 wt% or less. The content ratio (by mass) of zinc chloride is 1.4 wt% or more and 3.2 wt% or less. The content ratio (by mass) of ammonium chloride is 0.3 wt% or more and 0.4 wt% or less. The balance is water, and its content ratio (by mass) is 86.7 wt% or more and 98.1 wt% or less. More specifically, the component ratios of chlorine (Cl), zinc (Zn), and ammonia (NH3) contained in Azonil No. 1 are approximately 3.85 wt%, approximately 0.67 wt%, and approximately 0.13 wt%, respectively, with respect to Azonil No. 1 (100%). Azonil contains hydrochloric acid as the main acid, and in addition, ammonium chloride and zinc chloride. Therefore, in FIGS. 3 to 5, "Yes" is described in the columns of "zinc chloride solution" and "ammonium chloride", respectively.

[0084] The zero-crossing time ZT of each individual wettability test was evaluated according to the criteria that if it is less than 0.53 seconds, it is "◎"; if it is 0.53 seconds or more and 0.65 seconds or less, it is "○"; if it exceeds 0.65 and is 0.73 seconds or less, it is "△"; and if it exceeds 0.73 seconds, it is "×". As described above, since the zero-crossing time ZT of Test No. T0 is 0.65 seconds, if the evaluation of the zero-crossing time ZT is "◎" or "○", it means that the zero-crossing time ZT is equal to or shorter than that of Azonil (Test No. T0).

[0085] In FIGS. 3 to 5, when the zero-crossing time ZT cannot be measured, "unmeasurable" is described.

[0086] The maximum wetting force FF of each wetting test was evaluated according to the following criteria: "◎" if it exceeded 0.63 mN, "○" if it was 0.53 mN or more and 0.63 mN or less, "△" if it was 0.48 mN or more and less than 0.53 mN, and "×" if it was less than 0.48 mN. As described above, since the maximum wetting force FF of azonil (test number T0) is 0.53 mN, if the evaluation of the maximum wetting force FF is "◎" or "○", it means having a maximum wetting force FF equal to or greater than that of azonil. If the evaluation of the maximum wetting force FF is "×", it means having only a maximum wetting force FF inferior to that of azonil.

[0087] In FIGS. 3 to 5, when the maximum wetting force FF cannot be measured, "unmeasurable" is described.

[0088] Also, in each wetting test, considering the zero-crossing time ZT and the maximum wetting force FF, the wetting property of tin in each test was evaluated according to the criteria of "◎", "○", and "×". If the evaluation is "◎", it exhibits a wetting property superior to that of azonil. If the evaluation is "○", it exhibits a wetting property comparable to or slightly superior to that of azonil.

[0089] The test results are shown in FIGS. 3 to 5.

[0090] In the examples of the present invention, excellent wetting properties were obtained, while in the comparative examples that did not meet the conditions of the present invention, it was found that the wetting properties were poor.

[0091] Also, test number T35 is an example of the present invention, but tin plating was not formed on the wire. From this, it was found that when tartaric acid was used as the carboxylic acid, the wetting property of tin was extremely poor.

[0092] Also, test number T30 is also an example of the present invention, but tin plating was not formed on the wire. This is presumably due to the low concentration of the carboxylic acid and the slightly high pH value of the flux solution for hot dip plating.

[0093] Also, Test No. T7 is an example of the present invention, but the wettability of tin was poor. Test No. T7 is an example in which citric acid is used as the carboxylic acid. And the example of the present invention of Test No. T7 does not contain ammonium chloride.

[0094] In contrast, the wettability of tin in the example of the present invention of Test No. T11, which also uses citric acid as the carboxylic acid, was good. And the example of the present invention of Test No. T11 does not contain zinc chloride (aqueous zinc chloride solution).

[0095] On the other hand, the examples of the present invention of Test No. T18 and Test No. T20 are examples in which citric acid is used as the carboxylic acid and do not contain either ammonium chloride or zinc chloride (aqueous zinc chloride solution). However, in any of the examples of the present invention, the wettability of tin was good.

[0096] Also, in the examples of the present invention of Test Nos. T22 to T24 using malic acid as the carboxylic acid, it was found that the wettability of tin is excellent compared to other carboxylic acids such as citric acid.

[0097] Also, in the examples of the present invention of Test Nos. T25, T26, T27, T28, T29, T33, and T34 using a plurality of types (two types) of carboxylic acids, it was found that the wettability of tin is excellent compared to the case of using one type of carboxylic acid.

[0098] Also, in some wettability tests, the hydrogen chloride concentration contained in the atmosphere around the melting plating apparatus 2 was measured. Specifically, in the example of the present invention (Test No. T12) and the comparative example (Test No. T0), using a gas sampler (Gastec gas sampler set GV-100S), the atmosphere at the measurement position MP (Fig. 1) directly above the plating bath 6 was sampled, and the hydrogen chloride concentration contained in the atmosphere was measured. The measurement position MP is directly above the immersion position IP of the wire 3 (more specifically, a position 5 cm above the immersion position IP) on the upper surface (liquid surface) of the molten plating flux liquid stored in the plating bath 6. The measurement results are shown in Fig. 8.

[0099] As shown in FIG. 8, in the example of the present invention (test number T12), the hydrogen chloride concentration at the measurement position MP was 2 ppm, while in the comparative example (test number T0), the hydrogen chloride concentration at the measurement position MP was 30.4 ppm. From FIG. 8, when using the flux solution 1 for fusion plating containing carboxylic acid (citric acid) as the main acid, it was found that the hydrogen chloride concentration at the measurement position MP was significantly reduced compared to the case of using azonil (azonil No. 1) containing hydrochloric acid as the main acid.

[0100] From this, it can be seen that when using the flux solution 1 for fusion plating as the flux solution for fusion plating, the residual hydrogen chloride (HCl) in the atmosphere around the fusion plating apparatus 2 can be significantly reduced compared to the case of using azonil (azonil No. 1).

[0101] Therefore, according to the present embodiment, by using the flux solution 1 for fusion plating as the flux solution for fusion plating, while suppressing or preventing the vaporization and residue of hydrogen chloride in the surrounding atmosphere (while significantly suppressing the residue of hydrogen chloride in the surrounding atmosphere), the surface of the object to be plated can be well coated with metal plating.

Explanation of Signs

[0102] 1: Flux solution for fusion plating 3: Wire (object to be plated) 6: Plating tank

Claims

1. A flux solution for hot dip plating, containing a carboxylic acid, a surfactant, and at least one of zinc chloride and ammonium chloride.

2. The flux solution for hot dip plating according to Claim 1, wherein the carboxylic acid contains a hydroxy acid.

3. The flux solution for hot dip plating according to Claim 2, wherein the hydroxy acid contains at least one of malic acid and citric acid.

4. The flux solution for hot dip plating according to Claim 1, wherein the carboxylic acid contains at least one of acetic acid, malonic acid, maleic acid, butyric acid, and propanoic acid.

5. The flux solution for hot dip plating according to any one of Claims 1 to 4, wherein the carboxylic acid contains a plurality of carboxylic acids of different types from each other.

6. The flux solution for hot dip plating according to any one of Claims 1 to 4, wherein the surfactant contains an acetylene-based nonionic surfactant.

7. A hot dip plating method, including a fluxing step of fluxing the surface of an object to be plated using the flux solution for hot dip plating, and a hot dip plating step of immersing the object to be plated after the fluxing step in a plating bath and then pulling it up from the plating bath to coat the surface of the object to be plated with a metal plating, wherein the flux solution for hot dip plating used in the fluxing step contains a carboxylic acid, a surfactant, and at least one of zinc chloride and ammonium chloride.

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