Additive for acidic zinc alloy plating bath, acidic zinc alloy plating bath and zinc alloy plating film

Abstract

An additive for acidic zinc alloy plating bath according to the present invention is used for obtaining acidic zinc alloy plating bath that can provide a zinc alloy plating film having satisfactory appearance, and contains active components that are a glycine-containing water-soluble substance and an aliphatic polyamine having 12 or less carbon atoms. The glycine / polyamine ratio which is a ratio of the molar concentration in terms of glycine of the glycine-containing water-soluble substance to the molar concentration of the aliphatic polyamine may be preferably 0.1-40 inclusive. The present invention also provides acidic zinc alloy plating bath comprising the additive and a zinc alloy plating film formed with the acidic zinc alloy plating bath.

Description

Additives for acidic zinc alloy plating baths, acidic zinc alloy plating baths, and zinc alloy plating films

[0001] The present invention relates to an additive for an acidic zinc alloy plating bath, an acidic zinc alloy plating bath, and a zinc alloy plating film.

[0002] In this specification, zinc alloy plating refers to plating consisting of zinc, alloying elements, and inevitable impurities. The zinc alloy plating may have a higher zinc concentration (mass%) than the concentrations (mass%) of any other alloying elements, or may contain alloying elements with a higher concentration (mass%) than that of zinc.

[0003] Coatings made of zinc alloy plating such as zinc-nickel alloy, zinc-iron alloy, and tin-zinc alloy (also referred to as "zinc alloy plating films" in this specification) are widely used for improving functionality such as corrosion resistance and heat resistance in members around us, including steel sheets for automobiles and machine parts made of steel such as bolts and nuts.

[0004] A zinc alloy plating film is formed by electroplating, in which electrolysis is performed while a plated member is immersed in a plating bath for forming the zinc alloy plating film (also referred to as a "zinc alloy plating bath" in this specification). Zinc alloy plating baths are broadly classified into alkaline baths (e.g., Patent Document 1) and acidic baths (e.g., Patent Document 2). Alkaline baths include cyanide baths and zincate zinc alloy plating baths, while acidic baths include zinc chloride baths and zinc sulfate baths. An appropriate bath is selected from these zinc alloy plating baths, taking into consideration various conditions such as the desired hardness and brightness of the zinc alloy plating film, the shape and size of the plated member, and the working environment.

[0005] Patent Document 3 discloses a method for depositing a zinc-nickel alloy layer on a substrate, the method comprising contacting the substrate made of an iron or steel casting with an electrolytic composition comprising an acetate selected from the group consisting of sodium acetate, potassium acetate, ammonium acetate, and mixtures thereof, a zinc ion source, a nickel ion source, and aminoacetic acid, and applying an electric current to form on the substrate a zinc-nickel alloy layer having a nickel co-deposition rate of 10 to 18 mass % and substantially no internal stress, wherein the acetate and aminoacetic acid have a molar ratio of acetate:aminoacetic acid in the range of about 0.35:1 to about 0.91:1.

[0006] Japanese Patent Publication No. 1-298192 Japanese Patent Publication No. 4307810 U.S. Patent No. 8,435,398

[0007] Among these zinc alloy plating baths, acidic zinc alloy plating baths have the advantage of high current efficiency and excellent productivity. However, because the film thickness and appearance tend to be highly dependent on the current density, when the plated member has a complex shape, they tend to be prone to poor throwing power and poor appearance. In recent years, in order to improve productivity, there has been a trend toward increasing the input amount in barrel plating and increasing the applied voltage in rack plating. This trend is likely to lead to localized increases in current density, resulting in localized poor appearance.

[0008] An object of the present invention is to provide an additive used for obtaining an acidic zinc alloy plating bath capable of obtaining a zinc alloy plating film having a good appearance. Another object of the present invention is to provide an acidic zinc alloy plating bath capable of obtaining a zinc alloy plating film having a good appearance, and a zinc alloy plating film having a good appearance formed using the acidic zinc alloy plating bath.

[0009] The zinc alloy plated member refers to a member comprising a plated member and a zinc alloy plating film formed on the plated surface of the plated member. Furthermore, the term "good appearance" in relation to a zinc alloy plating film means that, compared with conventional methods, the lower limit of the current density at which abnormal deposition is likely to occur in the zinc alloy plating film is increased, and a zinc alloy plating film that was matte at a certain current density becomes bright or semi-bright at the same current density.

[0010] One aspect of the present invention, which is provided to solve the above-mentioned problems, is an additive for an acidic zinc alloy plating bath, which comprises, as active ingredients, a glycine-containing water-soluble substance and an aliphatic polyamine having 12 or less carbon atoms.

[0011] The aliphatic polyamine contained in the additive for an acidic zinc alloy plating bath may contain one or more selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0012] The glycine / polyamine ratio, which is the ratio of the glycine-equivalent molar concentration of the glycine-containing water-soluble substance contained in the additive for an acidic zinc alloy plating bath to the molar concentration of the aliphatic polyamine, may be preferably 0.1 or more and 40 or less, more preferably 1 or more and 35 or less, and particularly preferably 4 or more and 34 or less.

[0013] Another aspect of the present invention is an acidic zinc alloy plating bath comprising a bath-soluble zinc-containing substance, a bath-soluble metal-containing substance, and the active ingredient of the additive described above.

[0014] The acidic zinc alloy plating bath may have a pH of 4 or more and 6 or less.

[0015] It may be preferable that the acidic zinc alloy plating bath is boric acid-free.

[0016] It may be preferable that the acidic zinc alloy plating bath is ammonia-free.

[0017] The acidic zinc alloy plating bath may preferably contain an acetic acid-containing substance.

[0018] The acidic zinc alloy plating bath may contain a bath-soluble nickel-containing substance as the bath-soluble metal-containing substance, and in this case, the codeposition rate of nickel in the zinc alloy plating film formed from the acidic zinc alloy plating bath may be 5 mass % or more and 20 mass % or less.

[0019] It may be preferable that the acidic zinc alloy plating bath contains a bath-soluble nickel-containing substance, and that the glycine / nickel ratio, which is the ratio of the glycine-equivalent molar concentration of the glycine-containing water-soluble substance to the nickel-equivalent molar concentration of the bath-soluble nickel-containing substance, is 0.1 or more.

[0020] The acidic zinc alloy plating bath may contain at least one of a primary brightener and a secondary brightener.

[0021] Another aspect of the present invention is a zinc alloy plating film characterized in that, when a depth profile of a zinc alloy plated member in which a zinc alloy plating film is formed on a plated member made of an iron-based material is measured, the zinc alloy plating does not have an alloy element enriched region in which the alloy element concentration is relatively high on the side closer to the plated member.

[0022] The zinc alloy plating film is preferably a zinc alloy plating film containing nickel as an alloying element, and is formed from a plating bath containing glycine and an aliphatic polyamine having 12 or less carbon atoms.

[0023] In the depth profile of the above zinc alloy plating film, when the position where the zinc concentration is 60 mass % or more and closest to the outermost surface is defined as the surface side edge of the zinc alloy plating film, the position where the zinc concentration is equal to the iron concentration derived from the plated member is defined as the plated member side edge of the zinc alloy plating film, and the length of the region from the surface side edge to the plated member side edge is defined as the thickness of the zinc alloy plating film, it is sometimes preferable that the average value of the nickel concentration [Ni1] in an intermediate region ranging from the surface side edge to 40% to 60% of the thickness of the zinc alloy plating, and the maximum value of the nickel concentration [Ni2] in an initial region ranging from a position moved 30% of the thickness of the zinc alloy plating from the plated member side edge toward the surface, and the maximum value of the nickel concentration [Ni2] in the initial region ranging from the plated member side edge to the plated member side edge, satisfy the following formula (1): [Ni1]≧[Ni2] (1)

[0024] By using an acidic zinc alloy plating bath containing the additive of the present invention, a zinc alloy plating film having a good appearance can be obtained. Furthermore, by the present invention, a zinc alloy plated member having a zinc alloy plating film having a good appearance can be obtained.

[0025] Current density in the zinc-nickel alloy plating film of Example 2: 11 A / dm 2 The current density of the zinc-nickel alloy plating films of Example 1 and Comparative Example 1 was 11 A / dm 2 1 shows the depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 2 and Comparative Example 2 at a current density of 11 A / dm 2 1 shows the depth profile of the nickel concentration at a current density of 11 A / dm in the zinc-nickel alloy plating films of Example 3 and Comparative Example 3. 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 4 at a current density of 11 A / dm 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 5 at a current density of 11 A / dm 21 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 6 at a current density of 11 A / dm 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 7 at a current density of 11 A / dm 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 8 at a current density of 11 A / dm 2 10 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 9 at a current density of 11 A / dm 2 10 shows a depth profile of the nickel concentration at a current density of 11 A / dm 2 11 shows a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 11 at a current density of 11 A / dm 2 10 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 12 at a current density of 11 A / dm 2 10 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 13 at a current density of 11 A / dm 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Comparative Example 4 at a current density of 11 A / dm 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Comparative Example 6 at a current density of 11 A / dm 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Comparative Example 7 at a current density of 11 A / dm 2 1 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Comparative Example 8 at a current density of 11 A / dm 2 16 shows a depth profile of nickel concentration at a current density of 11 A / dm 2 10 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 17 at a current density of 11 A / dm 210 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 18 at a current density of 11 A / dm 2 10 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 19 at a current density of 11 A / dm 2 10 is a depth profile of the nickel concentration in the zinc-nickel alloy plating film of Example 20 at a current density of 11 A / dm 2 1 is a depth profile of nickel concentration in the portion of FIG.

[0026] The present invention will be described in detail below.

[0027] 1. Additive for Acidic Zinc Alloy Plating Bath An additive for an acidic zinc alloy plating bath according to one embodiment of the present invention (the present additive) contains, as active ingredients, a glycine-containing water-soluble substance and an aliphatic polyamine having a plurality of amino groups and 12 or less carbon atoms (sometimes abbreviated as "polyamine (A)" in this specification).

[0028] In this specification, the glycine-containing water-soluble substance refers to a water-soluble substance based on glycine produced in a plating bath from a glycine source, such as glycine or glycine hydrochloride, which is a substance capable of providing glycine in the plating bath. Since the plating bath according to this embodiment is acidic, a specific example of the glycine-containing water-soluble substance is glycinium ion. Specific examples of the glycine source also include glycine derivatives such as glycine methyl ester.

[0029] The polyamine (A) is an aliphatic amine having 12 or less carbon atoms, and other structures are not limited as long as it has a plurality of amino groups. The polyamine (A) may be any of a primary amine, a secondary amine, and a tertiary amine. In the plating solution, the polyamine (A) has one or more protons (H + ) may be added to the polyamine (A) to ionize it. Specific examples of the polyamine (A) will be described later.

[0030] A zinc alloy plating film having a bright appearance is easily obtained from an acidic zinc alloy plating bath containing a glycine-containing water-soluble substance and a polyamine (A). 2Even when electroplating is performed under conditions exceeding this, the resulting zinc alloy plating film is unlikely to suffer from poor appearance due to abnormal deposition. As will be described later, in zinc-nickel alloy plating films with poor appearance, the nickel concentration in the plating film in the region close to the end of the plated member, i.e., the plating formed in the early stage of the plating process (immediately after the start of current application) tends to be specifically higher than in other regions. When the nickel concentration becomes high in this way, the deposited plating film turns black, making it difficult to obtain a silvery-white appearance. In other words, abnormal deposition of the plating film, particularly poor appearance, is related to the phenomenon in which nickel is preferentially deposited in the early stage of plating (immediately after the start of current application) to form a nickel-enriched region (details will be described later).

[0031] By including a glycine-containing water-soluble substance and a polyamine (A) in the zinc alloy plating bath according to this embodiment, the formation of nickel-enriched regions in the zinc alloy plating film is suppressed, making the plating film less susceptible to poor appearance. The reason why the glycine-containing water-soluble substance and the polyamine (A) suppress the formation of nickel-enriched regions is unclear. While the additive may contain amino acids other than glycine, adding other amino acids (e.g., alanine, glutamine, glutamic acid, etc.) to the additive does not achieve the same effect as glycine. In other words, other amino acids are not active ingredients of the additive.

[0032] Acidic zinc alloy plating baths containing the present additive, which contains a glycine-containing water-soluble substance and a polyamine (A) as active ingredients, are less likely to form nickel-enriched regions, making it easier to consistently produce zinc alloy plating films with a bright appearance. For example, in barrel plating, high-current-density plating is performed intermittently, so the appearance of the zinc alloy plating film formed by barrel plating is easily affected by plating formed in the early stages of plating (immediately after the start of current application). Therefore, when using a plating bath according to a conventional technology, in which nickel-enriched regions are more likely to form, the appearance of the resulting plating film is likely to be poor. In contrast, the plating bath according to this embodiment is less likely to form nickel-enriched regions, making it less likely to produce poor appearance even in barrel plating.

[0033] Furthermore, the plating bath according to this embodiment is less likely to cause abnormal deposition in the resulting zinc alloy plating film, even when electroplating is performed under conditions of high current density. While rack plating tends to have a high plating current density in order to increase productivity, the plating bath according to this embodiment is less likely to cause poor appearance in the resulting zinc alloy plating film, even when the current density is increased.

[0034] The glycine / polyamine ratio, which is the ratio of the molar concentration of the glycine-containing water-soluble substance in terms of glycine acid to the molar concentration of the polyamine (A), is preferably 0.1 or more and 40 or less, more preferably 1 or more and 35 or less, and particularly preferably 4 or more and 35 or less, from the viewpoint of stably realizing that nickel-enriched regions are less likely to occur in the zinc alloy plating film.

[0035] In this way, since the glycine-containing water-soluble substance and polyamine (A) function as primary brighteners, the content of surfactants that are usually used as primary brighteners can be reduced, and the reduction in the content of surfactants in the plating bath can alleviate the problem of foaming that reduces the workability of zinc alloy plating.

[0036] When the zinc alloy plating bath is a zinc-nickel alloy plating bath, the zinc alloy plating bath containing a glycine-containing water-soluble substance and a polyamine (A) may make it easier to obtain a zinc-nickel alloy plating film having a nickel co-deposition rate of 10% by mass or more and 20% by mass or less, preferably 12% by mass or more and 18% by mass or less, and more preferably 14% by mass or more and 16% by mass or less.

[0037] Specific examples of the primary amine polyamine (A) include ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, dimethylaminopropylamine, diethylaminopropylamine, bis-(3-aminopropyl)ether, 1,2-bis-(3-aminopropoxy)ethane, 1,3-bis-(3-aminopropoxy)-2,2'-dimethylpropane, aminoethylethanolamine, 1,2-bisaminocyclohexane, 1,3-bisaminocyclohexane, 1,4-bisaminocyclohexane, 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, 1,3-bisaminoethylcyclohexane, 1,4-bisaminoethylcyclohexane, 1,3-bis Examples of the aminopropyl cyclohexane include aminopropyl cyclohexane, 1,4-bisaminopropyl cyclohexane, hydrogenated 4,4'-diaminodiphenylmethane, 2-aminopiperidine, 4-aminopiperidine, 2-aminomethylpiperidine, 4-aminomethylpiperidine, 2-aminoethylpiperidine, 4-aminoethylpiperidine, N-aminoethylpiperidine, N-aminopropylpiperidine, N-aminoethylmorpholine, N-aminopropylmorpholine, isophoronediamine, menthanediamine, 1,4-bisaminopropylpiperazine, diethylenetriamine, iminobispropylamine, methyliminobispropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-aminoethylpiperazine, N-aminopropylpiperazine, 1,4-bis(aminoethylpiperazine), and 1,4-bis(aminopropylpiperazine).

[0038] Specific examples of the secondary amine polyamine (A) include N,N'-dimethylethylenediamine, N,N'-dimethyl-1,2-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminobutane, N,N'-dimethyl-1,3-diaminobutane, N,N'-dimethyl-1,4-diaminobutane, N,N'-dimethyl-1,5-diaminopentane, and N,N'-dimethyl-1,6-diaminopentane. diaminohexane, N,N'-dimethyl-1,7-diaminoheptane, N,N'-diethylethylenediamine, N,N'-diethyl-1,2-diaminopropane, N,N'-diethyl-1,3-diaminopropane, N,N'-diethyl-1,2-diaminobutane, N,N'-diethyl-1,3-diaminobutane, N,N'-diethyl-1,4-diaminobutane, and N,N'-diethyl-1,6-diaminohexane.

[0039] Specific examples of the tertiary amine polyamine (A) include tetramethylethylenediamine, N,N'-dimethylpiperazine, N,N'-bis((2-hydroxy)propyl)piperazine, hexamethylenetetramine, N,N,N',N'-tetramethyl-1,3-butanamine, 2-dimethylamino-2-hydroxypropane, diethylaminoethanol, N,N,N-tris(3-dimethylaminopropyl)amine, 2,4,6-tris(N,N-dimethylaminomethyl)phenol, and heptamethylisobiguanide.

[0040] The polyamine (A) may have two or more of a primary amino group, a secondary amino group, and a tertiary amino group. Examples of such compounds include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and biguanide. Among these, from the viewpoints of high stability of the effect and high availability, it is preferable that the polyamine (A) contains diethylenetriamine, and more preferably is composed of diethylenetriamine.

[0041] The polyamine (A) may be composed of one type of compound or multiple types of compounds. When the polyamine (A) is composed of multiple types of compounds, the content ratio of these compounds is not limited and is appropriately set depending on the desired properties.

[0042] The number of carbon atoms in the polyamine (A) may preferably be 10 or less, more preferably 8 or less, and particularly preferably 6 or less.

[0043] Preferred examples of the polyamine (A) include ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, and among these, ethylenediamine, diethylenetriamine, and triethylenetetramine are more preferred examples of the polyamine (A).

[0044] In some cases, it may be preferred that the polyamine (A) has neither a carbonyl group nor a group containing a carbonyl group.

[0045] The present additive may contain components other than the polyamine (A). Examples of such components include primary brighteners, secondary brighteners, antioxidants, antifoaming agents, and sequestering agents. Note that, since the polyamine (A) contained in the additive according to one embodiment of the present invention functions as a primary brightener and a secondary brightener, the present additive does not necessarily contain at least one of the primary brightener and the secondary brightener.

[0046] 2. Acidic Zinc Alloy Plating Bath The zinc alloy plating bath according to one embodiment of the present invention is acidic, and therefore has higher current efficiency and superior productivity than alkaline zinc alloy plating baths. The zinc alloy plating bath according to one embodiment of the present invention contains a bath-soluble zinc-containing substance, a bath-soluble metal-containing substance, the above-mentioned glycine-containing water-soluble substance, and a polyamine (A). Therefore, the appearance of the silvery-white zinc alloy plating film formed from the zinc alloy plating bath according to this embodiment is likely to be good.

[0047] (1) Metal Components (1-1) Bath-Soluble Zinc-Containing Substance The zinc alloy plating bath according to this embodiment contains a bath-soluble zinc-containing substance. In this specification, the bath-soluble zinc-containing substance is a source of zinc to be deposited as a zinc alloy plating film, and refers to one or more components selected from the group consisting of zinc cations and bath-soluble substances containing the same. Since the zinc alloy plating bath according to this embodiment is acidic, an example of the bath-soluble zinc-containing substance is zinc ions (Zn 2+ Examples of raw materials (also referred to as "zinc sources" in the present invention) for supplying bath-soluble zinc-containing substances to the plating bath include zinc chloride, zinc sulfate, and zinc oxide.

[0048] The zinc-equivalent content of the soluble zinc-containing substance in the zinc alloy plating bath according to this embodiment (the zinc-equivalent content of the soluble zinc-containing substance in the bath) is not limited. If this content is too low, the zinc alloy plating film may be difficult to deposit, so the zinc-equivalent content is preferably 5 g / L or more, more preferably 10 g / L or more, and particularly preferably 15 g / L or more. If the zinc-equivalent content of the soluble zinc-containing substance is too high, poor appearance and reduced throwing power may easily occur, so the zinc-equivalent content is preferably 100 g / L or less, more preferably 80 g / L or less, and particularly preferably 60 g / L or less.

[0049] (1-2) Bath-soluble metal-containing substance A zinc alloy plating bath according to one embodiment of the present invention contains a bath-soluble metal-containing substance. As used herein, the bath-soluble metal-containing substance refers to a source of metals other than zinc contained in a zinc alloy plating film, and refers to one or more components selected from the group consisting of cations of metal elements and bath-soluble substances containing the cations. Examples of metal elements contained in the bath-soluble metal-containing substance include iron, nickel, and tin. In a preferred example, the metal element contained in the metal-containing substance is selected from the group consisting of iron, nickel, and tin.

[0050] The raw material (also referred to as "metal source" in the present invention) used to supply a bath-soluble metal-containing substance to the plating bath may be appropriately selected depending on the type of metal element contained in the bath-soluble metal-containing substance. For example, when the metal element contained in the bath-soluble metal-containing substance is iron, i.e., when the zinc alloy plating bath contains a bath-soluble iron-containing substance, examples of the iron source include Fe(SO)·7H0, FeSO·7H0, Fe(OH), FeCl·6H0, and FeCl·4H0. When the metal element contained in the bath-soluble metal-containing substance is nickel, i.e., when the zinc alloy plating bath contains a bath-soluble nickel-containing substance, examples of the nickel source include NiSO·6H0, NiCl·6H0, and Ni(OH). When the metal element contained in the bath-soluble metal-containing substance is tin, i.e., when the zinc alloy plating bath contains a bath-soluble tin-containing substance, examples of the tin source include SnSO4, SnCl2, and SnCl2.2H2O.

[0051] The metal-equivalent content of the bath-soluble metal-containing substance in a zinc alloy plating bath according to one embodiment of the present invention is appropriately set depending on the composition of the desired zinc alloy plating. When the zinc alloy plating bath contains a bath-soluble iron-containing substance, the iron-equivalent content of the bath-soluble iron-containing substance is, for example, about 1 g / L to 100 g / L. When the zinc alloy plating bath contains a bath-soluble nickel-containing substance, the nickel-equivalent content of the bath-soluble nickel-containing substance is, for example, about 0.1 g / L to 60 g / L. When the zinc alloy plating bath contains a bath-soluble tin-containing substance, the tin-equivalent content of the bath-soluble tin-containing substance is, for example, about 1 g / L to 100 g / L. The content of alloying elements (co-deposition rate) in the zinc alloy plating film is set depending on the characteristics of the plating bath, the type of alloying element, the application, etc.

[0052] When the alloying element contained in the zinc alloy plating bath according to one embodiment of the present invention is nickel, the nickel co-deposition rate of the zinc-nickel alloy plating film obtained using the zinc alloy plating bath is preferably 5% by mass or more and 20% by mass or less from the viewpoint of improving corrosion resistance. Since zinc-nickel alloys with a nickel content of 10% by mass or more have particularly excellent corrosion resistance, when particularly excellent corrosion resistance is required, the nickel co-deposition rate of the zinc-nickel alloy plating film is preferably 10% by mass or more and 20% by mass or less. From the viewpoint of improving corrosion resistance and uniformity of the film composition, the nickel co-deposition rate of the zinc-nickel alloy plating film is more preferably 12% by mass or more and 18% by mass or less. For applications that do not require particularly high corrosion resistance, it may be preferable to set the nickel co-deposition rate of the zinc-nickel alloy plating film to 5% by mass or more and less than 10% by mass, taking into account the balance between corrosion resistance and productivity (production costs). The nickel co-deposition rate can be adjusted by changing the bath composition and current density.

[0053] (2) Additive Components The zinc alloy plating bath according to one embodiment of the present invention contains the above-described glycine-containing water-soluble substance and polyamine (A) as active ingredients. It may also contain other additive components.

[0054] (2-1) Glycine-Containing Water-Soluble Substance The zinc alloy plating bath according to one embodiment of the present invention contains the aforementioned glycine-containing water-soluble substance. The content of the glycine-containing water-soluble substance is appropriately determined depending on the type and content of components other than the glycine-containing water-soluble substance contained in the zinc alloy plating bath, the composition of the zinc alloy plating film formed from the zinc alloy plating bath, and other factors. A non-limiting example of the glycine-equivalent content of the glycine-containing water-soluble substance in the zinc alloy plating bath according to one embodiment of the present invention is 0.1 g / L or more and 100 g / L or less. By having the glycine-containing water-soluble substance at 0.1 g / L or more, the effect of including the glycine-containing water-soluble substance can be more easily achieved. Furthermore, if the glycine-containing water-soluble substance is at 100 g / L or less, the substance can be sufficiently dissolved in the plating bath. When setting the composition of the plating bath, it may be preferable that the glycine-containing water-soluble substance be at 70 g / L or less, in order to minimize the effect on the adjustment range of the content of other components.

[0055] When the alloying element of the zinc alloy plating is nickel, as described above, the glycine-containing water-soluble substance and polyamine (A) can suppress the preferential deposition of nickel at the initial stage of plating (immediately after the start of current application). From the viewpoint of stably performing this function, the concentration of the glycine-containing water-soluble substance in the zinc alloy plating bath may be preferably 1 g / L or more, and more preferably 10 g / L or more.

[0056] Furthermore, since the glycine-containing water-soluble substance is closely related to nickel deposition, the glycine / nickel ratio, which is the ratio of the glycine-equivalent molar concentration of the glycine-containing water-soluble substance to the nickel-equivalent molar concentration of the bath-soluble nickel-containing substance, may preferably be 0.1 or more, more preferably 0.5 or more, particularly preferably 1.2 or more, and extremely preferably 1.4 or more. No upper limit for the glycine / nickel ratio is set from the viewpoint of improving the appearance of the plating film. If the content of the glycine-containing water-soluble substance is too high, it may be necessary to adjust the content of other components (e.g., potassium-containing components). Therefore, the glycine / nickel ratio may preferably be 3 or less, more preferably 2 or less. The glycine / nickel ratio has little effect on the codeposition rate of nickel in the zinc alloy plating film.

[0057] (2-2) Polyamine (A) The zinc alloy plating bath according to one embodiment of the present invention contains the aforementioned polyamine (A). The content of the polyamine (A) is appropriately set depending on the type of polyamine (A), the types and contents of components other than the polyamine (A) contained in the zinc alloy plating bath, and the composition of the zinc alloy plating film formed from the zinc alloy plating bath. A non-limiting example of the content of the polyamine (A) in the zinc alloy plating bath according to one embodiment of the present invention is 0.1 g / L or more and 100 g / L or less. By having the polyamine (A) content of 0.1 g / L or more, the effects of including the polyamine (A) can be more easily achieved. Furthermore, by having the polyamine (A) content of 100 g / L or less, the possibility of insoluble substances being generated in the bath is reduced.

[0058] Depending on the type of zinc alloy plating bath, the polyamine (A) content in the zinc alloy plating bath may be a predetermined value or less, which may enable the appearance of the zinc alloy plating film formed from the zinc alloy plating bath to be more consistently good. For example, when the zinc alloy plating is zinc-nickel alloy plating, the polyamine (A) content may be 30 g / L or less, which may facilitate the consistent improvement of the appearance of the zinc-nickel alloy plating film formed from the zinc-nickel alloy plating bath. From the viewpoint of ensuring a consistent improvement of the appearance of the zinc-nickel alloy plating film, the polyamine (A) content may preferably be 20 g / L or less.

[0059] (2-3) Other Additive Components The zinc alloy plating bath according to one embodiment of the present invention may contain additive components other than the above-mentioned polyamine (A). Examples of such additive components or materials that provide additive components in the zinc alloy plating bath include the following.

[0060] (2-3-1) Primary Brightener The zinc alloy plating bath according to one embodiment of the present invention may contain a primary brightener as one type of additive component. Examples of such primary brighteners include anionic surfactants, nonionic surfactants, and water-soluble organic compounds such as water-soluble cationic polymer compounds, which are used in various zinc plating baths.

[0061] The primary brightener may have both a structure found in anionic surfactants, such as sulfonic acid groups, and a structure found in nonionic surfactants, such as polyethers. Such compounds include alkali metal salts of aromatic or aliphatic polyether sulfates.

[0062] When the zinc alloy plating bath according to one embodiment of the present invention contains a primary brightener, it may be preferable that the primary brightener is a nitrogen-free surfactant. Specific examples of such surfactants include the above-mentioned alkali metal salts of aromatic or aliphatic polyether sulfates and polyether compounds of acetylenic dialcohols.

[0063] When the zinc alloy plating bath according to one embodiment of the present invention contains a primary brightener, the content of the primary brightener in the zinc alloy plating bath is not limited. The content is appropriately set depending on the type of primary brightener, the types and contents of components other than the primary brightener contained in the zinc alloy plating bath, and the composition of the zinc alloy plating film formed from the zinc alloy plating bath. For example, the content of the primary brightener is preferably 0.1 g / L or more and 100 g / L or less, and more preferably 0.5 g / L or more and 20 g / L or less.

[0064] As described above, since polyamine (A) functions as a primary brightener, the content of the primary brightener consisting of a surfactant can be reduced, and by reducing the content of the surfactant in the plating bath, the problem of foaming that reduces the workability of zinc alloy plating can be alleviated.

[0065] (2-3-2) Secondary Brightener The zinc alloy plating bath according to one embodiment of the present invention may contain a secondary brightener as one type of additive component. In particular, from the viewpoint of improving brightness, the secondary brightener may contain an aromatic compound having a carbonyl group. Examples of such compounds include aromatic aldehydes such as anisaldehyde, veratraldehyde, o-chlorobenzaldehyde (OCAD), salicylaldehyde, vanillin, piperonal, and p-hydroxybenzaldehyde; and acetones having an aromatic ring such as benzylidene acetone.

[0066] When the zinc alloy plating bath according to one embodiment of the present invention contains a secondary brightener, the content of the secondary brightener in the zinc alloy plating bath is not limited. The content is appropriately set depending on the type of secondary brightener, the types and contents of components other than the secondary brightener contained in the zinc alloy plating bath, and the composition of the zinc alloy plating film formed from the zinc-based plating bath. For example, the content of the secondary brightener is preferably 0.001 g / L or more and 10 g / L or less, and more preferably 0.005 g / L or more and 1 g / L or less.

[0067] (2-3-3) Others The zinc alloy plating bath according to one embodiment of the present invention may contain additive components other than the above-mentioned components. Examples of such additive components include antioxidants, antifoaming agents, and sequestering agents.

[0068] Examples of antioxidants include hydroxyphenyl compounds such as phenol, catechol, resorcinol, hydroquinone, and pyrogallol, as well as L-ascorbic acid and sorbitol.

[0069] Examples of the defoaming agent include silicone-based defoaming agents and organic defoaming agents such as surfactants, polyethers, and higher alcohols.

[0070] Examples of sequestering agents include silicates (specific examples include sodium silicate) and silica (specific examples include colloidal silica). The content of the sequestering agent in the zinc alloy plating bath is not limited and may be appropriately set taking into consideration the type of sequestering agent, the composition of the solvent, and the like. For example, the content of the sequestering agent is preferably 0.1 g / L or more and 100 g / L or less, and more preferably 0.5 g / L or more and 20 g / L or less.

[0071] (3) Buffering Agent, Inorganic Electrolyte The zinc alloy plating bath according to one embodiment of the present invention may contain a substance having a buffering effect as a buffering agent. By containing a buffering agent, the pH near the surface of the plated member is prevented from becoming excessively high. As a result, the deposition form of metals such as zinc on the plated member is stabilized, making abnormal deposition less likely to occur.

[0072] When the zinc alloy plating bath according to one embodiment of the present invention contains a buffer, the type of buffer is not limited. Specific examples of buffers include an acetic acid-containing substance containing at least one of acetic acid and acetate ions, an ammonia-containing substance containing at least one of ammonia and ammonium ions, and a boric acid-containing substance containing at least one of boric acid and borate ions. When the zinc alloy plating in the zinc alloy plating bath is zinc alloy plating, the inclusion of an acetic acid-containing substance as a buffer may stabilize the deposition of the zinc alloy plating. From the viewpoint of stabilizing the plating deposition, the alloying element in the zinc alloy plating is preferably nickel. Furthermore, potassium acetate is preferred as an acetic acid source for supplying the acetic acid-containing substance to the plating bath.

[0073] From the viewpoint of reducing the environmental load, the content of the acetic acid-containing substance in the zinc alloy plating bath according to one embodiment of the present invention is preferably 200 g / L or less, more preferably 100 g / L or less, and even more preferably 50 g / L or less, calculated as acetic acid. From the viewpoint of stably exhibiting the function as a buffer, the content of the acetic acid-containing substance in the zinc alloy plating bath according to one embodiment of the present invention is preferably 1 g / L or more, more preferably 5 g / L or more, and particularly preferably 10 g / L or more, calculated as acetic acid.

[0074] From the viewpoint of reducing the environmental load, the content of ammonia-containing substances in the zinc alloy plating bath according to one embodiment of the present invention is preferably 100 g / L or less, more preferably 50 g / L or less, and even more preferably 10 g / L or less, calculated as ammonia. It is particularly preferable that the zinc alloy plating bath according to one embodiment of the present invention is substantially free of ammonia-containing substances (ammonia-free). In this specification, ammonia-free means that the bath does not contain ammonia and ammonium ions to an extent that they function as a buffer in the plating bath.

[0075] From the viewpoint of reducing the environmental load, the content of the boric acid-containing substance in the zinc alloy plating bath according to one embodiment of the present invention is preferably 5 g / L or less, more preferably 1 g / L or less, and even more preferably 0.1 g / L or less, calculated as boric acid. It is particularly preferable that the zinc alloy plating bath according to one embodiment of the present invention is substantially free of the boric acid-containing substance (boric acid-free). In this specification, boric acid-free means that the bath does not contain boric acid and borate ions to an extent that they function as a buffer in the plating bath.

[0076] Thus, even when the zinc alloy plating bath according to this embodiment is free of boric acid or ammonia, or preferably both, if the zinc alloy plating bath contains an acetic acid-containing substance, the acetic acid-containing substance can serve as a buffer for the plating bath. Specific examples of acetic acid-containing substances include substances based on acetic acid sources such as potassium acetate and sodium acetate (acetic acid, acetate ions). When the zinc alloy plating bath is free of boric acid or ammonia, or preferably both, and potassium acetate is used as the acetic acid source, it is sometimes preferable to set the amount of potassium acetate to 100 g / L or less, and sometimes more preferable to set it to 70 g / L or less.

[0077] When the zinc alloy plating bath according to one embodiment of the present invention has a low content of ammonia-containing substances and boric acid-containing substances and the zinc alloy plating bath imposes a low load on the environment, this means that the zinc alloy plating bath according to one embodiment of the present invention has excellent wastewater treatability.

[0078] The zinc alloy plating bath according to one embodiment of the present invention may contain an inorganic electrolyte. Examples of inorganic electrolytes include chloride ions, sulfate ions, nitrate ions, phosphate ions, sodium ions, potassium ions, magnesium ions, and aluminum ions. These may be incorporated into the zinc alloy plating bath as salts consisting of cations and anions. Potassium salts, such as potassium chloride, may be preferred as such salts in terms of ease of solubility. The total content of inorganic electrolytes contained in the zinc alloy plating bath according to one embodiment of the present invention is not limited. It is appropriately determined depending on the type of inorganic electrolyte, the type and content of components other than the inorganic electrolyte contained in the zinc alloy plating bath, the composition of the zinc alloy plating film formed from the zinc alloy plating bath, plating conditions, and the like. For example, the total content of inorganic electrolytes contained in the zinc alloy plating bath is preferably 10 g / L or more and 1000 g / L or less, and more preferably 50 g / L or more and 500 g / L or less. When the alloying element of the zinc alloy plating is nickel and the acidic zinc alloy plating bath contains chloride ions, from the viewpoint of ensuring the stability of the bath, it may be preferable that the concentration of chloride ions in the bath be 100 g / L or more and 400 g / L or less, and it may be more preferable that the concentration be 120 g / L or more and 280 g / L or less.

[0079] (4) Solvent and Properties The solvent of the zinc alloy plating bath according to one embodiment of the present invention is mainly water. Other solvents, such as alcohol, ether, and ketone, which have high solubility in water, may be mixed in. In this case, from the viewpoint of the stability of the entire plating bath and easing the burden on wastewater treatment, the ratio of the solvent to the total solvent is preferably 10% by volume or less.

[0080] The zinc alloy plating bath according to one embodiment of the present invention is acidic, and its pH is preferably 4 or more and 6 or less, and more preferably 5.0 or more and 5.8 or less. The type of material used to adjust the pH of the plating bath is not particularly limited. Known materials such as hydrochloric acid, sulfuric acid, nitric acid, and alkali metal hydroxides such as sodium hydroxide and potassium hydroxide may be used.

[0081] (5) Preparation Method The method for preparing the zinc alloy plating bath according to this embodiment is not particularly limited. The zinc alloy plating bath can be prepared by dissolving a zinc source, a metal source, a glycine source, a polyamine (A) source, which is a substance capable of producing polyamine (A) in the plating bath, and, as necessary, the other additive components described above, a buffer, an inorganic electrolyte, and the like as optional additional components, in a solvent. The glycine source contains glycine, and the polyamine (A) source contains polyamine (A).

[0082] 3. Method for Producing Zinc Alloy-Plated Members Zinc alloy-plated members can be obtained by bringing a member to be plated into contact with the zinc alloy plating bath according to this embodiment and performing electrolysis using the member to be plated as the cathode (negative electrode). The method for bringing the zinc alloy plating bath into contact with the member to be plated is not limited. A typical example is bringing the member to be plated into contact with the zinc alloy plating bath, and the contact may also be achieved by spraying the plating solution constituting the zinc alloy plating bath onto the member to be plated.

[0083] The material of the member to be plated is not particularly limited as long as it is conductive. Examples include metal materials such as iron-based materials, and non-conductive materials such as resin-based materials and ceramic-based materials, on the surface of which a layer of conductive material is formed by electroless plating or the like. The shape of the member to be plated is also not particularly limited. Examples include primary processed products such as plates, bars, and wires; cut and ground products such as screws, bolts, and molds (which may be further polished); pressed products such as vehicle frames and equipment housings; and cast products such as brake calipers and engine blocks. Note that when the member to be plated is a cast product made of an iron-based material, it may not be possible to form a zinc alloy plating film from an alkaline zinc alloy plating bath due to the influence of components contained to improve castability.

[0084] The material constituting the anode (positive electrode) is not particularly limited. A metal-based material containing zinc or an alloying element may be used as the soluble anode. As the soluble anode, an anode made of a zinc-based material and an anode made of a material containing an alloying element may be separately prepared. These anodes may then be connected to different power sources, and the voltage applied to each anode may be independently controlled.

[0085] The current density in electrolysis is not particularly limited. If the current density is too low, the deposition rate of the resulting zinc alloy plating film may be low, resulting in poor productivity, while if the current density is too high, the appearance of the resulting zinc plating film may be deteriorated, and the throwing power, etc. may be reduced. Taking this into consideration, the current density may be set appropriately. From the viewpoint of achieving both improved productivity and improved quality of the plating film, a current density of 0.1 A / dm 2 15A / dm or more 2 It is preferable that the current is 0.5 A / dm or less. 2 13A / dm or more 2 As described above, since the acidic zinc alloy plating bath contains a glycine-containing water-soluble substance and a polyamine (A), a high current density, specifically 10 A / dm or less, can be achieved. 2 Even at a current density exceeding 1000 kJ / s, nickel-enriched regions are unlikely to form in the zinc-nickel alloy plating film, and therefore the resulting plating film is unlikely to have poor appearance.

[0086] The temperature of the plating bath during electrolysis (plating bath temperature) may be in the range of about 15°C to about 50°C, and may be about room temperature (about 25°C).

[0087] The electrolysis time (plating time) is appropriately set based on the deposition rate of the plating film, which is determined by the composition of the zinc alloy plating bath, the current density, the plating bath temperature, etc., and the desired thickness of the plating film.

[0088] The configuration of the plating equipment is not particularly limited. A member to be plated as a cathode may be placed in a zinc alloy plating bath so as to face a plate-shaped or rod-shaped anode, and electrolysis may be performed while appropriately stirring the solution in the zinc alloy plating bath to form a zinc alloy plating film on the member to be plated. In this case, the solution may be stirred using a liquid circulation pump, aeration, or by moving the member to be plated, etc., in the plating bath.

[0089] Another example of plating equipment is barrel plating equipment, in which a barrel containing a plated member, such as a bolt, is immersed in a zinc alloy plating bath and electrolysis is performed while the barrel is rotating to form a zinc alloy plating film on the plated member. Specific examples of plated members for which barrel plating equipment is used include bolts, nuts, screws, etc. By using a zinc alloy plating bath according to one embodiment of the present invention, even if the plated member is highly anisotropic (long and thin), such as a bolt, it is possible to reduce variations in appearance, film thickness, and codeposition rate between the end and other portions of the resulting zinc alloy plating film. When an acidic zinc alloy plating bath with high current efficiency is used instead of an alkaline zinc alloy plating bath with low current efficiency, it has traditionally been difficult to reduce variations in appearance, film thickness, and codeposition rate between the end and other portions.

[0090] 4. Zinc Alloy Plating Film In a zinc-nickel alloy plating film formed using the present additive, when the depth profile of a zinc alloy plated member formed on a plated member made of an iron-based material is measured, a nickel-enriched region in which the nickel concentration is relatively high is unlikely to be formed on the side closer to the plated member.

[0091] The nickel-enriched region can be identified by a graph (depth profile) showing the change in the component concentration of the plated member in the thickness direction of the plated film. Specifically, when measuring the depth profile of a zinc alloy plated member formed on a plated member made of an iron-based material, the position closest to the outermost surface where the zinc concentration is 60 mass % or more is defined as the surface-side edge of the zinc alloy plating film. Furthermore, the position where the zinc concentration is equal to the iron concentration derived from the plated member is defined as the plated member-side edge of the zinc alloy plating. The length of the region from the surface-side edge to the plated member-side edge is defined as the thickness of the zinc alloy plating film.

[0092] When defined in this way, if a partial region having a specifically higher nickel concentration (when the alloying element in the alloying element concentration is nickel) than a region closer to the surface than the initial region is found in an initial region consisting of the range between the end of the zinc alloy plating film on the side of the plated member and a position moved 30% of the thickness of the zinc alloy plating toward the surface, the partial region is called a nickel-enriched region (when the alloying element in the alloying element-enriched region is nickel).

[0093] The presence of a nickel-enriched region should be judged from the overall shape of the depth profile, but the following evaluation method also helps to confirm the presence of the nickel-enriched region. That is, when the range from 40% to 60% of the thickness of the zinc alloy plating from the surface side edge is defined as the intermediate region, in a zinc-nickel alloy plating film having a nickel-enriched region, if the average value of the nickel concentration in this intermediate region (this average value is also referred to as the "intermediate region average value") [Ni1] and the maximum value of the nickel concentration in the initial region (this maximum value is also referred to as the "initial region maximum value") [Ni2] satisfy the following formula (2), there is a high possibility that a nickel-enriched region has occurred in the initial region. [Ni1] < [Ni2] (2)

[0094] When such a nickel-enriched region exists on the side of the zinc-nickel alloy plating film that is close to the plated member, the film is likely to have a poor appearance, and this tendency becomes more pronounced when the current density is high.

[0095] In contrast, the zinc alloy plating film (zinc-nickel alloy plating film) according to this embodiment is formed from a plating bath containing a glycine-containing water-soluble substance and polyamine (A), and therefore is less likely to produce nickel-enriched regions and is more likely to satisfy the following formula (1): [Ni1]≧[Ni2] (1)

[0096] Therefore, the zinc alloy plating film (zinc-nickel alloy plating film) according to this embodiment has a high current density, specifically, 10 A / dm 2 Even in a portion formed under conditions exceeding this, poor appearance is unlikely to occur.

[0097] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0098] For example, a chemical conversion treatment may be applied to the zinc alloy plating film of the zinc alloy plated member.

[0099] The effects of the present invention will be explained below based on examples, but the present invention is not limited to these.

[0100] (Examples 1 to 3 and Comparative Examples 1 to 3) A zinc alloy plating bath having the following composition and a pH of 5.3 was prepared: Zinc chloride: 62.5 g / L (zinc concentration: 30 g / L) Nickel chloride hexahydrate: 81 g / L (nickel concentration: 20 g / L) Potassium chloride: 196 g / L (chlorine concentration including that from zinc chloride and nickel chloride hexahydrate: 150 g / L) Potassium acetate: 65 g / L Glycine source: glycine (Gly) was blended in the amount shown in Table 1 (units in the table are g / L) Polyamine (A) source: diethylenetriamine (DETA), a type of polyamine (A), was blended in the amount shown in Table 1 (units in the table are g / L) Sodium benzoate: 1 g / L Surfactant: 1.6 g / L Brightener: 0.01 g / L Boric acid: not contained Ammonia or ammonium salt: not contained

[0101] For each of the prepared plating baths, electrolysis was carried out using a Hull Cell Tester ("B-55" manufactured by Yamamoto Plating Tester Co., Ltd.) under the following conditions: Current: 8 A Time: 15 seconds Solution temperature: 35°C Solution stirring: None Anode plate: Nickel plate ("B-59-P02" manufactured by Yamamoto Plating Tester Co., Ltd.) Cathode plate: Iron plate ("B-60-P01A" manufactured by Yamamoto Plating Tester Co., Ltd.)

[0102] The current density in the silvery white zinc-nickel alloy plating film formed on the cathode plate was 11 A / dm 2 The results are shown in Table 1. In Table 1, "Gly / PA" means the glycine / polyamine ratio (the same applies hereinafter).

[0103]

[0104] As shown in Table 1, the zinc-nickel alloy plating film formed from the zinc-nickel plating bath according to this example containing glycine, which is a glycine-containing water-soluble substance, and diethylenetriamine, which is polyamine (A), exhibited a high plating efficiency at a current density of 11 A / dm 2 No particular defects in appearance were observed in this area.

[0105] The current density of the obtained zinc-nickel alloy plating film was 11 A / dm 2 The depth profile of the zinc-nickel alloy plating film of Example 2 was measured by glow discharge optical emission spectroscopy (GD-OES). The depth profile of the zinc-nickel alloy plating film of Example 2 is shown in Figure 1 as a specific example. Note that Figure 1 shows the depth profiles of the concentrations of zinc and nickel contained in the zinc-nickel alloy plating film and iron contained in the cathode plate.

[0106] The depth indicated by the arrow in Figure 1 at which the concentration of zinc derived from the zinc-nickel alloy plating film and the concentration of iron derived from the cathode plate, which is the plated member, are equal was defined as the end of the zinc-nickel alloy plating film on the plated member side. The position where the zinc concentration is 60 mass% or more and closest to the outermost surface was defined as the surface-side end of the zinc alloy plating film. The length from the surface-side end to the end on the plated member side (indicated by the open arrow in Figure 1) was defined as the thickness of the zinc alloy plating film. Based on the depth profile shown in Figure 1, the thickness of the zinc alloy plating film was 275 nm. The length between the surface-side end and the outermost surface was approximately 1 nm, which was virtually negligible considering the measurement accuracy of the GD-OES depth profile.

[0107] The current density in each of the zinc-nickel alloy plating films produced in the examples and comparative examples was 11 A / dm 2 The depth profile of the nickel concentration in the area was determined. The results are shown in Figures 2 to 4. In these figures, the horizontal axis is normalized by the thickness of each plating film, and the unit of current density is shown as ASD.

[0108] As shown in Figures 2 to 4, in the zinc-nickel alloy plating film according to the comparative example, a portion with a particularly high nickel concentration (nickel-enriched region) was observed in the initial region, which consisted of the range between the end of the zinc-nickel alloy plating and a position 30% of the thickness of the zinc-nickel alloy plating from the end of the member to be plated. Using Figure 3, which shows the depth profile of Comparative Example 2, where this tendency is prominent, the range indicated by the white arrow in Figure 3 is the initial region. The initial region contains a region with a higher nickel concentration than regions other than the initial region, for example, an intermediate region (indicated by the black arrow in Figure 3) extending from the end of the surface to 40% to 60% of the thickness of the zinc alloy plating. Since the plating film in such a nickel-enriched region is black rather than silvery white, in a plating bath that forms a nickel-enriched region, the resulting plating film has a black appearance due to the nickel-enriched region.

[0109] For confirmation, the average value of the nickel concentration in the intermediate region [Ni1] and the maximum value of the nickel concentration in the initial region [Ni2] were determined from the depth profiles shown in Figures 2 to 4. The results are shown in Table 2.

[0110]

[0111] As shown in Table 2, the zinc-nickel alloy plating film of the comparative example showed a tendency for the maximum value [Ni2] in the initial region to be larger than the average value [Ni1] in the intermediate region ([Ni1] < [Ni2]), confirming the presence of a nickel-enriched region. In contrast, the zinc-nickel alloy plating film of the example showed a tendency for the average value [Ni1] in the intermediate region to be equal to or larger than the maximum value [Ni2] in the initial region ([Ni1] ≥ [Ni2]), and no nickel-enriched region was confirmed.

[0112] (Examples 4 to 13 and Example 20) Using the plating solution composition of Example 1 as a base, several types of plating solutions were prepared, each with a different molar concentration of the bath-soluble nickel-containing substance in terms of nickel and a different molar concentration of glycine, as shown in Table 3. In Table 4, the numbers in the "Ni," "Gly," and "DETA" columns represent the molar concentration of nickel (unit: mol / L), the molar concentration of glycine (unit: mol / L), and the molar concentration of diethylenetriamine (unit: mmol / L), respectively. The numbers in the "Gly / Ni" column represent the calculation result (glycine / nickel ratio) of (molar concentration of glycine) / (molar concentration of nickel), and the numbers in the "Gly / PA" column represent the calculation result (glycine / polyamine ratio) of (molar concentration of glycine) / (molar concentration of diethylenetriamine).

[0113]

[0114] For each of the prepared plating solutions, electrolysis was carried out under the same conditions as in Example 1, and the current density in the zinc-nickel alloy plating film formed on the cathode plate was 11 A / dm 2 The results, as shown in Table 3, show that the coatings of all Examples were glossy (having a silvery white appearance, which could be clearly seen by the observer's eyes when viewed from the cathode plate).

[0115] The current density of the obtained zinc-nickel alloy plating film was 11 A / dm 2 The depth profile of the area was measured by glow discharge optical emission spectroscopy (GD-OES). The results are shown in Figures 5 to 14. As shown in these figures, no nickel-enriched region was observed in the initial region in the depth profile of any of the plating films. When the average value [Ni1] of the intermediate region was compared with the maximum value [Ni2] of the initial region, as shown in Table 3, there was a basic tendency for the average value [Ni1] of the intermediate region to be equal to or greater than the maximum value [Ni2] of the initial region ([Ni1] ≥ [Ni2]), and no results were obtained in which [Ni2] clearly exceeded [Ni1]. That is, when the current density was 10 A / dm 2 Even in the portion exceeding this range, a zinc-nickel alloy plating film having a suitable appearance was obtained when the glycine / nickel ratio was in the range of 0.1 or more and 2.0 or less and the glycine / polyamine ratio was in the range of 0.3 or more and 34.4 or less.

[0116] (Examples 14 to 19 and Comparative Examples 4 to 8) The plating baths shown in Table 4 were prepared. The plating bath of Comparative Example 4 falls within the scope of the electrolytic composition shown as Example 1 of Patent Document 3. The plating bath of Example 14 was prepared by adding diethylenetriamine, a type of polyamine according to the present invention, to the plating bath of Comparative Example 4 so that the glycine / polyamine ratio was equal to that of Example 1 (6.0). The plating bath of Example 15 had a composition substantially identical to that of Example 1. The plating bath of Comparative Example 5 was prepared by removing diethylenetriamine from the plating bath of Example 15 and adding the same amount of boric acid as the plating bath of Comparative Example 4. In other words, the plating bath of Comparative Example 5 was prepared by adjusting the nickel concentration and chlorine concentration to those of Example 15 with respect to the plating bath of Comparative Example 4. The plating bath of Comparative Example 6 was prepared by removing boric acid from the plating bath of Comparative Example 4. This composition differs from the plating bath of Comparative Example 1, shown for reference, in terms of the nickel concentration and chlorine concentration.

[0117] The plating baths shown in Table 5 were prepared. The plating bath of Comparative Example 7 was prepared by removing glycine from the plating bath of Comparative Example 4, which falls within the range of the electrolytic composition shown as Example 1 of Patent Document 3, and adding the same amount of diethylenetriamine as in Example 14. The plating bath of Comparative Example 8 was prepared by adding the same amount of boric acid as in Comparative Example 4 to the plating bath of Comparative Example 1. The plating bath of Example 16 had the same composition as the plating bath of Example 15. The plating bath of Example 17 was prepared by adding the same amount of boric acid as in Comparative Example 4 (15 g / L = 0.24 mol / L). The plating bath of Example 18 was prepared by adding 100 g / L (1.9 mol / L) of ammonium chloride to the plating bath of Example 16, reducing the potassium chloride concentration to 120 g / L (1.6 mol / L), and adjusting the chlorine concentration to 180 g / L (5.1 mol / L). The chlorine concentration (152 g / L) in Example 16 was 4.3 mol / L. The plating bath of Example 19 was the same as that of Example 16 except that it contained 220 g / L (4.1 mol / L) of ammonium chloride and the same amount of boric acid as in Comparative Example 4 (15 g / L = 0.24 mol / L).

[0118]

[0119]

[0120] For each of the plating baths prepared in Examples 14 to 20 and Comparative Examples 4 to 8, electrolysis was carried out using a Hull Cell Tester ("B-55L" manufactured by Yamamoto Plating Tester Co., Ltd.) under the following conditions: Current: 4 A Time: 5 minutes Solution temperature: 35°C Solution stirring: Stirrer stirring (700 rpm) Anode plate: Nickel plate ("B-59-P02" manufactured by Yamamoto Plating Tester Co., Ltd.) Cathode plate: Iron plate ("B-60-P01LA" manufactured by Yamamoto Plating Tester Co., Ltd.)

[0121] The appearance of each of the obtained zinc-nickel alloy plating films was evaluated, and the results are shown in Table 6.

[0122]

[0123] The cathode plate on which the zinc-nickel alloy plating film was formed was equally divided in the direction of different current densities to set 20 regions, and for each of the 19 regions excluding the region with the highest current density, the arithmetic mean value of the current density at the end on the high current density side and the current density at the end on the low current density side was calculated. The calculated arithmetic mean value was used as the average current density for that region. The values ​​in the second row of Table 6 (unit: A / dm 2 ) indicates this average current density.

[0124] The bold numbers in the rows for each Example and Comparative Example indicate the results of the appearance evaluation for each region, classified as follows: 1: Glossy (a silvery white appearance that can be clearly seen by the observer's eyes when looking at the cathode plate) 2: Semi-glossy (a silvery white appearance, but the observer's eyes appear blurred or reflections can be seen) 3: Black (the appearance is black, not silvery white) 4: Scorched (the plating surface is rough)

[0125] As shown in Table 6, the zinc-nickel alloy plating films according to Examples 15 to 20 all had an average current density of 0.01 A / dm 2 From the area of ​​11 A / dm 2 In contrast, the zinc-nickel alloy plating film according to the comparative example could not obtain a glossy appearance over such a wide range as the examples. In particular, the zinc-nickel alloy plating film according to comparative example 4, which falls within the range of the electrolytic composition shown as example 1 in patent document 3, exhibited a black appearance in the low current density range due to an excessively high nickel concentration in the plating film, and the average current density was 11 A / dm 2 In the region of , a burnt appearance was obtained due to excessive current density, and a glossy appearance could not be obtained even at a medium current density.

[0126] The current density in the zinc-nickel alloy plating films according to Comparative Example 4, Comparative Example 6 to Comparative Example 8, and Example 16 to Example 20 was 11 A / dm 2The nickel depth profiles were measured by glow discharge optical emission spectroscopy (GD-OES) for the portions (FIGS. 15 to 22). In each of these figures, as in FIG. 2 and other figures, the horizontal axis representing depth was normalized by the thickness of the respective plating films (the depth at which the zinc concentration and the iron concentration become equal). As shown in FIGS. 15 to 18, the zinc-nickel alloy plating films of Comparative Examples 4 and 6 to 8 exhibited nickel-enriched regions at normalized depths of approximately 0.8 to 0.85, where the nickel concentration was specifically elevated. In contrast, as shown in FIGS. 19 to 23, no nickel-enriched regions were observed in the zinc-nickel alloy plating films of Examples 16 to 20. In particular, even when the plating bath of Example 20 had a glycine / polyamine ratio of more than 30, no nickel-enriched regions were observed in the depth profiles of the zinc-nickel alloy plating films obtained.

Claims

1. An additive for an acidic zinc alloy plating bath, comprising as active ingredients a water-soluble substance containing glycine and an aliphatic polyamine having 12 or less carbon atoms.

2. 2. The additive according to claim 1, wherein the aliphatic polyamine comprises one or more selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

3. 3. The additive according to claim 1, wherein a glycine / polyamine ratio, which is a ratio of a glycine-equivalent molar concentration of the glycine-containing water-soluble substance to a molar concentration of the aliphatic polyamine, is 0.1 or more and 40 or less.

4. 4. An acidic zinc alloy plating bath comprising a bath-soluble zinc-containing substance, a bath-soluble metal-containing substance, and the active ingredient of the additive according to claim 1.

5. 5. The acidic zinc alloy plating bath according to claim 4, wherein the pH is 4 or more and 6 or less.

6. 6. The acidic zinc alloy plating bath according to claim 4, which is free of boric acid.

7. 7. The acidic zinc alloy plating bath according to claim 4, which is ammonia-free.

8. The acidic zinc alloy plating bath according to any one of claims 4 to 7, further comprising an acetic acid-containing substance.

9. The bath-soluble metal-containing material includes a bath-soluble nickel-containing material, 9. The acidic zinc alloy plating bath according to claim 4, wherein a co-deposition rate of nickel in a zinc alloy plating film formed from the acidic zinc alloy plating bath is 5 mass % or more and 20 mass % or less.

10. said bath soluble nickel-containing material; 10. The acidic zinc alloy plating bath according to claim 9, wherein a glycine / nickel ratio, which is a ratio of a glycine-equivalent molar concentration of the glycine-containing water-soluble substance to a nickel-equivalent molar concentration of the bath-soluble nickel-containing substance, is 0.1 or more.

11. The acidic zinc alloy plating bath according to any one of claims 4 to 10, comprising at least one of a primary brightener and a secondary brightener.

12. A zinc alloy plating film characterized in that, when a depth profile of a zinc alloy plated member in which a zinc alloy plating film is formed on a plated member made of an iron-based material is measured, the zinc alloy plating does not have an alloy element concentrated region in which the alloy element concentration is relatively high on the side close to the plated member.

13. The zinc alloy plating film according to claim 12, which is a zinc alloy plating film containing nickel as an alloying element and is formed from a plating bath containing glycine and an aliphatic polyamine having 12 or less carbon atoms.

14. In the depth profile, When a position where the zinc concentration is 60 mass% or more and closest to the outermost surface is defined as a surface side end of the zinc alloy plating film, and a position where the zinc concentration is equal to the iron concentration derived from the plated member is defined as a plated member side end of the zinc alloy plating film, and the length of the region from the surface side end to the plated member side end is defined as the thickness of the zinc alloy plating film, an average nickel concentration [Ni1] in an intermediate region that is in a range of 40% to 60% of the thickness of the zinc alloy plating from the surface side end portion; a maximum value [Ni2] of the nickel concentration in an initial region including a range between a position moved from the end of the plated member toward the surface side by 30% of the thickness of the zinc alloy plating from the end of the plated member and the end of the plated member; The zinc alloy plating film according to claim 12 or 13, which satisfies the following formula (1): [Ni1]≧[Ni2] (1)