EP4269663A1

EP4269663A1 - Method and system for electroplating article with metal

Info

Publication number: EP4269663A1
Application number: EP21915031.5A
Authority: EP
Inventors: Kota Kobayashi; Nobuya SUGAYA; Manabu Inoue
Original assignee: Dipsol Chemicals Co Ltd
Current assignee: Dipsol Chemicals Co Ltd
Priority date: 2020-12-28
Filing date: 2021-12-02
Publication date: 2023-11-01
Also published as: CN116670334A; TW202233528A; JPWO2022145170A1; WO2022145170A1

Abstract

The object of the present invention is to provide a method and system for electroplating without requiring ancillary facilities or anolyte control, while using an anode which can be relatively easily produced without requiring an expensive metal or special metal. When electroplating an article with metal, decomposition of an organic compound additive in a plating bath can be suppressed by using, as an anode, a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof.

Description

Technical Field

The present invention relates to a method and system for electroplating an article with metal. Specifically, the present invention relates to an electroplating method and system in which decomposition of an organic compound additive added to a plating bath comprising metal ions is suppressed.

Background Art

Zinc plating is used as a relatively inexpensive anti-corrosive plating, and its alkaline plating bath comprises an organic compound such as a quaternary amine polymer as an additive. When this organic compound is decomposed by anodization, dendrites with poor adhesion are deposited and make it impossible to form satisfactory anti-corrosive zinc plating.
Zinc alloy plating has corrosion resistance superior to zinc plating and therefore is widely used for automobile parts and so on. In particular, alkaline zinc-nickel alloy plating is used for fuel system parts required to have high corrosion resistance and engine parts to be placed under a high temperature environment. An alkaline zinc-nickel alloy plating bath is obtained by dissolving nickel by using an amine-based chelating agent suitable for a nickel co-deposition ratio, and is for forming a plating film in which zinc and nickel are co-deposited. The alkaline zinc-nickel alloy plating bath has a problem that during current application, the amine-based chelating agent is oxidatively decomposed on the surface of the anode to generate oxalic acid and sodium carbonate. When nickel ions and ions of iron-based metal such as iron ions coexist, these act as an oxidation catalyst, and further accelerate oxidative decomposition of the amine-based chelating agent. For this reason, when the alkaline zinc-nickel alloy plating bath comes into contact with the anode, the amine-based chelating agent is rapidly decomposed, resulting in a rapid deterioration of the plating performance. Accumulation of this decomposed product causes many problems such as decrease in current efficiency, increase in a bath voltage, reduction in plating film thickness, lowering of a nickel content in a plating film, narrowing of a range of current density in which plating is possible, lowering of gloss, and increase in chemical oxygen demand (COD). Therefore, the plating bath is not usable for a long term and must be replaced frequently.
Patent Literatures 1 and 2 describe a so-called anode cell system partitioned such that an anolyte is placed in a cell covered with a diaphragm and that a plating bath is out of contact with an anode plate, thereby making it possible to suppressing decomposition of an organic compound additive. Since oxalic acid and sodium carbonate generated in the plating bath migrate from the plating solution into the anode cell in this anode cell system, this system is expected to produce an effect of removing the decomposed products in the plating bath. On the other hand, the anode cell system requires many ancillary facilities such as an anode cell body, piping, and a pump. In addition, it is necessary to control the concentration of the anolyte, and to renew the anolyte every time a certain amount of current is applied.
Patent Literature 3 teaches that decomposition of an organic compound additive is suppressed by applying a coating to the surface of a conductive substrate of an anode. In this case, there is no need for ancillary facilities or anolyte control, but the cost for manufacturing the anode is a problem. Patent Literature 4 also teaches that a coating is applied to the surface of a conductive substrate of an anode, but further improvement is required.
On the other hand, Patent Literature 5 teaches that a metal oxide film can be formed by heat-treating a metal film formed by electroplating, and an iron oxide film has high water repellency while a nickel oxide film has low water repellency. Patent Literature 6 and Non Patent Literatures 1 and 2 teach that an electrode having a film layer formed of iron nitride or oxide of nickel and iron is used for oxygen generation reaction by water electrolysis. However, none of Patent Literatures 1 to 6 and Non Patent Literatures 1 and 2 teaches that a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof is used as an electrode for electroplating.

Citation List

Patent Literatures

Patent Literature 1: International Publication No. WO2016/075963
Patent Literature 2: International Publication No. WO2016/075964
Patent Literature 3: Japanese Patent No. 6582353
Patent Literature 4: Published Japanese Translation of PCT International Application No. 2019-530800
Patent Literature 5: International Publication No. WO2017/145915
Patent Literature 6: Japanese Patent Application Publication No. 2016-132813

Non Patent Literatures

Non Patent Literature 1: ACS Appl. Energy Mater. 2019 2, 1199-1209
Non Patent Literature 2: ACS Catal. 2017, 7, 2052-2057

Summary of Invention

Problems to be solved by the invention

The object of the present invention is to provide a method and system for electroplating without requiring ancillary facilities or anolyte control, while using an anode which can be relatively easily produced without requiring an expensive metal or special metal.

Means for solution of the problems

As a result of earnest study to solve the above problems, the present inventors found that, when electroplating an article with metal, decomposition of an organic compound additive in a plating bath can be suppressed by using, as an anode, a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof, and completed the present invention. In sum, the present invention provides the following method and system for electroplating an article with metal.

[1] A method for electroplating an article with metal, comprising the step of applying current in a plating bath comprising ions of the metal and an organic compound additive, wherein
the plating bath comprises the article as a cathode, and a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof as an anode.
[2] The method according to the above [1], wherein the metal comprises zinc.
[3] The method according to the above [1] or [2], wherein the plating bath is an alkaline plating bath.
[4] The method according to any one of the above [1] to [3], wherein the conductive substrate comprises at least one of nickel and iron.
[5] The method according to any one of the above [1] to [4], wherein a zinc or zinc alloy film is formed on a surface of the article.
[6] The method according to any one of the above [1] to [5], wherein the organic compound additive comprises at least one selected from the group consisting of amine-based chelating agents, brightening agents, smoothing agents, and defoamers.
[7] The method according to the above [6], wherein the amine-based chelating agent comprises at least one selected from the group consisting of alkyleneamine compounds, their alkylene oxide adducts, and alkanolamine compounds.
[8] The method according to any one of the above [1] to [7], wherein the layer comprising the oxide or nitride is formed by oxidizing or nitriding a conductive substrate having a plating film comprising nickel and iron, a conductive substrate comprising iron and having a plating film comprising nickel, a conductive substrate comprising nickel and having a plating film comprising iron, or a conductive substrate comprising nickel and iron.
[9] The method according to the above [8], wherein the plating film comprising nickel and iron, the plating film comprising nickel, or the plating film comprising iron is formed by using a plating bath comprising saccharin or a salt thereof.
[10] The method according to any one of the above [1] to [9], wherein the layer comprising the oxide or nitride further comprises phosphorus atoms and boron atoms.
[11] A system for electroplating an article with metal, comprising a plating bath comprising ions of the metal and an organic compound additive, wherein
the plating bath comprises the article as a cathode, and a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof as an anode.
[12] A method for producing an electrode comprising a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof, the method comprising the step of:
performing oxidation treatment or nitridation treatment on a conductive substrate having a plating film comprising nickel and iron, a conductive substrate comprising iron and having a plating film comprising nickel, a conductive substrate comprising nickel and having a plating film comprising iron, or a conductive substrate comprising nickel and iron to form the layer comprising the oxide or nitride of nickel and iron on the surface of the conductive substrate.
[13] The production method according to the above [12], further comprising the step of forming the plating film comprising nickel and iron, the plating film comprising nickel, or the plating film comprising iron by using a plating bath comprising saccharin or a salt thereof.
[14] A method for repairing an electrode comprising a conductive substrate having a layer comprising oxide of nickel and iron formed on a surface thereof, in which electrode the layer comprising the oxide is partly damaged on the surface, the method comprising the step of heating the electrode in an ambient atmosphere or an oxidizing atmosphere, wherein
the conductive substrate has a plating film comprising nickel and iron under the layer comprising the oxide of nickel and iron, or comprises iron and has a plating film comprising nickel under the layer comprising the oxide of nickel and iron, or comprises nickel and has a plating film comprising iron under the layer comprising the oxide of nickel and iron, or comprises nickel and iron.

Advantageous Effects of Invention

According to the present invention, it is possible to suppress decomposition of an organic compound additive in a plating bath in electroplating an article with metal by using, as an anode, a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof. Nickel and iron are metals available at relatively low prices, and no complicated processes are required to form a layer comprising oxide of these metals. Therefore, it is possible to perform metal plating such as zinc plating or zinc alloy plating with low manufacturing cost.

Brief Description of Drawings

Fig. 1A is a scanning electron microscope (SEM) image of a surface of an iron plate having a layer comprising oxide of nickel and iron (Ni-Fe oxide layer).
Fig. 1B presents elemental mapping (oxygen) on the surface of the iron plate having the Ni-Fe oxide layer by an energy-dispersive X-ray spectrometer (EDS).
Fig. 1C presents EDS elemental mapping (iron) on the surface of the iron plate having the Ni-Fe oxide layer.
Fig. 1D presents EDS elemental mapping (nickel) on the surface of the iron plate having the Ni-Fe oxide layer.
Fig. 2 presents an SEM image and EDS elemental mapping of a cross-section of the iron plate having the Ni-Fe oxide layer.

Description of Embodiments

Hereinafter, the present invention will be described in more details.
The present invention relates to a method for electroplating an article with metal. The metal is not particularly limited as long as it is usable for electroplating. For example, the metal may comprise zinc, nickel, iron, copper, cobalt, tin, manganese, and the like. When the metal consists of zinc only, a zinc film is formed on the article. When the metal comprises zinc and another metal, a zinc alloy film is formed on the article. The other metal is not particularly limited as long as it can form the zinc alloy film, but may be at least one selected from the group consisting of, for example, nickel, iron, cobalt, tin, manganese, and the like. For example, the zinc alloy film may be, but not particularly limited to, zinc-nickel alloy plating, zinc-iron alloy plating, zinc-cobalt alloy plating, zinc-manganese alloy plating, zinc-tin alloy plating, or the like, and is preferably zinc-nickel alloy plating.
The article is an article to be plated, and any article commonly used in this technical field can be employed without particular limitation. For example, the article may be made of any of various metals such as iron, nickel, copper, zinc, and aluminum and alloys of them. Also, its shape is not particularly limited. For example, any of various articles including: plate-shaped articles such as a steel plate and a plated steel plate; and shaped articles such as a rectangular parallelepiped article, a columnar article, a cylindrical article, and a spherical article are exemplified. Specific examples of the shaped articles include: fastening parts such as bolts, nuts, and washers; pipe parts such as fuel pipes; cast iron parts such as brake calipers and common rails; and various articles such as connectors, plugs, housings, bases or mouthpieces, and seatbelt anchors.
The method of the present invention comprises the step of applying current in a plating bath comprising ions of a metal to be plated and an organic compound additive, wherein the plating bath comprises the article as a cathode, and comprises, as an anode, a conductive substrate having a layer comprising oxide or nitride of nickel and iron on a surface thereof. For example, the plating bath may be, but not particularly limited to, any of acidic or neutral plating baths such as a sulfuric acid bath, a boron fluoride bath, and an organic acid bath, and alkaline plating baths such as a cyanide bath, a zincate bath, and a pyrophosphate bath, and is preferably an alkaline plating bath. The conductive substrate is not particularly limited as long as it can conduct electricity, but may be, for example, an iron, nickel, stainless steel, carbon, titanium, zirconium, niobium, tantalum, platinum, platinum-plated titanium, or palladium-tin alloy substrate, a substrate coated with any of them, or the like, and is preferably a substrate comprising at least one of nickel and iron.
The layer comprising the oxide or nitride of nickel and iron is formed on a liquid contact portion of the conductive substrate. Although it is not bound by any particular theory, it is considered that the organic compound additive is oxidatively decomposable in the vicinity of the anode, and thus the layer comprising the oxide or nitride of nickel and iron suppresses decomposition of the organic compound additive by functioning as a catalyst for an oxygen evolution reaction due to electrolysis of water, and thereby making the oxygen evolution reaction more dominant than the oxidative decomposition reaction in the vicinity of the anode. A method for forming the layer comprising the oxide or nitride is not particularly limited. For example, the layer comprising the oxide or nitride may be formed by oxidation or nitridation of a conductive substrate having a plating film comprising nickel and iron, a conductive substrate comprising iron and having a plating film comprising nickel, a conductive substrate comprising nickel and having a plating film comprising iron, or a conductive substrate comprising nickel and iron. Specifically, the conductive substrate may be plated with nickel and iron, and the film comprising nickel and iron may be treated with thermal oxidation to oxidize a part or all of the film. Alternatively, an alloy of nickel and iron may be used as the conductive substrate and the alloy may be treated with thermal oxidation to oxidize the surface of the alloy. In the case where the conductive substrate is plated with nickel and iron and only the surface of the film is oxidized, the conductive substrate would have, on its surface, two layers, that is, a layer comprising oxide of nickel and iron and a film layer comprising nickel and iron.
The plating film comprising nickel and iron, the plating film comprising nickel, and the plating film comprising iron for use to form the layer comprising the oxide or nitride of nickel and iron can be formed by a plating method commonly used in this technical field. In an embodiment, the plating film comprising nickel and iron, the plating film comprising nickel, or the plating film comprising iron may be formed by using a plating bath comprising saccharin or a salt thereof, or preferably using a plating bath comprising sodium saccharin. Use of an anode comprising the layer comprising the oxide or nitride of nickel and iron derived from the plating film formed in the plating bath comprising the saccharin or the salt thereof makes it possible to further improve the effect of suppressing decomposition of the organic compound additive. The concentration of the saccharin or the salt thereof in the plating bath is not particularly limited, but may be, for example, about 0.1 to about 2.0 g/L, and is preferably about 0.5 to about 1.9 g/L.
The amounts of nickel (Ni) and iron (Fe) constituting the layer comprising the oxide are not particularly limited. For example, the atomic percent of Ni in the layer comprising the oxide may be about 0.5% to about 45%, and is preferably about 1% to about 15%, and the atomic percent of Fe in the oxide-comprising layer may be about 5% to about 45%, and is preferably about 30% to about 40%. The thickness of the layer comprising the oxide is not particularly limited, but may be, for example, about 0.5 µm to about 10 µm, and is preferably about 1.5 µm to about 4 µm. When the thickness of the layer comprising the oxide is within the above range, it is possible to maintain the good performance of the anode and exert the effect of suppressing the decomposition of the organic compound additive more satisfactorily.
In an embodiment, the layer comprising the oxide or nitride of nickel and iron further contains phosphorus atoms or boron atoms. For example, when forming the plating film comprising nickel and iron, the plating film comprising nickel, or the plating film comprising iron in order to form the layer comprising the oxide or nitride of nickel and iron, a phosphorus compound or a boron compound may be added to the plating bath used therein.
The "organic compound additive" described in the present specification refers to an organic compound to be added to a plating bath for electroplating. A type of the organic compound additive is not particularly limited. For example, in the case of zinc plating, the organic compound additive may be at least one selected from the group consisting of brightening agents, auxiliary additives (such as smoothing agents), defoamers, and the like. In the case of zinc alloy plating, the organic compound additive may be at least one selected from the group consisting of amine-based chelating agents, brightening agents, auxiliary additives (such as smoothing agents), defoamers, and the like. In any case, the organic compound additive comprises a brightening agent in a preferred embodiment.
As the brightening agent, any agent commonly used in this technical field may be employed without particular limitation. Examples of the brightening agent include: (1) nonionic surfactants such as polyoxyethylene polyoxypropylene block polymer and acetylene glycol EO adduct, and anionic surfactants such as polyoxyethylene lauryl ether sulfate and alkyldiphenyl ether disulfonate; (2) polyamine compounds: such as polyallylamines such as copolymer of diallyldimethylammonium chloride and sulfur dioxide; polyepoxypolyamines such as condensation polymer of ethylenediamine and epichlorohydrin, condensation polymer of dimethylaminopropylamine and epichlorohydrin, condensation polymer of imidazole and epichlorohydrin, condensation polymer of an imidazole derivative such as 1-methylimidazole or 2-methylimidazole with epichlorohydrin, and condensation polymer of epichlorohydrin with heterocyclic amine including a triazine derivative such as acetoguanamine or benzoguanamine; polyamidepolyamines such as polyamine polyurea resin such as condensation polymer of 3-dimethylaminopropyl urea and epichlorohydrin or condensation polymer of bis(N,N-dimethylaminopropyl) urea and epichlorohydrin, and water-soluble nylon resin such as condensation polymer of N,N-dimethylaminopropylamine, alkylenedicarboxylic acid, and epichlorohydrin; and polyalkylene polyamines such as condensation polymer of diethylenetriamine, dimethylaminopropylamine, or the like with 2,2'-dichlorodiethyl ether, condensation polymer of dimethylaminopropylamine and 1,3-dichloropropane, condensation polymer of N,N,N',N'-tetramethyl-1,3-diaminopropane and 1,4-dichlorobutane, and condensation polymer of N,N,N',N'-tetramethyl-1,3-diaminopropane and 1,3-dichloropropan-2-ol; (3) condensation polymer of dimethylamine or the like with dichloroethyl ether; (4) aromatic aldehydes such as veratraldehyde, vanillin, and anisaldehyde, benzoic acid, or salts thereof; (5) quaternary ammonium salts such as cetyltrimethylammonium chloride, 3-carbamoylbenzyl chloride, and pyridinium; and the like. Preferably, the brightening agent comprises a quaternary ammonium salt or an aromatic aldehyde. The above brightening agents may be used alone or used in combination of two or more. The concentration of the brightening agent in the plating bath is not particularly limited. For example, in the case of an aromatic aldehyde, benzoic acid, or a salt thereof, the concentration of the brightening agent may be about 1 to about 500 mg/L, and is preferably about 5 to about 100 mg/L, and in the other cases, the concentration may be about 0.01 to about 10 g/L, and is preferably about 0.02 to about 5 g/L.
Alternatively, the brightening agent may comprise a nitrogen-containing heterocycle quaternary ammonium salt in addition to the quaternary ammonium salt not having a nitrogen-containing heterocycle. Preferably, the nitrogen-containing heterocycle quaternary ammonium salt is a nitrogen-containing heterocycle quaternary ammonium salt having a carboxyl group and/or a hydroxy group. The nitrogen-containing heterocycle in the nitrogen-containing heterocycle quaternary ammonium salt is not particularly limited, but may be, for example, pyridine ring, piperidine ring, imidazole ring, imidazoline ring, pyrrolidine ring, pyrazole ring, quinoline ring, or morpholine ring, and is preferably pyridine ring. More preferably, the nitrogen-containing heterocycle quaternary ammonium salt is a quaternary ammonium salt of nicotinic acid or a derivative thereof. In the nitrogen-containing heterocycle quaternary ammonium salt compound, the carboxyl group and/or the hydroxy group may be directly bonded to the nitrogen-containing heterocycle, or may be bonded via another substituent as in a carboxymethyl group. The nitrogen-containing heterocycle quaternary ammonium salt may contain an additional substituent such as, for example, an alkyl group, in addition to the carboxyl group and the hydroxy group. In the nitrogen-containing heterocycle quaternary ammonium salt, N substituent forming a heterocyclic quaternary ammonium cation is not particularly limited as long as it does not impair the effect as the brightening agent, but may be, for example, a substituted or unsubstituted alkyl, aryl, or alkoxy group. The counter anion forming the salt is not particularly limited, but may be, for example, a compound containing halogen anion, oxyanion, borate anion, sulfonate anion, phosphate anion, imide anion, or the like, and is preferably halogen anion. Such a quaternary ammonium salt is preferable because it contains both a quaternary ammonium cation and an oxyanion in its molecule, and also behaves as an anion.
An specific example of the nitrogen-containing heterocycle quaternary ammonium salt is N-benzyl-3-carboxypyridinium chloride, N-phenethyl-4-carboxypyridinium chloride, N-butyl-3-carboxypyridinium bromide, N-chloromethyl-3-carboxypyridinium bromide, N-hexyl-6-hydroxy-3-carboxypyridinium chloride, N-hexyl-6-3-hydroxypropyl-3-carboxypyridinium chloride, N-2-hydroxyethyl-6-methoxy-3-carboxypyridinium chloride, N-methoxy-6-methyl-3-carboxypyridinium chloride, N-propyl-2-methyl-6-phenyl-3-carboxypyridinium chloride, N-propyl-2-methyl-6-phenyl-3-carboxypyridinium chloride, N-benzyl-3-carboxymethylpyridinium chloride, 1-butyl-3-methyl-4-carboximidazolium bromide, 1-butyl-3-methyl-4-carboxymethylimidazolium bromide, 1-butyl-2-hydroxymethyl-3-methylimidazolium chloride, 1-butyl-1-methyl-3-methylcarboxypyrrolidinium chloride, 1-butyl-1-methyl-4-methylcarboxypiperidinium chloride, or the like. The nitrogen-containing heterocycle quaternary ammonium salts may be used alone or used in combination of two or more. The concentration of the nitrogen-containing heterocycle quaternary ammonium salt in the plating bath is not particularly limited, but may be, for example, about 0.01 to about 10 g/L and is preferably 0.02 to 5 g/L.
As the auxiliary additive, any additive commonly used in this technical field may be employed without particular limitation. For example, the auxiliary additive may comprise organic acid, silicate, or a mercapto compound and these may be used as a smoothing agent. The auxiliary additives may be used alone or used in combination of two or more. The concentration of the auxiliary additive in the plating bath is not particularly limited, but may be, for example, about 0.01 to about 50 g/L.
As the defoamer, any defoamer commonly used in this technical field may be employed without particular limitation. For example, the defoamer may be a surfactant or the like. The defoamers may be used alone or used in combination of two or more. The concentration of the defoamer in the plating bath is not particularly limited, but may be, for example, about 0.01 to about 5 g/L.
As the amine-based chelating agent, any agent commonly used in this technical field may be employed without particular limitation. For example, the amine-based chelating agent may comprise: alkyleneamine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine; alkylene oxide adducts of the above alkyleneamines such as ethylene oxide adducts and propylene oxide adducts; amino alcohols such as ethanolamine, diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, ethylenediaminetetra-2-propanol, N-(2-aminoethyl)ethanolamine, and 2-hydroxyethylaminopropylamine; alkanolamine compounds such as N-(2-hydroxyethyl)-N,N',N'-triethylethylenediamine, N,N'-di(2-hydroxyethyl)-N,N'-diethylethylenediamine, N,N,N',N'-tetrakis(2-hydroxyethyl)propylenediamine, and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine; poly(alkyleneimines) obtained from ethyleneimine, 1,2-propyleneimine, and the like; poly(alkyleneamines) obtained from ethylenediamine, triethylenetetramine, and the like; and so on. Preferably, the amine-based chelating agent comprises at least one selected from the group consisting of alkyleneamine compounds, their alkylene oxide adducts, and alkanolamine compounds. The amine-based chelating agents may be used alone or used in combination of two or more. The concentration of the amine-based chelating agent in the plating bath is not particularly limited, but may be, for example, about 5 to about 200 g/L, and is preferably about 30 to about 100 g/L.
In an embodiment, the plating bath, particularly the alkaline plating bath, comprises zinc ions. As an ion source for producing the zinc ions, any ion source commonly used in this technical field may be employed without particular limitation. For example, the ion source may be Na₂[Zn(OH)₄], K₂[Zn(OH)₄], or ZnO. The zinc ion sources may be used alone or used in combination of two or more. The concentration of the zinc ions in the alkaline plating bath is not particularly limited, but may be, for example, about 2 to about 20 g/L, and is preferably about 4 to about 12 g/L.
In an embodiment, the plating bath, particularly the alkaline plating bath, further comprises another kind of metal ions for forming the zinc alloy film in addition to the zinc ions. The other kind of metal ions is not particularly limited as long as it can form the zinc alloy film, but may be at least one kind selected from the group consisting of nickel ions, iron ions, cobalt ions, tin ions, manganese ions, and the like, and is preferably nickel ions. An ion source for producing the other kind of metal ions is not particularly limited, but may be, for example, nickel sulfate, iron(II) sulfate, cobalt sulfate, tin(II) sulfate, manganese sulfate, or the like. The ion sources for the other kinds of metal ions may be used alone or used in combination of two or more. The total concentration of the other kinds of metal ions in the alkaline plating bath is not particularly limited, but may be, for example, about 0.4 to about 4 g/L, and is preferably about 1 to about 3 g/L.
In an embodiment, the plating bath may comprise caustic alkali. The caustic alkali is not particularly limited, but may be, for example, sodium hydroxide, potassium hydroxide, or the like. More specifically, the plating bath may comprise sodium hydroxide when the plating bath is an alkaline plating bath or may comprise potassium hydroxide when the plating bath is an acidic plating bath. The concentration of the caustic alkali in the alkaline plating bath is not particularly limited, but may be, for example, about 60 to about 200 g/L, and is preferably about 100 to about 160 g/L.
Conditions for the current application step are not particularly limited as long as zinc or zinc alloy plating can be applied. For example, the current may be applied at a temperature of about 15°C to about 40°C and preferably about 25°C to about 35°C, or the current may be applied with a cathode current density of about 0.1 to 20 A/dm² and preferably 0.2 to 10 A/dm².
The method of the present invention may further comprise any step commonly used in this technical field as long as the step will not impair the object of the present invention. For example, the method of the present invention may further comprise a step of washing the article before the current application step, a step of washing the article after the current application step, and so on.
In another embodiment, the present invention relates to a system for electroplating an article with metal. The system of the present invention comprises a plating bath comprising the metal ions and an organic compound additive, and the plating bath comprises the article as a cathode and a conductive substrate having a layer comprising oxide or nitride of nickel and iron on a surface thereof as an anode. The system of the present invention may further comprise any facility commonly used in this technical field as long as the facility will not impair the object of the present invention.
In another embodiment, the present invention relates to a method for producing an electrode comprising a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof. The production method of the present invention comprises a step of performing oxidation treatment or nitridation treatment on a conductive substrate having a plating film comprising nickel and iron, a conductive substrate comprising iron and having a plating film comprising nickel, a conductive substrate comprising nickel and having a plating film comprising iron, or a conductive substrate comprising nickel and iron, thereby forming a layer comprising oxide or nitride of nickel and iron on a surface of the conductive substrate. In an embodiment, the production method of the present invention may further comprise a step of forming the plating film comprising nickel and iron, the plating film comprising nickel, or the plating film comprising iron by using a plating bath comprising saccharin or a salt thereof. The production method of the present invention may further comprise any step commonly used in this technical field as long as the step will not impair the object of the present invention.
In another embodiment, the present invention relates to a method for repairing an electrode comprising a conductive substrate with a surface having a layer comprising oxide of nickel and iron formed on a surface thereof, in which electrode the layer comprising the oxide is partly damaged on the surface. The repairing method of the present invention comprises a step of heating the electrode in an ambient atmosphere or oxidizing atmosphere. In this repairing method, the conductive substrate has a plating film comprising nickel and iron under the layer comprising the oxide of nickel and iron, or comprises iron and has a plating film comprising nickel under the layer comprising the oxide of nickel and iron, or comprises nickel and has a plating film comprising iron under the layer comprising the oxide of nickel and iron, or contains nickel and iron. An anode having a coating on a surface thereof has been heretofore known, but in the case where the coating is damaged, it is necessary to remove all the coating once and perform the coating process again. On the other hand, according to the repairing method of the present invention, without peeling off the partly damaged layer, it is possible to restore the oxide in the damaged part only by heating the electrode having the layer.
A heating unit for the heating step is not particularly limited, and the heating may be performed by, for example, a burner, a muffle furnace such as an electric furnace or gas furnace, a heater such as a ceramic heater or an infrared heater, an electromagnetic induction heater, a laser heating device, or the like. Conditions for the heating step are not particularly limited as long as the oxide in the damaged parts in the layer comprising the oxide can be regenerated, and may be adjusted as appropriate depending on the size of the electrode and the number and size of the damaged parts. For example, the electrode may be repaired by heating with a burner for about 5 to 30 minutes or may be repaired by heating in a muffle furnace for about 30 to 90 minutes. Since the inner flame in the flame of a burner or the like has a reducing effect, the electrode can be repaired effectively with indirect heating avoiding direct exposure of the damaged parts to the flame, or with heating in an apparatus such as a muffle furnace that does not emit a flame. In the case where the layer comprising the oxide is partly damaged again on the surface of the electrode repaired in the repairing method of the present invention, the electrode can be repaired any number of times by applying the repairing method of the present invention again.
Hereinafter, the present invention will be described specifically by using Examples, but the scope of the present invention should not be limited to these Examples.

Examples

[Preparation Example 1]

An iron plate (64×64×2.3 mm) was degreased and activated with hydrochloric acid by conventional methods. Then, the iron plate was plated under the conditions of 4 A/dm², 50°C, and 20 minutes using a plating bath having each of compositions specified in Table 1 below, thereby fabricating the iron plate with Ni-Fe plating.

[Table 1]

Table 1: Composition of Plating Bath [g/L]

Component	Example 1	Example 2
NiSO₄·6H₂O	250	250
NiCl₂·6H₂O	40	40
FeSO₄·7H₂O	7.2	7.2
H₃BO₃	30	30
Malonic Acid	5.2	5.2
Saccharin Na	0	0.5

The iron plate with Ni-Fe plating was washed, dried in room temperature, and then heated by using a muffle furnace at 650°C for one hour. After that, the iron plate was slowly cooled down to room temperature for about one hour to fabricate an iron plate electrode. A surface and a cross-section of this iron plate electrode were observed with a scanning electron microscope (SEM) and elemental mapping was performed with an energy dispersive X-ray spectrometer (EDS). Figs. 1A to 1D and Fig. 2 show the results of the iron plate electrode in Example 1.
On the surface of the iron plate electrode in Example 1, oxygen atoms, iron atoms, and nickel atoms were detected (Figs. 1A to 1D). When the cross-section of the iron plate electrode in Example 1 was observed, Ni-Fe plating (region b in Fig. 2) comprising 4% by mass of iron relative to the mass of the plating film was deposited with a thickness of about 15 µm on the iron substrate (region c in Fig. 2). Then, a layer with a thickness of about 2 µm (region a in Fig. 2) comprising, as elements, nickel and iron and also oxygen was observed on top of the Ni-Fe plating film layer. In sum, a layer comprising oxide of nickel and iron (Ni-Fe oxide layer) was formed on the surface of the iron plate electrode (Table 2). X-ray diffraction analysis of this Ni-Fe oxide layer revealed that NiO, Fe₂O₃, and NiFe₂O₄ were contained in both the electrodes. In addition, when the element concentrations in the plated part of each of the iron plate electrodes were measured by EDS before and after the heat treatment, the element concentrations of nickel atoms (Ni), iron atoms (Fe), and oxygen atoms (O) were obtained as shown in Table 2 below.

[Table 2]

Table 2: Element Concentration in Electrode Before and After Heat Treatment [at.%]

	Example 1			Example 2
	Ni	Fe	O	Ni	Fe	O
Before Heat Treatment (After Plating)	84.9	15.1	Not Detected	88.4	11.6	Not Detected
After Heat Treatment	7.0	35.3	57.7	10.1	34.7	55.2

[Test Example 1]

Alkaline zinc-nickel plating using the iron plate electrode with the Ni-Fe oxide layer of Example 1 or 2 as the anode and using an ordinary iron plate electrode (electrode degreased and activated with hydrochloric acid) as a cathode was performed in 500 mL of a plating bath having the composition specified in Table 3 below.

[Table 3]

Table 3: Composition of Plating Bath

Component	Concentration
ZnO	10 g/L (8 g/L in terms of Zn ions)
NiSO₄·6H₂O	7.3 g/L (1.6 g/L in terms of Ni ions)
Caustic Soda	130 g/L
IZ-250YB^∗1	60 g/L
IZ-250YR1^∗2	0.6 mL/L (polyamine 0.1 g/L)
IZ-250YR2^∗3	0.5 mL/L (quaternary ammonium salt of nicotinic acid 0.2 g/L)

^∗1 Amine-based chelating agent (ethylene oxide adduct of alkyleneamine) manufactured by DIPSOL CHEMICALS Co., Ltd.
^∗2 Brightening agent (polyamine) manufactured by DIPSOL CHEMICALS Co., Ltd.
^∗3 Brightening agent (quaternary ammonium salt of nicotinic acid) manufactured by DIPSOL CHEMICALS Co., Ltd.

The temperature of the plating bath was set to 25°C and controlled by cooling to keep a constant temperature during current application. An anode current density was set to 8 A/dm² and a cathode current density was set to 2.56 A/dm². A cathode iron plate was replaced every application of 5.1 Ah/L during the current application. The ion concentrations in the plating bath were maintained during the current application in such a way that metallic zinc was immersed in the plating bath for replenishment of the zinc ion concentration and IZ-250YNi (nickel replenisher manufactured by DIPSOL CHEMICALS Co., Ltd) was added for replenishment of the nickel ion concentration. The concentration of the caustic soda was periodically measured and was kept constant during the current application with replenishment with the caustic soda. IZ-250YB was replenished at 80 mL/kAh. IZ-250YR1 and IZ-250YR2 were replenished at 15 mL/kAh.
Before the start of current application and after a current application of 100 Ah/L, 30 mL of the plating solution was collected. Then, the concentrations of IZ-250YB and the oxalic acid were measured by ion chromatography, and the concentration of the sodium carbonate (Na₂CO₃) was measured by titration. The results are shown in Table 4.

[Table 4]

Table 4: Test Results [g/L]

	IZ-250YB	Oxalic Acid	Na₂CO₃
Before Current application	60	Not Detected	Not Detected
After Current Application with Anode in Example 1	53	0.2	3.9
After Current Application with Anode in Example 2	60	0.1	3.2

When an ordinary nickel plate is used as the anode, the amine-based chelating agent (IZ-250YB) is decomposed during current application (see Comparative Test Example below). In contrast, when the iron plate electrode with the Ni-Fe oxide layer was used as the anode, the decomposition of the amine-based chelating agent (IZ-250YB) during the current application was suppressed. In addition, regarding the oxalic acid and the sodium carbonate, which are electrolyte aging products increasing along with the current application, increases in their concentrations were suppressed by use of the iron plate electrode with the Ni-Fe oxide layer. Also, a Ni-Fe nitride layer is expected to produce such effect.

[Preparation Example 2]

Iron plate electrodes with Ni-Fe oxide layers in Examples 3 to 8 were fabricated in the same way as in Preparation Example 1 except that the iron plate was plated under the conditions of 4 A/dm², 50°C, and 20 minutes using a plating bath having each of compositions specified in Table 5 below. Then, a plated portion of each of the iron plate electrodes was measured by EDS and the element concentration of iron atoms (Fe) was checked (Table 6).

[Table 5]

Table 5: Composition of Plating Bath [g/L]

Component	Ex. 3	Ex. 4	Ex. 5	Ex. 6	Ex. 7	Ex. 8
NiSO₄·6H₂O	250	250	250	250	250	250
NiCl₂·6H₂O	40	40	40	40	40	40
FeSO₄·7H₂O	1.5	2.3	7.2	4.8	7.2	18
H₃BO₃	30	30	30	30	30	30
Malonic Acid	5.2	5.2	5.2	5.2	5.2	5.2
Saccharin Na	0	0	0	0.5	1.0	1.9

[Table 6]

Table 6: EDS Measurement Results [at.%]

	Ex. 3	Ex. 4	Ex. 5	Ex. 6	Ex. 7	Ex. 8
Fe Element Concentration	10.1	16.5	37.2	8.7	15.2	37.0

[Test Example 2]

In an electrolytic cell (inner dimensions 64×64×55 mm), the iron plate electrode with the Ni-Fe oxide layer in each of Examples 3 to 8 was set as the anode, a satin steel plate of SPCC was set as the cathode, and 160 mL of an electrolytic liquid with the composition specified in Table 7 below was added. Then, current application was started with a current value of 2.6 A. The anode current density at that time was 8.1 A/dm².

[Table 7]

Table 7: Composition of Electrolytic Liquid

Component	Concentration
NiSO₄·6H₂O	7.3 g/L (1.6 g/L in terms of Ni ions)
Caustic Soda	130 g/L
IZ-250YB^∗1	60 g/L
IZ-250YR1^∗2	0.5 mL/L (polyamine 0.1 g/L)
IZ-250YR2^∗3	1.0 mL/L (quaternary ammonium salt of nicotinic acid 0.4 g/L)

The current application was continued for 7 hours 42 minutes, and the temperature of the electrolytic liquid was adjusted at 25°C during the current application. Then, in the electrolytic liquid before and after the current application, the concentrations of IZ-250YB and the oxalic acid were measured by ion chromatography, the concentration of the quaternary ammonium salt of nicotinic acid was measured by capillary electrophoresis, and the concentration of the sodium carbonate (Na₂CO₃) was measured by titration. The results are shown in Table 8.

[Table 8]

Table 8: Test Results [g/L]

		IZ-250YB	Quaternary Ammonium Salt of Nicotinic Acid	Oxalic Acid	Na₂CO₃
Before Current Application		60	0.4	Not Detected	Not Detected

After Current Application With Iron Plate Electrode with Ni-Fe Oxide Layer Produced without Using Saccharin
	Electrode in Example 3	48	0.24	0.1	Not Detected
	Electrode in Example 4	43	0.2	0.2	4.2
	Electrode in Example 5	50	0.24	0.2	3.2

After Current Application With Iron Plate Electrode with Ni-Fe Oxide Layer Produced by Using Saccharin
	Electrode in Example 6	46	0.2	0.3	5.6
	Electrode in Example 7	52	0.24	0.1	Not Detected
	Electrode in Example 8	55	0.28	0.2	Not Detected

When an ordinary iron plate is used as the anode, the amine-based chelating agent (IZ-250YB) and the brightening agent (IZ-250YR2) are decomposed during current application (see Comparative Test Example below). In contrast, when the iron plate electrode with the Ni-Fe oxide layer was used as the anode, the decomposition of the amine-based chelating agent (IZ-250YB) and the brightening agent (IZ-250YR2) during the current application was suppressed. Regarding the oxalic acid and the sodium carbonate that tend to increase along with current application, the increases in their concentrations were suppressed by use of the iron plate electrode with the Ni-Fe oxide layer. In the case of the iron plate electrodes with the Ni-Fe oxide layers which were derived from the Ni-Fe plating formed in the presence of the sodium saccharin and which had the high Fe element concentrations, in particular, the remarkable effects were observed in suppression of the decomposition of the amine-based chelating agent (IZ-250YB) and suppression of the increases in the electrolyte aging products.

[Comparative Test Examples]

Each of a nickel plate (64×64×2.3 mm) and an iron plate (64×64×2.3 mm) was placed in a muffle furnace, was heated at 650°C for 30 minutes, and then was slowly cooled down to room temperature for about one hour, thereby fabricating electrodes for comparison (the nickel plate with a nickel oxide layer and the iron plate with an iron oxide layer). Then, current was applied to the electrolytic liquid in the same manner as in Test Example 2 except that an ordinary nickel plate (Comparative Example 1), an ordinary iron plate (Comparative Example 2), the nickel plate with the nickel oxide layer (Comparative Example 3), or the iron plate with the iron oxide layer (Comparative Example 4) was used as the anode, and the concentrations of IZ-250YB, the quaternary ammonium salt of nicotinic acid (IZ-250YR2), the oxalic acid, and the sodium carbonate (Na₂CO₃) in the electrolytic liquid before and after the current application were measured. The results are shown in Table 9.

[Table 9]

Table 9: Comparative Test Results [g/L]

	IZ-250YB	Quaternary Ammonium Salt of Nicotinic Acid	Oxalic Acid	Na₂CO₃
Before Current Application	60	0.4	Not Detected	Not Detected
After Current Application with Anode in Comparative Example 1	26	0.12	1.7	15.3
After Current Application with Anode in Comparative Example 2	29	0.12	1.2	11.6
After Current Application with Anode in Comparative Example 3	26	0.12	1.6	14.2
After Current Application with Anode in Comparative Example 4	37	0.16	0.3	4.7

When the ordinary nickel plate or the ordinary iron plate was used as the anode, the amine-based chelating agent (IZ-250YB) and the brightening agent (IZ-250YR2) were decomposed during the current application and the electrolyte aging products (the oxalic acid and the sodium carbonate) increased along with the current application (Comparative Examples 1 and 2). Then, when the nickel oxide layer and the iron oxide layer were just provided to these metal plates, respectively, the decomposition of the amine-based chelating agent (IZ-250YB) and the brightening agent (IZ-250YR2) was not suppressed, and in the case of the nickel oxide layer, the increases in the electrolyte aging products were not suppressed (Comparative Examples 3 and 4). Therefore, it was found that the effects of suppressing the decomposition of the organic compound additive and suppressing the increases in the electrolyte aging products in the plating bath are characteristics of an anode having a layer comprising oxide of nickel and iron formed on the surface thereof.

[Test Example 3]

An iron plate electrode with a Ni-Fe oxide layer was fabricated in the same manner as in Example 3 of Preparation Example 2. Using this iron plate electrode as an anode, alkaline zinc-nickel plating was performed according to the method described in Test Example 1 to consume the anode. Then, after 300 hours, the anode was taken out and current application was performed for 7 hours and 42 minutes according to the method described in Test Example 2. The concentrations of the amine-based chelating agent (IZ-250YB), the brightening agent (quaternary ammonium salt of nicotinic acid; IZ-250YR2), the oxalic acid, and the sodium carbonate in the electrolytic liquid were measured.
The anode consumed by the alkaline zinc-nickel plating was repaired by heating with a gas burner. Specifically, four places on the side of the anode that was unconsumed due to contact with the inner surface of the electrolytic cell during the current application were each heated for 5 minutes, then allowed to stand at room temperature and cooled. Then, for the repaired anode, the current application was also performed for 7 hours and 42 minutes according to the method described in Test Example 2, and the concentrations of the amine-based chelating agent (IZ-250YB), the brightening agent (quaternary ammonium salt of nicotinic acid; IZ-250YR2), the oxalic acid, and the sodium carbonate in the electrolytic liquid were measured.
The anode repaired after the current application for 300 hours was consumed by being further used for additional current application for 100 hours. Then, this consumed electrode was repaired by heating with the burner in the same manner as in the case of the current application for 300 hours. For each of the anode consumed by the additional current application for 100 hours and the anode repaired after that, the current application was also performed for 7 hours and 42 minutes according to the method described in Test Example 2, and the concentrations of the amine-based chelating agent (IZ-250YB), the brightening agent (quaternary ammonium salt of nicotinic acid; IZ-250YR2), the oxalic acid, and the sodium carbonate in the electrolytic liquid were measured. The results of all the measurements are presented in Table 10.

[Table 10]

Table 10: Test Results [g/L]

	IZ-250YB	Quaternary Ammonium Salt of Nicotinic Acid	Oxalic Acid	Na₂CO₃
Before Current Application	60	0.4	Not Detected	Not Detected
After Current Application with Unconsumed Anode	49	0.24	0.1	Not Detected

Consumption with Current Application for 300 Hours
	After Current Application with Unrepaired Anode	39	0.2	0.6	9.3
	After Current Application with Repaired Anode	49	0.24	0.2	Not Detected

Consumption with Additional Current Application for 100 Hours
	After Current Application with Unrepaired Anode	45	0.24	0.4	6.6
	After Current Application with Repaired Anode	48	0.36	0.2	2.0

As the time of the current application was increased, the anode was consumed more, and the effects of suppressing the decomposition of the organic compound additive and suppressing the increases in the electrolyte aging products in the plating bath were decreased. On the other hand, these effects were recovered by heating the consumed anodes. The same recovery effect was also confirmed by heating the consumed anode in the muffle furnace at 650°C for one hour. In addition, even when the repaired anode was consumed, the effects of suppressing the decomposition of the organic compound additive and suppressing the increases in the electrolyte aging products in the plating bath were recovered by heating the anode again.
The reason why the once-decreased effects of the anode were recovered by heating is presumably that the partial damages of the Ni-Fe oxide layer were at least involved in the decrease, and the Ni-Fe oxide at the damaged parts was regenerated by heating. In fact, when checked in elemental mapping with the scanning electron microscope and EDS, the surface of the consumed anode had circular damages generated, and at the damaged parts, Ni atoms and Fe atoms were detected but oxygen atoms were not detected. On the other hand, on the surface of the anode repaired by heating, oxygen atoms were also detected even at the damaged parts, which confirmed that the Ni-Fe oxide layer was repaired.
From the above results, it was found that in electroplating of an article with metal, decomposition of an organic compound additive in a plating bath can be suppressed by using, as an anode, a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof. In addition, it was found that the layer comprising the oxide of nickel and iron of the anode can be easily repaired even after the layer is partially damaged. Therefore, it is possible to perform metal plating such as zinc plating or zinc alloy plating with low manufacturing cost.

Claims

A method for electroplating an article with metal, comprising the step of applying current in a plating bath comprising ions of the metal and an organic compound additive, wherein
the plating bath comprises the article as a cathode and a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof as an anode.
The method according to claim 1, wherein the metal comprises zinc.
The method according to claim 1 or 2, wherein the plating bath is an alkaline plating bath.
The method according to any one of claims 1 to 3, wherein the conductive substrate comprises at least one of nickel and iron.
The method according to any one of claims 1 to 4, wherein a zinc or zinc alloy film is formed on a surface of the article.
The method according to any one of claims 1 to 5, wherein the organic compound additive comprises at least one selected from the group consisting of amine-based chelating agents, brightening agents, smoothing agents, and defoamers.
The method according to claim 6, wherein the amine-based chelating agent comprises at least one selected from the group consisting of alkyleneamine compounds, their alkylene oxide adducts, and alkanolamine compounds.
The method according to any one of claims 1 to 7, wherein the layer comprising the oxide or nitride is formed by oxidizing or nitriding a conductive substrate having a plating film comprising nickel and iron, a conductive substrate comprising iron and having a plating film containing nickel, a conductive substrate comprising nickel and having a plating film comprising iron, or a conductive substrate comprising nickel and iron.
The method according to claim 8, wherein the plating film comprising nickel and iron, the plating film comprising nickel, or the plating film comprising iron is formed by using a plating bath comprising saccharin or a salt thereof.
The method according to any one of claims 1 to 9, wherein the layer comprising the oxide or nitride further comprises phosphorus atoms and boron atoms.
A system for electroplating an article with metal, comprising a plating bath comprising ions of the metal and an organic compound additive, wherein
the plating bath comprises the article as a cathode, and a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof as an anode.
A method for producing an electrode comprising a conductive substrate having a layer comprising oxide or nitride of nickel and iron formed on a surface thereof, the method comprising the step of:
performing oxidation treatment or nitridation treatment on a conductive substrate having a plating film comprising nickel and iron, a conductive substrate comprising iron and having a plating film comprising nickel, a conductive substrate comprising nickel and having a plating film comprising iron, or a conductive substrate comprising nickel and iron to form the layer comprising the oxide or nitride of nickel and iron on the surface of the conductive substrate.
The production method according to claim 12, further comprising the step of forming the plating film comprising nickel and iron, the plating film comprising nickel, or the plating film comprising iron by using a plating bath comprising saccharin or a salt thereof.
A method for repairing an electrode comprising a conductive substrate having a layer comprising oxide of nickel and iron formed on a surface thereof, in which electrode the layer comprising the oxide is partly damaged on the surface,
the method comprising the step of heating the electrode in an ambient atmosphere or an oxidizing atmosphere, wherein

the conductive substrate has a plating film comprising nickel and iron under the layer comprising the oxide of nickel and iron, or contains iron and has a plating film comprising nickel under the layer comprising the oxide of nickel and iron, or contains nickel and has a plating film comprising iron under the layer comprising the oxide of nickel and iron, or comprises nickel and iron.