Composite coating, preparation method thereof and product

Abstract

The invention relates to a composite coating, a preparation method thereof and a product. The composite coating comprises a nickel-plated layer, a gold-plated layer and a nickel-based transition layer arranged between the nickel-plated layer and the gold-plated layer, the nickel-based transition layer is made of nickel and alloy elements, the alloy elements comprise one or more of molybdenum, cobalt, phosphorus, tungsten and iron, and the mass percentage of the alloy elements in the nickel-based transition layer is 10%-40%. According to the composite coating, the nickel-based transition layer is arranged between the nickel-plated layer and the gold-plated layer, the mass percentage content of alloy elements in the nickel-based transition layer is adjusted, the potential and the corrosion resistance of the nickel-based transition layer are improved, and a microbattery reaction caused by a potential difference is reduced, so that the corrosion resistance of an electrogilded product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plating, in particular to a composite plating layer and a preparation method thereof, and an article. BACKGROUND

[0002] With the continuous improvement of people's living standards, the traditional electroplating surface treatment cannot meet people's more functional requirements for bathroom products. The gold plating layer has a golden luster, and the appearance is beautiful, which can improve the decorative property of bathroom products. Therefore, more and more bathroom products are plated with a nickel layer to improve corrosion resistance and brightness, and then plated with a gold layer to improve the appearance and decoration. However, the products containing the gold plating layer still have the problem that the corrosion resistance needs to be improved. SUMMARY

[0003] Therefore, the present application provides a composite plating layer and a preparation method thereof, which have improved corrosion resistance.

[0004] In addition, the present application also provides an article comprising the composite plating layer.

[0005] A composite plating layer comprises a nickel plating layer, a gold plating layer, and a nickel-based transition layer arranged between the nickel plating layer and the gold plating layer. The composition of the nickel-based transition layer comprises a nickel element and an alloy element, the alloy element comprises one or more of molybdenum, cobalt, phosphorus, tungsten and iron, and the mass percentage of the alloy element in the nickel-based transition layer is 10% to 40%.

[0006] Optionally, the thickness of the nickel-based transition layer is 3 μm to 5 μm.

[0007] Optionally, the nickel-based transition layer comprises a nickel-molybdenum alloy layer, the mass percentage of molybdenum element is 35% to 40%; or the nickel-based transition layer comprises a nickel-cobalt alloy layer, the mass percentage of cobalt element is 25% to 30%; or the nickel-based transition layer comprises a nickel-phosphorus alloy layer, the mass percentage of phosphorus element is 10% to 12%; or the nickel-based transition layer comprises a nickel-tungsten alloy layer, the mass percentage of tungsten element is 20% to 25%; or the nickel-based transition layer comprises a nickel-iron alloy layer, the mass percentage of iron element is 10% to 15%.

[0008] Optionally, the nickel-based transition layer is obtained by electroplating an electroplating solution, and the electroplating solution comprises 50 g / L to 250 g / L of nickel sulfate, 15 g / L to 30 g / L of nickel chloride, and 25 g / L to 70 g / L of a salt containing an alloy element.

[0009] Optionally, the salt containing an alloy element comprises one or more of ferrous sulfate, cobalt sulfate, sodium hypophosphite, sodium tungstate and sodium molybdate.

[0010] Optionally, the electroplating solution further comprises: a pH buffer 10 g / L-60 g / L, a complexing agent 20 g / L-100 g / L, ammonium chloride 15 g / L-20 g / L, a brightener 1 g / L-3 g / L, and a surfactant 0.05 g / L-0.1 g / L.

[0011] Optionally, the pH buffer comprises one or more of boric acid and ammonia.

[0012] Optionally, the complexing agent comprises one or more of sodium citrate, phosphoric acid, and citric acid.

[0013] Optionally, the brightener comprises one or more of saccharin, sodium benzenesulfonate, and 1,4-butynediol.

[0014] Optionally, the surfactant comprises sodium dodecyl sulfate.

[0015] Optionally, the nickel plating layer comprises a semi-bright nickel layer and a bright nickel layer arranged in a stack, and the nickel-based transition layer is arranged on a side surface of the bright nickel layer away from the semi-bright nickel layer.

[0016] Optionally, the total thickness of the nickel plating layer is 15 μm-20 μm; and / or,

[0017] the thickness of the semi-bright nickel layer is 5 μm-7 μm, and the thickness of the bright nickel layer is 9 μm-13 μm; and / or,

[0018] the semi-bright nickel layer and the bright nickel layer are both obtained by electroplating.

[0019] Optionally, the thickness of the gold plating layer is 0.3 μm-0.5 μm; and / or,

[0020] the gold plating layer is an electroplated gold layer.

[0021] A preparation method of a composite plating layer, comprising the following steps:

[0022] forming a nickel-based transition layer between the nickel plating layer and the gold plating layer to prepare the composite plating layer;

[0023] wherein the composition of the nickel-based transition layer comprises nickel elements and alloy elements, the alloy elements comprising one or more of molybdenum, cobalt, phosphorus, tungsten, and iron, and the mass percentage content of the alloy elements in the nickel-based transition layer is 10%-40%.

[0024] Optionally, the step of forming a nickel-based transition layer between the nickel plating layer and the gold plating layer comprises:

[0025] The nickel plating layer is plated with an electroplating solution, the electroplating solution comprising: 50 g / L-250 g / L of nickel sulfate, 15 g / L-30 g / L of nickel chloride, and 25 g / L-70 g / L of a salt containing an alloying element.

[0026] Optionally, the salt containing the alloying element comprises one or more of ferrous sulfate, cobalt sulfate, sodium hypophosphite, sodium tungstate, and sodium molybdate.

[0027] Optionally, the electroplating conditions comprise: a current density of 1 A / dm 2 ~5 A / dm 2 , and a temperature of 45°C-60°C.

[0028] An article comprising a substrate and a composite plating layer disposed on a surface of the substrate, the composite plating layer being as described above or being prepared by the method described above, the composite plating layer having the nickel plating layer closer to the substrate than the gold plating layer.

[0029] Optionally, further comprising a passivation layer disposed on a side of the composite plating layer distal from the substrate.

[0030] Optionally, the passivation layer has a thickness of 200 nm-500 nm.

[0031] Optionally, the article comprises a sanitary ware.

[0032] The present application has found that, although the gold plating layer is chemically stable and is not easily corroded in common environments such as air, water, and most acids and bases, the gold plating layer is thin and nano-sized pores are easily formed on the surface of the gold plating layer during preparation, leading to penetration of corrosion media and causing a micro-battery reaction between the gold plating layer and the nickel plating layer. The potential difference between the nickel plating layer and the gold plating layer is too large, which accelerates the micro-battery reaction and significantly reduces the corrosion resistance, resulting in “white embroidery” and affecting the appearance. Based on this, the present application provides a composite plating layer, a nickel-based transition layer is disposed between the gold plating layer and the nickel plating layer, the content of the alloying element in the nickel-based transition layer is adjusted, the potential of the nickel-based transition layer is higher, and the corrosion resistance of the nickel-based transition layer is better, the potential difference between the nickel-based transition layer and the gold plating layer is reduced, the micro-battery reaction between the nickel-based transition layer and the gold plating layer is slowed down, and thus the corrosion resistance of the composite plating layer is improved. In addition, if the nickel-based transition layer is directly used to replace the nickel plating layer, although the potential difference between the nickel-based transition layer and the gold plating layer is improved, the potential difference between the nickel-based transition layer and the substrate is also increased, which is not conducive to corrosion resistance. Therefore, in the present application, a specific nickel-based transition layer is disposed between the gold plating layer and the nickel plating layer, the nickel-based transition layer and the gold plating layer, the nickel-based transition layer and the nickel plating layer, and the nickel plating layer and the substrate all have a suitable potential difference, and thus the corrosion resistance of the composite plating layer is improved. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A structural schematic diagram of a composite coating of some embodiments of the present application.

[0035] Legend: composite coating 100, plated nickel layer 110, plated gold layer 120, and nickel-based transition layer 130. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of the present application, the following will be a more comprehensive description of the present application in combination with specific embodiments. The preferred embodiments of the present application are given in the specific embodiments. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0038] Unless otherwise stated or contradictory, the terms or phrases used in the present application have the following meanings:

[0039] In the present application, "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features.

[0040] In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited. "Multiple" refers to any two or more.

[0041] In the present application, the percentage concentration involved, unless otherwise specified, refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the component is added.

[0042] In this application, "further", "furthermore", "in particular", "for example", "for instance", "such as", "for example", "for instance" and the like are used for descriptive purposes only and are not intended to limit the scope of the preceding or following technical solutions. In this application, A (such as B) means that B is one non-limiting example of A, and it can be understood that A is not limited to B.

[0043] In this application, "optionally", "optional" and "optional" mean optional, i.e. selected from "yes" or "no" two parallel schemes. If there are multiple "optional" in a technical solution, unless otherwise specified, and there is no contradiction or mutual restriction, each "optional" is independent of each other. In this application, "optionally contains", "optionally contains" and the like, means "contains or does not contain". "Optional component X" means that component X exists or does not exist, or means that it contains or does not contain the component X.

[0044] When a numerical range is disclosed in this application, the above range is considered to be continuous, and includes the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value. Further, when the range is referred to as an integer, every integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe characteristics or properties, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all sub-ranges included therein.

[0045] In this application, the technical features described in an open manner include both the closed technical solutions consisting of the listed features and the open technical solutions containing the listed features.

[0046] In this application, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or components inherent to the process, method, product or device.

[0047] In this application, the phrase "embodiment" means that the specific features, structures or properties described in conjunction with the embodiment can be included in at least one embodiment of the application. The phrase appears at various places in the specification does not necessarily refer to the same embodiment, nor is it independent or alternative to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0048] Please refer toFigure 1 The first aspect of the present application provides a composite coating 100, comprising a nickel plating layer 110, a gold plating layer 120, and a nickel-based transition layer 130 arranged between the nickel plating layer 110 and the gold plating layer 120, the material of the nickel-based transition layer 130 comprising a nickel element and an alloy element, the alloy element comprising one or more of molybdenum, cobalt, phosphorus, tungsten, and iron, and the mass percentage of the alloy element in the nickel-based transition layer 130 being 10% to 40%.

[0049] The composite coating 100 of some embodiments of the present application adjusts the content of the alloy element in the nickel-based transition layer 130, so that the potential of the nickel-based electroplating layer is higher and the corrosion resistance is better, reduces the potential difference between the nickel-based transition layer 130 and the gold plating layer 120, slows down the micro-battery reaction of the nickel-based transition layer 130 and the gold plating layer 120, thereby improving the corrosion resistance of the composite coating 100.

[0050] In addition, in the related art, a sealing agent is used to seal the pores of the gold plating layer 120 to improve its corrosion resistance, but this method affects the metallic texture of the gold plating layer 120. In some embodiments of the present application, the nickel-based transition layer 130 is arranged to improve the corrosion resistance without using a sealing agent, and the metallic texture of the gold plating layer 120 is not affected.

[0051] In some embodiments, the mass percentage of the alloy element in the nickel-based transition layer 130 is 10% to 40%. For example, the mass percentage of the alloy element can be, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or a range formed by any two of these values.

[0052] In some embodiments, the nickel-based transition layer 130 comprises a combination of one or more of a nickel-molybdenum alloy layer, a nickel-cobalt alloy layer, a nickel-phosphorus alloy layer, a nickel-tungsten alloy layer, and a nickel-iron alloy layer. It can be understood that when the nickel-based transition layer 130 is a combination of multiple types, it can be arranged in a multi-layer structure, or the same layer can contain multiple alloys.

[0053] In some embodiments, the nickel-based transition layer 130 comprises a nickel-molybdenum alloy layer, and the mass percentage of the molybdenum element is 35% to 40%. In other embodiments, the nickel-based transition layer 130 comprises a nickel-cobalt alloy layer, and the mass percentage of the cobalt element is 25% to 30%. In yet other embodiments, the nickel-based transition layer 130 comprises a nickel-phosphorus alloy layer, and the mass percentage of the phosphorus element is 10% to 12%. In yet other embodiments, the nickel-based transition layer 130 comprises a nickel-tungsten alloy layer, and the mass percentage of the tungsten element is 20% to 25%. In yet other embodiments, the nickel-based transition layer 130 comprises a nickel-iron alloy layer, and the mass percentage of the iron element is 10% to 15%.

[0054] In some embodiments, the thickness of the nickel-based transition layer 130 is 3-5 μm. With the above settings, it is beneficial to further improve the corrosion resistance while reducing the cost. If the thickness of the nickel-based transition layer 130 is smaller, the corrosion resistance is limited to improve, and if the thickness of the nickel-based transition layer 130 is larger, it causes waste and increases the cost.

[0055] In some embodiments, the nickel-based transition layer 130 is obtained by electroplating using an electroplating solution including: nickel sulfate 50-250 g / L, nickel chloride 15-30 g / L, and an alloy element-containing salt 25-70 g / L. Specifically, the alloy element-containing salt includes one or more of ferrous sulfate (FeS04·7H20), cobalt sulfate (CoS04·7H20), sodium hypophosphite (NaH2P02·H20), sodium tungstate (Na2W04·2H20), and sodium molybdate (Na2Mo04·2H20).

[0056] Specifically, in the electroplating solution, the concentration of nickel sulfate can be but is not limited to 50 g / L, 80 g / L, 100 g / L, 120 g / L, 150 g / L, 180 g / L, 200 g / L, 220 g / L, 250 g / L, or a range consisting of any two of these values. In the electroplating solution, the concentration of nickel chloride can be but is not limited to 15 g / L, 18 g / L, 20 g / L, 22 g / L, 25 g / L, 28 g / L, 30 g / L, or a range consisting of any two of these values. In the electroplating solution, the concentration of the alloy element-containing salt can be but is not limited to 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, or a range consisting of any two of these values.

[0057] The nickel-based transition layer 130 is prepared by electroplating, which is beneficial to improve the production efficiency.

[0058] In some embodiments, the electroplating solution further includes: a pH buffer 10-60 g / L, a complexing agent 20-100 g / L, ammonium chloride 15-20 g / L, a brightener 1-3 g / L, and a surfactant 0.05-0.1 g / L.

[0059] In some embodiments, the pH buffer includes one or more of boric acid (H3BO3) and ammonia water (NH4OH). The pH buffer is mainly used to adjust the pH of the electroplating solution.

[0060] In some embodiments, the complexing agent includes one or more of sodium citrate (Na3C6H5O7), phosphoric acid (H3PO4), and citric acid (C6H8O7). The complexing agent is mainly used to stabilize metal ions, prevent the precipitation or decomposition of metal ions, and improve the stability of the electroplating solution.

[0061] In some embodiments, the brightener includes one or more of saccharin, sodium benzenesulfonate, and 1,4-butynediol. The brightener is mainly used to make the plating layer have a certain brightness, further improving the decorative effect.

[0062] In some embodiments, the surfactant includes sodium dodecyl sulfate. The surfactant is mainly used to disperse the components in the electroplating solution uniformly.

[0063] In some embodiments, the electroplating solution used for the nickel-based transition layer 130 can also include activated carbon. The activated carbon is added to the electroplating solution as a purification material to maintain the stability of the electroplating solution.

[0064] In some embodiments, the nickel plating layer 110 includes a semi-bright nickel layer and a bright nickel layer stacked, and the nickel-based transition layer 130 is arranged on the side surface of the bright nickel layer away from the semi-bright nickel layer. The semi-bright nickel layer has moderate gloss, soft surface, and good corrosion resistance. The bright nickel layer has mirror surface effect, high gloss, and strong decoration. The above arrangement is beneficial to further improve the corrosion resistance and brightness of the composite plating layer 100.

[0065] In some embodiments, the total thickness of the nickel plating layer 110 is 15 μm to 20 μm.

[0066] In some embodiments, the thickness of the semi-bright nickel layer is 5 μm to 7 μm, and the thickness of the bright nickel layer is 9 μm to 13 μm.

[0067] In some embodiments, the semi-bright nickel layer and the bright nickel layer are both obtained by electroplating. Electroplating has higher efficiency and lower cost than chemical plating, and is more suitable for industrial production.

[0068] In some embodiments, the thickness of the gold plating layer 120 is 0.3 μm to 0.5 μm.

[0069] In some embodiments, the gold plating layer 120 is an electroplated gold layer.

[0070] The second aspect of the present application provides a preparation method of a composite plating layer, including the following steps:

[0071] forming a nickel-based transition layer between the nickel plating layer and the gold plating layer to prepare a composite plating layer;

[0072] The nickel-based transition layer includes nickel element and alloy elements, the alloy elements include one or more of molybdenum, cobalt, phosphorus, tungsten and iron, and the mass percentage of the alloy elements in the nickel-based transition layer is 10% to 40%.

[0073] The preparation method of the composite coating forms the nickel-based transition layer between the nickel plating layer and the gold plating layer, adjusts the content of the alloy elements in the nickel-based transition layer, makes the potential of the nickel-based electroplating layer higher and the corrosion resistance better, reduces the potential difference between the nickel-based transition layer and the gold plating layer, slows down the micro-battery reaction of the nickel-based transition layer and the gold plating layer, and thus improves the corrosion resistance of the composite coating.

[0074] In some embodiments, the step of forming the nickel-based transition layer between the nickel plating layer and the gold plating layer includes:

[0075] The electroplating is performed on the surface of the nickel plating layer by using an electroplating solution, and the electroplating solution includes 50 g / L to 250 g / L of nickel sulfate, 15 g / L to 30 g / L of nickel chloride, and 25 g / L to 70 g / L of a salt containing alloy elements, and the salt containing alloy elements includes one or more of ferrous sulfate, cobalt sulfate, sodium hypophosphite, sodium tungstate and sodium molybdate.

[0076] In some embodiments, the electroplating conditions include that the current density is 1 A / dm 2 ~5 A / dm 2 , and the temperature is 45°C to 60°C.

[0077] The deposition rate of electroless plating is slow, and generally, the deposition rate of electroless plating is usually a few microns to tens of microns per hour. For some workpieces that require thick plating layers, the plating time is long, and the production efficiency is low. In addition, the plating solution of electroless plating is easy to fail, and in some embodiments of the present application, the nickel-based transition layer is prepared by electroplating, which is more conducive to improving production efficiency than electroless plating, and the electroplating solution is not easy to fail, which is more conducive to industrial application.

[0078] In some embodiments, the preparation process of the nickel plating layer can be commonly used in the art, for example, prepared by electroplating. The electroplating solution used for the nickel plating layer can be commonly used in the art, for example, semi-bright nickel electroplating solution and full-bright nickel electroplating solution, which will not be described in detail here.

[0079] In some embodiments, the preparation process of the gold plating layer can be commonly used in the art, for example, prepared by electroplating, and the electroplating solution used can be commonly used in the art. The process is more common and will not be described in detail. The gold plating layer gives the composite coating a noble gold appearance.

[0080] In some embodiments, the electroplating solution used for the gold plating layer includes 1 g / L to 10 g / L of potassium gold cyanide and 20 g / L to 60 g / L of ammonium citrate.

[0081] The third aspect of the present application provides an article comprising a substrate and a composite coating layer disposed on a surface of the substrate. The composite coating layer is as described in the first aspect above or is prepared by the method of the second aspect above, and the nickel plating layer in the composite coating layer is closer to the substrate than the gold plating layer.

[0082] In some embodiments, the substrate is a metal substrate. Specifically, the substrate comprises one of copper alloy, zinc alloy and stainless steel. In other embodiments, the substrate can also be a plastic substrate. For example, the substrate is an ABS (acrylonitrile butadiene styrene) substrate.

[0083] In some embodiments, the substrate is cleaned before plating. Specifically, when the substrate is a metal substrate, the cleaning process before plating can be commonly used in the art and is not described in detail here. The cleaning before plating removes grease, dirt and the like on the surface of the substrate.

[0084] When the substrate is a plastic substrate, the pre-plating treatment includes, in sequence, oil and wax removal, palladium activation, debonding and chemical nickel plating. The oil removal removes surface oil stains. The wax removal process removes the wax on the surface of the plastic substrate by using wax removal water to ensure the quality of subsequent electroplating. Palladium activation aims to form a layer of noble metal with catalytic activity on the surface of the plastic substrate. After palladium activation, the surface adsorbs colloidal palladium particles, and these particles do not have catalytic activity because they are stabilized by the divalent tin hydrolysis gel layer. The debonding process removes the unstable layer on the colloidal palladium to activate its catalytic activity. After debonding, the surface is metallized by chemical nickel plating, which is beneficial to subsequent electroplating.

[0085] In some embodiments, the article further comprises a passivation layer disposed on the side of the composite coating layer away from the substrate. By disposing the passivation layer, the corrosion resistance of the article is further improved.

[0086] In some embodiments, the thickness of the passivation layer is 200 nm to 500 nm.

[0087] The specific material and preparation process of the passivation layer can be commonly used in the art and are not described in detail here. Specifically, the substrate containing the composite coating layer is placed in a passivation solution for passivation protection, which is a common process and is not described in detail.

[0088] In some embodiments, the article comprises a bathroom article.

[0089] In order to make the purposes and advantages of the present application more clear, the composite coating, the preparation method and the effects thereof are further described in detail below in combination with specific examples. It should be understood that the specific examples described herein are only used to explain the present application and should not be used to limit the present application. The following examples do not include other components except for inevitable impurities, if not otherwise specified. The drugs and instruments used in the examples are selected according to the conventional selection in the art, if not otherwise specified. The experimental methods in the examples are implemented according to the conventional conditions, such as the conditions described in the literature, books or the methods recommended by the manufacturers.

[0090] Example 1

[0091] The present example provides an article, which comprises a copper alloy as a substrate and a composite coating and a passivation layer disposed on the surface of the substrate. The composite coating comprises a semi-bright nickel layer, a full-bright nickel layer, a nickel-based transition layer and an electroplated gold layer disposed on the surface of the metal substrate copper alloy in sequence. The thickness of the semi-bright nickel layer is 6±0.5 μm, the thickness of the full-bright nickel layer is 10±0.5 μm, the material of the nickel-based transition layer is a nickel-molybdenum alloy with a mass percentage of molybdenum of 37.2%, the thickness of the nickel-molybdenum alloy is 4±0.5 μm, the thickness of the electroplated gold layer is 0.4 μm, and the thickness of the passivation layer is 300 nm.

[0092] The preparation method of the article of the present example comprises the following steps:

[0093] (1) The metal substrate copper alloy is subjected to pre-plating cleaning to remove grease, dirt and the like on the surface of the metal substrate.

[0094] (2) The metal substrate subjected to the pre-plating cleaning is sequentially placed in a semi-bright nickel plating solution and a full-bright nickel plating solution to form a semi-bright nickel layer and a full-bright nickel layer on the surface of the metal substrate in sequence. The semi-bright nickel plating solution comprises nickel sulfate 280 g / L, nickel chloride 60 g / L, boric acid 45 g / L, Pre-ORIO softener 4 mL / L and Pre-ORIO leveling agent 1.2 mL / L. The electroplating process conditions of the semi-bright nickel layer are as follows: temperature 55°C, pH value 4.0, voltage 7 V and time 600 s. The full-bright nickel plating solution comprises nickel sulfate 280 g / L, nickel chloride 60 g / L, boric acid 45 g / L, 520 additive 15 mL / L and TRA nickel additive 3 mL / L. The process conditions of the full-bright nickel layer are as follows: temperature 55°C, pH value 4.0, voltage 7 V and time 600 s.

[0095] (3) A nickel-molybdenum alloy plating solution is prepared, and the nickel-molybdenum alloy plating solution is used for electroplating to obtain a nickel-molybdenum alloy layer. The step of preparing the nickel-molybdenum alloy plating solution is as follows:

[0096] a. Sodium citrate (90 g) is dissolved in hot water (800 mL) at 50°C to 60°C to obtain a first solution;

[0097] b. Add nickel sulfate (200 g), sodium molybdate (30 g) and nickel chloride (30 g) into the first solution in sequence and continue stirring until clear to obtain a second solution;

[0098] c. Adjust the pH of the second solution to 4.0-4.5 with dilute sulfuric acid (10%) (avoiding pH < 3 to cause reduction of molybdate to low valence state) to obtain a third solution;

[0099] d. Dissolve ammonium chloride (15 g), boric acid (10 g), saccharin (2 g) and sodium dodecyl sulfate (0.1 g) in water (200 mL) and add to the third solution, and stir uniformly to obtain the nickel-molybdenum alloy plating solution of the present example.

[0100] The process conditions for electroplating using the nickel-molybdenum alloy plating solution are as follows: pH value: 3-4.5; temperature: 57°C; current density: 5 A / dm 2 ; electroplating time: 4 min; stirring mode: mechanical stirring; anode: nickel anode.

[0101] (4) The copper alloy substrate after step (3) of electroplating the nickel-molybdenum alloy layer is placed in a gold plating solution to deposit a gold plating layer. The gold plating solution is composed of potassium gold cyanide 5 g / L and ammonium citrate 40 g / L, and the electroplating conditions are as follows: current density 0.15 A / dm 2 , temperature 77°C, pH 5.5, and electroplating time 8 min.

[0102] (5) The copper alloy substrate after step (4) of electroplating the gold plating layer is placed in a passivation solution to perform passivation protection to obtain a passivation layer. The passivation solution is composed of potassium dichromate 30 g / L and phosphoric acid 10 mL / L. The process parameters for passivation treatment include temperature 30°C and time 35 s.

[0103] Example 2

[0104] The present example provides an article similar to the article of Example 1, with the difference being that the nickel-based transition layer in the composite plating layer is different. In the present example, the material of the nickel-based transition layer is a nickel-cobalt alloy with a cobalt mass percentage of 27%, and the thickness is 3.5±0.5 μm. The other layers are the same as in Example 1 and are not described again.

[0105] The preparation method of the article of the present example is similar to that of Example 1, with the difference being that step (3) is different. Step (3) of the present example is as follows:

[0106] A nickel-cobalt alloy plating solution is configured, and electroplating is performed using the nickel-cobalt alloy plating solution to obtain a nickel-cobalt alloy layer. The steps for configuring the nickel-cobalt alloy plating solution are as follows:

[0107] a. Dissolve nickel sulfate (200 g), nickel chloride (30 g), cobalt sulfate (30 g) and boric acid (30 g) in hot water (900 mL) at 50-60°C to obtain a first solution;

[0108] b. Add activated carbon (2 g) to the first solution, stir thoroughly for 2 h, stand for 10 h and filter to obtain a second solution;

[0109] c. Dissolve 1,4-butynediol (2 g) and sodium dodecyl sulfate (0.1 g) in water (100 mL) and add to the second solution. Stir until uniform to obtain the nickel-cobalt alloy plating solution of this example.

[0110] The process conditions for electroplating using the nickel-cobalt alloy plating solution are as follows: pH value: 3.7-4.2; temperature: 47°C; current density: 3 A / dm 2 ; electroplating time: 5.5 min; stirring mode: mechanical stirring; anode: nickel anode.

[0111] Example 3

[0112] This example provides an article similar to the article of Example 1, except that the nickel-based transition layer in the composite coating is different. In this example, the material of the nickel-based transition layer is a nickel-phosphorus alloy with a mass percentage of phosphorus of 11% and a thickness of 4±0.5 μm. The other layers are the same as in Example 1 and will not be repeated.

[0113] The preparation method of the article of this example is similar to that of Example 1, except that step (3) is different. Step (3) of this example is as follows:

[0114] Prepare a nickel-phosphorus alloy plating solution and electroplate using the nickel-phosphorus alloy plating solution to obtain a nickel-phosphorus alloy layer. The steps for preparing the nickel-phosphorus alloy plating solution are as follows:

[0115] a. Dissolve nickel sulfate (200 g), nickel chloride (15 g) and boric acid (20 g) in hot water (700 mL) at 60-70°C to obtain a first solution;

[0116] b. Dissolve sodium hypophosphite (25 g) and phosphoric acid (20 g) in warm water (200 mL) and stir to dissolve to obtain a second solution;

[0117] c. Pour the second solution into the first solution while stirring to mix uniformly. Filter to obtain a third solution;

[0118] d. Dissolve saccharin (1.5 g) and sodium dodecyl sulfate (0.075 g) in water (100 mL) and add to the third solution. Stir until uniform to obtain the nickel-phosphorus alloy plating solution of this example.

[0119] The process conditions for electroplating using the nickel-phosphorus alloy plating solution are as follows: pH value: 2.7-3.5; temperature: 65°C; current density: 1.5 A / dm 2 ; electroplating time: 15 min; stirring mode: mechanical stirring; anode: nickel anode + titanium anode (area ratio 6:1).

[0120] Example 4

[0121] This example provides an article similar to the article of Example 1, except that the nickel-based transition layer in the composite coating layer is different. In this example, the material of the nickel-based transition layer is a nickel-tungsten alloy with a mass percentage of tungsten of 22%, and the thickness is 4±0.5 μm. The other layers are the same as in Example 1 and will not be repeated.

[0122] The preparation method of the article of this example is similar to that of Example 1, except that step (3) is different. Step (3) of this example is as follows:

[0123] A nickel-tungsten alloy plating solution is configured, and electroplating is performed using the nickel-tungsten alloy plating solution to obtain a nickel-tungsten alloy layer. The steps for configuring the nickel-tungsten alloy plating solution are as follows:

[0124] a. Dissolve sodium citrate (100 g) and citric acid (30 g) in hot water (800 mL) at 50-60°C to obtain a first solution;

[0125] b. Add nickel sulfate (50 g), nickel chloride (15 g), and sodium tungstate (70 g) to the first solution in sequence, continue to stir until clear, and obtain a second solution;

[0126] c. Slowly add ammonia water (60 g) to the second solution, adjust the pH to 9.0-9.5, and obtain a third solution;

[0127] d. Dissolve ammonium chloride (20 g), boric acid (10 g), saccharin (2 g), and sodium dodecyl sulfate (0.1 g) in water (200 mL) and add to the third solution, stir uniformly, and obtain the nickel-tungsten alloy plating solution of this example.

[0128] The process conditions for electroplating using the nickel-tungsten alloy plating solution are as follows: pH value: 9-10; temperature: 60°C; current density: 3.7 A / dm 2 ; electroplating time: 7 min; stirring mode: mechanical stirring; anode: nickel anode.

[0129] Example 5

[0130] The present example provides an article similar to the article of Example 1, except that the nickel-based transition layer in the composite coating layer is different. In the present example, the material of the nickel-based transition layer is a nickel-iron alloy with a mass percentage of 12% iron and a thickness of 4±0.5 μm. The other layers are the same as in Example 1 and will not be repeated here.

[0131] The preparation method of the article of the present example is similar to the preparation method of Example 1, except that step (3) is different. Step (3) of the present example is as follows:

[0132] A nickel-iron alloy plating solution is configured, and the nickel-iron alloy plating solution is used for electroplating to obtain a nickel-iron alloy layer. The steps of configuring the nickel-iron alloy plating solution are as follows:

[0133] a. Dissolve nickel sulfate (250 g), nickel chloride (20 g) and boric acid (40 g) in hot water (700 mL) at 60-70 °C to obtain a first solution;

[0134] b. Dissolve sodium citrate (70 g) in warm water (200 mL), add ferrous sulfate (25 g), and stir to dissolve to obtain a second solution;

[0135] c. Pour the second solution into the first solution under stirring and mix uniformly, and then filter to obtain a third solution;

[0136] d. Dissolve saccharin (2 g), sodium benzenesulfonate (0.3 g) and sodium dodecyl sulfate (0.1 g) in water (100 mL) and then add to the third solution, and stir uniformly to obtain the nickel-iron alloy plating solution of the present example.

[0137] The process conditions for electroplating using the nickel-iron alloy plating solution are as follows: pH value: 2.6-3.4; temperature: 52 °C; current density: 2.5 A / dm 2 ; electroplating time: 8 min; stirring mode: mechanical stirring; anode: nickel anode + iron anode (area ratio 6:1).

[0138] Example 6

[0139] The present example provides an article similar to the article of Example 1, except that the composite coating layer does not contain a semi-bright nickel layer. That is, the composite coating layer of the present example includes a full-bright nickel layer, a nickel-based transition layer and an electroplated gold layer arranged in sequence on the surface of the metal substrate.

[0140] The preparation method of the article of the present example is similar to the preparation method of Example 1, except that the semi-bright nickel layer in step (2) is not included.

[0141] Comparative Example 1

[0142] Comparative Example 1 provides an article similar to the article of Example 1, except that the composite coating does not include a nickel-based overcoat layer. That is, the composite coating of Comparative Example 1 includes a semi-bright nickel layer, a bright nickel layer, and an electroplated gold layer disposed on the surface of the metal substrate.

[0143] The method of making the article of Comparative Example 1 is similar to the method of making the article of Example 1, except that step (3) is not included.

[0144] Comparative Example 2

[0145] Comparative Example 2 provides an article similar to the article of Example 1, except that the material of the nickel-based transition layer in the composite coating is different. In Comparative Example 2, the material of the nickel-based transition layer is a nickel-molybdenum alloy having a mass percentage of molybdenum of 45% and a thickness of 4 ± 0.5 μιη. The other layers are the same as in Example 1 and are not described again.

[0146] The method of making the article of Comparative Example 2 is similar to Example 1, except that step (3) is different. Step (3) of Comparative Example 2 is as follows:

[0147] A nickel-molybdenum alloy plating solution is prepared and used for electroplating to obtain a nickel-molybdenum alloy layer. The steps of preparing the nickel-molybdenum alloy plating solution are as follows:

[0148] a. Sodium citrate (90 g) is dissolved in hot water (800 mL) at 50-60 °C to obtain a first solution;

[0149] b. Nickel sulfate (160 g), sodium molybdate (45 g), and nickel chloride (25 g) are sequentially added to the first solution with continued stirring until clear to obtain a second solution;

[0150] c. Dilute sulfuric acid (10%) is used to adjust the pH of the second solution to 4.0-4.5 (to avoid reducing the molybdate to a low valence state when the pH is less than 3) to obtain a third solution;

[0151] d. Ammonium chloride (12 g), boric acid (10 g), saccharin (2 g), and sodium dodecyl sulfate (0.1 g) are dissolved in water (200 mL) and added to the third solution, which is stirred until uniform to obtain the nickel-molybdenum alloy plating solution of Comparative Example 2.

[0152] The process conditions for electroplating using the nickel-molybdenum alloy plating solution are as follows: pH: 3-4.5; temperature: 57 °C; current density: 4 A / dm 2 ; electroplating time: 4 min; stirring mode: mechanical stirring; anode: nickel anode.

[0153] Comparative Example 3

[0154] Comparative Example 3 provides an article similar to the article of Example 1, except that the material of the nickel-based transition layer in the composite coating is different. In Comparative Example 3, the material of the nickel-based transition layer is a nickel-iron alloy with a mass percentage of 8% iron and a thickness of 4±0.5 μm. The other layers are the same as in Example 1 and are not repeated here.

[0155] The preparation method of the article of Comparative Example 3 is similar to that of Example 1, except that step (3) is different. Step (3) of Comparative Example 3 is as follows:

[0156] A nickel-iron alloy plating solution is configured and used for electroplating to obtain a nickel-iron alloy layer. The steps of configuring the nickel-iron alloy plating solution are as follows:

[0157] a. Dissolve nickel sulfate (260 g), nickel chloride (23 g) and boric acid (40 g) in hot water (700 mL) at 60-70°C to obtain a first solution;

[0158] b. Dissolve sodium citrate (70 g) in warm water (200 mL), add ferrous sulfate (18 g), and stir to dissolve to obtain a second solution;

[0159] c. Pour the second solution into the first solution under stirring to mix uniformly, and filter to obtain a third solution;

[0160] d. Dissolve saccharin (2 g), sodium benzenesulfonate (0.3 g) and sodium dodecyl sulfate (0.1 g) in water (100 mL) and add to the third solution. After stirring uniformly, the nickel-iron alloy plating solution of this example is obtained.

[0161] The process conditions for electroplating using the nickel-iron alloy plating solution are as follows: pH value: 2.6-3.4; temperature: 52°C; current density: 2.7 A / dm 2 ; electroplating time: 8 min; stirring mode: mechanical stirring; anode: nickel anode + iron anode (area ratio 6:1).

[0162] The following is the specific test section:

[0163] 1. Self-corrosion potential test

[0164] The article samples prepared in each example and comparative example are subjected to electrochemical tests on an electrochemical workstation with model RST5200. A three-electrode test system is used, i.e. the working electrode is a nickel electrode (1 cm 2 ), the counter electrode is a platinum-gold electrode, and the reference electrode is a saturated calomel electrode. The test solution is 0.5 M H2SO4 solution at room temperature. The potential-time curve test lasts for 3400 s; the polarization curve test has a scanning rate of 2 mV / s; and the electrochemical impedance test has an amplitude of 7 mV / s and a frequency of 0.01-10 Hz.

[0165] 2. Salt spray test

[0166] In the AASS salt spray test, a certain amount of glacial acetic acid is added to a 3.5% mass concentration sodium chloride solution to make the pH value of the solution reach 3.1-3.3. The sample is fixed on the sample holder in the test box, and the sample is placed at an angle according to the standard requirements. Generally, the flat sample is at an angle of 15°-30° to the vertical direction, and the test surface is exposed to the salt spray as much as possible. Pour the prepared salt solution into the solution tank of the salt spray test box, start the test box, and set the temperature of the test box to 35°C±2°C. The test time is set according to the use environment and requirements of the sample. After the test is completed, the sample is taken out, washed with clean water, and then naturally dried at room temperature or dried with a hair dryer or other equipment.

[0167] The evaluation method includes appearance inspection and corrosion rating. Specifically, the corrosion degree is divided into different levels according to the percentage of the corrosion area to the total area, from level 10 (no corrosion) to level 0 (severe corrosion). Level 10 means that there is no corrosion phenomenon, and the surface state is the same as before the test; level 0 means that the corrosion area is more than 95%, and the material is severely damaged.

[0168] Table 1 Corrosion resistance test results

[0169]

[0170] As can be seen from the above Table 1, compared with the composite coating of Comparative Example 1 only including a nickel plating layer and a gold plating layer, in the embodiments of the present application, a nickel-based transition layer is arranged between the nickel plating layer and the gold plating layer, the alloy elements in the nickel-based transition layer include one or more of molybdenum, cobalt, phosphorus, tungsten and iron, and the mass percentage of the alloy elements is 10%-40%, which is beneficial to improve the potential and corrosion resistance of the nickel-based transition layer, reduce the micro-battery reaction caused by the potential difference, and thus improve the corrosion resistance of the electroplated gold product. In Comparative Examples 2 and 3, although a nickel-based transition layer is arranged, compared with Comparative Example 1, the corrosion resistance is slightly improved, but compared with the embodiments, the content of the alloy elements in the nickel-based transition layer is too high or too low, and the corrosion potential and corrosion resistance are significantly lower than those of the embodiments.

[0171] Further, by optimizing the nickel plating layer, the full bright nickel layer and the semi-bright nickel layer are used in cooperation, which is beneficial to further improve the corrosion resistance of the electroplated gold product.

[0172] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0173] The above-described embodiments only express several implementation manners of the present application, facilitate specific and detailed understanding of the technical solutions of the present application, but cannot be understood as a limitation on the patent protection scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. It should be understood that, on the basis of the technical solutions provided by the present application, the technical solutions obtained by logical analysis, reasoning or limited experiments by the skilled person in the art all belong to the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the content of the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A composite coating, characterized by, The nickel-based transition layer comprises nickel and alloying elements, the alloying elements comprise one or more of molybdenum, cobalt, phosphorus, tungsten and iron, and the mass percentage of the alloying elements in the nickel-based transition layer is 10% to 40%.

2. The composite coating according to claim 1, characterized in that The thickness of the nickel-based transition layer is 3 μm to 5 μm; and / or, The nickel-based transition layer comprises a nickel-molybdenum alloy layer, the mass percentage of molybdenum is 35% to 40%; or the nickel-based transition layer comprises a nickel-cobalt alloy layer, the mass percentage of cobalt is 25% to 30%; or the nickel-based transition layer comprises a nickel-phosphorus alloy layer, the mass percentage of phosphorus is 10% to 12%; or the nickel-based transition layer comprises a nickel-tungsten alloy layer, the mass percentage of tungsten is 20% to 25%; or the nickel-based transition layer comprises a nickel-iron alloy layer, the mass percentage of iron is 10% to 15%.

3. The composite coating according to claim 1 or 2, characterized in that The nickel-based transition layer is obtained by electroplating using an electroplating solution, the electroplating solution comprises: nickel sulfate 50 g / L to 250 g / L, nickel chloride 15 g / L to 30 g / L, and a salt containing alloying elements 25 g / L to 70 g / L; Optionally, the salt containing alloying elements comprises one or more of ferrous sulfate, cobalt sulfate, sodium hypophosphite, sodium tungstate and sodium molybdate.

4. The composite coating according to claim 3, wherein The electroplating solution further comprises: pH buffer 10 g / L to 60 g / L, complexing agent 20 g / L to 100 g / L, ammonium chloride 15 g / L to 20 g / L, brightener 1 g / L to 3 g / L, and surfactant 0.05 g / L to 0.1 g / L; Optionally, the pH buffer comprises one or more of boric acid and ammonia; Optionally, the complexing agent comprises one or more of sodium citrate, phosphoric acid and citric acid; Optionally, the brightener comprises one or more of saccharin, sodium benzenesulfonate and 1,4-butynediol; Optionally, the surfactant comprises sodium dodecyl sulfate.

5. The composite coating of claim 1, wherein The nickel plating layer comprises a semi-bright nickel layer and a bright nickel layer arranged in layers, and the nickel-based transition layer is arranged on a side surface of the bright nickel layer away from the semi-bright nickel layer.

6. The composite coating according to claim 5, wherein The total thickness of the nickel plating layer is 15 μm to 20 μm; and / or, The thickness of the semi-bright nickel layer is 5 μm to 7 μm, and the thickness of the bright nickel layer is 9 μm to 13 μm; and / or, The semi-bright nickel layer and the bright nickel layer are both obtained by electroplating.

7. The composite coating of claim 1, wherein The thickness of the gold plating layer is 0.3 μm to 0.5 μm; and / or, The gold plating layer is an electroplated gold layer.

8. A method for producing a composite coating, characterized by, The method comprises the following steps: forming a nickel-based transition layer between the nickel plating layer and the gold plating layer to prepare a composite plating layer; The composition of the nickel-based transition layer comprises nickel and alloying elements, the alloying elements comprise one or more of molybdenum, cobalt, phosphorus, tungsten and iron, and the mass percentage of the alloying elements in the nickel-based transition layer is 10% to 40%.

9. The method for producing a composite coating layer according to claim 8, characterized by, The step of forming a nickel-based transition layer between the nickel plating layer and the gold plating layer comprises: The surface of the nickel plating layer is electroplated using an electroplating solution, the electroplating solution comprising: 50-250 g / L of nickel sulfate, 15-30 g / L of nickel chloride, and 25-70 g / L of a salt containing an alloying element; Optionally, the salt containing the alloying element comprises one or more of ferrous sulfate, cobalt sulfate, sodium hypophosphite, sodium tungstate, and sodium molybdate. Optionally, the electroplating conditions include: current density of 1 A / dm 2 5 A / dm 2 , temperature of 45℃~60℃.

10. An article of manufacture characterized by, The composite plating layer is prepared by the method of any one of claims 8-9.

11. The article of claim 10, wherein, A passivation layer is further provided on the side of the composite plating layer away from the substrate; optionally, the thickness of the passivation layer is 200-500 nm.

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