Method for forming multi-layered plating structure of zinc-nickel alloy and nickel in single plating bath and multi-layered plating structure of zinc-nickel and nickel

Abstract

Disclosed are a method for forming a multi-layered plating structure of a zinc-nickel alloy and nickel in a single plating bath and a multi-layered plating structure of zinc-nickel and nickel. The method for forming a multi-layered plating structure of a zinc-nickel alloy and nickel in a single plating bath comprises: a first step of preparing an aqueous solution and a substrate in one plating bath, the aqueous solution including an electrolyte, a zinc precursor, and a nickel precursor as a plating bath; a second step of applying a first current to form a pure nickel plating layer on one surface of the substrate; and a third step of applying a second current having a current density higher than the current density of the first current to form a zinc-nickel alloy plating layer on one surface of the substrate.

Description

Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath and a multilayer plating structure of zinc-nickel and nickel

[0001] The present invention relates to a method for forming a multilayer structure in which a pure nickel layer and a zinc-nickel alloy layer are alternated through current control in a single plating bath.

[0002] The corrosion resistance and mechanical properties of a plating layer depend significantly on its structure. Generally, using a multilayer structure provides superior durability and corrosion resistance compared to a single layer, and further enhanced corrosion resistance can be achieved through the galvanic corrosion inhibition effect utilizing interlayer potential differences. Due to the composition and potential differences of each layer, multilayer plating exhibits the effect of slowing down corrosion rates and increasing durability in external environments. Thanks to these characteristics, multilayer plating is widely utilized in various industrial sectors requiring high durability, such as automotive, electronics, aerospace, and marine industries.

[0003] Conventional multilayer plating methods require a complex process involving the alternating use of two or more plating baths to form individual metal layers. For example, this method completes a multilayer structure by repeatedly switching plating baths to form different metal layers after depositing a specific metal layer. Since this process requires depositing each layer individually, it is time-consuming, increases production costs, and incurs substantial management and maintenance expenses. Furthermore, the use of multiple plating baths places a significant environmental burden due to the wastewater and waste generated. With the tightening of environmental regulations, there is a growing need for new plating methods capable of addressing these issues.

[0004] To overcome these limitations, a technical solution is provided that simultaneously realizes process simplification, time and cost reduction, and environmental burden mitigation by presenting a method to alternately deposit pure nickel layers and zinc-nickel alloy layers in a single plating bath by controlling the current density.

[0005] The objective of the present invention is to overcome the limitations of existing multilayer plating processes and to provide a simple and efficient method for forming a multilayer plating structure by controlling the current density in a single plating bath.

[0006] In one aspect, the present invention provides a method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath, comprising: a first step of preparing a substrate and an aqueous solution comprising an electrolyte, a zinc precursor, and a nickel precursor as a plating bath in a plating bath; a second step of forming a pure nickel plating layer on one surface of the substrate by applying a first current; and a third step of forming a zinc-nickel alloy plating layer on one surface of the substrate by applying a second current having a current density higher than the current density of the first current.

[0007] The present invention relates to a method for forming a multilayer structure in which a pure nickel layer and a zinc-nickel alloy layer are alternately formed by controlling the current in a single plating bath. By selectively controlling the composition and thickness of each layer by adjusting the current density within a single plating bath, a uniform and precise multilayer structure can be realized without repetitive processes. The multilayer plating layer formed by the present invention has a galvanic corrosion inhibition effect due to the interlayer potential difference and provides superior corrosion resistance and mechanical strength compared to conventional single-layer plating. Through this, the present invention can be effectively applied to various industrial fields requiring high-performance surface treatment.

[0008] The present invention is characterized by performing alternating deposition by repeating the second and third steps.

[0009] The electrolyte of the present invention is characterized by comprising ammonium chloride (NH4Cl). The ammonium chloride can play a role in increasing the strength of ions and enhancing the solubility of metal ions due to increased conductivity of the electrolyte.

[0010] The above aqueous solution may further contain boric acid (H3BO3). The boric acid can serve to stabilize the pH, prevent instantaneous electrodeposition of zinc, and increase the relative amount of nickel in the alloy layer.

[0011] The zinc precursor of the present invention is characterized as being ZnCl2.

[0012] The nickel precursor of the present invention is characterized as being NiCl2·H2O.

[0013] The pH range of the plating bath of the present invention is characterized as being 3.5 to 5.5, and preferably can be performed at pH 4.5. The pH within the above range plays an important role in the composition and uniformity of the plating layer formed.

[0014] The plating temperature of the present invention is characterized as being 35 to 55 ℃, and preferably can be performed at 45 ℃. By maintaining the plating temperature within the above range, the solubility of ions and the reaction rate can be optimized, thereby contributing to the stability of the plating process.

[0015] The first current of the present invention is 0.25 to 10 mA / cm 2 It is characterized by being 1 mA / cm² 2 It can be performed at 0.25 mA / cm 2 At 10 mA / cm 2 At current densities up to 10 mA / cm², the nickel content in the alloy layer is 70.4 to 98.5%, forming the target nickel layer. Since this corresponds to the pure nickel phase in the zinc-nickel binary phase diagram, it means that the target pure nickel plating layer has been formed. 2 If exceeded, the nickel content decreases, forming a zinc-nickel alloy layer instead of pure nickel, which reduces corrosion resistance and mechanical properties.

[0016] The second current of the present invention is 30 to 100 mA / cm 2 It is characterized by being 60 mA / cm² 2This can be performed in the above range. A zinc-nickel alloy layer with the best corrosion resistance composition among existing literature results containing 12 to 15 weight percent nickel is formed at the above range of current densities.

[0017] The present invention is characterized in that the thickness of the nickel plating layer formed in the second step is 0.1 to 0.3 μm. The main variables affecting the plating layer thickness in the plating process are as follows: plating current density, plating time, electrolyte composition and concentration, pH and temperature conditions, and stirring speed. If the plating layer becomes too thin, less than 0.1 μm, mechanical stability and corrosion resistance may be reduced. In addition, if the thickness of the plating layer increases excessively to more than 0.3 μm, it reduces process efficiency, leading to an increase in the process rate, and increases the likelihood of reduced uniformity of the plating layer.

[0018] The present invention is characterized by the thickness of the zinc-nickel alloy plating layer formed in the third step being 0.7 to 0.9 μm. Similar to the nickel plating layer, if the zinc-nickel alloy plating layer becomes too thin (less than 0.7 μm), mechanical stability and corrosion resistance may be reduced, and if the thickness increases excessively (more than 0.9 μm), the efficiency of the process is reduced, leading to an increase in the process ratio and a higher likelihood of reduced uniformity of the plating layer.

[0019] In another aspect, the present invention provides a zinc-nickel and nickel multilayer plating structure manufactured by the method described above, wherein the thickness of the formed multilayer plating structure is 10 to 12 μm.

[0020] The present invention simplifies the complex processes required in conventional multilayer plating methods and increases production efficiency by forming a multilayer structure of a pure nickel layer and a zinc-nickel alloy layer through the control of current density in a single plating bath. Since there is no need to alternate plating baths, working time and costs are reduced, and it is suitable for continuous mass production.

[0021] Furthermore, it provides superior corrosion resistance compared to single-layer plating due to the galvanic corrosion inhibition effect resulting from the interlayer potential difference. In addition, the multilayer structure increases surface hardness, enhancing mechanical strength and durability, and enables stable use in various applications requiring high reliability.

[0022] In addition, using a single plating bath reduces the generation of wastewater and waste that occurs when using multiple plating baths, thereby minimizing the environmental impact of the process and enabling the implementation of an eco-friendly and sustainable manufacturing process.

[0023] In addition, since there is no need to manage or maintain two plating baths, equipment installation and maintenance costs are reduced, equipment management in industrial settings becomes easier, and process stability is enhanced, providing advantages in terms of quality control.

[0024] FIG. 1 is a schematic diagram of a multilayer plating structure according to one embodiment of the present invention.

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention is susceptible to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. Similar reference numerals have been used for similar components in the description of each drawing. In the attached drawings, the dimensions of the structures are shown enlarged compared to the actual dimensions for the clarity of the present invention.

[0026] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention.

[0027] In addition, the description of one aspect of the present invention may be applied identically or similarly to the description of other aspects for identical or similar configurations or terms.

[0028] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0029] The embodiments of the present invention are described below. However, the embodiments described below are merely partial embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0030] Experimental method

[0031] 1) Composition of the plating bath

[0032] (Comparative Example) A single layer of Zn-Ni plating was formed using a conventional high-corrosion-resistant zinc-nickel alloy plating bath of 1.5 M ZnCl2 and 0.8 M NiCl2·H2O.

[0033] (Example) To form a multilayer Ni / Zn-Ni plating layer by controlling the current in a single plating bath, an aqueous solution containing 0.7 M ZnCl2, 0.5 M NiCl2·H2O, and 2.1 M NH4Cl was used as the plating bath. The pH of the plating bath was set to 4.5, which plays an important role in the composition and uniformity of the plating layer, and the plating temperature was maintained at 45℃ to optimize the solubility of ions and the reaction rate, thereby ensuring the stability of the plating process.

[0034] 2) Current density adjustment

[0035] (Comparative Example) A 12 μm thick Zn-Ni alloy monolayer plating was formed with a current density of 5 A / dm².

[0036] (Example) To form a plating layer, a layer was selectively deposited by adjusting the current density. The current density was 1 mA / cm² 2 A 0.2 μm thick pure nickel (Ni) layer was formed by setting the value, and subsequently, the current density was 60 mA / cm². 2 A Zn-Ni alloy layer with a thickness of 0.8 μm was deposited by increasing the current density, and it was confirmed that the Zn-Ni alloy layer was formed by the simultaneous reduction of zinc and nickel ions at high current densities. This plating cycle was repeated 12 times to finally form a multilayer Ni / Zn-Ni plating structure with a thickness of approximately 12 μm.

[0037] Confirmation of multilayer plating formation

[0038] The structure and composition of the formed multilayer plating layer were evaluated through energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. EDS analysis confirmed that the Ni layer consists of 96 wt% nickel, and the Zn-Ni alloy layer contains 12 wt% nickel. Additionally, XRD analysis confirmed that the Ni layer and the Zn-Ni alloy layer clearly intersect to form a multilayer structure.

[0039] Zn and Ni content by plating layer Ni (wg%) Zn (wg%) Comparative Example 1 3.108 6.90 Example 1 (Ni plating layer) 96.03 3.97 Example 2 (Zn-Ni plating layer) 12.338 7.67

[0040] Corrosion resistance comparison

[0041] The corrosion resistance of the formed multilayer plating layer was evaluated through a potentiodynamic polarization test. The test results confirmed that the galvanic couple current density decreased by approximately 48.9% compared to a conventional single Zn-Ni plating layer, and the galvanic couple potential increased, indicating a significant improvement in corrosion resistance. This suggests that the galvanic corrosion delay effect due to the interlayer potential difference, when the multilayer structure forms a galvanic couple with the substrate steel sheet, results in a lower corrosion rate and maintains the sacrificial anode effect for a long period.

[0042] Galvanic couple current / potential density according to multilayer plating (change rate after plating in parentheses) Comparative Example Example E couple (V)- 0.971- 0.875 (+ 11.0 %)i couple (μA / cm 2 )97.14647.484 (- 48.9 %)

[0043] Hardness comparison

[0044] The mechanical properties of the plating layer were evaluated through micro-Vickers hardness testing. The Ni / Zn-Ni plating layer formed by a multilayer plating method exhibited a hardness approximately 220% higher than that of a single layer formed from a single Zn-Ni alloy. This is interpreted as a result of improved mechanical strength and durability due to the fine grain structure and uniform layer formation. This increase in hardness demonstrates that the multilayer structure enhances resistance to mechanical loads, providing properties suitable for various applications requiring high durability.

[0045] Comparison of Vickers Hardness According to Multilayer Plating (Percentage of change in hardness after plating in parentheses) Vickers Hardness (HV) Comparison Example 165 Example 363 (+ 220%)

[0046] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims.

[0047] 001: Zn-Ni plating layer

[0048] 002: Ni plating layer

Claims

1. A first step of preparing an aqueous solution comprising an electrolyte, a zinc precursor, and a nickel precursor and a substrate as a plating bath in a plating bath; A second step of forming a pure nickel plating layer on one surface of the substrate by applying a first current; and A third step of forming a zinc-nickel alloy plating layer on one surface of the substrate by applying a second current having a current density higher than the current density of the first current; Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

2. In Paragraph 1, Repeating the above second and third steps to perform alternating deposition, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

3. In Paragraph 1, The above electrolyte includes ammonium chloride (NH4Cl), Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

4. In Paragraph 3, The above zinc precursor is characterized as being ZnCl2, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

5. In Paragraph 4, The above nickel precursor is characterized as being NiCl2·H2O, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

6. In Paragraph 5, Characterized that the pH range of the plating bath is 3.5 to 5.5, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

7. In Paragraph 1, Characterized by a plating temperature of 35 to 55 ℃, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

8. In Paragraph 5, The first current is 0.25 to 10 mA / cm 2 Characterized by, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

9. In Paragraph 8, The second current is 30 to 100 mA / cm 2 Characterized by, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

10. In Paragraph 1, Characterized that the thickness of the nickel plating layer formed in the second step is 0.1 to 0.3 μm, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

11. In Paragraph 1, Characterized that the thickness of the zinc-nickel alloy plating layer formed in the third step is 0.7 to 0.9 μm, Method for forming a multilayer plating structure of zinc-nickel alloy and nickel in a single plating bath.

12. Manufactured by a method according to any one of paragraphs 1 to 11, and The thickness of the formed multilayer plating structure is 10 to 12 μm, Multilayer plating structure of zinc-nickel and nickel.

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