Surface treatment method of aluminum die casting material using vacuum deposition plating hybrid process and manufacturing method thereof

Abstract

The present invention relates to a surface treatment method of an aluminum die casting material, including a pretreatment step, a first metal layer formation step by vacuum deposition, a second metal layer formation step by electroless plating, and a third metal layer formation step by electroplating. The surface treatment method of the present invention can form a multi-layered surface treatment layer having excellent adhesion, corrosion resistance, and wear resistance through a vacuum deposition and electroplating melting process. In particular, it has an advantage of uniform surface treatment even for a product having a complex shape, and is easy to apply to industry due to excellent process stability and repeatability.

Description

Technical Field

[0001] This invention relates to a surface treatment method for aluminum die-casting materials, and more specifically, to a method for forming a multi-layer surface treatment layer with improved corrosion resistance and wear resistance through a melting process of vacuum deposition and electroplating. Background Technology

[0002] Generally, anodizing is widely used as a surface treatment method for aluminum die-casting materials. Anodizing is a method that uses aluminum as the anode in an electrolyte to form an oxide film on the surface through electrolysis. However, this anodizing process suffers from problems such as uneven oxide film thickness, insufficient corrosion resistance, and difficulty in forming a uniform film, especially for products with complex shapes.

[0003] Furthermore, when using conventional wet or dry plating alone, there are issues with insufficient adhesion to the aluminum material or poor coating durability. In particular, the surface of die-cast aluminum materials may have casting defects or porosity, making it difficult to achieve a stable surface treatment.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Korean Patent No. 10-2005-0064066

[0007] Patent Document 2: Korean Patent No. 10-2001-0058129

[0008] Patent Document 3: Korean Patent No. 10-1997-0021366

[0009] Patent Document 4: Korean Patent No. 10-1998-0052509 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The present invention aims to solve the problems in the prior art described above, and has the following objectives:

[0012] First, we want to provide a method for forming a surface treatment layer with excellent adhesion through vacuum deposition and electroplating melting processes of aluminum die-casting materials.

[0013] Secondly, through a multi-layered surface treatment layer, we intend to provide a surface treatment method that can simultaneously improve corrosion resistance and wear resistance.

[0014] Third, we hope to provide a method that can form a uniform surface treatment layer even in products with complex shapes.

[0015] Fourth, the process has excellent stability and repeatability, and we hope to provide a surface treatment method suitable for mass production.

[0016] Methods for solving problems

[0017] This invention is based on an aluminum 100 weight component, and involves pretreatment steps of degreasing, etching, neutralizing, and drying the surface of the aluminum die-cast material, including the Si4-10 weight portion and the Cu2-5 weight portion; metal deposition is performed on the pretreated surface under a vacuum of 10⁻⁵ to 10⁻⁶ Torr to form a first metal layer; chemical plating is performed on the first metal layer to form a second metal layer; and electroplating is performed on the second metal layer to form the third metal layer; its characteristic is that it includes this.

[0018] At this point, the pretreatment steps are as follows: degreasing in an alkaline solution containing 100 parts sodium hydroxide at 60-70°C for 5-10 minutes; deposition in an acidic solution containing 100 parts sulfuric acid at 40-50°C for 3-7 minutes; neutralization in a neutralizing solution containing 100 parts phosphoric acid at 35-45°C for 2-5 minutes; and hot air drying at 80-90°C for 5-10 minutes; in this order.

[0019] At this point, the first metal layer comprises 60-70 kg of Cu, 20-30 kg of Ni, and 5-15 kg of Cr, based on a total deposited metal weight of 100 kg, and is characterized by a thickness of 0.1-1.0 μm.

[0020] At this point, the second metal layer is a chemically plated nickel layer, comprising 80-85% by weight of nickel and 15-20% by weight of phosphorus (based on a total plating layer of 100% by weight, in an electroplating solution with a pH of 4.5-5.0), formed at a temperature of 80-85°C with a thickness of 3-5 μm. The third metal layer is an electrolytically plated nickel layer comprising 90-95% by weight of nickel and 5-10% by weight of boron, based on a total electroplating layer of 100% by weight, characterized by a current density of 2.0-3.0 A / dm³. 2 An electrolytic nickel layer with a thickness of 20-25 μm is formed at a temperature of 55-60℃.

[0021] At this point, the electrolytic nickel plating solution is based on an aqueous solution of 1000 parts by weight, including 25-30 parts by weight of nickel sulfate, 20-25 parts by weight of sodium hypophosphite, 15-20 parts by weight of sodium acetate, and 1-3 parts by weight of stabilizer. The electrolytic nickel plating solution is characterized by being based on an aqueous solution of 1000 parts by weight, including 250-300 parts by weight of nickel sulfate, 30-40 parts by weight of nickel chloride, 35-45 parts by weight of boric acid, and 0.5-1.5 parts by weight of brightener.

[0022] Invention Effects

[0023] The surface treatment method for aluminum die-casting materials of the present invention has the following effects:

[0024] First, the first metal layer formed by vacuum deposition has excellent adhesion to aluminum material, which provides a foundation for the stable formation of subsequent electroplating layers.

[0025] Secondly, the second metal layer formed by chemical plating has a uniform thickness and excellent corrosion resistance, while the third metal layer formed by electrolytic plating has high hardness and wear resistance.

[0026] Third, in the multi-layer surface treatment, each layer plays a complementary role to improve the overall surface properties.

[0027] Fifth, by optimizing process conditions, stable and repeatable surface treatments can be achieved, making it suitable for large-scale production. Detailed Implementation

[0028] In the following descriptions of the specific structures or functions of the disclosed embodiments, the information is for illustrative purposes only and may be modified and performed in various forms. Therefore, the embodiments are not limited to the particular form of disclosure, and the scope of this specification includes changes, uniformities, or substitutions incorporated into the descriptive concepts.

[0029] Terms such as "first" or "second" can be used to describe various components, but the interpretation of these terms should only be used to distinguish one component from another. For example, the first component can be named the second component, and similarly, the second component can be named the first component.

[0030] When a component is said to be "connected" to another component, it should be understood that it may be directly connected to or connected to another component, but there may be another component between them.

[0031] The terminology used in the embodiments is for illustrative purposes only and should not be construed as restrictive. Singular expressions include plural expressions unless the context clearly implies otherwise. In this specification, the terms "comprising" or "having" should be understood to mean the presence of the functions, numbers, steps, actions, components, parts, or combinations thereof described herein, and should not exclude the presence or addition of one or more other functions or numbers, steps, actions, components, parts, or combinations thereof.

[0032] Unless otherwise defined, all terms used herein, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments pertain. Terms such as those defined in common dictionaries shall be interpreted as having the meaning consistent with their meaning in the relevant descriptive context and shall not be interpreted in an ideal or overly formal sense unless expressly defined herein.

[0033] This invention is intended to be practiced in many different forms and is not limited to the embodiments disclosed below, but is only intended to ensure that the disclosure of this invention is complete and to provide a complete introduction to those skilled in the art to which this invention pertains, and this invention should be defined only by the class of the claims.

[0034] In this embodiment of the invention, all terms used herein, including technical or scientific terms, unless otherwise defined, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms such as those defined in common dictionaries should be interpreted as having the meaning consistent with their meaning in the relevant descriptive context and should not be interpreted in an ideal or overly formal sense unless explicitly defined in the embodiments of the invention.

[0035] In describing this invention, detailed descriptions of relevant known technologies may be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essential points of the invention. When using terms such as 'comprising,' 'having,' and 'completed' as used in this specification, additional parts may be added unless 'only' is used. This includes cases where components are expressed in the singular and contain a plural, unless specifically stated otherwise.

[0036] When interpreting components, even if not explicitly stated, they will be interpreted as including the error magnitude.

[0037] Each feature in the various embodiments of the present invention can be combined with each other in part or in whole, and as those skilled in the art will fully understand, they can be technically linked and driven together, and each embodiment can be performed independently of each other or together in an associated relationship.

[0038] This invention is based on an aluminum 100 weight component, and involves pretreatment steps of degreasing, etching, neutralizing, and drying the surface of the aluminum die-cast material, including the Si4-10 weight portion and the Cu2-5 weight portion; metal deposition is performed on the pretreated surface under a vacuum of 10⁻⁵ to 10⁻⁶ Torr to form a first metal layer; chemical plating is performed on the first metal layer to form a second metal layer; and electroplating is performed on the second metal layer to form the third metal layer; its characteristic is that it includes this.

[0039] At this point, the pretreatment steps are as follows: degreasing in an alkaline solution containing 100 parts sodium hydroxide at 60-70°C for 5-10 minutes; etching in an acidic solution containing 100 parts sulfuric acid at 40-50°C for 3-7 minutes; neutralizing in a neutralizing solution containing 100 parts phosphoric acid at 35-45°C for 2-5 minutes; and hot air drying at 80-90°C for 5-10 minutes; in sequence.

[0040] In this case, the first metal layer comprises 60-70 wt% Cu, 20-30 wt% Ni, and 5-15 wt% Cr, based on a total deposited metal of 100 wt%, characterized by a thickness of 0.1-1.0 μm.

[0041] At this point, the second metal layer is a chemically plated nickel layer, comprising 80-85% by weight of nickel and 15-20% by weight of phosphorus (based on a total plating layer of 100% by weight, in an electroplating solution with a pH of 4.5-5.0), formed at a temperature of 80-85°C with a thickness of 3-5 μm. The third metal layer is an electrolytically plated nickel layer comprising 90-95% by weight of nickel and 5-10% by weight of boron, based on a total electroplating layer of 100% by weight, characterized by a current density of 2.0-3.0 A / dm³. 2 An electrolytic nickel layer with a thickness of 20-25 μm is formed at a temperature of 55-60℃.

[0042] At this point, the electrolytic nickel plating solution is based on an aqueous solution of 1000 parts by weight, including 25-30 parts by weight of nickel sulfate, 20-25 parts by weight of sodium hypophosphite, 15-20 parts by weight of sodium acetate, and 1-3 parts by weight of stabilizer. The electrolytic nickel plating solution is characterized by being based on an aqueous solution of 1000 parts by weight, including 250-300 parts by weight of nickel sulfate, 30-40 parts by weight of nickel chloride, 35-45 parts by weight of boric acid, and 0.5-1.5 parts by weight of brightener.

[0043] The technical significance of selecting each material used in this invention is as follows.

[0044] Specific criteria for material selection

[0045] 1. Composition of aluminum die-casting materials

[0046] In this invention, based on an aluminum weight fraction of 100, the composition consisting of a Si weight fraction of 4-10 and a Cu weight fraction of 2-5 is selected as follows. Si is a fundamental element for improving castability and fluidity; less than 4 by weight may result in casting defects, and more than 10 by weight leads to increased material embrittlement. Adding Cu improves mechanical strength, but the strength improvement is negligible for parts weighing less than 2 by weight, and corrosion resistance decreases when the weight exceeds 5 by weight.

[0047] 2. Composition of the first metal layer (vacuum deposition layer)

[0048] The first metal layer formed by vacuum deposition was designed to include 60-70 kg of Cu, 20-30 kg of Ni, and 5-15 kg of Cr, totaling 100 weight ranges based on the deposited metal. Cu exhibits excellent adhesion and conductivity to aluminum, but adhesion is insufficient below 60 kg, and corrosion resistance decreases above 70 kg. Ni improves corrosion resistance and wear resistance, but its effect is negligible below 20 kg, and there is an issue of increased interlayer stress above 30 kg. Cr improves surface stability and corrosion resistance, but its effect is insufficient below 5 kg, and embrittlement increases above 15 kg.

[0049] 3. Composition of the second metal layer (chemical plating layer)

[0050] The second metal layer is formed by chemical plating and is designed to consist of 80-85 nickel weights and 15-20 phosphorus weights, based on a total of 100 weight plates. This composition ratio of the nickel-phosphorus alloy provides optimal corrosion resistance and hardness. If the phosphorus content is less than 15 parts by weight, corrosion resistance is insufficient; if it exceeds 20 parts by weight, there is increased embrittlement of the plating layer and reduced adhesion to subsequent electrolytic layers.

[0051] 4. Composition of the third metal layer (electroplating layer)

[0052] The third metal layer formed by electroplating is designed to contain 90-95% nickel and 5-10% boron based on 90 counterweights. This composition provides excellent wear resistance and hardness as a surface layer. If the boron content is less than 5 weights, the hardness improvement is insufficient; if it exceeds 10 weights, the internal stress of the coating increases, which may lead to cracking.

[0053] 5. Select slaughter volume

[0054] The electroplating composition is based on a 1000-part aqueous solution weight ratio, with each component designed to exhibit optimal electroplating performance. In the case of electroless plating, 25-30 parts by weight of nickel sulfate provides a stable supply of nickel ions, 20-25 parts by weight of sodium hypophosphite acts as a reducing agent, 15-20 parts by weight of sodium acetate provides a buffering effect, and 1-3 parts by weight of stabilizer provides stability to the plating solution. In the case of electrolytic plating, 250-300 parts by weight of nickel sulfate and 30-40 parts by weight of nickel chloride are crucial for a stable supply of nickel ions, 35-45 parts by weight of boric acid is used for pH buffering, and 0.5-1.5 parts by weight of polishing agent is used to form a smooth plating surface.

[0055] The selection and composition ratio of these materials were derived through extensive experimentation and optimization processes, and are essential for achieving the objectives of this invention.

[0056] [The key significance of each process step and component]

[0057] 1. The key significance of the preprocessing step

[0058] Detailed conditions for the preprocessing step:

[0059] - Degreasing: 60-70℃ for minutes

[0060] -Etching: 40-50℃ for minutes

[0061] Neutralization: 35-45℃ for minutes

[0062] Drying: 80-90℃ for minutes

[0063] Significance:

[0064] During the degreasing process, surface contaminant removal is insufficient when the temperature is below 60℃, and excessive oxidation occurs on the aluminum surface if the temperature exceeds 70℃. Cleaning is incomplete if the processing time is less than 5 minutes, and surface etching occurs if it exceeds 10 minutes, which will adversely affect subsequent processes.

[0065] In etching processes, there is a problem: insufficient surface activation occurs below 40°C, and surface roughness increases due to uneven etching above 50°C. Processing for less than 3 minutes results in insufficient surface activation, while processing for more than 7 minutes leads to a decrease in the dimensional accuracy of the material.

[0066] The neutralization process slows the reaction rate to below 35°C, thus reducing process efficiency. When the temperature exceeds 45°C, the degradation of the neutralizing agent accelerates, thereby reducing the treatment effect. Treatment time less than 2 minutes will result in incomplete neutralization, while treatment time exceeding 5 minutes may lead to surface recontamination.

[0067] 2. The key significance of the vacuum deposition stage

[0068] Vacuum degree and composition conditions:

[0069] - Vacuum level: 10⁻⁵ to 10⁻⁶ Torr

[0070] - Copper: 60-70 weight range

[0071] -Ni: 20-30 weight range

[0072] -Cr: 5-15 for heavy parts

[0073] Significance:

[0074] If the vacuum level is below 10⁻⁵ Torr, the purity of the deposited layer will decrease, and impurity entrainment will increase. If the vacuum level exceeds 10⁻⁶ Torr, the processing time and cost will increase dramatically, thus reducing economic viability. If the Cu content is less than 60 weights, the adhesion to aluminum is insufficient; if it exceeds 70 weights, corrosion resistance will decrease. Ni has insufficient hardness and wear resistance at 20 weights, and above 30 weights, increased internal stress may lead to delamination. The effect of Cr on improving the corrosion resistance of parts weighing less than 5 weights is negligible; above 15 weights, the brittleness of parts increases, making them prone to cracking.

[0075] 3. The key significance of the electroless plating stage

[0076] Electroplating conditions:

[0077] pH value: 4.5-5.0

[0078] Temperature: 80-85℃

[0079] Thickness: 3-5μm

[0080] Significance:

[0081] If the pH value is less than 4.5, the electroplating reaction is unstable and the precipitation rate decreases; if it exceeds 5.0, spontaneous degradation of the plating solution may occur. If the temperature is below 80℃, the electroplating speed will be too slow, and the physical properties of the coating will deteriorate; if the temperature exceeds 85℃, the stability of the plating solution will deteriorate rapidly. If the coating thickness is less than 3μm, the corrosion resistance and abrasion resistance will be insufficient; if it exceeds 5μm, delamination may occur due to increased internal stress.

[0082] 4. The key significance of the electroplating stage

[0083] Electroplating conditions:

[0084] - Current density: 2.0-3.0 A / dm 2

[0085] pH value: 3.8-4.2

[0086] Temperature: 55-60℃

[0087] Thickness: 20-25μm

[0088] Significance:

[0089] If the current density is less than 2.0 A / dm 2 If the current density exceeds 3.0 A / dm³, the electroplating speed will be too slow, reducing productivity. 2If the pH value is below 3.8, stress concentration and porosity will occur in the electroplated layer. If the pH value is below 3.8, hydrogen production increases, which increases the brittleness of the plating layer; if it exceeds 4.2, the stability of the plating solution will decrease. If the temperature is below 55℃, the ductility of the plating layer is insufficient; if the temperature exceeds 60℃, the evaporation of the plating solution becomes severe, making it difficult to control the concentration.

[0090] These threshold values ​​for process conditions were derived through extensive experimentation and optimization, and represent the fundamental requirements for achieving optimal surface treatment results at each stage.

[0091] [Detailed Description of the Invention]

[0092] This invention relates to a surface treatment method for aluminum die-casting materials, specifically a method for forming a surface treatment layer with excellent corrosion resistance and wear resistance by sequentially performing a pretreatment process, a vacuum deposition process, a chemical plating process, and an electroplating process.

[0093] The pretreatment of the aluminum die-casting material used in this invention is a very important process. First, it is degreased for 5-10 minutes in an alkaline solution containing 100 parts by weight of sodium hydroxide at a temperature of 60-70°C. If the temperature is below 60°C, surface contaminants cannot be sufficiently removed, and if the temperature exceeds 70°C, the aluminum surface may be excessively corroded.

[0094] The degreasing process involves thorough rinsing with purified water followed by etching in an acidic solution containing 100 kg of sulfuric acid at 40-50°C for 3-7 minutes. This process removes the surface oxide film, creating fine irregularities that play a crucial role in subsequent processes by enhancing the adhesion of the vacuum-deposited layer.

[0095] After the etching process, the material is washed again with pure water and then neutralized in a neutralization solution containing 100 g / w of phosphoric acid at 35-45°C for 2-5 minutes. The neutralized material is then dried with hot air at 80-90°C for 5-10 minutes to complete the pretreatment process.

[0096] The vacuum deposition process is performed under a high vacuum of 10⁻⁵ to 10⁻⁶ Torr. The first layer of metal deposited is based on a total weight fraction of 100 units of the deposited metal, including 60-70 units of Cu, 20-30 units of Ni, and 5-15 units of Cr. Vacuum deposition is carried out at a substrate temperature of 200-300 °C, preferably [missing value]. The deposition rate is determined.

[0097] In the electroless plating process, an electroplating solution containing 25-30 parts by weight of nickel sulfate, 20-25 parts by weight of sodium hypophosphite, 15-20 parts by weight of sodium acetate, and 1-3 parts by weight of stabilizer is used as the base of a 1000 parts by weight aqueous solution. Electroplating is carried out for 30-40 minutes at a pH of 4.5-5.0 and a temperature of 80-85°C, during which stirring at 150-200 rpm is important.

[0098] The electroplating solution used in the electroplating process contains 250-300 parts by weight of nickel sulfate, 30-40 parts by weight of nickel chloride, 35-45 parts by weight of boric acid, and 0.5-1.5 parts by weight of polishing agent, based on a 1000 parts by weight aqueous solution. Electroplating is performed at a current density of 2.0-3.0 A / dm³. 2 Perform the test at a temperature of 40-50℃ for 60-60 minutes, ideally maintaining a distance of 15-20cm between the anode and cathode.

[0099] For quality control of the surface treatment layer formed according to the present invention, the surface roughness (Ra) shall be controlled within 0.2-0.5 μm, and a result of 4B or higher must be obtained in the adhesion test according to ASTM D3359 standard. Furthermore, the salt spray test should show corrosion resistance of more than 500 hours and a Vickers hardness of more than 500 Hv, and the thickness uniformity should be controlled within ±10% deviation.

[0100] The advantage of the surface treatment method of the present invention is that by applying optimized conditions to each process step, a surface treatment layer with excellent adhesion, corrosion resistance and wear resistance can be stably formed.

[0101] Example

[0102] [Examples and Comparative Examples]

[0103] [Table 1]

[0104] Process conditions and comparative examples of each embodiment

[0105]

[0106]

[0107] [Detailed Description of Specific Implementation Examples]

[0108] Example 1 is the most representative embodiment of the present invention, wherein the degreasing process is carried out at 65°C for 7 minutes, etching is carried out at 45°C for 5 minutes, and neutralization treatment is carried out at 40°C for 3 minutes. Vacuum deposition is performed at a vacuum degree of 2×10⁻⁵ Torr, with a composition of Cu65, Ni25, and Cr10 by weight. The sample prepared under these conditions showed a 5B grade in the adhesion test and no corrosion occurred after 600 hours of salt spray testing.

[0109] [Analysis of problems in comparative examples]

[0110] Comparative Example 1 shows a case where insufficient pretreatment temperature and time resulted in incomplete surface cleaning, leading to deterioration of adhesion in subsequent processes (Grade 2B). Comparative Example 2 shows a case where excessive processing conditions caused surface damage to the aluminum material, resulting in deterioration of mechanical properties.

[0111] Comparative Examples 3-5 illustrate cases where the composition ratio of the vacuum-deposited layers exceeds the optimal range, and the following problems were identified:

[0112] Comparative Example 3: Insufficient Cu content leads to poor adhesion (Grade 3B)

[0113] - Comparative Example 4: Excess copper led to deterioration of corrosion resistance (corrosion occurred after 300 hours of salt spray).

[0114] Comparative Example 5: Excessive Cr leads to increased brittleness and cracking.

[0115] [Analysis of Evaluation Results]

[0116] [Table 2]

[0117] Example of physical performance evaluation results and comparative case

[0118]

[0119]

[0120] In Examples 1-5, all samples exhibited excellent adhesion of 4B or higher and corrosion resistance exceeding 570 hours. In particular, Example 1 demonstrated the best overall performance, which was attributed to the optimization of pretreatment conditions and the composition of the vacuum-deposited layer.

[0121] The results of these experiments confirm that the process conditions and component ratios proposed in this invention are crucial for forming an excellent surface treatment layer.

Claims

1. A surface treatment method for aluminum die-casting materials, wherein, include: Pretreatment steps for degreasing, etching, neutralizing and drying the surface of aluminum die-casting materials, including Si4-10 weight parts and Cu2-5 weight parts based on aluminum 100 weight parts. Metal deposition is performed on the pretreated surface at a vacuum of 10⁻⁵ to 10⁻⁶ Torr to form a first metal layer; A second metal layer is formed by electroless plating on the first metal layer; and Electroplating is performed on the second metal layer to form the third metal layer.

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