WO2019144492A1

WO2019144492A1 - Metal surface coloring process as replacement for die-cast aluminum anodization

Info

Publication number: WO2019144492A1
Application number: PCT/CN2018/080470
Authority: WO
Inventors: 王颖; 黄翠刚
Original assignee: 宁波沈鑫电子有限公司
Priority date: 2018-01-23
Filing date: 2018-03-26
Publication date: 2019-08-01
Also published as: CN108300996A; CN108300996B

Abstract

Disclosed is a metal surface coloring process as a replacement for die-cast aluminum anodization, the process involving polishing a die-cast aluminum product and then sandblasting same; subjecting the sandblasted aluminum product to a surface nickelizing treatment and a surface aluminum nitride layer forming treatment; subjecting the treated aluminum product to high pressure water washing and then to a de-oiling procedure; placing the de-oiled aluminum product in sodium hydroxide vapor for corrosion and then in a sulfuric acid solution for neutralization, and then washing same with water; plating the surface of the aluminum product with a nickel plating layer in an alkaline electroless nickel-plating solution; and in a designed electrolyte solution, plating the outer surface of the nickel plating layer of the nickel-plated aluminum product with a protective paint layer of a designed color by means of an anodizing process. By means of the nickel-plating treatment carried out on the surface of the aluminum product, the types of colors that can be used for a protective paint on the surface of the aluminum product are increased, due to the fact that the nickel plating layer has a good adhesion effect for electrolyte solutions for protective paints of all colors in the prior art.

Description

Metal surface coloring process instead of die-cast aluminum anode

Technical field

The invention belongs to the technical field of metal surface treatment, in particular to a metal surface coloring process instead of a die-cast aluminum anode.

Background technique

Although aluminum and its alloys are widely used, since aluminum has a low electrode potential, contact corrosion is highly likely to occur when it is in contact with a high-potential metal in a humid environment. In addition, in the manufacturing process, aluminum alloys are added with various alloying elements due to the pursuit of high mechanical properties and other comprehensive properties. The presence of these elements makes the internal chemical composition and organization of the aluminum alloy uneven, plus heat treatment and processing. The existence of residual stress makes the aluminum alloy material easily cause micro-cell corrosion in the use environment. Moreover, in the environment of use of aluminum alloy, there is inevitably humid air. These humid air condense on the surface of the aluminum alloy material to form a water film, and more serious is the presence of a certain amount of Cl-, SO2, H2S, CO2, etc. in humid air. Substance, in this case, aluminum alloy materials are more prone to pitting, intergranular corrosion, stress corrosion and other forms of damage.

Die-casting aluminum anodizing is a difficult point in the die-casting industry, and the die-cast aluminum anodized products have a single color, limited to limited color types such as black and aluminum, and cannot meet the color requirements of die-cast aluminum products.

Summary of the invention

The invention provides a metal surface coloring process instead of a die-cast aluminum anode, and the purpose thereof is to solve the problem that the corrosion resistance of the die-cast aluminum in the prior art is not high and the color of the die-cast aluminum product is single.

The invention is achieved by the following technical solutions:

A metal surface coloring process for replacing a die-cast aluminum anode, comprising the following steps;

1) After the aluminum product finished by die casting is polished, sandblasting is performed;

2) subjecting the blasted aluminum product to surface nickel plating and forming a surface aluminum nitride layer;

3) the aluminum product treated in step 3) is subjected to a degreasing process after being subjected to high pressure water washing;

4) The aluminum product after degreasing is eroded in 0.3-0.5 MPa sodium hydroxide vapor for 2 minutes, then placed in a 10-20% sulfuric acid solution and then washed with water;

5) step 4) the water-washed aluminum product is electroplated with a nickel layer on the surface of the aluminum product in an alkaline electroless nickel plating solution;

6) In the designed electrolyte, an aluminum alloy for electroplating the nickel layer is coated with a protective paint layer of a design color on the outer surface of the nickel layer of the aluminum product by an anodizing process.

The blasting treatment is ceramic blasting, and the surface roughness of the die-cast aluminum parts is controlled to be 40-60 μm.

The method for preparing nickel on the surface of the die-cast aluminum part and forming a surface aluminum nitride layer is

The processed die-cast aluminum parts are sealed, and the sealed die-cast aluminum parts are buried in a mixture of nickel nitride and carbon, heated to 350 ° C -380 ° C under a nitrogen atmosphere of 0.3-1 MPa, and kept at 0.5-2. Hours, then to room temperature;

The mass ratio of the nickel nitride to the carbon is 1:10-1:5.

The degreaser in the degreasing step is an organic degreaser and an alkaline salt solution, a caustic degreaser or an alkaline salt deoiling solution.

The sodium hydroxide is 3-10 grams per cubic meter of sodium hydroxide vapor.

The alkaline electroless nickel plating solution is calculated by weight percentage, and its composition is:

The beneficial effects of the invention are:

Before the nickel plating layer is carried out, the surface is first nickel-plated and the surface aluminum nitride layer is formed, so that nickel is infiltrated between the gaps of the aluminum product by the nickel-plating process, and then the aluminum and the surface of the aluminum product are passed through the aluminum. The aluminum nitride protective layer is formed, which can prevent oxidation reaction between aluminum and oxygen, and can improve the bonding force between the nickel plating layer and the surface of the aluminum product.

The technical solution is to use the sodium hydroxide vapor erosion instead of immersing the aluminum product in the sodium hydroxide solution, which is the erosion shape of the surface of the aluminum product by using pressurized sodium hydroxide vapor and the erosive shape of the aluminum product immersed in the sodium hydroxide solution. Differently, the sodium hydroxide vapor has a uniform shape and similar shape on the surface of the aluminum product, which can ensure the uniform bonding force between the protective paint layer and the surface of the aluminum product, and improve the adhesion effect.

The technical solution increases the type of color of the protective lacquer that can be used for the surface of the aluminum product by treating the nickel plating layer on the surface of the aluminum product, because the nickel plating layer can have a very strong electrolyte for the protective lacquer of all colors of the prior art. Good with the effect.

Detailed ways

The following is a detailed description of the technical solutions of the present invention by way of examples, and the following embodiments are merely illustrative and are not to be construed as limiting the technical solutions of the present invention.

The technical solution provides a metal surface coloring process instead of the die-cast aluminum anode, comprising the following steps: 1) subjecting the die-cast aluminum product to a sandblasting treatment after being polished; in the present application, the polishing process is prior art Any process suitable for the polishing process in the prior art is applicable to the technical solution of the present application, and therefore, in the present application, the polishing process will not be described in detail.

In the present application, the ceramic blasting technique is used, and the surface roughness of the aluminum product is controlled to be 40-60 μm. In the present technical solution, the reason why the other sand blasting technique is not used is that the ceramic used in the present application is an alumina ceramic to prevent the infiltration of elements such as silicon and iron during the sand blasting process due to the action of pressure. It affects the final treatment effect on the surface of the aluminum product, especially the adhesion between the nickel plating layer and the surface of the aluminum product.

2) subjecting the blasted aluminum product to nickel in surface and forming a surface aluminum nitride layer; sealing the processed aluminum product, and burying the sealed aluminum product in a mixture of nickel nitride and carbon In the case of 0.3-1 MPa nitrogen atmosphere, it is heated to 350 ° C - 380 ° C, and kept for 0.5-2 hours, and then lowered to room temperature.

The mass ratio of nickel nitride to carbon is 1:10-1:5.

In this process, nickel nitride is decomposed into nitrogen and metallic nickel at 350 ° C - 380 ° C. At this temperature, metallic nickel in contact with the surface of the aluminum product penetrates into the surface of the aluminum product, and at this temperature, carbon does not It will penetrate into the surface of the aluminum product and will not react with the aluminum on the surface of the aluminum product to form aluminum carbide, which will affect the subsequent processing. Here, the surface of the treated aluminum product was subjected to electron microscope observation and spectral analysis to obtain a composition in which carbon penetrated into the surface of the aluminum product and aluminum carbide.

By nickel permeation on the surface of the aluminum product, it first closes the pores on the surface of the aluminum product, prevents the entry of air, avoids contact with oxygen, and on the other hand, the nickel-plated layer has a high degree of bonding with the surface of the aluminum product, and can avoid the use of electroplating. In the nickel process, because the plating time is short, the nickel layer covers quickly, and the pores on the surface of the aluminum product are covered by the nickel plating layer instead of being filled, that is, in the prior art nickel plating layer, the pores on the surface of the aluminum product are not Filled, but only covered, so that the pores on the surface of the aluminum product after nickel plating still exist, and some of the pores have water molecules in the plating solution, so that a chemical battery is formed at the pores, and Affect the corrosion resistance of aluminum products.

The technical solution is to infiltrate into the gap of the aluminum product by the infiltration method before the nickel plating layer is carried out, and fill the pores of the aluminum product, which is also the prior art even the zinc coating layer. The problem of pores on the surface of aluminum products cannot be solved, and at the same time, the technique of using a sacrificial layer of a zinc coating layer is not required.

3) The aluminum product treated in the step 3) is subjected to a degreasing process after being subjected to high-pressure water washing; the degreasing agent in the degreasing step is an organic degreaser and an alkaline salt solution, a caustic degreaser or an alkaline salt degreasing. liquid.

The specific degreasing agent used is determined according to the oil stain on the surface of the aluminum product.

4) The aluminum product after degreasing is eroded in 0.3-0.5 MPa sodium hydroxide vapor for 2 minutes, then placed in 10-20% sulfuric acid solution and then washed with water; sodium hydroxide per cubic meter of sodium hydroxide vapor It is 3-10 grams. In the present application, the preparation of sodium hydroxide vapor is prior art, and therefore, in each of the examples of the present application, the method of preparing sodium hydroxide will not be described.

The technical solution uses sodium hydroxide vapor to erode the surface of the aluminum product because the aluminum product is immersed in the sodium hydroxide solution, no matter how fast, it forms a liquid on the surface of the aluminum product before the neutralization of the acid solution. The flow of the droplets and the flow paths formed by the flow of the sodium hydroxide solution on the surface of the aluminum product. These flow paths cause the erosion of the aluminum product to continue, and some portions of the erosion are stopped, thus resulting in erosion. The erosion shape of the surface of the aluminum product is uneven and the contact area of the surface of the aluminum product is increased.

The steam of the present application achieves erosion of the surface of the aluminum product by collision, does not form a flow path on the surface of the aluminum product, and under the same pressure, the shape of the surface of the aluminum product after erosion is substantially the same, and increases The area is much larger than the area of erosion intrusion into the sodium hydroxide solution.

5) The aluminum product after the step 4) is washed with a nickel layer on the surface of the aluminum product in an alkaline electroless nickel plating solution; in the present application, the pH of the electroless nickel plating solution is 8.0-9.0.

6) In the designed electrolyte, an aluminum alloy for electroplating a nickel layer is subjected to an anodizing process to coat a protective paint layer of a design color on the outer surface of the nickel layer of the aluminum product.

Alkaline electroless nickel plating solution, calculated by weight percentage, consisting of:

In the embodiments of the present application, the surface treatment process of the aluminum product is completely the same, and the difference can only be the surface nickel plating and the parameters for forming the surface aluminum nitride layer, the pressure of the sodium hydroxide vapor, and the alkaline electroless nickel plating solution. The composition is different.

Example 1

The method for preparing nickel in surface and forming a surface aluminum nitride layer is

The processed aluminum product is sealed, and the sealed aluminum product is buried in a mixture of nickel nitride and carbon, heated to 350 ° C under a nitrogen atmosphere of 0.3 MPa, and kept for 0.5 hour, and then lowered to room temperature;

The mass ratio of nickel nitride to carbon is 1:5.

The degreased aluminum product was etched in 0.3 MPa sodium hydroxide vapor for 2 minutes, then placed in a 20% sulfuric acid solution and then washed with water; sodium hydroxide was 3 grams per cubic meter of sodium hydroxide vapor.

NaCL12.6H ₂ O is 8%; NiSO ₄ .6H ₂ O is 10%; NaHPO ₂ .2H ₂ O is 9%; (NH ₄ ) ₃ C ₆ H ₅ O ₇ is 20%; complexing agent is 20% NH ₄ CL was 12%; NH ₄ OH was 21%.

Example 2

The processed aluminum product is sealed, and the sealed aluminum product is buried in a mixture of nickel nitride and carbon, heated to 380 ° C in a nitrogen atmosphere of 1 MPa, and kept for 2 hours, and then cooled to room temperature;

The mass ratio of nickel nitride to carbon is 1:10.

The degreased aluminum product was etched in 0.5 MPa sodium hydroxide vapor for 2 minutes, then placed in a 10% sulfuric acid solution and then washed with water; sodium hydroxide was 5 g per cubic meter of sodium hydroxide vapor.

NaCL12.6H ₂ O is 9%; NiSO ₄ .6H ₂ O is 11%; NaHPO ₂ .2H ₂ O is 8%; (NH ₄ ) ₃ C ₆ H ₅ O ₇ is 19%; complexing agent is 19% NH ₄ CL is 12%; NH ₄ OH is 22%.

Example 3

The processed aluminum product is sealed, and the sealed aluminum product is buried in a mixture of nickel nitride and carbon, heated to 360 ° C under a nitrogen atmosphere of 0.5 MPa, and kept for 1 hour, and then cooled to room temperature;

The mass ratio of nickel nitride to carbon is 1:8.

The degreased aluminum product was etched in 0.4 MPa sodium hydroxide vapor for 2 minutes, then placed in a 15% sulfuric acid solution and then washed with water; sodium hydroxide was 4 grams per cubic meter of sodium hydroxide vapor.

NaCL12.6H ₂ O is 8%; NiSO ₄ .6H ₂ O is 10.5%; NaHPO ₂ .2H ₂ O is 8.5%; (NH ₄ ) ₃ C ₆ H ₅ O ₇ is 19.5%; complexing agent is 19.5% NH ₄ CL was 12.5%; NH ₄ OH was 21.5%.

Although the technical solutions of the present invention have been described in detail, it is apparent to those skilled in the art that the modifications, substitutions, and modifications of the present invention are all within the scope of the present application.

Claims

A metal surface coloring process for replacing a die-cast aluminum anode, characterized by comprising the following steps;

1) After the aluminum product finished by die casting is polished, sandblasting is performed;

2) subjecting the blasted aluminum product to surface nickel plating and forming a surface aluminum nitride layer;

3) the aluminum product treated in step 3) is subjected to a degreasing process after being subjected to high pressure water washing;

4) The aluminum product after degreasing is eroded in 0.3-0.5 MPa sodium hydroxide vapor for 2 minutes, then placed in a 10-20% sulfuric acid solution and then washed with water;

5) step 4) the water-washed aluminum product is electroplated with a nickel layer on the surface of the aluminum product in an alkaline electroless nickel plating solution;

6) In the designed electrolyte, an aluminum alloy for electroplating the nickel layer is coated with a protective paint layer of a design color on the outer surface of the nickel layer of the aluminum product by an anodizing process.
The metal surface coloring process for replacing a die-cast aluminum anode according to claim 1, wherein the blasting treatment is ceramic blasting, and the surface roughness of the die-cast aluminum part is controlled to be 40-60 μm.
The metal surface coloring process for replacing a die-cast aluminum anode according to claim 1, wherein the surface of the die-cast aluminum part is nickel-plated and a surface aluminum nitride layer is formed,

The processed die-cast aluminum parts are sealed, and the sealed die-cast aluminum parts are buried in a mixture of nickel nitride and carbon, heated to 350 ° C -380 ° C under a nitrogen atmosphere of 0.3-1 MPa, and kept at 0.5-2. Hours, then to room temperature;

The mass ratio of the nickel nitride to the carbon is 1:10-1:5.
The metal surface coloring process for replacing a die-cast aluminum anode according to claim 1, wherein the degreasing agent of the degreasing step is an organic degreaser and an alkaline salt solution, a caustic degreaser or an alkaline solution. Salt removes oil.
The metal surface coloring process for replacing a die-cast aluminum anode according to claim 1, wherein the sodium hydroxide is 3-10 grams per cubic meter of the sodium hydroxide vapor.
The metal surface coloring process for replacing a die-cast aluminum anode according to claim 1, wherein the alkaline electroless nickel plating solution is calculated by weight percentage, and the composition thereof is: