US20160168742A1

US20160168742A1 - Method for anodizing aluminum alloy workpiece, method for surface treating aluminum alloy workpiece, and anodizing solution mixes

Info

Publication number: US20160168742A1
Application number: US14/754,270
Authority: US
Inventors: Shyan-Juh Liu; Sha-Sha Liu
Original assignee: Futaihua Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Current assignee: Futaihua Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Priority date: 2014-12-12
Filing date: 2015-06-29
Publication date: 2016-06-16
Also published as: CN105734640A; TW201621095A

Abstract

A method for surface treating an aluminum alloy workpiece having zinc and magnesium includes: providing the aluminum alloy workpiece; polishing the aluminum alloy to achieve a mirror effect; degreasing the aluminum alloy workpiece; stripping a black film formed on the aluminum alloy workpiece; anodizing the aluminum alloy workpiece in an anodizing solution which includes acidic solution and an additive with a concentration of 0.5 mg/L to 25 g/L to form an oxidation film on the surface of the aluminum alloy workpiece, wherein the additive including at least one compound selected from a group consisting of adipic acid, 1,2,3-Benzotriazole, oxalic acid, sodium malate, and glycerin; and sealing the aluminum alloy workpiece. This disclosure further provides an anodizing solution applied in the method for surface treating an aluminum alloy workpiece and a method for anodizing the aluminum alloy workpiece using the same.

Description

FIELD

The subject matter herein generally relates to a method for anodizing aluminum alloy workpiece, a method for surface treating aluminum alloy workpiece, and anodizing solution mixes.

BACKGROUND

Aluminum alloy having zinc and magnesium is light, has low density, high strength, and good heat dissipation, so it is widely used as housings of electronics. However, if the aluminum alloy having zinc and magnesium is anodized to acquire a mirror surface, intermetallic compounds, such as Cu, Zn or MgZn2, may dissolved prior to the aluminum base, thus there may be some bank marks and corrosion spots occurred on the surface of the aluminum alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by way of example only, with reference to the attached figures.

FIG. 1 is a flowchart of an embodiment of a method for surface treating an aluminum alloy workpiece.

FIG. 2 is a table showing steps and parameters of embodiment 1 through embodiment 6 and comparative embodiment 1 through embodiment 6.

FIG. 3 is a table showing steps and parameters of embodiment 7 through embodiment 9 and comparative embodiment 7.

FIG. 4 is a table showing test results of gloss and observation of surface topography of embodiment 1 through embodiment 9.

FIG. 5 is a table showing test results of gloss and observation of surface topography of comparative embodiment 1 through embodiment 4.

FIG. 6 is a table showing test results of gloss and observation of surface topography of comparative embodiment 5 through embodiment 7.

FIG. 7 is a microphotograph of the surface of the aluminum alloy workpiece in embodiment 1.

FIG. 8 is a microphotograph of the surface of the aluminum alloy workpiece in comparative embodiment 1.

FIG. 9 is a three dimensional surface topography photo of the aluminum alloy in embodiment 1.

FIG. 10 is a three dimensional surface topography photo of the aluminum alloy in comparative embodiment 1.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure.
The present disclosure is relation to methods for surface treating and anodizing an aluminum alloy having zinc and magnesium, and anodizing solution thereof.
Referring to FIG. 1, a flowchart of an example embodiment of a method for surface treating an aluminum alloy having zinc and magnesium which being thus illustrated. The example method 100 is provided by way of example, as there are a variety of ways to carry out the method. Each block shown in FIG. 1 represents one or more processes, methods or subroutines, carried out in the example method 100. Additionally, the illustrated order of blocks is by example only and the order of the blocks can change according to the present disclosure. The example method 100 can begin at block 101.
At block 101, an aluminum alloy workpiece having zinc and magnesium can be provided.
At block 102, the aluminum alloy workpiece can be polished to achieve a bright, smooth mirror effect. In at least one embodiment, an surface of the aluminum alloy workpiece can be polished by chemical mechanical polishing, and the polishing step can include a sanding step and a precision grinding step. A temperature of the sanding step can be in a range from about 23 degrees centigrade to about 30 degrees centigrade, and a period of the sanding step can be in a range from about 10 minutes to about 15 minutes. A temperature of the precision grinding step can be in a range from about 23 degrees centigrade to about 30 degrees centigrade, and a period of the precision grinding step can be in a range from about 10 minutes to about 15 minutes.
At block 103, the aluminum alloy workpiece can be degreased to remove oil from the surface thereof, and the surface of the aluminum alloy workpiece can be hydrophilic. A period of the degreasing step can be in a range from about 3 minutes to about 5 minutes, and a temperature of the degreasing step can be in a range from about 50 degrees centigrade to 60 degrees centigrade. A degreasing solution can include sodium phosphate, and a mass concentration of the sodium hydroxide can be in a range from about 40 grams per liter (g/L) to about 70 grams per liter (g/L).
At block 104, a black layer formed after polishing can be stripped away from the surface of the aluminum alloy workpiece by immersing the aluminum alloy workpiece into an acid solution. A temperature of the degreasing step can be room temperature. A period can be in a range from about 20 seconds to about 120 seconds. The acid solution can be a sulfuric acid solution, and a volume ratio of the sulfuric acid solution can be in a range from about 15 percent to about 35 percent.
At block 105, the aluminum alloy workpiece can be anodized by an anodizing treatment, such that an oxidation film is formed on the surface of the aluminum alloy workpiece. The oxidation film can be a porous Al₂O₃film having a plurality of micro-holes therein. A period of the anodizing step can be in a range from about 20 minutes to about 50 minutes. A voltage of the anodizing step can be in a range from about 6 volts to about 10 volts, and a temperature can be about 18 degrees Celsius to 26 degrees Celsius. An anodizing solution can include a sulfuric acid solution with a mass concentration from about 150 g/L to about 230 g/L and an additive with a mass concentration from about 0.5 milligram per liter (mg/L) to about 25 g/L. The additive can include at least one compound selected from a group consisting of adipic acid, 1,2,3-Benzotriazole, oxalic acid, sodium malate and glycerin.
At block 106, the aluminum alloy workpiece can be sealed by a sealing treatment in a sealing solution, such that the oxidation film can have a good wear resistance. A period of the sealing treatment can be in a range from about 15 minutes to about 20 minutes. A temperature of the sealing treatment can be in a range from about 90 degrees centigrade to 95 degrees centigrade. A sealing solution can be a nickel acetate solution with a mass concentration from about 5 g/L to about 10 g/L.
At block 107, the aluminum alloy workpiece can be dried by heating.
In other embodiments, between step 103 and step 107, there may be at least one step for washing the aluminum alloy workpiece.
In other embodiments, the aluminum alloy workpiece can be polished by other methods, such as mechanical polishing, chemical polishing, or electrolytic polishing. In other embodiments, the process at block 104 can be omitted if there is no black layer formed on the surface of the aluminum alloy workpiece after mechanical polishing.
In other embodiments, the degreasing solution at block 103 can be a caustic soda solution, a sodium carbonate solution, a sodium silicate solution, or a mixture solution. In other embodiments, the solution for stripping the black layer at block 104 can be a nitric acid solution or other solutions.
In other embodiments, the solution for anodizing at block 105 can be other acid solutions, such as a phosphoric acid solution, a chromic acid solution, an oxalic acid solution, or a mixture solution of the above solutions. In other embodiments, the sealing solution can be nickel sulfate, nickel fluoride, or a mixture solution of the above solutions.
For further explanation, detailed embodiments and comparative embodiments are described as follows.
Sixteen groups of aluminum alloy workpieces can be provided. Materials of the aluminum alloy workpieces can be AZ91D type Al—Mg—Zn aluminum alloys. The first group through the ninth group of aluminum alloy workpieces are treated by the method of the illustrated embodiment of this disclosure, serving and provided as embodiment 1 through embodiment 9. The tenth group through the sixteenth group of the aluminum alloy workpieces are treated by a method similar to the method of this disclosure, expect that the anodizing solution has no additive. The tenth group through the sixteenth group of the aluminum alloy workpieces are served and provided as comparative embodiment 1 through comparative embodiment 7. FIG. 2 and FIG. 3 shows the steps and respective corresponding parameters (i.e., the period, temperature) of embodiments 1-9 and comparative embodiment 1-7. The material ingredients and the concentrations of the solutions of embodiment 1-9 are described as follows. The material ingredients and the concentrations of the solutions of comparative embodiment 1-7 can be similar with the embodiments 1-9 expect that anodizing solution has no additive.

Embodiment 1

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 60 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid is about 20 percent.
In the anodizing step: the mass concentration of the sulfuric acid is about 200 g/L, and the additive is oxalic acid with a mass concentration of about 10 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 10 g/L.

Embodiment 2

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 50 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid is about 15 percent.
In the anodizing step: the mass concentration of the sulfuric acid solution is about 230 g/L, and the additive is adipic acid with a mass concentration of about 4 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 5 g/L.

Embodiment 3

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 40 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid is about 25 percent.
In the anodizing step: the mass concentration of the sulfuric acid solution is about 220 g/L, and the additive is 1,2,3-Benzotriazole with a mass concentration of about 4 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 10 g/L.

Embodiment 4

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 70 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid solution is about 30 percent.
In the anodizing step: the mass concentration of the sulfuric acid is about 190 g/L, and the additive is a mixture of oxalic acid and 1,2,3-Benzotriazole. A mass concentration of the oxalic acid is about 10 g/L, and a mass concentration of the 1,2,3-Benzotriazole is about 4 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 7 g/L.

Embodiment 5

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 45 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid solution is about 23 percent.
In the anodizing step: the mass concentration of the sulfuric acid solution can be 205 g/L, and the additive can be a mixture of oxalic acid and glycerin. A mass concentration of the oxalic acid is about 10 g/L, and a mass concentration of the glycerin is about 10 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 8 g/L.

Embodiment 6

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 48 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid solution is about 26 percent.
In the anodizing step: the mass concentration of the sulfuric acid is about 180 g/L, and the additive can be a mixture of oxalic acid and sodium malate. A mass concentration of the oxalic acid is about 10 g/L, and a mass concentration of the sodium malate is about 5 g/L.
In the sealing step: the mass concentration of the nickel acetate can be about 9 g/L.

Embodiment 7

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 42 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid solution is about 35 percent.
In the anodizing step: the mass concentration of the sulfuric acid is about 150 g/L, and the additive is a mixture of oxalic acid and glycerin. A mass concentration of the oxalic acid is about 10 g/L, and a mass concentration of the glycerin is about 15 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 8 g/L.

Embodiment 8

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 60 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid is about 20 percent.
In the anodizing step: the mass concentration of the sulfuric acid solution is about 200 g/L, and the additive is oxalic acid with a mass concentration of about 5 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 8 g/L.

Embodiment 9

The material ingredients and concentrations of the solutions are as follows.
In the degreasing step: the mass concentration of the sodium phosphate is about 50 g/L.
In the black layer stripping step: the volume concentration of the sulfuric acid is about 15 percent.
In the anodizing step: the mass concentration of the sulfuric acid is about 180 g/L, and the additive is adipic acid with a mass concentration of about 8 g/L.
In the sealing step: the mass concentration of the nickel acetate is about 5 g/L.
Three samples of each group of the Al—Mg—Zn aluminum alloy workpieces can be selected to test gloss and observe surface topography. The two dimensional surface topography of the samples can be observed under a microscope at 40 times magnification, and the three dimensional surface topography of the samples can be observed under a 3D surface profiler. FIG. 4 and FIG. 5 illustrate the results of gloss test and the observation of embodiment 1 through embodiment 9. Most of the gloss values of the Al—Mg—Zn aluminum alloy workpieces processed by the method of the embodiments of this disclosure are larger than 1300, and the largest gloss value is 1422. FIG. 6 illustrate the results of gloss test and the observation of comparative embodiment 1 through embodiment 7. Most of the gloss values of the Al—Mg—Zn aluminum alloy workpieces processed by the comparative embodiments are less than 1300, and the largest gloss value is 1303.
As the surface topography of the samples in embodiment 1 to embodiment 9 are similar, only a microphotograph of the sample processed by the method of embodiment 1 is provided. A microphotograph of the sample of comparative embodiment 1 is also provided.
FIG. 7 illustrates that the there is no obvious bank mark or corrosion spot on the surface of the Al—Mg—Zn aluminum alloy workpiece processed by the method of embodiment 1 observed under microscope at 40 times magnification. FIG. 8 illustrates that there are obvious stripped bank marks and white corrosion spots on the surface of the Al—Mg—Zn aluminum alloy workpiece processed by the method of comparative embodiment 1 observed under microscope at 40 times magnification. FIG. 9 illustrates that three dimensional surface of the Al—Mg—Zn aluminum alloy workpiece processed by the method of embodiment 1 is smooth. FIG. 10 illustrates that three dimensional surface of the Al—Mg—Zn aluminum alloy workpiece processed by the method of the comparative embodiment 1 is rough. The appearance of the Al—Mg—Zn aluminum alloy processed by the method of embodiment can have no bank mark and have good gloss.
In the surface treating method for aluminum alloy having magnesium and zinc, the additive selected from a group consisting of adipic acid, 1,2,3-Benzotriazole, oxalic acid, sodium malate and glycerin is added in the anodizing solution. The additive can prevent preferential dissolution of intermetallic compounds, thus the appearance of the aluminum alloy can be improved, and the gloss of the aluminum alloy can be increased than conventional method.
The embodiments shown and described above are only examples. Many details are often found in the art such as the other features of methods of surface treating and anodizing aluminum alloy workpiece and a anodizing solution. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, comprising in matters of shape, size and arrangement of the parts within the principles of the present disclosure up to, and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.

Claims

What is claimed is:

1. An anodizing solution for an aluminum alloy workpiece having zinc and magnesium, the anodizing solution comprising:

a sulfuric acid with a mass concentration from about 150 g/L to 230 g/L; and

an additive with a mass concentration from about 0.5 mg/L to 25 mg/L;

wherein the additive comprises at least one compound selected from a group consisting of adipic acid, 1,2,3-Benzotriazole, oxalic acid, sodium malate, and glycerin.

2. A method for anodizing an aluminum alloy workpiece having zinc and magnesium, the method comprising:

anodizing the aluminum alloy workpiece using an anodizing solution, the anodizing solution comprising an acid solution and an additive with a mass concentration from about 0.5 mg/L to 25 mg/L;

3. The method as claimed in claim 2, wherein the acid solution is a sulfuric acid solution with a mass concentration from about 150 g/L to 230 g/L, a period of the anodizing process is from about 20 minutes to 50 minutes, a temperature of the anodizing process is from about 18 degrees Celsius to about 26 degrees Celsius, and a voltage of the anodizing process is from about 6 volts to about 10 volts.

4. A method for surface treating an aluminum alloy workpiece having zinc and magnesium , the method comprising:

supplying the aluminum alloy workpiece;

polishing a surface of the aluminum alloy workpiece such that a surface of the aluminum alloy workpiece achieve a mirror effect;

degreasing the aluminum alloy workpiece;

anodizing the aluminum alloy to form an oxidation film on the surface of the aluminum alloy workpiece using an anodizing solution which comprising an acid solution and an additive with a mass concentration from about 0.5 mg/L to 25 mg/L, the additive comprising at least one compound selected from a group consisting of adipic acid, 1,2,3-Benzotriazole, oxalic acid, sodium malate, and glycerin; and

sealing the aluminum alloy workpiece using a sealing solution.

5. The method as claimed in claim 4, further comprising stripping a black film formed on the surface of the aluminum alloy workpiece after degreasing the aluminum alloy workpiece.

6. The method as claimed in claim 5, wherein the black film is stripped using a sulfuric acid solution, a period of stripping the black film is in a range from about 20 seconds to 120 seconds, and a temperature of stripping the black film is room temperature.

7. The method as claimed in claim 4, wherein the acid solution of anodizing the aluminum alloy workpiece is a sulfuric acid solution with a mass concentration from about 150 g/L to about 230 g/L, a period of anodizing is in a range from about 20 minutes to about 50 minutes, a temperature of anodizing is in a range from about 18 degrees Celsius to about 26 degrees Celsius, and a voltage of anodizing is in range from about 6 volts to about 10 volts.

8. The method as claimed in claim 4, wherein a period of degreasing the aluminum alloy workpiece is in a range from about 3 minutes to 5 minutes, a temperature of degreasing is in a range from about 50 minutes to about 60 minutes, and a degreasing solution comprises sodium phosphate with a mass concentration of 40 g/L to 70 g/L.

9. The method as claimed in claim 4, wherein a period of sealing the aluminum alloy workpiece is in a range from about 15 minutes to about 20 minutes, a temperature of the sealing is in a range from 90 degrees Celsius to about 95 degrees Celsius, and a sealing solution comprises nickel acetate with a mass concentration of 5 g/L to 10 g/L.

10. The method as claimed in claim 4, wherein aluminum alloy is washed in water and dried after being sealed.