U.S. patent application number 17/242554 was filed with the patent office on 2022-07-07 for electrolyte for micro-arc oxidation and method for dyeing substrate therein.
The applicant listed for this patent is GIANT GLORY INTERNATIONAL LIMITED. Invention is credited to Steven HONG, Dunstan HUANG, Huan LIU.
Application Number | 20220213611 17/242554 |
Document ID | / |
Family ID | 1000005598314 |
Filed Date | 2022-07-07 |
United States Patent
Application |
20220213611 |
Kind Code |
A1 |
HONG; Steven ; et
al. |
July 7, 2022 |
ELECTROLYTE FOR MICRO-ARC OXIDATION AND METHOD FOR DYEING SUBSTRATE
THEREIN
Abstract
Disclosed is an electrolyte for micro-arc oxidation, which
includes silicate, a fluoride, an alkali metal hydroxide, a pore
modifier selected from at least one of triethanolamine and
diethanolamine, and a polar solvent. Also disclosed is a method for
dyeing a substrate which includes immersing a metal substrate as an
anode into the electrolyte, oxidizing the substrate to form an
oxide layer on the substrate, applying a solution containing a dye
on the oxide layer, and allowing the dye to adhere on the oxide
layer, so as to obtain a half-finished product, and forming a
sealing layer on the half-finished product.
Inventors: |
HONG; Steven; (Taizhou,
CN) ; HUANG; Dunstan; (New Taipei City, TW) ;
LIU; Huan; (Taizhou, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GIANT GLORY INTERNATIONAL LIMITED |
Apia |
|
WS |
|
|
Family ID: |
1000005598314 |
Appl. No.: |
17/242554 |
Filed: |
April 28, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 11/30 20130101;
C25D 11/026 20130101 |
International
Class: |
C25D 11/02 20060101
C25D011/02; C25D 11/30 20060101 C25D011/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 5, 2021 |
CN |
202110007847.2 |
Claims
1. An electrolyte used for micro-arc oxidation, comprising: a
silicate; a fluoride; an alkali metal hydroxide; a pore modifier
selected from at least one of triethanolamine and diethanolamine;
and a polar solvent.
2. The electrolyte used for micro-arc oxidation as claimed in claim
1, wherein said pore modifier has a concentration ranging between
0.1 g/L and 5 g/L.
3. The electrolyte used for micro-arc oxidation as claimed in claim
1, wherein said silicate is selected from at least one of sodium
silicate and potassium silicate.
4. The electrolyte used for micro-arc oxidation as claimed in claim
1, wherein said fluoride is selected from at least one of sodium
fluoride and potassium fluoride.
5. The electrolyte used for micro-arc oxidation as claimed in claim
1, wherein said alkali metal hydroxide is selected from at least
one of sodium hydroxide and potassium hydroxide.
6. The electrolyte used for micro-arc oxidation as claimed in claim
1, wherein said silicate is selected from at least one of sodium
silicate and potassium silicate, said fluoride is selected from at
least one of sodium fluoride and potassium fluoride, and said
alkali metal hydroxide is selected from at least one of sodium
hydroxide and potassium hydroxide.
7. The electrolyte used for micro-arc oxidation as claimed in claim
1, wherein said polar solvent is water.
8. The electrolyte used for micro-arc oxidation as claimed in claim
1, wherein said electrolyte has a pH value greater than 7 and not
greater than 11.
9. A method for dyeing a substrate, comprising: providing a
substrate made of magnesium or magnesium alloy; immersing the
substrate as an anode into the electrolyte as claimed in claim 1;
oxidizing the substrate to form an oxide layer on the substrate,
the oxide layer having a plurality of pores; applying a solution
containing a dye on the oxide layer, and allowing the dye to adhere
on the oxide layer and to enter into at least a part of the pores,
so as to obtain a half-finished product; and forming a sealing
layer on the half-finished product so that the sealing layer wraps
the oxide layer and the dye.
10. The method as claimed in claim 9, wherein oxidizing the
substrate is conducted by micro-arc oxidation.
11. The method as claimed in claim 10, wherein oxidizing the
substrate is conducted in a voltage ranging between 450 V and 550
V, and an average current density across the substrate is 2
A/dm.sup.2.
12. The method as claimed in claim 9, wherein in oxidizing the
substrate, the electrolyte is maintained at a temperature ranging
between 25.degree. C. and 40.degree. C.
13. The method as claimed in claim 9, wherein oxidizing the
substrate is carried out for a period not less than 10 minutes.
14. The method as claimed in claim 9, wherein the oxide layer has a
thickness not less than 10 .mu.m, and the appearance of the oxide
layer is white.
15. The method as claimed in claim 9, wherein the pores have a pore
size ranging from 10 .mu.m to 25 .mu.m.
16. The method as claimed in claim 9, further comprising, after
oxidizing the substrate, cleaning the substrate and the oxide layer
so as to remove residue of the electrolyte.
17. The method as claimed in claim 9, wherein forming the sealing
layer is conducted by contacting the half-finished product with a
sealing solution that contains nickel acetate at a temperature
ranging from 25.degree. C. to 35.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority of Chinese Invention Patent
Application No. 202110007847.2, filed on Jan. 5, 2021.
FIELD
[0002] The disclosure relates to an electrolyte and a method for
dyeing a substrate therein, and more particularly to an electrolyte
for micro-arc oxidation and a method for dyeing a substrate
therein.
BACKGROUND
[0003] Portable electronic devices on the market are mainly
required to be thin and lightweight. Therefore, light metals, such
as aluminium alloys or magnesium alloys, are popular materials for
manufacturing casings of portable electronic devices due to their
excellent mechanical properties and low specific gravity. In
particular, magnesium alloys are valued for their good thermal
conductivity and shock resistance.
[0004] Casings made from magnesium alloys are usually subjected to
a dyeing process to modify the appearance thereof, so as to fulfill
the needs of consumers and to diversify the appearance of the
products thus made. However, magnesium alloys are highly reactive,
and thus, a substrate made of the magnesium alloys is usually
subjected to an anodic oxidation surface treatment to form an inert
porous film before the substrate is subjected to a dyeing process,
so as to prevent the substrate from corrosion that might result
from reaction thereof with vapor or other chemicals. During the
subsequent dyeing process, the inert porous film formed by the
anodic oxidation surface treatment allows more dye to be adhered on
the substrate, which results in an improved coloring effect.
[0005] Nevertheless, such dye tend to non-uniformly adhere to the
inert porous film due to the non-uniform distribution and the
non-uniform pore size of the pores formed in the inert porous film
by the anodic oxidation surface treatment, resulting in non-uniform
coloring of the substrate. Additionally, some pores are too small
in size such that the dye would not be effectively infiltrated into
the inert porous film, creating problems such as difficulty in
coloring and/or an inferior color fixation effect.
SUMMARY
[0006] Therefore, an object of the disclosure is to provide an
electrolyte for micro-arc oxidation that can alleviate at least one
of the drawbacks of the prior art.
[0007] Another object of the disclosure is to provide a method for
dyeing a substrate that can alleviate at least one of the drawbacks
of the prior art.
[0008] According to a first aspect of the disclosure, there is
provided an electrolyte used for micro-arc oxidation. The
electrolyte includes a silicate, a fluoride, an alkali metal
hydroxide, a pore modifier, and a polar solvent. The pore modifier
is selected from at least one of triethanolamine and
diethanolamine.
[0009] According to a second aspect of the disclosure, there is
provided a method for dyeing a substrate, which includes:
[0010] providing a substrate made of magnesium or magnesium
alloy;
[0011] immersing the substrate as an anode into the abovementioned
electrolyte;
[0012] oxidizing the substrate to form an oxide layer on the
substrate, the oxide layer having a plurality of pores;
[0013] applying a solution containing a dye on the oxide layer, and
allowing the dye to adhere on the oxide layer and to enter into at
least a part of the pores, so as to obtain a half-finished product;
and
[0014] forming a sealing layer on the half-finished product so that
the sealing layer wraps the oxide layer and the dye.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other features and advantages of the disclosure will become
apparent in the following detailed description of the embodiment
(s) with reference to the accompanying drawings, of which:
[0016] FIG. 1 is a schematic view illustrating a magnesium alloy
product made by an embodiment of a method for dyeing a substrate
according to the disclosure;
[0017] FIG. 2 is a scanning electron microscopic (SEM) image of an
oxide layer formed on a magnesium alloy substrate by micro-arc
oxidation in an embodiment of an electrolyte according to the
disclosure; and
[0018] FIG. 3 is an SEN image of an oxide layer formed on a
magnesium alloy substrate by micro-arc oxidation in a conventional
electrolyte.
DETAILED DESCRIPTION
[0019] Before the disclosure is described in greater detail, it
should be noted that where considered appropriate, reference
numerals or terminal portions of reference numerals have been
repeated among the figures to indicate corresponding or analogous
elements, which may optionally have similar characteristics.
[0020] An embodiment of an electrolyte used for micro-arc oxidation
according to the disclosure includes a silicate, a fluoride, an
alkali metal hydroxide, a pore modifier, and a polar solvent. The
pore modifier is selected from at least one of triethanolamine and
diethanolamine.
[0021] In some embodiments, the silicate is selected from at least
one of sodium silicate and potassium silicate.
[0022] In some embodiments, the fluoride is selected from at least
one of sodium fluoride and potassium fluoride.
[0023] In some embodiments, the alkali metal hydroxide is selected
from at least one of sodium hydroxide and potassium hydroxide.
[0024] In some embodiments, the silicate has a concentration
ranging from 20 g/L to 100 g/L, the alkali metal hydroxide has a
concentration ranging from 20 g/L to 100 g/L, and the fluoride has
a concentration ranging from 2 g/L to 15 g/L.
[0025] In some embodiments, the pore modifier has a concentration
ranging from 0.1 g/L to 5 g/L. When the electrolyte is used to
subject a magnesium alloy substrate to micro-arc oxidization, an
oxide layer having a plurality of pores is formed on the magnesium
alloy substrate. If the pore modifier has a concentration that is
too low, the amount of pores formed in the oxide layer will
decrease significantly and the size of the pore will also decrease,
such that in a dyeing process, a dye will not infiltrate deeply
into the oxide layer, which adversely affects the dyeing effect on
the magnesium alloy substrate. On the other hand, if the pore
modifier has a concentration that is too high, growth of the oxide
layer will be inhibited, and the thus formed oxide layer will have
a thickness of less than 10 .mu.m.
[0026] In some embodiments, the polar solvent is water (e.g.,
commercially available water, deionized water, etc.). In some
embodiments, the electrolyte has a pH value greater than 7 and not
greater than 11. In some embodiments, the polar solvent is
deionized water, which can be used to prevent additional impurities
from being produced by reduction of excess ions contained in the
water during the micro-arc oxidation.
[0027] Referring to FIG. 1, the aforementioned electrolyte is
hereby applied to an embodiment of a method for dyeing a substrate
according to the disclosure, which includes:
[0028] providing a substrate made of magnesium or magnesium
alloy;
[0029] immersing the substrate 1 as an anode into the
electrolyte;
[0030] oxidizing the substrate 1 to form an oxide layer 2 on the
substrate 1, the oxide layer 2 having a plurality of pores 22;
[0031] applying a solution containing a dye on the oxide layer 2,
and allowing the dye to adhere on the oxide layer 2 and to enter
into at least a part of the pores 22, so as to obtain a
half-finished product; and
[0032] forming a sealing layer 3 on the half-finished product so
that the sealing layer 3 wraps the oxide layer 2 and the dye.
[0033] In the step of immersing the substrate 1 as an anode into
the electrolyte, a carbon cathode is immersed into the electrolyte
as well. In the step of oxidizing the substrate 1, the substrate 1
is oxidized inwardly from a surface thereof to form an oxide layer
2 thereon. The oxide layer 2 is made of a metal oxide that is
formed by oxidation of magnesium or magnesium alloy. The oxide
layer 2 has a main body 21 and a plurality of pores 22 recessed
downwardly from atop surface of the main body 21. The pore size of
the pores 22 ranges from 10 .mu.m to 25 .mu.m, and the oxide layer
2 has a thickness not less than 10 .mu.m.
[0034] In some embodiments, the substrate 1 is oxidized by a
micro-arc oxidation. During the micro-arc oxidation, the
temperature of the electrolyte is controlled to range between
25.degree. C. and 40.degree. C., the applied voltage is controlled
to range between 450 V and 550 V, and the average current density
across the substrate 1 is controlled at 2 A/dm.sup.2. During
oxidation of the substrate 1, the substrate 1 serving as the anode
and the carbon cathode are immersed into the electrolyte, where a
gradually increasing voltage is applied continuously, such that a
discharge plasma reaction occurs continuously on a surface of the
substrate 1, permitting the magnesium or magnesium alloy on the
surface of the substrate 1 to form into metal oxide so as to obtain
the oxide layer 2. In some embodiments, oxidation of the substrate
1 is carried out for a period of not less than 10 minutes. The
oxide layer 2 has a thickness not less than 10 .mu.m, and the
appearance thereof is white.
[0035] According to the disclosure, triethanolamine or
diethanolamine is added into the electrolyte as the pore modifier,
such that the pores 22 produced during micro-arc oxidation of
magnesium or magnesium alloy have larger pore sizes and improved
uniformity. To be specific, when the substrate 1 as the anode is
oxidized, an electrolytic oxidation reaction will take place
thereon, such that a plurality of oxygen bubbles are generated near
the substrate 1. At the same time, the pore modifier is adsorbed on
the substrate 1, and thus, the size of the oxygen bubbles and the
adsorption intensity of the oxygen bubbles to the substrate 1 are
altered, which further enhance the uniformity of the pores 22
formed in the oxide layer 2. During the electrolytic oxidation
reaction, the pore modifier releases hydroxide ions to increase the
charge quantity on the substrate 1, thereby generating a micro-arc
discharge effect, which has a penetration effect on the oxide layer
2 and which is beneficial for increasing the pore size of the pores
22 in the oxide layer 2.
[0036] FIG. 2 is a scanning electron microscope (SEM) image of an
oxide layer 2 formed on a magnesium alloy substrate 1 by micro-arc
oxidation in the electrolyte of the disclosure, which includes
triethanolamine as the pore modifier in addition to silicate,
fluoride, alkali metal hydroxide, and water. As shown in FIG. 2,
the pores 22 in the oxide layer 2 formed after micro-arc oxidation
using the electrolyte of the disclosure have pore sizes mainly
ranging between 10 .mu.m and 25 .mu.m, and are evenly distributed
in the oxide layer 2. FIG. 3 is an SEM image of an oxide layer
formed on a magnesium alloy substrate by micro-arc oxidation in a
conventional electrolyte, which merely includes silicate, fluoride,
alkali metal hydroxide and water without the pore modifier. As
shown in FIG. 3, since the conventional electrolyte does not
include the pore modifier, the pore size of the pores formed in the
oxide layer ranges mainly between 3 .mu.m and 8 .mu.m, and only a
small portion of the pores have pore sizes ranging between 16 .mu.m
and 25 .mu.m. In other words, compared with a magnesium alloy
substrate treated by a conventional electrolyte for micro-arc
oxidation, a magnesium alloy substrate 1 treated by the electrolyte
of the disclosure for micro-arc oxidation has an increased pore
size and distribution uniformity of the pores 22 in the oxide layer
2, such that more filling space can be provided in the oxide layer
2 for adhering a dye in a subsequent dyeing step, which can improve
the uniformity of dyeing. In addition, the color of the oxide layer
2 formed by the electrolyte of the disclosure is white, which is
advantageous compared with the grayish-white color of the oxide
layer formed by using the conventional electrolyte since the white
oxide layer 2 does not affect the color fineness of the dye formed
thereon, resulting in a product having excellent color purity.
[0037] In this embodiment, the method further includes, after
oxidizing the substrate 1, cleaning the substrate 1 and the oxide
layer 2 so as to remove residue of the electrolyte. In some
embodiments, the substrate 1 and the oxide layer 2 are cleaned with
water.
[0038] The dye is adhered on the oxide layer 2 by applying a
solution containing the dye on the main body 21 of the oxide layer
2, such that the dye adheres on the main body 21 and enters into at
least part of the pores 22, so as to obtain a half-finished
product. In some embodiments, water cleaning can be conducted as
needed after the dye is completely adhered, in order to remove
residue of the solution or the dye that is not adhered on the oxide
layer 2, so that the coloring of the dye on the oxide layer 2 is
more uniform. In addition, since the oxide layer 2 has a thickness
not less than 10 .mu.m, the intensity of dyeing of the oxide layer
2 is thus increased. That is to say, since the oxide layer 2 formed
by the aforementioned micro-arc oxidization has a thickness not
less than 10 .mu.m, and also has the pores with high uniformity in
position and size distribution, the substrate 1, after adherence of
the dye, will have an appearance that is more uniform in color, and
occurrence of non-uniform adherence of the dye may be reduced.
[0039] The half-finished product is sealed by forming a sealing
layer 3 thereon so that the sealing layer 3 wraps the oxide layer 2
and the dye of the half-finished product. In this embodiment, the
sealing layer 3 is formed by contacting the half-finished product
with a sealing solution containing inorganic salt, which has a
temperature controlled to range between 25.degree. C. and
35.degree. C., such that the inorganic salt in the sealing solution
is deposited to fill the pores 22 in the oxide layer 2, so as to
form the sealing layer 3 on the oxide layer 2, thereby obtaining a
magnesium alloy product as shown in FIG. 1. In this embodiment, the
inorganic salt in the sealing solution is nickel acetate, but is
not limited thereto. By wrapping the dye in the sealing layer 3
formed by the sealing process, color fastness of the dyed magnesium
alloy product is further improved.
[0040] It should be noted that in addition to use of the sealing
solution containing the inorganic salt, the sealing layer 3 may be
formed by organic material sealing, moderate temperature sealing,
high temperature sealing, or other sealing techniques.
[0041] In some embodiments, after forming the sealing layer 3, a
cleaning and drying procedure can be conducted as needed to remove
residue of the sealing solution.
[0042] Examples of the disclosure will be described hereinafter. It
is to be understood that these examples are exemplary and
explanatory and should not be construed as a limitation to the
disclosure.
Example 1
[0043] Sodium silicate having a concentration of 30 g/L, potassium
fluoride having a concentration of 8 g/L and triethanolamine having
a concentration of 0.5 g/L were sequentially added into deionized
water, which was used as a solvent, and were mixed well by stirring
to obtain a solution. Potassium hydroxide was then added into the
solution to adjust the pH value of the solution to 8.5, so as to
obtain an electrolyte.
[0044] A substrate 1 made of AZ31B magnesium alloy was prepared for
oxidation. The substrate 1 as the anode and a carbon cathode were
immersed into the electrolyte, and a voltage of 450 V was applied
to generate an electric current so as to conduct micro-arc
oxidation. Oxidization of the substrate 1 was carried out for a
period of 10 minutes using an average current density of 2
A/dm.sup.2 across the substrate 1. The substrate 1 was oxidized
inwardly from its surface to form an oxide layer 2 thereon, the
oxide layer 2 being made of metal oxide formed from oxidation of
the magnesium alloy. The oxide layer 2 was white in color, and had
a thickness ranging between 10 .mu.m and 15 .mu.m. A plurality of
pores 22 were formed in the oxide layer 2, and the pore size of the
pores 22 ranged from 10 .mu.m to 25 .mu.m. The uniformity of the
location distribution of the pores 22 was 53%
( uniformity = 1 - D MAX - D min D avg .times. 100 .times. % ,
##EQU00001##
wherein D.sub.MAX is the maximum pore size of the pores 22 in a
specific region, D.sub.min is the minimum pore size of the pores 22
in the specific region, and D.sub.avg is the average pore size of
the pores 22 in the specific region), and the porosity of the oxide
layer 2 was 41%.
[0045] Subsequently, the substrate 1 formed with the oxide layer 2
was cleaned by washing with deionized water to avoid residue of the
electrolyte remaining on the oxide layer 2 and on the substrate
1.
[0046] Next, the substrate 1 formed with the oxide layer 2 was
immersed into a solution containing blue dye (TAC BLUE-RCD, Okuno
Chemical Industries Co., Ltd.) having a concentration of 5 g/L, so
as to dye the substrate 1 formed with the oxide layer 2 by virtue
of dip coating. The substrate 1 formed with the oxide layer 2 was
dyed for 17 minutes at a solution temperature of 55.degree. C. such
that the blue dye was adsorbed on the main body 21 of the oxide
layer 2 and entered into the pores 22. Pure water was then employed
to clean the substrate 1 twice to make sure that residue of the dye
was removed, thereby obtaining a half-finished product.
[0047] Finally, the half-finished product was immersing into a
sealing solution (Top Seal DX-500, Okuno Chemical Industries Co.,
Ltd.) having a concentration of 10 g/L and a temperature of
95.degree. C. for a period of 180 seconds, such that a sealing
layer 3 was formed on the oxide layer 2 to seal the half-finished
product. Residual sealing solution was then removed by a washing
procedure, in which the sealing layer 3 was sequentially washed
twice with water having an ambient temperature and once with hot
water having a temperature of 65.degree. C. A drying procedure was
then conducted at a drying temperature of 100.degree. C. for 600
seconds, thereby obtaining a magnesium alloy product with a light
blue appearance.
Example 2
[0048] An electrolyte similar to that in Example 1 was provided,
and a substrate 1 made of AZ31B magnesium alloy was prepared for
oxidation.
[0049] The procedures and conditions for oxidizing the substrate 1
were substantially the same as those in Example 1 except that the
applied voltage was 465 V. The oxide layer 2 thus obtained has a
white color, and the thickness thereof ranged from 10 .mu.m to 15
.mu.m. A plurality of pores 22 were formed in the oxide layer 2.
The pore size of the pores 22 ranged from 10 .mu.m to 25 .mu.m, the
uniformity of position distribution of the pores 22 was 53%, and
the porosity of the oxide layer 2 was 41%. Subsequently, the
substrate 1 formed with the oxide layer 2 was cleaned by washing
with deionized water to avoid residue of the electrolyte remaining
on the oxide layer 2 and the substrate 1.
[0050] Next, the substrate 1 formed with the oxide layer 2 was
immersed into a solution containing blue dye (TAC BLUE-RCD, Okuno
Chemical Industries Co., Ltd.) having a concentration of 5 g/L and
a temperature of 55.degree. C. for a period of 10 minutes, so that
the substrate 1 is dyed. The blue dye was adsorbed on the main body
21 of the oxide layer 2 and entered into at least part of the pores
22. Pure water was then employed to clean the substrate 1 twice to
make sure that residue of the dye was removed from the oxide layer
2, thereby obtaining a half-finished product. Finally, the
half-finished product was sealed by forming a sealing layer 3
according to the procedures described in Example 1, so as to obtain
a magnesium alloy product with a blue appearance.
Example 3
[0051] Sodium silicate having a concentration of 35 g/L, potassium
fluoride having a concentration of 7.5 g/L, and triethanolamine
having a concentration of 1 g/L were sequentially added into
deionized water that serves as a solvent, and then were mixed by
stirring to obtain a solution. Then, the pH value of the solution
was adjusted to 8.5 by adding potassium hydroxide, thereby
obtaining an electrolyte.
[0052] A substrate 1 made of AZ31B magnesium alloy was prepared for
oxidation. The substrate 1 as an anode and a carbon cathode were
immersed into the electrolyte, and a voltage of 550 V was applied
to generate an electric current so as to conduct micro-arc
oxidation that was carried out for a period of 10 minutes using an
average current density of 2 A/dm.sup.2 across the substrate 1. The
substrate 1 was oxidized inwardly from its surface to form an oxide
layer 2 thereon, the oxide layer 2 being made of metal oxide formed
by oxidation of magnesium alloy. The oxide layer 2 was white in
color, and had a thickness ranging between 12 .mu.m and 16 .mu.m. A
plurality of pores 22 were formed in the oxide layer 2. The pore
size of the pores 22 ranged from 10 .mu.m to 25 .mu.m, the
uniformity of the position distribution of the pores 22 was 50%,
and the porosity of the oxide layer 2 was 37%.
[0053] Subsequently, the substrate 1 formed with the oxide layer 2
was cleaned by washing with deionized water to avoid residue of the
electrolyte remaining on the oxide layer 2 and the substrate 1.
[0054] Next, the substrate 1 formed with the oxide layer 2 was dyed
in a manner similar to that in Example 1. The substrate 1 formed
with the oxide layer 2 was immersed into a solution containing blue
dye (TAC BLUE-RCD, Okuno Chemical Industries Co., Ltd.) having a
concentration of 5 g/L. The substrate 1 was dyed for a period of 10
minutes at a solution temperature of 55.degree. C. The blue dye was
adsorbed on the main body 21 of the oxide layer 2, and entered into
at least part of the pores 22. Pure water was then employed to
clean the substrate 1 twice to make sure that residue of the dye
remaining on the oxide layer 2 and the substrate 1 was removed,
thereby obtaining a half-finished product.
[0055] Finally, the half-finished product was sealed by immersing
into a sealing solution (Top Seal DX-500, Okunc Chemical Industries
Co., Ltd.) having a concentration of 10 g/L, such that a sealing
layer 3 was formed to wrap the blue dye and the oxide layer 2 of
the half-finished product. The sealing procedure for forming the
sealing layer 3 was the same as that in Example 1. A magnesium
alloy product with a dark blue appearance was thus obtained.
Example 4
[0056] An electrolyte similar to that in Example 3 was provided,
and a substrate 1 made of AZ31B magnesium alloy was prepared for
oxidation.
[0057] The procedures and conditions for oxidization of the
substrate 1 were similar to those of Example 3. The substrate 1 was
oxidized by immersing the substrate 1 as an anode into the
electrolyte, so as to form an oxide layer 2 on the substrate 1. The
oxide layer 2 was made of oxidized metal formed from oxidation of
magnesium alloy. The oxide layer 2 was white in color, and had a
thickness ranging from 12 .mu.m to 16 .mu.m. A plurality of pores
22 were formed in the oxide layer 2. The pore size of the pores 22
ranged from 10 .mu.m to 25 .mu.m, uniformity of the position
distribution of the pores 22 was 48%, and the porosity of the oxide
layer 2 was 42%.
[0058] Subsequently, the substrate 1 formed with the oxide layer 2
was cleaned by washing using deionized water, so as to avoid
residue of the electrolyte remaining on the oxide layer 2 and on
the substrate 1.
[0059] Next, the substrate 1 formed with the oxide layer 2 was
immersed into a solution containing brown dye (TAC BROWN-GR, Okuno
Chemical Industries Co., Ltd.) which has a concentration of 5 g/L.
The oxide layer 2 was dyed by dip coating. The substrate 1 formed
with the oxide layer 2 was dyed for a period of 8 minutes at a
solution temperature of 55.degree. C. The brown dye was adhered on
the main body 21 of the oxide layer 2, and entered into at least
part of the pores 22. Then, pure water was employed to clean the
substrate 1 twice to make sure that residue of the dye was removed
from the oxide layer 2, thereby obtaining a half-finished
product.
[0060] Finally, the half-finished product was sealed by forming a
sealing layer 3 using procedures similar to those of Example 1,
thereby obtaining a magnesium alloy product with a brown
appearance.
Example 5
[0061] An electrolyte similar to that in Example 3 was provided,
and a substrate 1 made of AZ31B magnesium alloy was prepared for
oxidation. The substrate 1 as the anode was immersed into the
electrolyte to conduct the oxidation as described in Example 3, so
as to form an oxide layer 2 on the substrate 1. The oxide layer 2
was made of metal oxide formed by oxidation of magnesium alloy. The
oxide layer 2 was white in color, and had a thickness ranging
between 12 .mu.m and 16 .mu.m. A plurality of pores 22 were formed
in the oxide layer 2. The pore size of the pores 22 ranged from 10
.mu.m to 25 .mu.m, the uniformity of the position distribution of
the pores 22 was 52%, and the porosity of the oxide layer 2 was
39%. Subsequently, the substrate 1 formed with the oxide layer 2
was cleaned by washing with deionized water to avoid residue of the
electrolyte remaining on the oxide layer 2 and on the substrate
1.
[0062] Next, the substrate 1 formed with the oxide layer 2 was
immersed into a solution containing green dye (TAC Green-GM(1),
Okuno Chemical Industries Co., Ltd.) which has a concentration of 5
g/L, and the oxide layer 2 was dyed by dip coating. The substrate 1
formed with the oxide layer 2 was dyed for a period of 10 minutes
at a solution temperature of 55.degree. C. The green dye was
adhered on the main body 21 of the oxide layer 2, and entered into
at least part of the pores 22. Pure water was then employed to
clean the substrate 1 twice to make sure that residue of the dye
was removed from the oxide layer 2, thereby obtaining a
half-finished product.
[0063] Finally, the half-finished product was sealed for a period
of 60 seconds such that a sealing layer 3 was formed thereon,
thereby obtaining a magnesium alloy product with an army green
appearance.
Comparative Example 1
[0064] Sodium silicate having a concentration of 55 g/L and
potassium fluoride having a concentration of 2 g/L were
sequentially added into deionized water that was used as a solvent,
and then were mixed by stirring, so as to obtain a solution. Sodium
hydroxide was then added into the solution to adjust pH value of
the solution to 8.5, so as to obtain an electrolyte.
[0065] Next, a substrate made of AZ31B magnesium alloy was prepared
for oxidation. The substrate as an anode and a carbon cathode were
immersed into the electrolyte that was not added with the pore
modifier. A voltage of 500 V was then applied to generate an
electric current, and to control the average current density of 2
A/dm.sup.2 across the substrate. The substrate was oxidized for a
period of 10 minutes, i.e., the substrate was subjected to
micro-arc oxidation inwardly from its surface so as to form an
oxide layer on the substrate. The oxide layer was grayish-white in
color, and had a thickness ranging between 4 .mu.m and 10 .mu.m. A
plurality of pores were formed in the oxide layer. The pore size of
the pores ranged from 5 .mu.m to 15 .mu.m, the uniformity of the
position distribution of the pores was 10%, and the porosity of the
oxide layer was 8%.
Evaluation of Color Value
[0066] The color value for each of the magnesium alloy products
obtained in Examples 1 to 5 and Comparative Example 1 was performed
using a spectrophotometer and the color values were determined
based on the coordinates of the CIELAB color space. The color
values L*, a* and b* were obtained, wherein the color value L*
represents the perceptual lightness of the color (the higher the
value, the lighter the color is), the color value a* represents the
green-red chromaticity coordinate (negative values indicate green
and positive values indicate red), and the color value b*
represents the blue-yellow chromaticity coordinate (negative values
indicate blue and positive values indicate yellow).
[0067] The composition (except water) of the electrolytes used in
Examples 1 to 5 and Comparative Example 1, and the color value
evaluation results of the magnesium alloy products obtained in
Examples 1 to 5 and Comparative Example 1 are summarized in Table
1.
TABLE-US-00001 TABLE 1 Comparative Examples Example 1 2 3 4 5 1
Electrolyte Sodium 30 30 35 35 35 55 silicate (g/L) Potassium 8 8
7.5 7.5 7.5 2 fluoride (g/L) Triethanol- 0.5 0.5 1.0 1.0 1.0 --
amine (g/L) Oxidation time (min.) 10 10 10 10 10 10 Voltage(V) 450
465 550 550 550 500 Dye TAC TAC TAC TAC TAC -- BLUE-RCD BLUE-RCD
BLUE-RCD BROWN-GR Green-GM (blue) (blue) (blue) (brown) (green)
Dyeing temperature(.degree. C.) 55 55 55 55 55 -- Dyeing period
(min.) 17 10 10 8 10 -- Sealing temperature (.degree. C.) 95 95 95
95 95 -- Sealing time (s) 180 180 180 180 60 -- Appearance Oxide
Thickness (.mu.m) 10~15 10~15 12~16 12~16 12~16 4~10 layer Pore
size (.mu.m) 10~25 10~25 10~25 10~25 10~25 5~15 Pore uniformity (%)
53% 53% 50% 48% 52% 10% Porosity (%) 41% 41% 37% 42% 39% 8% Color
of magnesium Light Blue Dark Brown Army Grayish- alloy product blue
blue green white Color L* 55~57 46~52 40~45 55~57 70~80 78~85 value
a* -3.89 -1.77 2.69 9.47 -23.80 -0.11 b* -16.33 -20.53 -24.14 7.62
62.11 0.92
[0068] Results in Table 1 show that the magnesium alloy products of
Examples 1 to 5, which were obtained by oxidizing the substrates
using the electrolyte of the disclosure, all have an oxide layer 2
having a thickness not less than 10 .mu.m. The porosity of the
oxide layer 2 ranges from 37% to 42%, the pore size of the pores 22
ranges from 10 .mu.m and 25 .mu.m, and the uniformity of the pores
22 ranges from 48% to 53%. Compared with the magnesium alloy
product of Comparative Example 1, which was obtained by subjecting
the magnesium alloy substrate to micro-arc oxidation using a
conventional electrolyte for the same oxidation period, it is shown
that by using the electrolyte of the disclosure, the thickness of
the oxide layer 2, the pore size of the pores 22, and the
uniformity of the distribution of the pores 22 can be effectively
increased.
[0069] In addition, the results show that the period needed for
dyeing the oxide layer 2 formed on the magnesium alloy substrate 1
is no more than 20 minutes, i.e., to have the dye adsorbed
effectively on the main body 21 and filled in the pores 22,
indicating that a favorable dyeing effect is achieved, as shown by
an increase in the pore size and the distribution uniformity of the
pores 22 formed in the oxide layer 2 of the magnesium alloy
substrate 1 made by micro-arc oxidization using the electrolyte of
the disclosure.
[0070] In summary, by including the pore modifier in the
electrolyte of the disclosure, the pore size of the pores 22 in the
oxide layer 2 formed by micro-arc oxidation and the porosity of the
oxide layer 2 can be increased, which provides the dye with
sufficient adsorption area and filling space, and thus, the
dyeability of the oxide layer 2 can be increased. Since the
distribution uniformity of the pore size and the position of the
pores 22 are enhanced, the color uniformity of the dyed oxide layer
2 can be improved. Additionally, the color durability can be
further prolonged by wrapping the dye and the oxide layer 2 in the
sealing layer 3.
[0071] In the description above, for the purposes of explanation,
numerous specific details have been set forth in order to provide a
thorough understanding of the embodiment(s). It will be apparent,
however, to one skilled in the art, that one or more other
embodiments may be practiced without some of these specific
details. It should also be appreciated that reference throughout
this specification to "one embodiment," "an embodiment," an
embodiment with an indication of an ordinal number and so forth
means that a particular feature, structure, or characteristic may
be included in the practice of the disclosure. It should be further
appreciated that in the description, various features are sometimes
grouped together in a single embodiment, FIG., or description
thereof for the purpose of streamlining the disclosure and aiding
in the understanding of various inventive aspects, and that one or
more features or specific details from one embodiment may be
practiced together with one or more features or specific details
from another embodiment, where appropriate, in the practice of the
disclosure.
[0072] While the disclosure has been described in connection with
what is (are) considered the exemplary embodiment(s), it is
understood that this disclosure is not limited to the disclosed
embodiment(s) but is intended to cover various arrangements
included within the spirit and scope of the broadest interpretation
so as to encompass all such modifications and equivalent
arrangements.
* * * * *