GB2129016A - Anodic oxidation on Al or Al alloys - Google Patents
Anodic oxidation on Al or Al alloys Download PDFInfo
- Publication number
- GB2129016A GB2129016A GB08328359A GB8328359A GB2129016A GB 2129016 A GB2129016 A GB 2129016A GB 08328359 A GB08328359 A GB 08328359A GB 8328359 A GB8328359 A GB 8328359A GB 2129016 A GB2129016 A GB 2129016A
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- chemical production
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- Granted
Links
- 230000003647 oxidation Effects 0.000 title claims abstract description 31
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 31
- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 13
- 229910045601 alloy Inorganic materials 0.000 title description 5
- 238000000576 coating method Methods 0.000 claims abstract description 81
- 239000011248 coating agent Substances 0.000 claims abstract description 80
- 238000012824 chemical production Methods 0.000 claims abstract description 61
- 239000003792 electrolyte Substances 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 29
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 19
- 235000011149 sulphuric acid Nutrition 0.000 claims abstract description 19
- 239000001117 sulphuric acid Substances 0.000 claims abstract description 19
- 239000000463 material Substances 0.000 claims abstract description 18
- 238000005275 alloying Methods 0.000 claims abstract description 14
- 150000007524 organic acids Chemical class 0.000 claims abstract description 8
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 6
- 239000004411 aluminium Substances 0.000 claims abstract description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 5
- 238000006243 chemical reaction Methods 0.000 claims abstract description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 15
- 150000003839 salts Chemical class 0.000 claims description 8
- 239000012266 salt solution Substances 0.000 claims description 7
- 239000011148 porous material Substances 0.000 claims description 6
- 238000007789 sealing Methods 0.000 claims description 6
- 238000009835 boiling Methods 0.000 claims description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 5
- 235000006408 oxalic acid Nutrition 0.000 claims description 5
- 239000000243 solution Substances 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 239000007864 aqueous solution Substances 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000010949 copper Substances 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052745 lead Inorganic materials 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 claims description 3
- 229910052709 silver Inorganic materials 0.000 claims description 3
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 claims description 2
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 claims description 2
- 229940046892 lead acetate Drugs 0.000 claims description 2
- 239000005864 Sulphur Substances 0.000 abstract description 6
- -1 sulphur compound Chemical class 0.000 abstract description 6
- 230000007547 defect Effects 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 5
- 230000001965 increasing effect Effects 0.000 description 4
- 239000000956 alloy Substances 0.000 description 3
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 3
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910018084 Al-Fe Inorganic materials 0.000 description 2
- 229910018192 Al—Fe Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 229910018131 Al-Mn Inorganic materials 0.000 description 1
- 229910018185 Al—Co Inorganic materials 0.000 description 1
- 229910018461 Al—Mn Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241000220317 Rosa Species 0.000 description 1
- 235000009470 Theobroma cacao Nutrition 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 244000240602 cacao Species 0.000 description 1
- 235000019646 color tone Nutrition 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000006193 liquid solution Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 150000002815 nickel Chemical class 0.000 description 1
- 210000000056 organ Anatomy 0.000 description 1
- 230000003405 preventing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/04—Anodisation of aluminium or alloys based thereon
- C25D11/12—Anodising more than once, e.g. in different baths
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/04—Anodisation of aluminium or alloys based thereon
- C25D11/14—Producing integrally coloured layers
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/04—Anodisation of aluminium or alloys based thereon
- C25D11/18—After-treatment, e.g. pore-sealing
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrochemical Coating By Surface Reaction (AREA)
- Chemical Treatment Of Metals (AREA)
Abstract
A method in which a coloured anodic oxidation coating is formed on a surface of a material comprising aluminium to which an alloying element is added or an aluminium alloy, the alloying element developing a colour upon reaction with a sulphur compound, by chemically forming an anodic coating by passage of an electric current through an electrolyte containing either or both of sulphuric acid and an and organic acid is described. The method comprises the steps of: (a) primary chemical production utilizing an alternating current (Figure 1A) with a short negative reversing period in each cycle, and (b) secondary chemical production comprising subsequently utilizing in the same electrolyte an alternating current (Figure 1B) of a longer negative reversing period than that of step (a) for a relatively short time, whereby an anodic oxidation coating is formed on the surface with enhanced colour and hardness. d
Description
SPECIFICATION
Anodic oxidation coating on Al or Al alloys
This invention relates generally to methods in which a coloured anodic oxidation coating is formed on a surface of a material comprising aluminium to which an alloying element is added or an aluminium alloy, the alloying element developing a colour upon reaction with a sulphur compound, by chemically forming an anodic coating by passage of an electric current through an electrolyte containing sulphuric acid.
Generally, the anodic oxidation coating chemically produced on Al alloy is porous so that it can be easily coloured by utilising its fine pores and is extensively utilised in ornaments, machine parts, kitchenware, building materials and so on. In conventional colouring methods, however, an organic dye is merely adsorbed in the fine pores of the coating and there have been defects that the coloured coat has such a poor weatherproofness that it cannot be utilised as a material for a part exposed to the sun and that, in the case of a light colour, it will fade away even if the alloy having the coating is disposed in a room in which it is not exposed directly to the sunlight.
For eliminating these defects, there have been suggested such methods as follows, but they still involve certain defects as will be detailed, respectively: (1) Method of alloying: An alloying element which easily develops a colour upon the anodic oxidation is added in advance into an Al material so that the colour will be naturally developed when the anodic oxidation coating is chemically produced. However, there are defects that, in this case, the tone of the colour developed by the added alloying element is limited, that the colour will not develop unless the thickness of the coating is made larger, and that, while the weatherproofness can be improved by such thicker coating, it has been required to employ a high voltage of more than 40V for chemically producing the coating.
(2) Method using an electrolyte: An alloying element easily developing a colour upon the anodic oxidation is also added in advance into an Al material and a special electrolyte easily developing a colour when the anodic oxidation coating is chemically produced is used to improve the colour developing efficiency to be higher than in the foregoing method (1). There are defects that, in this case, though the colour of this coat has good weatherproofness, the electrolyte is more complicated to control and is more expensive than such sulphuric acid or electrolyte containing sulphuric acid as is used in the method (1), that a high electrical voltage will be required when the anodic oxidation coating is chemically produced, and that the tone of the developed colour is limited as in the case of (1).
(3) Method using chromic acid: This is a methodof chemically producing an anodic oxidation coating on an Al alloy by adding chromic acid into the electrolyte and properly adjusting the chemically producing voltage. The appearance of the coating is opaque and presents an enamel-like colour tone but there have been defects that the coating is so thin as to be 2 to 5 Fm and lacks mechanical durability.Further, since it is necessary to so adjust the chemically producing voltage as, for example, to be gradually elevated from 0 to 40V during the first 10 minutes, to be maintained at 40V during the next 20 minutes and to held at 50V during the last 5 minutes, there have been defects that the adjusting operation is complicated, it is necessary to use a high voltage and, in addition, it is necessary to use chromic acid which is a detrimental substance.
(4) Ematal process: This is a method wherein such salts as of Ti, Zr or the like are added into the electrolyte (oxalic acid) and an oxide of such metal is adsorbed in an anodic oxidation coating while being chemically produced at a chemically-producing voltage of 120V. In this case, there are advantages that the anodic oxidation coating is opaque and presents an enamel-like milky white tone, whereas defects have been involved in such that a very high chemically-producing voltage and a costly metallic salt are required and the electrolyte in the electrolytic bath requires a complicated control.
In accordance with the present invention, a method in which a coloured anodic oxidation coating is formed on a surface of a material comprising aluminium to which an alloying element is added or an aluminium alloy, the alloying element developing a colour upon reaction with a sulphur compound by chemically forming an anodic coating by passage of an electric current through an electrolyte containing either or both of sulphuric acid and an organic acid, comprises the steps of (a) primary chemical production utilizing an alternating current with a short negative reversing period in each cycle, and (b) secondary chemical production comprising subsequently utilizing in the same electrolyte an alternating current of a longer negative reversing period than that of step (a) for a relatively short time, whereby an anodic oxidation coating is formed on the surface with enhanced colour hardness.
The present invention therefore provides a method for enhancing the naturally developed colour of an anodic oxidation coating chemically produced on Al or Al alloy, wherein an anodic oxidation coating high in weatherproofness and colour developing efficiency can be easily produced econonically even with a coating of relatively small thickness.
Furthermore, the present invention provides a method for enhancing the naturally developed colour of an anodic oxidation coating chemically produced on Al orAl alloy, wherein a primary developed selective colour of the anodic oxidation coating can be easily and quickly enhanced at low cost while increasing the thickness of the coating.
Conveniently, after the chemical production ends, the coated material is dipped in a warmed aqueous solution of a metallic salt, or is dipped and heated in a warmed pore sealing liquid containing a metallic salt, or is dipped in boiling water so as to colour the coating.
Preferably, the added alloying~element is one of Ni, Co, Ag, Fe, Cu, and Pb.
Typically the current used in the primary chemical production may be reversed for up to 15% of the time while the current used in the secondary chemical production may be reversed for a greater amount of time and generally from 10 to 50% of the time.
Figures 1A and Figure 7B show examples of voltage wave forms used in the chemical production of an anodic oxidation coating according to the present invention, wherein Figure 1A shows the wave form used in the initial period of the chemical production (which shall be hereinafter referred to as the primary chemical production) and Figure 1 B shows the wave form used in the terminating period (which shall be hereinafter referred to as the secondary chemical production);
Figure 2A shows an example of a chemically producing voltage wave form in the chemical production of an anodic oxidation coating; and
Figure 2B shows a positive current wave form and negative current wave form corresponding to the wave form of Figure 2A.
Some Examples of methods in accordance with the present invention will now be described.
Table I illustrates the relationship between the reversing period (that is the period in each cycle in which alternating current has negative polarity represented by a percentage), the hardness, and the thickness of the coating when the chemical production of anodic oxidation coatings on Al or an Al alloy were carried out in an electrolyte containing an inorganic acid or organic acid in accordance with the invention.
TABLE I
Reversing period (%) 0 5 15 25 35
Coating hardness (Hv) 354 416 412 384 352
Coat thickness ( > m) 36.4 36.5 35.1 29.4 14.1
That is, the longer the reversing period, the less the hardness and thickness of the coating. In the case of such material on which a compact coating is easy to produce as pure Al or an anticorrosive Al alloy, the reversing period made longer than 25% resulted in that the positive current preventing action of the coating became so large that the chemically producing voltage rose and no coating thicker than a fixed thickness could be chemically produced.Therefore, in the present invention, the primary chemical production of the anodic oxidation coating is carried out with an electric current of a short reversing period and then the secondary chemical production is carried out with an electric current with a longer reversing period in the same electrolytic bath, that is, the same electrolyte, to produce chemically a coating of a sufficient thickness and hardness and then the coating is varied in the microstructure so as to enhance the naturally developed colour of the coating. In the present invention, further, a sulphur compound is accumulated in the coating in the secondary chemical production and is combined with a metal element added in advance into the Al alloy or added in a subsequent heat treatment so as to develop well the colour of the coating.It will be clear that such metal elements such as Ni, Co, Ag, Fe, Cu, Pb and the like can be utilized.
Example l: Electrolyte: 20 % by weight sulphuric acid
Electrolyte temperature: 25%C
Current condition: 13.3 HZ
Positive current density: 4A/dm2 Primary chemical
production condition: Reversing period of 5% for 20 minutes
Secondary chemical
production condition: Reversing period of 35%
Maximum chemically
producing voltage: 30V
Under these conditions, an anodic oxidation coating was chemically produced on Al material with a carbon plate as an opposed electrode. A coating of a high hardness was chemically produced in the primary chemical production and then the secondary chemical production was carried out by extending the reversing period in the same electrolytic bath, that is, in the same electrolyte.When the maximum value of the chemically producing voltage was raised to 30V, the coating has developed its colour to be opaque as in
Table 2 depending on the Al material and secondary chemical production time. Even when the secondary chemical production time was 3 minutes, as evident from Table 2, the colour has developed and, as the secondary chemical production time became longer, the degree of colour development has further advanced. Even when the maximum value of the chemically producing voltage was made 50V, the tone of the coating was substantially the same as in the case of 30V. Therefore, it is found that, when the reversing period is switched over and increased in the course of the chemical production, a well coloured anodic oxidation coating of a high hardness will be obtained.
TABLE 2 Al materials* Secondary chemical production time
3 min 5 min 10 min
3003 Ivory Beige Deep beige
6061 Light grayish Deep Grayish
yellow Grayish yellow yellow
6063 Ivory Light beige Beige
5052 Light beige Beige Grayish yellow * Standard identification of Aluminium Association of America, throughout the following Tables.
Example ll: Electrolyte: 20% by weight sulphuric acid
Electrolyte temperature: 25"C Current condition: 18Hz
Positive current density: 4Aldm2
Primary chemical production
condition: Reversing period of 7%
Secondary chemical production Reversing period of 30% for
conditions: 5 minutes
Maximum chemically
producing voltage: 30V
Under these conditions, a coating was chemically produced in the same manner as in the case of Example
I. The tone of the coating varied as shown in Table 3 depending on the primary chemical production time. In
the case when the primary coating was thin, it tended to take a long time until the chemically producing
voltage reached the maximum value of 30V in the secondary chemical production.
TABLE 3
Al materials Primary chemical production time
10 min 20 min 30 min
Tone Ivory Beige Deep beige
6063
Thickness ( > m) 12.4 24.5 37.0
Tone Light Grayish Deep
grayish yellow grayish
6061 yellow yellow
Thickness (clam) 12.2 24.6 37.1
Tone Bright Gray Dark Gray
Gray Al-Fe(1 .4wt%) Thickness 12.4 23.9 36.5 (ELm) When the primary chemical production time was, for example, 10 minutes, an opaque colour developed with the secondary chemical production time of about 4 minutes.Further, even when the primary chemical production time was 5 minutes and the coating thickness was about 6Cim, the chemically producing voltage could be raised within a short time to enhance the primary developed colour, if the reversing period at the time of the secondary chemical production was further extended. Therefore, it is found that, if the primary chemically produced coating is thick, it will be able to enhance its developed colour by the secondary chemical production for a certain time and that, if the primary chemically produced coating is thin, it will be able also to enhance its developed colour within a short time by extending the reversing period in the secondary chemical production. It is also found that the larger the coating thickness of the primary chemically producing coating, the deeper the coloured tone.Also, it is found that various tones can be obtained depending on the composition of the Al material and that, for example, if Fe is contained a grayish tone will be made and, if small amounts of Si and Mg are contained as in the 6063 alloy, a beigish tone can be developed.
Example Ill:
Electrolyte: 35% by weight sulphuric acid + 10gaze of oxalic acid
Electrolyte temperature 25"C Current condition: 13.3 Hz
Positive current density: 4A/dm2 Primary chemical production Reversing period of 5%
condition:
Secondary chemical production Reversing period of 30% for
condition: 5 minutes
Maximum chemically producing 30V
voltage:
Under these conditions, a coating was chemically produced in the same manner as in Example II.The results were as in Table 4:
TABLE 4
Primary chemical production time
Al materials
5 min 10 min 20 min
3003 Ivory Beige Grayish yellow
6063 Light Ivory Ivory Beige
Even when a mixture of sulphuric acid and oxalic acid was used for the electrolyte, the coating could develop a colour substantially in the same tone as in the case of using only sulphuric acid for the electrolyte. When an organic acid such as oxalic acid was added in the electrolyte, the chemically producing voltage could be easily raised by the secondary chemical production even if the primary chemically produced coating was thin. Therefore, it is found that, even if an organic acid other than sulphuric acid is added in the electrolyte, the developed colour of the coating was thin.Therefore, it is found that, even if an organic acid other than sulphuric acid is added in the electrolyte, the developed colour of the coating can be further enhanced and, in addition, the time required for the respective primary and secondary chemical productions can be reduced if an organic acid is added.
Example IV:
Electrolyte: 20% by weight sulphuric acid
Electrolyte temperature: 25"C Current condition: 13.3 Hz
Positive current density 4Aldm2 Primary chemical production Reversing period of 5% for
conditions: 20 minutes
Secondary chemical production Reversing period of 30% for
conditions: 5 minutes
Maximum chemically producing 30V
Voltage:
Under the conditions and in the same manner as in Examples I and II, an anodic oxidation coating was chemically produced by the primary and secondary chemical productions and was thereafter dipped for 20 minutes while boiling in a solution containing 20gaze of nickel sulphate or a pore sealing liquid containing a nickel salt. The results were as shown in Table 5.When the thus chemically produced coating was heated in a metallic salt solution or a pore sealing liquid containing a metallic salt, the sulphur compound contained and accumulated in the coating by the reduction of the sulphuric acid electrolyte at the time of the chemical production reacted with the metal ions to make the tone thicker than in the case of the colour naturally developed merely by the chemical production.
TABLE 5
Heating
Al materials Not heated
Nickel sulphate Sealing liquid
solution containing Ni salt
6063 Beige Very dark Dark grey
grayish yellow Al-Fe(1.4wt%) Gray Dark gray Dark gray Al-Co(1.Owt%) Beige Gray Dark gray
Therefore, it is found that a compound tone of the colour developed by the metal salt in addition to the opaque colour naturally developed by the primary and secondary chemical productions can be attained. It is also found that, even if the primary chemical production is made with a direct current, the tone will not substantially vary.
Example V
Electrolyte: 20% by weight sulphuric acid
Electrolyte temperature: 25"C Current condition: 18Hz
Positive current density: 4A/dm2 Primary chemical production Reversing period of 7% for
conditions: 20 minutes
Secondary chemical production Reversing period of 35% for
conditions: 5 minutes
Maximum chemically producing 30V
voltage:
Al material (ailoy): Al-Mn(2wt%)-Fe(1wt%) Under these conditions, an anodic oxidation coating was chemically produced and was heated in various metal solutions to enhance the naturally developed colour of the coating.The metal salt solution was maintained at the boiling point and the coating was heated as dipped in the solution for 20 minutes, then such colours as shown in Table 6 were thereby attained:
TABLE 6
Metallic salt solution Colour
20 gif of cobalt sulphate Dark gray yellowish red
5 glf of copper nitrate Deep green
2 glf of lead acetate Cocoa
A chemically producing current of a frequency of 18 Hz was used but, even in the case of 13.3 Hz, substantially the same results were obtained. It is found that the colour can be selected as desired depending on the composition of the metallic salt solution. When the reversing period in the secondary chemical production was made longer, the colour was not seen to vary even if the time was reduced.
The method of the present invention may be evaluated as follows on the basis of the foregoing Examples I toV: (1) In chemically producing an anodic oxidation coating on Al organ Al alloy in a simple and inexpensive electrolyte containing sulphuric acid, an opaque colour can be developed in the coating only by increasing the reversing period at least at the terminating stage of the chemical production.
(2) The chemically producing voltage can be reduced to be lower and the electric power consumption can be saved to be lower than in the conventional natural colour developing methods using a special electrolyte high in cost and difficult to control. In addition, the voltage control can be well simplified.
(3) As the current reversing period is increased at the terminating stage of the chemical production of the coating and a large amount of a sulphur compound can be accumulated in the coating, the coating colour can be well developed in the subsequent heating treatment even if the coating is thin.
(4) The colour development achieved by the subsequent treatment can be superposed on the colour naturally developed at the time of the chemical production of the coating and various tones can be thereby realized.
(5) As the current reversing period can be made short except at the terminating stage of the chemical production of the coating, excellent mechanical properties of the coating can be well maintained.
Claims (10)
1. A method in which a coloured anodic oxidation coating is formed on a surface of a material comprising aluminium to which an alloying element is added or an aluminium alloy, the alloying element developing a colour upon reaction with a sulphurcompoud by chemically forming an anodic coating by passage of an electric current through an electrolyte containing either or both of sulphuric acid and an organic acid, the method comprising the steps of:: (a) primary chemical production utilizing an alternating current with a short negative reversing period in each cycle, and (b) secondary chemical production comprising subsequently utilizing in the same electrolyte an alternating current of a longer negative reversing period than that of step (a) for a relatively short time, whereby an anodic oxidation coating is formed on the surface with enhanced colour and hardness.
2. A method according to claim 1, wherein the electrolyte is of an aqueous solution of 20% by weight sulphuric acid, the primary chemical production is performed with a current having a reversing period of 5 to 7% for 10 to 30 minutes, and the secondary chemical production is performed with a current having a reversing period of 30 to 35% for 3 to 10 minutes.
3. A method according to claim 1, wherein the electrolyte is an aqueous solution of 35% by weight sulphuric acid and 10gut oxalic acid, the primary chemical production is performed with a current having a reversing period of 5% for 5 to 20 minutes, and the secondary chemical production is performed with a current having a reversing period of 30% for 5 minutes.
4. A method according to claim 2, further comprising a step (c) of heating the material subsequent to step (b) at least in a boiling metallic salt solution for 20 minutes.
5. A method according to claim 4, wherein the metallic salt solution is 20 g/ cobalt sulphate, 5 gle copper nitrate or 2 gle lead acetate solution.
6. A method according to claim 4, wherein the step (c) is performed in a pore sealing compound or in a boiling sealing liquid containing a Ni salt.
7. A method according to claim 6, wherein the metallic salt solution is a nickel sulphate solution.
8. A method according to any one of the preceding claims, wherein the alternating current is of a frequency of 13.3 or 18 Hz.
9. A method according to any one of the preceding claims, wherein the added alloying element is one of
Ni, Co, Fe, Ag, Cu, and Pb.
10. A method according to claim 1, substantially as described with reference to any of the Examples and accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18499580A JPS5836075B2 (en) | 1980-12-27 | 1980-12-27 | Coloring method for anodic oxide films on aluminum and its alloys by two-stage current reversal electrolysis |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8328359D0 GB8328359D0 (en) | 1983-11-23 |
| GB2129016A true GB2129016A (en) | 1984-05-10 |
| GB2129016B GB2129016B (en) | 1985-06-19 |
Family
ID=16162937
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB838323818A Pending GB8323818D0 (en) | 1980-12-27 | 1983-09-06 | Anodic oxidation on al alloys |
| GB08328359A Expired GB2129016B (en) | 1980-12-27 | 1983-10-24 | Anodic oxidation on a1 or a1 alloys |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB838323818A Pending GB8323818D0 (en) | 1980-12-27 | 1983-09-06 | Anodic oxidation on al alloys |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5836075B2 (en) |
| GB (2) | GB8323818D0 (en) |
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|---|---|---|---|---|
| CN1301345C (en) * | 2004-02-26 | 2007-02-21 | 陈刚 | Hardencing anode treating process of electronic actuator |
| CN109778281A (en) * | 2019-03-27 | 2019-05-21 | 珠海市玛斯特恒新铝合金加工有限公司 | Two-part voltage oxide improves the corrosion proof method of aluminium alloy |
| CN110029378A (en) * | 2019-04-15 | 2019-07-19 | 广东长盈精密技术有限公司 | Gradient color electroplating method and electronic equipment |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI727560B (en) * | 2019-12-20 | 2021-05-11 | 周文三 | Air compressor having pressure gauge |
-
1980
- 1980-12-27 JP JP18499580A patent/JPS5836075B2/en not_active Expired
-
1983
- 1983-09-06 GB GB838323818A patent/GB8323818D0/en active Pending
- 1983-10-24 GB GB08328359A patent/GB2129016B/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1301345C (en) * | 2004-02-26 | 2007-02-21 | 陈刚 | Hardencing anode treating process of electronic actuator |
| CN109778281A (en) * | 2019-03-27 | 2019-05-21 | 珠海市玛斯特恒新铝合金加工有限公司 | Two-part voltage oxide improves the corrosion proof method of aluminium alloy |
| CN110029378A (en) * | 2019-04-15 | 2019-07-19 | 广东长盈精密技术有限公司 | Gradient color electroplating method and electronic equipment |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2129016B (en) | 1985-06-19 |
| GB8328359D0 (en) | 1983-11-23 |
| JPS57110694A (en) | 1982-07-09 |
| JPS5836075B2 (en) | 1983-08-06 |
| GB8323818D0 (en) | 1983-10-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19941009 |