EP0112439A2 - Procédé d'oxydation anodique d'alliages de l'aluminium - Google Patents

Procédé d'oxydation anodique d'alliages de l'aluminium Download PDF

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Publication number
EP0112439A2
EP0112439A2 EP83108951A EP83108951A EP0112439A2 EP 0112439 A2 EP0112439 A2 EP 0112439A2 EP 83108951 A EP83108951 A EP 83108951A EP 83108951 A EP83108951 A EP 83108951A EP 0112439 A2 EP0112439 A2 EP 0112439A2
Authority
EP
European Patent Office
Prior art keywords
voltage
duration
workpieces
current
anodic oxidation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP83108951A
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German (de)
English (en)
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EP0112439A3 (en
EP0112439B1 (fr
Inventor
Reinhard Dr. Nissen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Electro Chemical Engineering GmbH
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Electro Chemical Engineering GmbH
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Publication date
Application filed by Electro Chemical Engineering GmbH filed Critical Electro Chemical Engineering GmbH
Priority to AT83108951T priority Critical patent/ATE33858T1/de
Publication of EP0112439A2 publication Critical patent/EP0112439A2/fr
Publication of EP0112439A3 publication Critical patent/EP0112439A3/de
Application granted granted Critical
Publication of EP0112439B1 publication Critical patent/EP0112439B1/fr
Expired legal-status Critical Current

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    • 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
    • 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
    • C25D11/024—Anodisation under pulsed or modulated current or potential

Definitions

  • the invention relates to methods for the anodic oxidation of workpieces made of an aluminum alloy, in particular with a high content of copper and / or nobler metals, the workpieces being arranged in a moving aqueous electrolyte together with one or more cathodes and a voltage essentially periodically Generation of short-term current pulses with high current flow is applied to the workpieces and the cathode (s).
  • hard oxide layers have hardness values that correspond to 5 to 10 times the hardness of the base material.
  • electrolytes have been developed for hard anodization, with which it is possible to form thick, hard and abrasion-resistant oxide layers.
  • the best known of these electrolytes are based on sulfuric acid, whereby on the one hand pure sulfuric acid of different concentrations and on the other hand mixed electrolytes (e.g. sulfuric acid and oxalic acid) have been used.
  • electrolytes have a redissolving power of the oxide layer formed. 'To reduce this redissolving power and the desired thick, hard and abrasion resistant oxide to reach layers, the electrolyte is cooled.
  • the released Joule heat is dissipated by the electrolyte, which is moved for better heat dissipation, and by the workpiece.
  • the heat dissipation through the workpiece itself is negligible.
  • the majority of Joule's heat is therefore dissipated by the electrolyte. It should be noted, however, that as the layer thickness increases, the heat flow from the oxidized metal side to the electrolyte is increasingly impeded. In the case of anodic oxidation with direct current, the current density is therefore limited.
  • the layer thickness is initially small, so that there is only a slight drop in electrical power.
  • the resulting Joule heat can easily be dissipated by the electrolyte flowing past the aluminum oxide / electrolyte interface, so that no heat build-up can occur in the oxide layer.
  • the drop in performance also increases, ie that increasing warming occurs.
  • the redissolving power of the: electrolyte increases with ' heating too strong, so that the formation of thick, hard layers is hindered. Layer growth no longer occurs when the rate of dissolution of the oxide by the electrolyte is equal to the rate of formation of the oxide.
  • the anodization is carried out with pulsating direct current, the frequency of which is the network frequency corresponds.
  • Voltage pulses are cut out of the positive (or negative) half-waves by means of a phase control.
  • the current flow time i.e. the duration of a single pulse, corresponds to approximately one third of the subsequent switch-off time. During this switch-off time, practically no more Joule heat is generated; the switch-off time is used to dissipate the Joule heat generated during the previous voltage pulse.
  • the oxide layers produced by this known method are not always satisfactory.
  • practical tests have shown that even with relatively short-term voltage pulses and, accordingly, inevitably longer rest periods between the individual voltage pulses, a uniform layer growth is not always achieved.
  • the heat dissipation at the critical points is not sufficient. Accordingly, the layer formation at critical points and with special alloys is not satisfactory.
  • US Pat. No. 3,857,766 discloses a method for anodic oxidation, especially of copper-containing aluminum alloys, in which a pulsating direct current, which has at least 6 voltage pulses per second, is superimposed on a basic direct current of low voltage. The oxidation takes place with a constant current. A mixture of sulfuric acid and oxalic acid is used as the electrolyte.
  • the hard anodization layers produced by this process are also not always satisfactory, especially in the case of special aluminum alloys. The layer formation is poor or incomplete at critical points.
  • the object of the invention is to avoid the disadvantages of the known methods and to provide a method of the type mentioned at the outset with which hard oxide layers can also be produced on thin-walled and pointed, sharp-edged workpieces which have sufficient mechanical properties, in particular with regard to abrasion resistance and thickness.
  • This object is achieved in that the voltage remains switched on for as long as there is a noticeable build-up of the oxide layer and is then switched off until the Joule heat generated is essentially dissipated.
  • the duration of the voltage pulses is advantageously longer than 1/1 second, it is, for example, between 0.1 and 1.5 seconds and is therefore relatively long.
  • a relatively high voltage is applied during the specified period of time.
  • the anodization rate is high from the start, so that despite the described, preferred high rate of dissolution of intermetallic phases (e.g. copper), the aluminum matrix is activated to form nuclei and an even layer formation is achieved even on critical parts.
  • intermetallic phases e.g. copper
  • concentration equalization After the current is switched off, a concentration equalization will occur due to the moving electrolyte.
  • the concentration gradient can be reduced by reducing the concentration polarization using an elec Detect electron beam oscillographs. It was found that the anodization voltage does not immediately drop to a value of approximately 0 after the current is switched off, but that the reduction in the potential of approximately 3 to 5 volts takes a time of 0.1 to 0.5 seconds.
  • the specified, in comparison to the prior art, long period of time during which the voltage pulses are present is extremely favorable for the construction of an oxide layer.
  • the interruption of the voltage between two voltage pulses should last 0.1 to 2 seconds, advantageously this time period is between 0.1 and 1 seconds.
  • the ratio of the duration of a voltage pulse to the duration of a switch-off time should be 0.5 to 5.
  • the temperature of the electrolyte or of the workpiece, in particular at critical points, is advantageously measured.
  • a new voltage pulse is only applied after the temperature measured in this way has dropped back to a predetermined value.
  • the switch-off times are longer or shorter at the beginning or at the end of the oxidation.
  • the hard anodization according to the method according to the invention can be used for workpieces made of cast or wrought alloys.
  • workpieces made of sintered aluminum can also be coated satisfactorily with high alloy proportions of electrochemically more noble elements, such as copper, using the method according to the invention. Due to the high formation rate of the oxide layer and the reduced redissolution, it is possible to form relatively homogeneous layers on the porous sintered metal material.
  • FIG. 1 shows the device used to carry out the method according to the invention.
  • An anode 3 and a cathode 4 are immersed in this electrolyte bath 2 and connected to a voltage supply device 7 via leads 5 and 6.
  • the anode 3 is composed of an anode holder 8 and the workpieces 9 to be treated.
  • a cooler 13 heat exchanger
  • This cooling unit 14 is controlled by a contact thermometer 15, which also extends into the electrolyte bath 2.
  • the voltage supply device 7 supplies a rectified output voltage over a time t 1 -t 2 , as is shown graphically in FIG. 2.
  • This tension can, as from the A bb. have form - be apparent to a rectangular shape or any technically feasible ripple voltage.
  • This voltage U is applied to the cathode 4 and the anode 3 via the leads 5 and 6 and causes a current to flow through the electrolyte.
  • the time course of this current flow i is shown graphically in FIG.
  • the voltage supplied by the voltage supply device 7 is constant during each individual voltage pulse, and it also remains at the same value for the entire anodization time.
  • the power supply device 7 has a current limitation which limits the current during a time t 1 to t 4 , so that the current pulses are also approximately rectangular. If there is no current limitation, the current curve begins to decrease immediately after the time t 4 .
  • a DC voltage between 20 and 60 volts generated within the voltage supply device 7 is expediently switched on and off by a switch in such a way that the voltage curve shown in FIG. 2 results.
  • the switch-on times t 1 to t 2 are between 0.1 and 3 seconds
  • the pause times t 2 to t 3 are between 0.1 and 2 seconds.
  • the ratio of operating times to break times is approximately in the range from 0.5 to 5, in the exemplary embodiment shown this ratio is 2.
  • the first current pulses are constant until time t 4 , as already explained and due to the automatic current limitation. Due to the structure of the oxide layer, as can be seen from FIG. 4, and the associated increase in the volume resistance of this oxide layer, the current i decreases continuously with time t 4 , since the voltage U is constant according to FIG. Accordingly, the layer thickness (FIG. 4) increases approximately constant during the time t 1 to t 4 . The layer thickness increase will decrease as the current i decreases.
  • anodization can also be carried out, for example, in the time t 1 to t 4 over the entire anodization time with constant current of the current pulses or with constant voltage starting from time t 4 to t 5 .
  • FIG. 5 shows the temperature increase compared to the initial state.
  • the temperature increase in the layer increases during the time t 1 to t 4 and then fluctuates by a constant value.
  • the curves shown in FIGS. 2 to 5 are intended to illustrate the pulse current technology according to the invention purely schematically.
  • the shape of the voltage and the current does not always correspond to what is technically achievable.
  • the tension and Current increases are not linear from O to the nominal value, and the drops at the end of the pulse are not always as sharp as shown. Many experiments have shown that the rise time and the fall time are about 1/10 seconds. However, the curve shape has no influence on the anodization result.
  • the method according to the invention enables very thin-walled workpieces such as those with sharp edges and corners to be anodized in spite of very high pulse current densities of at most 8o A / dm without any signs of combustion.
  • the process according to the invention is characterized in that the anodization is started directly with a high current density.
  • the current can optionally be limited, as shown in FIG. 3.
  • the method according to the invention proves to be particularly advantageous. It is the only process that makes it possible to oxidize all workpieces without combustion phenomena with a high current density and short anodization times. Furthermore, the tables show that the layer qualities can be improved with the method according to the invention, even of such Al alloys with low levels of electrochemically nobler metals, as shown in Table 3.
  • Continuous anodization is understood to mean the anodization of strips or workpieces which are continuously drawn through the anodization bath and, if appropriate, through rinsing or post-compression baths.
  • the maximum achievable layer thickness is also limited by the limitation of the applied voltage.
  • the current density is very high due to the high voltage applied and can have values of up to 80 A / dm 2 .
  • the Jould heat is transported away by the moving electrolyte and, as described, the polarization voltages are also reduced.
  • the process of the pulse current method according to the invention thus makes it possible to reduce the anodization time considerably, so that the throughput in existing strip anodization systems can be increased considerably if the same layer thickness is to be achieved.
  • an aluminum foil made of AlMg1 (dimensions: thickness 1.0 mm, width 300 mm, length 500 mm) was placed in a moving electrolyte at a lowering speed of 0.2 m / min. introduced and after the film has been completely lowered in the electrolyte, the anodization is continued for 2 minutes.
  • the voltage applied was 35 volts and the current switch-on time was 0.4 seconds, the switch-off time 0.2 seconds.
  • the sample film showed no burns despite the high initial current density of about 9o A / dm 2 .
  • the layer thickness was 40 to 55 ⁇ m, the part of the film with the longest anodization time, of course, having the greatest layer thickness.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Chemical Treatment Of Metals (AREA)
EP83108951A 1982-11-30 1983-09-10 Procédé d'oxydation anodique d'alliages de l'aluminium Expired EP0112439B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83108951T ATE33858T1 (de) 1982-11-30 1983-09-10 Verfahren zur anodischen oxydation von aluminiumlegierungen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19823244217 DE3244217A1 (de) 1982-11-30 1982-11-30 Verfahren zur anodischen oxydation von aluminiumlegierungen
DE3244217 1982-11-30

Publications (3)

Publication Number Publication Date
EP0112439A2 true EP0112439A2 (fr) 1984-07-04
EP0112439A3 EP0112439A3 (en) 1986-11-05
EP0112439B1 EP0112439B1 (fr) 1988-04-27

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EP83108951A Expired EP0112439B1 (fr) 1982-11-30 1983-09-10 Procédé d'oxydation anodique d'alliages de l'aluminium

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EP (1) EP0112439B1 (fr)
AT (1) ATE33858T1 (fr)
DE (2) DE3244217A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993003207A1 (fr) * 1991-07-30 1993-02-18 Minsky Radiotekhnichesky Institut Procede de production d'une sous-couche en metal a base d'aluminium ou de ses aliages
EP2166200A1 (fr) 2008-09-23 2010-03-24 Franz Rübig & Söhne GmbH & Co. KG Cuvette de ressort de soupape et son procédé de fabrication
KR101160472B1 (ko) * 2004-03-11 2012-06-28 알카텔-루센트 유에스에이 인코포레이티드 데이터와 호 대 호 센터를 연관시키는 방법
CN113981500A (zh) * 2021-12-09 2022-01-28 陕西宝成航空仪表有限责任公司 硬铝合金壳体零件的草酸阳极氧化工艺方法

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3442591A1 (de) * 1984-11-22 1986-05-22 Vereinigte Aluminium-Werke AG, 1000 Berlin und 5300 Bonn Verfahren zur hartanodisation von im vakuumdruckguss hergestellten aluminium-gussteilen
DE4445007A1 (de) * 1994-12-16 1996-06-20 Fissler Gmbh Verfahren zur Ausstattung eines Geschirrgegenstandes mit einer Antihaftbeschichtung
DE19507472C2 (de) * 1995-03-03 1999-09-02 Electro Chem Eng Gmbh Gas- oder Stromdüse einer Schutzgasschweißanlage
EP2162632B1 (fr) 2007-05-15 2014-06-11 SEW-EURODRIVE GmbH & Co. KG Support de garniture, frein, embrayage ou moteur électrique
DE102008019284B4 (de) 2008-04-16 2015-05-13 Sew-Eurodrive Gmbh & Co Kg Belagträger, Bremse, Kupplung oder Elektromotor

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1150882A (en) * 1965-07-14 1969-05-07 Alcan Res & Dev Anodising Treatment For Aluminium And Its Alloys
US3473103A (en) * 1966-02-28 1969-10-14 Murdock Inc Aluminum anodizing apparatus
US4026781A (en) * 1969-08-07 1977-05-31 Scionics Of California Inc. Anodizing means and techniques
US4152221A (en) * 1977-09-12 1979-05-01 Nancy Lee Kaye Anodizing method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2920018A (en) * 1957-04-22 1960-01-05 Electro Chem Mfg Co Inc Anodizing process and system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1150882A (en) * 1965-07-14 1969-05-07 Alcan Res & Dev Anodising Treatment For Aluminium And Its Alloys
US3473103A (en) * 1966-02-28 1969-10-14 Murdock Inc Aluminum anodizing apparatus
US4026781A (en) * 1969-08-07 1977-05-31 Scionics Of California Inc. Anodizing means and techniques
US4152221A (en) * 1977-09-12 1979-05-01 Nancy Lee Kaye Anodizing method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PLATING AND SURFACE FINISHING, Band 69, Nr. 7, Juli 1982, Seiten 62-65, Winterpark, Florida, US; K. YOKOYAMA et al.: "Advantages of pulse anodizing" *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993003207A1 (fr) * 1991-07-30 1993-02-18 Minsky Radiotekhnichesky Institut Procede de production d'une sous-couche en metal a base d'aluminium ou de ses aliages
KR101160472B1 (ko) * 2004-03-11 2012-06-28 알카텔-루센트 유에스에이 인코포레이티드 데이터와 호 대 호 센터를 연관시키는 방법
EP2166200A1 (fr) 2008-09-23 2010-03-24 Franz Rübig & Söhne GmbH & Co. KG Cuvette de ressort de soupape et son procédé de fabrication
CN113981500A (zh) * 2021-12-09 2022-01-28 陕西宝成航空仪表有限责任公司 硬铝合金壳体零件的草酸阳极氧化工艺方法

Also Published As

Publication number Publication date
DE3244217A1 (de) 1984-05-30
DE3376430D1 (en) 1988-06-01
EP0112439A3 (en) 1986-11-05
EP0112439B1 (fr) 1988-04-27
ATE33858T1 (de) 1988-05-15

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