EP1664391B1 - Electropolishing method - Google Patents

Electropolishing method Download PDF

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EP1664391B1
EP1664391B1 EP04764662A EP04764662A EP1664391B1 EP 1664391 B1 EP1664391 B1 EP 1664391B1 EP 04764662 A EP04764662 A EP 04764662A EP 04764662 A EP04764662 A EP 04764662A EP 1664391 B1 EP1664391 B1 EP 1664391B1
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Prior art keywords
electrolyte
electropolishing
phosphoric acid
iii
iron
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German (de)
French (fr)
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EP1664391A1 (en
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Siegfried Piesslinger-Schweiger
Olaf BÖHME
Razmik Abedian
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Poligrat GmbH
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Poligrat GmbH
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F3/00—Electrolytic etching or polishing
    • C25F3/16—Polishing
    • C25F3/18—Polishing of light metals

Definitions

  • electropolishing usually use electrolytes based on phosphoric acid-sulfuric acid-chromic acid mixtures, phosphoric acid-chromic acid mixtures, phosphoric acid-sulfuric acid mixtures and phosphoric acid-nitric acid mixtures. All these electrolytes have in common that satisfactory results in terms of gloss and smoothness can only be achieved on materials with a silicon content of less than 3%.
  • the present invention has thus set itself the goal of providing an electropolishing, which makes it possible to polish light alloys, in particular aluminum and aluminum-magnesium alloys having a silicon content of greater than 3%, with good results electrochemically and deburr.
  • the silicon content of such alloys is usually between 6 and 20%.
  • the inventors have observed that the electrochemical dissolution behavior of aluminum and magnesium on the one hand and silicon on the other hand differs greatly. Based on this observation, they have set themselves the goal of developing an electrolyte in which the removal rate of both components is adjusted so that finally a homogeneous and smooth surface can be obtained. In addition, it has been desired to obtain an electrolyte which can dispense with environmentally harmful chemicals such as chromic acid or nitric acid (due to NO x evolution).
  • the present invention solves the above-mentioned problems by providing an electrolyte substantially containing phosphoric acid, sulfuric acid and a fluoride compound, ferric ion.
  • the fluoride compound may be an alkali fluoride, ammonium fluoride or hydrogen fluoride. Ammonium hydrogen bifluoride has proven to be particularly suitable.
  • the iron (III) ions surprisingly act at least as well as an inhibitor such as chromic acid or other chromates and are not harmful to health or the environment.
  • the iron (III) ion content of 0.1 to 8 wt .-% therefore makes it possible, the surface of aluminum and aluminum-silicon compounds without the addition of chromic acid or nitric acid in an electrolyte based on phosphoric acid or phosphoric acid-sulfuric acid Polishing glossy mixtures without the electro-polished surface being chemically attacked and etched by the electrolyte at short notice.
  • a preferred electrolyte comprises phosphoric acid, sulfuric acid, iron (III) ions, ammonium hydrogen difluoride (NH 4 HF 2 ) in addition to conventional inhibitors and brighteners.
  • the phosphoric acid (85% strength) is used in an amount of 40 to 60 wt .-%.
  • the sulfuric acid (86%) is used in an amount of 30 to 50 wt .-%.
  • the fluoride compound is used in an amount of 0.5 to 6 wt .-%, preferably between 2 to 4 wt .-%.
  • the ferric ions are used in an amount of 0.1 to 8% by weight, preferably 2 to 3.5% by weight.
  • alkanolamines such as ethanolamine, triisopropanolamine, diethanolamine in an amount of 1-10 wt .-%, preferably 4-6 wt .-% used. Mixtures of different brighteners, e.g. different alkanolamines are also possible.
  • the iron (III) ions used as inhibitor can be in the form of iron (III) citrate, iron (III) sodium cyanate, iron (III) phosphate, iron (III) sulfate, iron (III) oxide in one Amount of 0.1-8 wt .-%, preferably from 2-3 wt .-% (based on the Fe / electrolyte ratio) are used. It is possible to use mixtures of different inhibitors, e.g. Use mixtures of various iron (III) salts.
  • the present invention further relates to a method for electropolishing light metal alloy surfaces having a silicon content of more than 3% by weight in an electrolyte containing essentially phosphoric acid, wherein the surface is anodically switched and the electrolyte contains a fluoride.
  • the process is usually operated at a current density of 5-20 A / dm 2 .
  • the process comprises, as a first optional step, the degreasing of the alloy side to be processed.
  • any commercial degreasing solution can be used.
  • the workpiece to be polished is rinsed with a solvent (for example water), and then dipped into the electropolishing bath and anodically connected to the circuit.
  • the processing time is between one and 30 minutes.
  • the current density used is between 5-20 A / dm 2 at a voltage between 5 and 30 volts.
  • the electropolishing is carried out at a temperature of 40 to 90 ° C.
  • the workpiece is removed from the electrolyte and usually rinsed with a solvent (eg water) and then dried.
  • a solvent eg water
  • Castings of material AIMg2Si8 were electropolished in a conventional electropolishing electrolyte (Comparative Example) and in an electrolyte according to the present invention (Example 1).
  • the parts were previously degreased by immersion in a commercial degreasing solution for 5 minutes, then rinsed with water, immersed in the electropolishing and anodically connected to the circuit.
  • the processing time was uniformly 12 minutes. After electropolishing, the parts were rinsed with water and dried.
  • Electrolyte consisting of 80.0% by weight of phosphoric acid (85% strength), 8.0% by weight of sulfuric acid (96% strength), 7.0% by weight of chromic acid, balance water.
  • the surface showed a black-gray coating after electropolishing, which can be partially wiped off. There is no smoothing and leveling of the surface.
  • Electrolyte consisting of 49% by weight phosphoric acid (85% strength), 38% by weight sulfuric acid (96% strength), 2.5% by weight iron (III) ions of iron (III) citrate, 5% by weight of triisopropanolamine, 3% by weight of ammonium hydrogenbifluoride, balance water.
  • the surface was metallically shiny after electropolishing. Due to the silicon content in the alloy, the gloss was slightly weaker and the color slightly darker compared to alloys with a silicon content below 2%. The surface was metallically clean and had no wipeable residue.

Abstract

The invention relates to a method for electropolishing light metal alloy surfaces containing a portion of silicon greater than 3 wt. % in an electrolyte which essentially contains phosphoric acid. The surface is anodically connected and the electrolyte contains a fluoride and iron (III) ions. The invention also relates to an electrolyte used for carrying out said method.

Description

Es sind eine Vielzahl von Verfahren zum Elektropolieren von Aluminium und Aluminium-Magnesium-Legierungen bekannt. Hierbei handelt es sich in der Regel um Legierungen, die durch Walzen, Pressen oder Schmieden umgeformt werden. Durch Elektropolieren wird auf den Oberflächen dieser Legierungen ein guter Glanz erzielt, wenn der Gehalt an Silizium unter ca. 3 % liegt. Bei einem höheren Gehalt an Silizium liegt dieses im Gefüge der Legierung als eigene Phase vor. Da Silizium durch herkömmliche Elektropolierverfahren nicht angegriffen wird, wird das Aluminium beim Elektropolieren selektiv abgetragen und das Silizium bleibt auf der Oberfläche stehen. Die Oberflächen werden dadurch während des Elektropolierens nicht glatt und glänzend, sondern rau und dunkelgrau, wobei das Silizium teilweise als schwärzlicher Belag abgewischt werden kann.There are a variety of methods for electropolishing aluminum and aluminum-magnesium alloys known. These are usually alloys that are formed by rolling, pressing or forging. By electropolishing a good gloss is achieved on the surfaces of these alloys, if the content of silicon is less than about 3%. With a higher content of silicon, this is present in the structure of the alloy as a separate phase. Since silicon is not attacked by conventional electropolishing, the aluminum is selectively removed during electropolishing and the silicon remains on the surface. The surfaces are thereby not smooth and shiny during electropolishing, but rough and dark gray, the silicon can be partially wiped off as a blackish coating.

Herkömmliche Elektropolierverfahren verwenden zumeist Elektrolyten auf der Basis von Phosphorsäure-Schwefelsäure-Chromsäure-Gemischen, Phosphorsäure-Chromsäure-Gemischen, Phosphorsäure-Schwefelsäure-Gemischen sowie Phosphorsäure-Salpetersäure-Gemischen. All diesen Elektrolyten ist gemeinsam, dass befriedigende Ergebnisse hinsichtlich Glanz und Glätte nur auf Werkstoffen mit einem Siliziumgehalt unter 3 % erzielbar sind.Conventional electropolishing usually use electrolytes based on phosphoric acid-sulfuric acid-chromic acid mixtures, phosphoric acid-chromic acid mixtures, phosphoric acid-sulfuric acid mixtures and phosphoric acid-nitric acid mixtures. All these electrolytes have in common that satisfactory results in terms of gloss and smoothness can only be achieved on materials with a silicon content of less than 3%.

Die Industrie nutzt zunehmend Gießverfahren als einfaches, materialsparendes und wirtschaftliches Verfahren zur Herstellung komplex geformter Serienteile. Die zum Giessen verwendeten Legierungen weisen jedoch durchwegs einen Siliziumanteil in der Legierung von deutlich über 3 % auf, um das für die Gießverfahren erforderliche Schmelz- und Fließverhalten zu erzielen. Diese Legierungen gelten deshalb bisher als nicht geeignet für die Bearbeitung durch Elektropolieren. Lediglich das Elektropolierverfahren gemäß SU 817104 A auf Basis von Phosphorsäure, Chromsäure und Amoniumbifluorid bezieht sich auf Aluminium-Silizium-Legierungen mit höherem Siliziumgehalt. In diesem Elektrolyten wirkt Chromsäure als Inhibitor, um einen chemischen Angriff des Elektrolyten auf die elektropolierte Oberfläche zu unterbinden. Dieser Angriff würde die Wirkung der Elektropolitur sofort wieder zerstören, da die Aluminiumoberfläche ohne den Inhibitor gegen den Angriff der Säuremischung nicht ausreichend beständig ist, um die Zeitspanne zwischen Abschalten des Stromes und Abspülen des Elektrolyten unbeschädigt zu überstehen. Chromsäure ist ebenso wie andere Verbindungen des sechswertigen Chroms als sehr giftig, krebserregend und fruchtschädigend eingestuft.The industry is increasingly using casting processes as a simple, material-saving and economical process for the production of complex shaped serial parts. However, the alloys used for casting consistently have a silicon content in the alloy of well over 3% in order to achieve the melting and flow properties required for the casting processes. Therefore, these alloys have hitherto not been considered suitable for machining by electropolishing. Only the electropolishing method according to SU 817104 A based on phosphoric acid, chromic acid and ammonium bifluoride refers to aluminum-silicon alloys with higher silicon content. In this electrolyte chromic acid acts as an inhibitor to prevent a chemical attack of the electrolyte on the electropolished surface. This attack would immediately destroy the effect of electropolishing, since the aluminum surface is not sufficiently resistant without the attack of the acid mixture to survive the period between switching off the current and rinsing the electrolyte undamaged. Chromic acid is as well other compounds of hexavalent chromium are classified as very toxic, carcinogenic and teratogenic.

Aus der EP 1 270 761 ist ein Verfahren zum Reinigen von Leichtmetalllegierungsoberflächen bekannt, bei dem mit einer Lösung gearbeitet wird, welche Phosphorsäure und einen Alkohol enthält. Unter anderem beschreibt dieses Dokument auch ein Reinigungsverfahren, bei dem eine Lösung eingesetzt wird, die zusätzlich Fluorid-Ionen enthält. Die Fluorid-Ionen dienen dem Zweck, bei der vorgeschlagenen anodischen Reinigung die Oberfläche durch eine Fluoridschicht zu passivieren. Mit diesem Verfahren nach dem Stand der Technik wird aber keine Elektropolitur erreicht, da einmal in Gegenwart beträchtlicher Mengen Alkohol und zum anderen bei erheblich geringeren Stromdichten gearbeitet wird (10 bis 500 A/m2). Im Ergebnis wird also eine raue Oberfläche erhalten (wohl durch die Passivierungsschicht). Ein substantieller Materialabtrag wie im Falle einer Elektropolitur wird bei diesem Verfahren weder angestrebt noch beobachtet.From the EP 1 270 761 For example, a method of cleaning light alloy surfaces using a solution containing phosphoric acid and an alcohol is known. Among other things, this document also describes a purification process using a solution which additionally contains fluoride ions. The fluoride ions serve the purpose of passivating the surface through a fluoride layer in the proposed anodic cleaning. With this method according to the prior art, however, no electropolishing is achieved because once in the presence of considerable amounts of alcohol and on the other hand at significantly lower current densities is used (10 to 500 A / m 2 ). As a result, a rough surface is obtained (probably through the passivation layer). Substantial material removal, as in the case of electropolishing, is neither sought nor observed in this process.

Die vorliegende Erfindung hat sich somit zum Ziel gesetzt, ein Elektropolierverfahren anzugeben, das es ermöglicht, Leichtmetalllegierungen, insbesondere Aluminium- und Aluminium-Magnesium-Legierungen mit einem Siliziumgehalt von größer als 3 %, mit gutem Ergebnis elektrochemisch zu polieren und zu entgraten. Der Siliziumgehalt solcher Legierungen liegt üblicherweise zwischen 6 und 20 %.The present invention has thus set itself the goal of providing an electropolishing, which makes it possible to polish light alloys, in particular aluminum and aluminum-magnesium alloys having a silicon content of greater than 3%, with good results electrochemically and deburr. The silicon content of such alloys is usually between 6 and 20%.

Die Erfinder haben beobachtet, dass sich das elektrochemische Auflösungsverhalten von Aluminium und Magnesium einerseits und Silizium andererseits stark unterscheidet. Auf der Grundlage dieser Beobachtung haben sie sich zum Ziel gesetzt, einen Elektrolyten zu entwickeln, bei dem die Abtragungsgeschwindigkeit beider Komponenten so angeglichen wird, dass schließlich eine homogene und glatte Oberfläche erhalten werden kann. Zusätzlich war wünschenswert einen Elektrolyten zu erhalten, bei dem man auf umweltschädliche Chemikalien wie Chromsäure oder Salpetersäure (aufgrund der NOx-Entwicklung) verzichten kann.The inventors have observed that the electrochemical dissolution behavior of aluminum and magnesium on the one hand and silicon on the other hand differs greatly. Based on this observation, they have set themselves the goal of developing an electrolyte in which the removal rate of both components is adjusted so that finally a homogeneous and smooth surface can be obtained. In addition, it has been desired to obtain an electrolyte which can dispense with environmentally harmful chemicals such as chromic acid or nitric acid (due to NO x evolution).

Die vorliegende Erfindung löst die vorstehend genannten Probleme durch die Bereitstellung eines Elektrolyten, der im wesentlichen neben Phosphorsäure, Schwefelsäure und einer Fluoridverbindung, Eisen(III)-Ionen enthält. Die Fluoridverbindung kann ein Alkalifluorid, Ammoniumfluorid oder Hydrogenfluorid sein. Als besonders geeignet hat sich Ammoniumhydrogenbifluorid erwiesen. Die Eisen(III)-Ionen wirken überraschend mindestens ebenso gut als Inhibitor wie Chromsäure oder andere Chromate und sind nicht gesundheits- oder umweltschädigend. Der Eisen(III)-Ionengehalt von 0,1 bis 8 Gew.-% ermöglicht es daher, die Oberfläche von Aluminium- und Aluminium-Silizium-Verbindungen ohne Zusatz von Chromsäure oder Salpetersäure in einem Elektrolyten auf Basis von Phosphorsäure oder Phosphorsäure-Schwefelsäure-Gemischen glänzend zu polieren, ohne dass die elektropolierte Oberfläche durch den Elektrolyten kurzfristig chemisch angegriffen und verätzt wird.The present invention solves the above-mentioned problems by providing an electrolyte substantially containing phosphoric acid, sulfuric acid and a fluoride compound, ferric ion. The fluoride compound may be an alkali fluoride, ammonium fluoride or hydrogen fluoride. Ammonium hydrogen bifluoride has proven to be particularly suitable. The iron (III) ions surprisingly act at least as well as an inhibitor such as chromic acid or other chromates and are not harmful to health or the environment. The iron (III) ion content of 0.1 to 8 wt .-% therefore makes it possible, the surface of aluminum and aluminum-silicon compounds without the addition of chromic acid or nitric acid in an electrolyte based on phosphoric acid or phosphoric acid-sulfuric acid Polishing glossy mixtures without the electro-polished surface being chemically attacked and etched by the electrolyte at short notice.

Ein bevorzugter Elektrolyt umfasst Phosphorsäure, Schwefelsäure, Eisen(III)-Ionen, Ammoniumhydrogenbifluorid (NH4HF2) neben üblichen Inhibitoren und Glanzbildnern. Die Phosphorsäure (85 %-ig) wird dabei in einer Menge von 40 bis 60 Gew.-% eingesetzt. Die Schwefelsäure (86 %-ig) wird in einer Menge von 30 bis 50 Gew.-% eingesetzt. Die Fluoridverbindung wird in einer Menge von 0,5 bis 6 Gew.-%, bevorzugt zwischen 2 bis 4 Gew.-% eingesetzt. Die Eisen(III)-Ionen werden in einer Menge von 0,1 bis 8 Gew.%, vorzugsweise 2 bis 3,5 Gew.% eingesetzt.A preferred electrolyte comprises phosphoric acid, sulfuric acid, iron (III) ions, ammonium hydrogen difluoride (NH 4 HF 2 ) in addition to conventional inhibitors and brighteners. The phosphoric acid (85% strength) is used in an amount of 40 to 60 wt .-%. The sulfuric acid (86%) is used in an amount of 30 to 50 wt .-%. The fluoride compound is used in an amount of 0.5 to 6 wt .-%, preferably between 2 to 4 wt .-%. The ferric ions are used in an amount of 0.1 to 8% by weight, preferably 2 to 3.5% by weight.

Als Glanzbildner werden Alkanolamine wie z. B. Ethanolamin, Triisopropanolamin, Diethanolamin in einer Menge von 1-10 Gew.-%, bevorzugt zwischen 4-6 Gew.-% eingesetzt. Mischungen verschiedener Glanzbildner z.B. verschiedene Alkanolamine sind ebenfalls möglich.As brighteners alkanolamines such. As ethanolamine, triisopropanolamine, diethanolamine in an amount of 1-10 wt .-%, preferably 4-6 wt .-% used. Mixtures of different brighteners, e.g. different alkanolamines are also possible.

Die als Inhibitor verwendeten Eisen(III)-ionen können in Form von Eisen(III)-citrat, Eisen(III)-natriumcyanat, Eisen(III)-phosphat, Eisen(III)-sulfat, Eisen(III)-oxid in einer Menge von 0,1-8 Gew.-%, bevorzugt von 2-3 Gew.-% (bezogen auf das Verhältnis Fe / Elektrolyt), eingesetzt werden. Es ist möglich Mischungen verschiedener Inhibitoren z.B. Mischungen verschiedene Eisen(III)-Salze einzusetzen.The iron (III) ions used as inhibitor can be in the form of iron (III) citrate, iron (III) sodium cyanate, iron (III) phosphate, iron (III) sulfate, iron (III) oxide in one Amount of 0.1-8 wt .-%, preferably from 2-3 wt .-% (based on the Fe / electrolyte ratio) are used. It is possible to use mixtures of different inhibitors, e.g. Use mixtures of various iron (III) salts.

Die verschiedenen Bestandteile des Elektrolyten neben den Säuren und dem Fluorid werden insgesamt so eingestellt, dass bei Durchführung des erfindungsgemäßen Verfahrens eine glatte Oberfläche erhalten wird. Dabei können auch weitere Inhibitoren neben den Eisen(III)-verbindungen zugesetzt werden Gegebenenfalls sind auch Glanzbildner erforderlich, wie die hier genannten Amine Ethanolamin, Diethanolamin und/oder Triisopylamin. Bei dem erfindungsgemäßen Verfahren soll schließlich der Abtrag des Aluminiums sowie des Siliziums im gleichen Maße erfolgen. Die Erfinder, ohne dass diese Erläuterung in irgendeiner Weise die vorliegende Erfindung beschränken sollte, gehen davon aus, dass mit Hilfe des erfindungsgemäßen Elektrolyten der elektrochemische Abtrag des Aluminiums einerseits und der chemische Abtrag des Siliziums andererseits in einer Art Gleichgewicht gehalten werden. Neben der eingesetzten Säure (im wesentlichen Phosphorsäure) spielt möglicherweise das eingesetzte Fluorid eine entscheidende Rolle bei der Steuerung des chemischen Abtrags des Siliziums.The various constituents of the electrolyte in addition to the acids and the fluoride are adjusted overall so that a smooth surface is obtained when carrying out the process according to the invention. It is also possible to add further inhibitors in addition to the iron (III) compounds. Where appropriate, brighteners are also required, such as the amines ethanolamine, diethanolamine and / or triisopylamine mentioned here. Finally, in the method according to the invention, the removal of the aluminum and of the silicon should take place to the same extent. The inventors, without that explanation in any way limiting the present invention, assume that with the aid of the electrolyte according to the invention the electrochemical removal of the aluminum on the one hand and the chemical removal of the silicon, on the other hand, be kept in a kind of equilibrium. In addition to the acid used (essentially phosphoric acid) possibly used fluoride plays a crucial role in the control of the chemical removal of silicon.

Die vorliegende Erfindung betrifft weiterhin ein Verfahren zum Elektropolieren von Leichtmetalllegierungsoberflächen mit einem Siliziumanteil von mehr als 3 Gew.-% in einem Elektrolyten, der im wesentlichen Phosphorsäure enthält, wobei die Oberfläche anodisch geschaltet wird und der Elektrolyt ein Fluorid enthält. Das Verfahren wird üblicherweise bei einer Stromdichte von 5-20 A/dm2 betrieben.The present invention further relates to a method for electropolishing light metal alloy surfaces having a silicon content of more than 3% by weight in an electrolyte containing essentially phosphoric acid, wherein the surface is anodically switched and the electrolyte contains a fluoride. The process is usually operated at a current density of 5-20 A / dm 2 .

Das Verfahren umfasst als ersten optionalen Schritt das Entfetten der zu bearbeitenden Legierungsteite. Hierzu kann jede handelsübliche Entfettungslösung verwendet werden. Üblicherweise wird das zu polierende Werkstück mit einem Lösungsmittel (z.B. Wasser) abgespült, und anschließend in das Elektropolierbad getaucht und anodisch mit dem Stromkreis verbunden. Gewöhnlich beträgt die Bearbeitungszeit zwischen einer und 30 Minuten. Die verwendete Stromdichte liegt zwischen 5-20 A/dm2 bei einer Spannung zwischen 5 und 30 Volt. Die Elektropolitur wird bei einer Temperatur von 40 bis 90 °C durchgeführt. Als abschließender Schritt wird das Werkstück aus dem Elektrolyten entnommen und üblicherweise mit einem Lösungsmittel (z.B. Wasser) gespült und anschließend getrocknet.The process comprises, as a first optional step, the degreasing of the alloy side to be processed. For this purpose, any commercial degreasing solution can be used. Usually, the workpiece to be polished is rinsed with a solvent (for example water), and then dipped into the electropolishing bath and anodically connected to the circuit. Usually the processing time is between one and 30 minutes. The current density used is between 5-20 A / dm 2 at a voltage between 5 and 30 volts. The electropolishing is carried out at a temperature of 40 to 90 ° C. As a final step, the workpiece is removed from the electrolyte and usually rinsed with a solvent (eg water) and then dried.

BeispieleExamples

Gussteile aus Werkstoff AIMg2Si8 wurden in einem herkömmlichen Elektropolierelektrolyten (Vergleichsbeispiel) und in einem Elektrolyten gemäß der vorliegenden Erfindung (Beispiel 1) elektropoliert. In beiden Fällen wurden die Teile zuvor entfettet durch Tauchen in einer handelsüblichen Entfettungslösung für die Dauer von 5 Minuten, anschließend mit Wasser abgespült, in das Elektropolierbad getaucht und anodisch mit dem Stromkreis verbunden. Die Bearbeitungszeit betrug einheitlich 12 Minuten. Nach dem Elektropolieren wurden die Teile mit Wasser abgespült und getrocknet.Castings of material AIMg2Si8 were electropolished in a conventional electropolishing electrolyte (Comparative Example) and in an electrolyte according to the present invention (Example 1). In both cases, the parts were previously degreased by immersion in a commercial degreasing solution for 5 minutes, then rinsed with water, immersed in the electropolishing and anodically connected to the circuit. The processing time was uniformly 12 minutes. After electropolishing, the parts were rinsed with water and dried.

VergleichsbeispielComparative example

Elektrolyt bestehend aus 80,0 Gew.-% Phosphorsäure (85 %-ig), 8,0 Gew.-% Schwefelsäure (96 %-ig), 7,0 Gew.-% Chromsäure, Rest Wasser.Electrolyte consisting of 80.0% by weight of phosphoric acid (85% strength), 8.0% by weight of sulfuric acid (96% strength), 7.0% by weight of chromic acid, balance water.

Bearbeitungsparameter:Processing parameters:

Spannung:Tension: 18 V18 v Temperatur:Temperature: 70°C70 ° C Stromdichte:Current density: 10 A/dm2 10 A / dm 2

Die Oberfläche zeigte nach dem Elektropolieren einen schwarzgrauen Belag, der sich teilweise abwischen lässt. Es ist keine Glättung und Einebnung der Oberfläche erfolgt.The surface showed a black-gray coating after electropolishing, which can be partially wiped off. There is no smoothing and leveling of the surface.

Beispiel 1: Example 1 :

Elektrolyt bestehend aus 49 Gew.-% Phosphorsäure (85 %-ig), 38 Gew.-% Schwefelsäure (96 %-ig), 2,5 Gew.-% Eisen(III)-ionen aus Eisen(III)-citrat, 5 Gew.-% Triisopropanolamin, 3 Gew.-% Ammoniumhydrogenbifluorid, Rest Wasser.Electrolyte consisting of 49% by weight phosphoric acid (85% strength), 38% by weight sulfuric acid (96% strength), 2.5% by weight iron (III) ions of iron (III) citrate, 5% by weight of triisopropanolamine, 3% by weight of ammonium hydrogenbifluoride, balance water.

Bearbeitungsparameter:Processing parameters:

Spannung:Tension: 18 V18 v Temperatur:Temperature: 65°C65 ° C Stromdichte:Current density: 10 A/dm2 10 A / dm 2

Die Ober-fläche war nach dem Elektropolieren metallisch glänzend. Bedingt durch den Siliziumanteil in der Legierung war der Glanz geringfügig schwächer und die Farbe etwas dunkler im Vergleich zu Legierungen mit einem Siliziumgehalt unter 2 %. Die Oberfläche war metallisch sauber und wies keine abwischbaren Rückstände auf.The surface was metallically shiny after electropolishing. Due to the silicon content in the alloy, the gloss was slightly weaker and the color slightly darker compared to alloys with a silicon content below 2%. The surface was metallically clean and had no wipeable residue.

Claims (5)

  1. A method for electropolishing light metal alloy surfaces having a portion of silicon greater than 3 wt.% in an electrolyte which essentially contains phosphoric acid or a phosphoric acid-sulphuric acid mixture and a fluoride, wherein the surface is anodically connected and the electrolyte contains iron(III) ions.
  2. The method according to claim 1, which is operated at a current density of 5 to 20 A/dm2.
  3. An electrolyte for carrying out a method of claim 1 or 2, characterized in that the electrolyte comprises
    - phosphoric acid (85%) in an amount of 40 to 60 wt.%,
    - sulphuric acid (86%) in an amount of 30 to 50 wt.%,
    - a fluoride compound in an amount of 0.5 to 6 wt.%, and
    - iron(III) ions in an amount of 0.1 to 8 wt.%.
  4. The electrolyte of claim 3, characterized in that it further contains brighteners.
  5. The electrolyte according to claim 4, characterized in that the brightener is ethanolamine, diethanolamine and/or triisopropylamine and is present in an amount of 1 to 10 wt.%.
EP04764662A 2003-09-05 2004-08-31 Electropolishing method Not-in-force EP1664391B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10341061A DE10341061B4 (en) 2003-09-05 2003-09-05 Electropolishing process for light metal alloys and electrolyte
PCT/EP2004/009697 WO2005024099A1 (en) 2003-09-05 2004-08-31 Electropolishing method

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EP1664391A1 EP1664391A1 (en) 2006-06-07
EP1664391B1 true EP1664391B1 (en) 2010-05-05

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CN104032363A (en) * 2014-06-19 2014-09-10 南昌航空大学 Phosphoric-acid-free electrochemical polishing process for siliceous aluminum alloy

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CN104032365B (en) * 2014-06-19 2017-04-19 南昌航空大学 Formula and process aiming at electrolytic polishing of siliceous aluminum alloy
CN104032364A (en) * 2014-06-19 2014-09-10 南昌航空大学 Formula and process aiming at phosphoric-acid-free electrolytic polishing of siliceous aluminum alloy
US11737867B2 (en) 2015-11-03 2023-08-29 Biotronik Ag Method for reducing paravalvular leaks with decellularized tissue
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EP3269848B1 (en) * 2016-07-13 2019-09-11 Airbus Defence and Space GmbH A method for the surface finishing of metals and alloys
CN106757298B (en) * 2016-12-21 2019-08-02 江苏和兴汽车科技有限公司 A kind of Chrome-free electropolishing liquid, aluminium alloy electric polishing method and automobile aluminum decoration

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CN104032363A (en) * 2014-06-19 2014-09-10 南昌航空大学 Phosphoric-acid-free electrochemical polishing process for siliceous aluminum alloy

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