EP0249650B1 - Electrolyte for electrochemically polishing metal surfaces - Google Patents

Electrolyte for electrochemically polishing metal surfaces Download PDF

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Publication number
EP0249650B1
EP0249650B1 EP86108474A EP86108474A EP0249650B1 EP 0249650 B1 EP0249650 B1 EP 0249650B1 EP 86108474 A EP86108474 A EP 86108474A EP 86108474 A EP86108474 A EP 86108474A EP 0249650 B1 EP0249650 B1 EP 0249650B1
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EP
European Patent Office
Prior art keywords
electrolyte
acid
electrolyte according
aluminum
stabilizer
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EP86108474A
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German (de)
French (fr)
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EP0249650A1 (en
Inventor
Friedrich Ruhstorfer
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Poligrat-Holding Te Muenchen Bon GmbH
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Poligrat GmbH
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Priority to DE8686108474T priority Critical patent/DE3667505D1/en
Priority to AT86108474T priority patent/ATE48661T1/en
Priority to EP86108474A priority patent/EP0249650B1/en
Priority to US07/064,095 priority patent/US4740280A/en
Priority to JP62151525A priority patent/JPS634100A/en
Publication of EP0249650A1 publication Critical patent/EP0249650A1/en
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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
    • C25F3/20—Polishing of light metals of aluminium
    • 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
    • C25F3/22—Polishing of heavy metals
    • 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
    • C25F3/22—Polishing of heavy metals
    • C25F3/24—Polishing of heavy metals of iron or steel

Definitions

  • the electrochemical polishing or glossing of metal surfaces is widely used in technology to treat smaller or larger objects made of steel, stainless steel, nickel alloys as well as aluminum and aluminum alloys on the surface.
  • the electrolytes used here usually contain phosphoric and sulfuric acid and optionally chromic acid, the workpieces being switched anodically.
  • the objects to be polished which hang on corresponding support elements or are arranged in baskets or the like, are placed in the electrolyte, i.e. the polishing bath, sunk and lifted out of it after a certain polishing time. After the bath liquid has drained off the polished surfaces, the objects are then immersed in rinsing baths in order to remove the electrolyte.
  • Electrolytes containing sulfuric acid / phosphoric acid and optionally chromic acid are used for the electrochemical polishing of steel, in particular stainless steel, and nickel alloys.
  • the gloss that can be achieved by electrochemical polishing largely depends on the degree of leveling, which is improved with increasing polishing time.
  • satisfactory results are generally achieved at a current density of approximately 25 A / dm 2 in 7 minutes or of approximately 10 A / dm 2 in approximately 20 minutes.
  • DD-A 205 198 describes an electrolyte for the electrochemical polishing of metal products which is essentially anhydrous and consists of a mixture of sulfuric acid and ethylene glycol with the addition of 1 to 10% organic phosphonic acids.
  • the object of the invention is to provide a chromic acid-free electrolyte for electrochemical deburring and polishing, i.e. for the electrolytic or electrochemical removal of metal unevenness from the surface of moldings made of aluminum and aluminum alloys on the one hand and steel, stainless steel and nickel alloys on the other hand, which in aluminum and aluminum alloys Protection against the subsequent etching and matting of the treated surfaces before rinsing off the electrolyte from the freshly polished surface and gives high shine to steel, stainless steel and nickel alloys.
  • this object is now achieved in that chelating agents based on phosphonic acids, preferably in an amount of 1 to 100 g / l, are added to a chromic acid-free electrolyte which contains sulfuric and phosphoric acid but does not contain ethylene glycol.
  • 20 to 30 g / l is preferred for the aluminum electrolyte and 10 to 20 g / l of phosphonic acid, based on the acid electrolyte, is preferred for the electrolyte for workpieces made of steel or nickel alloys.
  • Morpholinomethane diphosphonic acid of the general formula proved to be a particularly advantageous phosphonic acid for the purpose according to the invention: But 1-hydroxyethane-1,1-diphosphonic acid, aminotrismethylenephosphonic acid, diethylenetriamine-pentamethylenephosphonic acid and hydroxymethyldiphosphonic acid are also very suitable.
  • polishing of aluminum and aluminum alloys is carried out with a current density of 5 to 15 A / dm 2 , preferably 8 to 10 A / dm 2 , a polishing time of 15 to 20 minutes and an electrolyte temperature of about 80 ° C.
  • the current density should be 10 to 15 A / dm2, preferably about 15 A / dm 2 , at about 50 ° C and for nickel alloys 5 to 30 A / dm 2 at temperatures of the same order of magnitude, with a polishing time of approx . 15 minutes.
  • the inherently good resistance of phosphonic acids to acidic electrolytes can be improved by the addition of stabilizers in difficult working conditions, such as a very high working temperature and thus increased aggressiveness of the electrolyte.
  • stabilizers are nitrilotriacetic acid, in particular its sodium salt, in a concentration of 0.5 to 2% by weight, in particular about 1% by weight, and sodium glucoheptonate in a concentration of 0.5 to 2% by weight, in particular about 1 wt .-%, particularly proven.
  • the etching begins after 3 s.

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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)
  • ing And Chemical Polishing (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Abstract

The electrolyte according to the invention for electrochemically polishing articles made of steel, stainless steel, nickel alloys, aluminum, and aluminum alloys, and containing phosphoric acid and sulfuric acid comprises an addition of a chelating agent on the basis of phosphonic acids and, if desired, a stabilizer for the latter.

Description

Das elektrochemische Polieren oder Glänzen von Metalloberflächen wird in der Technik vielfach angewendet, um kleinere oder größere Gegenstände aus Stahl, Edelstahl, Nickellegierungen sowie Aluminium und Aluminiumlegierungen oberflächlich zu behandeln. Die hierbei verwendeten Elektrolyte enthalten in der Regel Phosphor- und Schwefelsäure und gegebenenfalls Chromsäure, wobei die Werkstücke anodisch geschaltet werden. Bei diesem Elektropolieren werden die zu polierenden Gegenstände, die an entsprechenden Tragelementen hängen oder in Körben oder dergleichen angeordnet sind, in den Elektrolyt, d.h. das Polierbad, eingesenkt und nach einer gewissen Polierzeit aus diesem herausgehoben. Nach dem Abfließen der BadFlüssigkeit von den polierten Oberflächen werden anschließend die Gegenstände in Spülbäder getaucht, um den Elektrolyt zu entfernen.The electrochemical polishing or glossing of metal surfaces is widely used in technology to treat smaller or larger objects made of steel, stainless steel, nickel alloys as well as aluminum and aluminum alloys on the surface. The electrolytes used here usually contain phosphoric and sulfuric acid and optionally chromic acid, the workpieces being switched anodically. In this electropolishing, the objects to be polished, which hang on corresponding support elements or are arranged in baskets or the like, are placed in the electrolyte, i.e. the polishing bath, sunk and lifted out of it after a certain polishing time. After the bath liquid has drained off the polished surfaces, the objects are then immersed in rinsing baths in order to remove the electrolyte.

Für das elektrochemische Polieren von Aluminium und Aluminiumlegierungen werden nach dem Stand der Technik Elektrolyte auf der Basis Schwefelsäure/Phosphorsäure/Chromsäure eingesetzt. Die Chromsäure soll durch ihre inhibitorische Wirkung ein Anätzen des Aluminiums im stromlosen Zustand verhindern, hat aber zwei Nachteile.

  • a) Während des elektrochemischen Polierens wird ein gewisser Anteil an Chromsäure zu Chrom-(III)-ionen reduziert, die sich mit der Zeit im Elektrolyten anreichern. Ab etwa 2 Gew.-% Chrom-(III)-ionen wird der Poliervorgang beeinträchtigt.
  • b) Chrom-(VI)-ionen gelangen mit dem Spülwasser in das Abwasser und erfordern wegen ihrer hohen Giftigkeit eine besondere Stufe in der Abwasseraufbereitung zur Reduzierung zu Chrom-(III)-ionen, die weniger giftig sind.
According to the prior art, electrolytes based on sulfuric acid / phosphoric acid / chromic acid are used for the electrochemical polishing of aluminum and aluminum alloys. The inhibitory effect of chromic acid is to prevent the aluminum from being etched in the currentless state, but has two disadvantages.
  • a) During electrochemical polishing, a certain proportion of chromic acid is reduced to chromium (III) ions, which accumulate in the electrolyte over time. From about 2% by weight of chromium (III) ions, the polishing process is impaired.
  • b) Chromium (VI) ions get into the wastewater with the rinsing water and, because of their high toxicity, require a special step in the wastewater treatment to reduce to chromium (III) ions, which are less toxic.

Daher war man bestrebt, chromsäurefreie Elektrolyte anzuwenden, bei denen jedoch das Problem der raschen Anätzung der polierten Oberflächen im stromlosen Zustand auftritt. Ein soches nachträgliches Anätzen ist aber sehr unerwünscht, weil es zum Mattieren der bereits polierten Oberfläche führt und dadurch sowohl das dekorative Aussehen der glänzenden Oberfläche gestört als auch durch die damit verbundene Aufrauhung der Oberfläche deren Widerstandsfähigkeit bei der späteren Anwendung der Gegenstände beeinträchtigt wird. Um dies zu vermeiden, ist schnelles Überheben aus dem Elektrolyten in das Spülbad notwendig. Dies führt wiederum zu einer hohen Elektrolytverschleppung und damit hohem Chemikalienverbrauch mit entsprechender Belastung und Verteuerung der Abwasseraufbereitung.Therefore, efforts have been made to use chromic acid-free electrolytes, which, however, have the problem of rapid etching of the polished surfaces in the currentless state. Such subsequent etching is, however, very undesirable because it leads to the matting of the already polished surface and thus both disturbs the decorative appearance of the glossy surface and is impaired by the roughening of the surface associated with this, its resistance to later use of the objects. To avoid this, rapid lifting from the electrolyte into the rinsing bath is necessary. This in turn leads to a high carryover of electrolytes and thus a high consumption of chemicals with a corresponding burden and increase in the cost of wastewater treatment.

Zum elektrochemischen Polieren von Stahl, insbesondere Edelstahl, sowie Nickellegierungen werden Elektrolyte enthaltend Schwefelsäure/Phosphorsäure und gegebenenfalls Chromsäure eingesetzt. Der durch das elektrochemische Polieren erzielbare Glanz ist weitgehend abhängig vom Grad der Einebnung, die mit zunehmender Polierdauer verbessert wird. Zufriedenstellende Ergebnisse werden je nach Zusammensetzung des Elektrolyten in der Regel bei einer Stromdichte von etwa 25 A/dm2 in 7 min bzw. von etwa 10 A/dm2 in ca. 20 min erreicht.Electrolytes containing sulfuric acid / phosphoric acid and optionally chromic acid are used for the electrochemical polishing of steel, in particular stainless steel, and nickel alloys. The gloss that can be achieved by electrochemical polishing largely depends on the degree of leveling, which is improved with increasing polishing time. Depending on the composition of the electrolyte, satisfactory results are generally achieved at a current density of approximately 25 A / dm 2 in 7 minutes or of approximately 10 A / dm 2 in approximately 20 minutes.

Die DD-A 205 198 beschreibt einen Elektrolyten zum elektrochemischen Polieren von Metallerzeugnissen, der im wesentlichen wasserfrei ist und aus einem Gemisch von Schwefelsäure und Ethylenglykol unter Zusatz von 1 bis 10% organischen Phosphonsäuren besteht.DD-A 205 198 describes an electrolyte for the electrochemical polishing of metal products which is essentially anhydrous and consists of a mixture of sulfuric acid and ethylene glycol with the addition of 1 to 10% organic phosphonic acids.

Aufgabe der Erfindung ist es, einen chromsäurefreien Elektrolyten zum elektrochemischen Entgraten und Polieren, also zum elektrolytischen oder elektrochemischen Abtrag von Metall-Unebenheiten von der Oberfläche von Formkörpern aus Aluminium und Aluminiumlegierungen einerseits und Stahl, Edelstahl und Nickellegierungen andererseits bereitzustellen, welcher bei Aluminium und Aluminiumlegierungen einen Schutz gegen das nachträgliche Ätzen und Mattieren der behandelten Oberflächen vor dem Abspülen des Elektrolyten von der frisch polierten Oberfläche bringt und bei Stahl, Edelstahl und Nickellegierungen hohen Glanz ergibt.The object of the invention is to provide a chromic acid-free electrolyte for electrochemical deburring and polishing, i.e. for the electrolytic or electrochemical removal of metal unevenness from the surface of moldings made of aluminum and aluminum alloys on the one hand and steel, stainless steel and nickel alloys on the other hand, which in aluminum and aluminum alloys Protection against the subsequent etching and matting of the treated surfaces before rinsing off the electrolyte from the freshly polished surface and gives high shine to steel, stainless steel and nickel alloys.

Diese Aufgabe wird erfindungsgemäß nun dadurch gelöst, daß einem chromsäurefreien Elektrolyten, der Schwefel- und Phosphorsäure, jedoch kein Ethylenglykol enthält, Chelatbildner auf der Basis von Phosphonsäuren - vorzugsweise in einer Menge von 1 bis 100 g/I - zugesetzt sind.According to the invention, this object is now achieved in that chelating agents based on phosphonic acids, preferably in an amount of 1 to 100 g / l, are added to a chromic acid-free electrolyte which contains sulfuric and phosphoric acid but does not contain ethylene glycol.

Für den Aluminium-Elektrolyten bevorzugt man 20 bis 30 g/i und für den Elektrolyten für Werkstücke aus Stahl oder Nickellegierungen 10 bis 20 g/l Phosphonsäure, bezogen auf den Säure-Elektrolyten.20 to 30 g / l is preferred for the aluminum electrolyte and 10 to 20 g / l of phosphonic acid, based on the acid electrolyte, is preferred for the electrolyte for workpieces made of steel or nickel alloys.

Es ist sehr überraschend, daß derartige Phosphonsäurezusätze zu dem Elektrolyten auf die frisch polierte Metallfläche eine Inhibitor-Wirkung haben, durch die das Anätzen von Aluminium-Werkstücken im stromlosen Zustand bei der Überführung aus dem Elektrolyten in die Spülbäder weitestgehend herabgesetzt ist. Man hat daher mit dem erfindungsgemäßen Elektrolyt die Möglichkeit, die frisch polierten Gegenstände aus dem Elektrolyt herauszuheben, ablaufen zu lassen und dann erst in das erste Spülbad zu tauchen, ohne die Gefahr des Anätzens und des Einschleppens von großen Säuremengen in das Spülbad zu erreichen - führt zu einem geringeren Metallabtrag insgesamt und dadurch zu längerer Arbeitsfähigkeit des Elektrolyten.It is very surprising that such phosphonic acid additions to the electrolyte on the freshly polished metal surface have an inhibitory effect, by means of which the etching of aluminum workpieces in the currentless state is largely reduced when they are transferred from the electrolyte to the rinsing baths. It is therefore possible with the electrolyte according to the invention to lift the freshly polished objects out of the electrolyte, to allow them to run off and then to immerse them in the first rinsing bath without the risk of etching and introducing large amounts of acid into the rinsing bath to a lower metal removal overall and therefore to a longer working capacity of the electrolyte.

Als besonders vorteilhafte Phosphonsäure für den erfindungsgemäßen Zweck erwies sich Morpholinomethandiphosphonsäure der allgemeinen Formel:

Figure imgb0001
Aber auch 1-Hydroxyethan-1,1-diphosphonsäure, Aminotrismethylenphosphonsäure, Diethylentriamin-pentamethylenphosphonsäure und Hydroxymethyldiphosphonsäure sind sehr geeignet.Morpholinomethane diphosphonic acid of the general formula proved to be a particularly advantageous phosphonic acid for the purpose according to the invention:
Figure imgb0001
 But 1-hydroxyethane-1,1-diphosphonic acid, aminotrismethylenephosphonic acid, diethylenetriamine-pentamethylenephosphonic acid and hydroxymethyldiphosphonic acid are also very suitable.

Beim elektrolytischen Polieren kommt es durch Wasser-Elektrolyse zur Wasserstoff- und Sauerstoffentwicklung. Es it bekannt, daß diese Gase, besonders in statu nascendi, außerordentlich aggresiv sind. Es ist daher erforderlich, daß alle Zusätze zu dem Elektrolyten eine außerordentlich hohe Stabilität, insbesondere Reduktions- und Oxidations-Stabilität, besitzen. Falls es dennoch zu einer geringfügigen Zersetzung kommen sollte, so sind die Zusätze im Hinblick darauf auszuwählen, daß diese Zersetzungsprodukte nicht toxisch und insbesondere cancerogen sein dürfen. Im Hinblick auf diese Anforderungen, insbesondere der Stabilität gegenüber nascierendem Sauerstoff und Wasserstoff, ist nun gerade die Morpholinomethandiphosphonsäure für den erfindungsgemäßen Elektrolyt besonders geeignet.In electrolytic polishing, hydrogen and oxygen are evolved through water electrolysis. It is known that these gases, particularly in statu nascendi, are extremely aggressive. It is therefore necessary that all additives to the electrolyte have an extremely high stability, in particular reduction and oxidation stability. If there is nevertheless a slight decomposition, the additives should be selected so that these decomposition products must not be toxic and in particular carcinogenic. In view of these requirements, in particular the stability to nascent oxygen and hydrogen, morpholinomethane diphosphonic acid is now particularly suitable for the electrolyte according to the invention.

Die Wirkung dieser chelatbildenden Phosphonsäuren beim elektrolytischen Polieren oder Entgraten von Metalloberflächen ist deshalb so überraschend, weil Chelatbildner in elektrolytischen Bädern für die Elektroplattierung, d.h. also bei der elektrolytischen Abscheidung von Metallüberzügen, insbesondere von Gold und anderen Edelmetallen sowie deren Legierungen, auf kathodisch geschalteten Gegenständen verwendet wurden, um besonders fest haftende Überzüge und Metaliabscheidungen zu erhalten.The effect of these chelating phosphonic acids in the electrolytic polishing or deburring of metal surfaces is so surprising because chelating agents in electrolytic baths for electroplating, i.e. thus in the electrolytic deposition of metal coatings, in particular gold and other noble metals and their alloys, on cathodically connected objects, in order to obtain particularly firmly adhering coatings and metal deposits.

Im allgemeinen arbeitet man für das Polieren von Aluminium und Aluminiumlegierungen mit einer Stromdichte von 5 bis 15 A/dm2, vorzugsweise 8 bis 10 A/dm2, einer Polierzeit von 15 bis 20 min und einer Elektrolyt-Temperatur von etwa 80°C. Für Stahl und Edelstahl soll die Stromdichte 10 bis 15 A/dm2, vorzugsweise etwa 15 A/dm2, bei etwa 50°C und für Nickellegierungen 5 bis 30 A/dm2 bei Temperaturen in der gleichen Größenordnung sein, bei einer Polierzeit von ca. 15 min.In general, polishing of aluminum and aluminum alloys is carried out with a current density of 5 to 15 A / dm 2 , preferably 8 to 10 A / dm 2 , a polishing time of 15 to 20 minutes and an electrolyte temperature of about 80 ° C. For steel and stainless steel the current density should be 10 to 15 A / dm2, preferably about 15 A / dm 2 , at about 50 ° C and for nickel alloys 5 to 30 A / dm 2 at temperatures of the same order of magnitude, with a polishing time of approx . 15 minutes.

Die an sich gute Beständigkeit von Phosphonsäuren gegenüber sauren Elektrolyten kann bei erschwerten Arbeitsbedingungen, wie sehr hoher Arbeitstemperatur und dadurch erhöhte Aggressivität des Elektrolyten, durch den Zusatz von Stabilisatoren noch verbessert werden. Als derartige Stabilisatoren haben sich Nitrilotriessigsäure, inbesondere deren Natriumsalz, in einer Konzentration von 0,5 bis 2 Gew.-%, insbesondere etwa 1 Gew.-%, und Natriumglukoheptonat in einer Konzentration von 0,5 bis 2 Gew.-%, insbesondere etwa 1 Gew.-%, besonders bewährt.The inherently good resistance of phosphonic acids to acidic electrolytes can be improved by the addition of stabilizers in difficult working conditions, such as a very high working temperature and thus increased aggressiveness of the electrolyte. Such stabilizers are nitrilotriacetic acid, in particular its sodium salt, in a concentration of 0.5 to 2% by weight, in particular about 1% by weight, and sodium glucoheptonate in a concentration of 0.5 to 2% by weight, in particular about 1 wt .-%, particularly proven.

Die Erfindung wird an folgenden Beispielen weiter erläutert.The invention is further illustrated by the following examples.

Beispiel 1example 1

Zum Polieren von Gegenständen aus Aluminium bzw. einer Aluminiumlegierung wurde ein Elektrolyt enthaltend

  • 900 cm3/1 Phosphorsäure (85 gew.-%-ig) und
  • 100 cm3/1 Schwefelsäure (96 gew.-%-ig)

mit einem Zusatz von 25 g/1 Morpholinomethandiphosphonsäure verwendet und bei einer Stromdichte von 9 A/dm2 und 80°C 10 min poliert. Die Gegenstände wurden dann aus dem Polierbad herausgehoben; der Elektrolyt konnte in Ruhe ablaufen, ohne daß nach 60 s eine Anätzung der Oberfläche festgestellt werden konnte. Anschließend wurden die Gegenstände säurefrei gespült. Durch Erhöhung der Phosphonsäuremenge kann diese Zeit noch verlängert werden.An electrolyte was used to polish objects made of aluminum or an aluminum alloy
  • 900 cm 3/1 phosphoric acid (85 wt .-% - ig) and
  • 100 cm 3/1 sulfuric acid (96 wt .-% - ig)

used with an addition of 25 g / 1 morpholinomethane diphosphonic acid and polished for 10 min at a current density of 9 A / dm 2 and 80 ° C. The objects were then lifted out of the polishing bath; the electrolyte could run off at rest without the surface being etched after 60 s. The objects were then rinsed acid-free. This time can be extended by increasing the amount of phosphonic acid.

Wird jedoch ein Elektrolyt ohne dem erfindungsgemäßen Zusatz verwendet, so beginnt das Anätzen bereits nach 3 s.However, if an electrolyte is used without the additive according to the invention, the etching begins after 3 s.

Beispiel 2Example 2

Einem Elektrolyt enthaltend 660 cm3/1 Phosphorsäure (85 gew.-%-ig) und 340 cm3/l Schwefelsäure (96 gew.-%-ig) wurden 10 gfl Morpholinomethandiphosphonsäure sowie 1 Gew.-% Nitrilotriessigsäure zugesetzt und darin Gegenstände aus Edelstahl poliert. Man erhielt bei einer Stromdichte von 15 A/dm2 und 50°C in einer Polierzeit von 6 bis 7 min einwandfreien Glanz.To an electrolyte containing 660 cm3 / 1 phosphoric acid (85% by weight) and 340 cm 3 / l sulfuric acid (96% by weight) were added 10 gfl morpholinomethane diphosphonic acid and 1% by weight nitrilotriacetic acid and therein stainless steel objects polished. A perfect gloss was obtained at a current density of 15 A / dm 2 and 50 ° C. in a polishing time of 6 to 7 minutes.

In einem Elektrolyten ohne dem Phosphonsäurezusatz benötigte man für den gleichen Glanz 10 min.In an electrolyte without the addition of phosphonic acid, it took 10 minutes for the same gloss.

Beispiel 3Example 3

Elektrolyt für Nickellegierungen:

  • 600 cm3/1 Phosphorsäure (85 gew.-%-ig)
  • 400 cm3/1 Schwefelsäure (96 gew.-%-ig)
  • 30 g/I Diethylentriamin-pentamethylenphosphonsäure
  • Stromdichte 15 A/dm2
  • Polierzeit 7 min
Electrolyte for nickel alloys:
  • 600 cm3 / 1 phosphoric acid (85% by weight)
  • 400 cm3 / 1 sulfuric acid (96% by weight)
  • 30 g / l diethylenetriamine-pentamethylenephosphonic acid
  • Current density 15 A / dm2
  • Polishing time 7 min

Wird jedoch ein Elektrolyt ohne dem erfindungsgemäßen Zusatz verwendet, so benötigt man für den gleichen Glanz etwa 10,5 min.However, if an electrolyte is used without the additive according to the invention, about 10.5 minutes are required for the same gloss.

Claims (6)

1. An elektrolyte free of chromic acid for electrochemically polishing articles made from steel, stainless steel, nickel alloys, aluminium and aluminium alloys, said electrolyte containing phosphoric acid and sulphuric acid, with a proviso that the electrolyte does not contain ethylene glycol, characterized by addition of a chelating agent on basis of phosphonic acids.
2. Electrolyte according to claim 1, characterized in that the bath contains from 1 to 100 g/l chelating agent.
3. Electrolyte according to claims 1 or 2, characterized in that the chelating agent is morpholinometh- anediphosphonic acid.
4. Electrolyte according to claims 1 to 3, characterized in that it additionally contains a stabilizer for the phosphonic acid.
5. Electrolyte according to claim 4, characterized in that it contains 0,5 to 2 percent by weight of stabilizer.
6. Electrolyte according to claim 4 or 5, characterized in that the stabilizer is nitrilotriacetic acid or a salt thereof or sodium glucoheptonate.
EP86108474A 1986-06-20 1986-06-20 Electrolyte for electrochemically polishing metal surfaces Expired EP0249650B1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
DE8686108474T DE3667505D1 (en) 1986-06-20 1986-06-20 ELECTROLYT FOR ELECTROCHEMICAL POLISHING OF METAL SURFACES.
AT86108474T ATE48661T1 (en) 1986-06-20 1986-06-20 ELECTROLYTE FOR ELECTROCHEMICAL POLISHING OF METAL SURFACES.
EP86108474A EP0249650B1 (en) 1986-06-20 1986-06-20 Electrolyte for electrochemically polishing metal surfaces
US07/064,095 US4740280A (en) 1986-06-20 1987-06-18 Electrolyte for electrochemically polishing metal surfaces
JP62151525A JPS634100A (en) 1986-06-20 1987-06-19 Electrolyte for electrochemical polishing of metal surface

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EP86108474A EP0249650B1 (en) 1986-06-20 1986-06-20 Electrolyte for electrochemically polishing metal surfaces

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EP0249650A1 EP0249650A1 (en) 1987-12-23
EP0249650B1 true EP0249650B1 (en) 1989-12-13

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10151180A1 (en) * 2001-10-17 2003-04-30 Norbert Nowack Stripping coating containing nickel from metal article, e.g. of iron, steel, aluminum or alloy, uses chelant containing phosphonic acid groups under acid to neutral, oxidative conditions
WO2016030506A1 (en) 2014-08-29 2016-03-03 Poligrat Gmbh Electrolyte for polishing stainless steels, containing a pyridinecarboxylic acid

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JPS634100A (en) 1988-01-09
US4740280A (en) 1988-04-26
EP0249650A1 (en) 1987-12-23
DE3667505D1 (en) 1990-01-18

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