WO1987005056A1 - Electrolytic bath for forming a glossy black chromium coating layer - Google Patents

Electrolytic bath for forming a glossy black chromium coating layer Download PDF

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Publication number
WO1987005056A1
WO1987005056A1 PCT/HU1987/000006 HU8700006W WO8705056A1 WO 1987005056 A1 WO1987005056 A1 WO 1987005056A1 HU 8700006 W HU8700006 W HU 8700006W WO 8705056 A1 WO8705056 A1 WO 8705056A1
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concentration
ions
phosphate
ammonium
bath
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PCT/HU1987/000006
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German (de)
French (fr)
Inventor
Ferenc Magyar
Jeno^" POJBICS
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Látszerészeti Eszközök Gyára
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Publication of WO1987005056A1 publication Critical patent/WO1987005056A1/en

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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
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/04—Electroplating: Baths therefor from solutions of chromium
    • C25D3/08—Deposition of black chromium, e.g. hexavalent chromium, CrVI

Definitions

  • the invention is an electrolytic bath for creating a shiny black chrome coating on a substrate of iron, steel, non-ferrous metal and their alloys.
  • Black chrome plating is manufactured in industry for a variety of purposes.
  • the objects covered with it have an elegant, appealing exterior. Glasses covered with black chrome have been particularly modern nowadays.
  • the common galvanic black chrome coatings were produced in such an electrolytic bath, which contains 15-27 g / l ammonium vanadate, approx. 3 g / l ammonium nitrate, 300-440 g / l.
  • Chromic acid anhydride, 5-8 g / l Barium carbonate continues to contain fluoride ions in a concentration of 90 mg / l.
  • Such baths can be used at room temperature with a voltage of 5-10 V and a current density of 10-20 A / dm 2 using a tin and lead-containing electrode, and the deposition rate achievable with electrolysis is 1.5 ⁇ / 30 Minutes.
  • the coating can only be produced after the surface has been coated with nickel.
  • ammonium vanadate was necessary to ensure the required NH 4 + ion concentration. It is a practical experience that the bath must not contain any sulfate ions and the use of barium carbonate was necessary to immediately bind any sulfate ions that might arise.
  • the supply of fluoride ions was solved by adding ammonium fluoride crystal or sodium silicon fluoride.
  • the electrolytic coating carried out in an electrolytic bath of such a composition was accompanied by numerous disadvantageous properties. In addition to the slow settling speed, the spreadability of the bath was also poor.
  • Scatterability is understood to mean the property of the electrolytic coating, the extent to which it settles in depressions, on covered areas located on articulated surfaces of the object and far away from the electrode, or to what extent a uniform coating thickness can be achieved. Due to the unfavorable spreading ability, the use of an auxiliary electrode was often necessary when objects were to be coated from an articulated surface.
  • the object of the invention is. the creation of such a bath, which enables the reduction of the deficiencies listed here, i.e. higher coating speed, more advantageous spreadability, achieving a perfect gloss, in which no previous nickel coating is necessary on the surface of the metal object.
  • the solution to the problem was guided by the knowledge that the presence of phosphate ions is necessary in the bath, which can be entered with the addition of ammonium phosphate or trisodium phosphate, the first in 15-20 g / l and the second in 10-30 g / l concentration.
  • the presence of the phosphate ions makes it possible to reduce those in the bath Concentration of nitrate ions, the usual concentration of the nitrate of 3 g / l can be reduced to 1-2 g / l.
  • the bath contains. Incidentally, a concentration of 300-440 g / l chromic acid anhydride and 5-8 g / l barium carbonate.
  • ammonium ions With the phosphate and ammonium ions, it is not necessary to maintain the stoichiometric equilibrium, but it is advisable to safeguard an excess of ammonium ions, the value of which does not improve the coating speed, but the absence thereof worsens the scatterability, and the coating can turn gray.
  • the excess of ammonium ions can also be secured by adding ammonium hydroxide to the bath from time to time.
  • the use of the bath modified in this way ensures that a much higher coating speed is achieved at a voltage of 5-10 V and a current density of 10-20 A / dm 2 , the value of which is characteristic of 7 ⁇ / 15 minutes, ie approximately ten times of the usual value in known baths.
  • the electroplating can be carried out up to a temperature of 26oC.
  • the spreadability also improves significantly, the coating of very limp objects can be solved even without using the auxiliary electrode, the thickness of the coating even at the concealed areas is hardly noticeably less.
  • the fluoride concentration can also be reduced in the proposed new bath. It is sufficient if the concentration drops from 90 mg / l to 5-20 mg / l instead of the usual value. This reduction improves the toughness and adhesiveness of the coating.
  • the black chrome coatings produced in the bath according to the invention are brilliantly shiny and result in a homogeneous surface, a shine which was previously impossible for any known bath to secure.
  • the creation of an intermediate layer made of nickel is not necessary; the black, shiny chrome cover can be applied to the surface of objects made of iron, steel, non-ferrous metals and their Alloys can be applied immediately.
  • the coating was created using a 10% tin-containing lead electrode at a temperature of 20 ° C. with a voltage of 8 V and a current density of 15 A / dm 2, first on objects made of iron, later copper and then of brass and nickel silver . The surface of the objects was previously polished. The result was an evenly shining, shiny black chrome coating, the
  • the corrosion resistance was increased by increasing the ratio of chromium trioxide to chromium in the material of the layer.
  • composition of the other bath to create the black chrome coating isoctyl
  • this bath is essentially equivalent to that listed in the first example.
  • composition for another bathroom used to create black chrome plating is as follows:
  • the trisodium phosphate secured the phosphate concentration.
  • the characteristic and coating formation rate of the chrome coating as well as the scatterability is equivalent to that of baths of similar characteristics used in Examples 1 and 2.

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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 And Plating Baths Therefor (AREA)
  • Chemical Treatment Of Metals (AREA)

Abstract

An electrolytic bath for the formation of a glossy black chromium coating layer on a substrate of iron, steel, nonferrous heavy metal or alloys thereof comprises a concentration between 300 and 440 g/l of chromic anhydride, 10 and 30 g/l of phosphate ions and nitrate ions of which the concentration corresponds to the presence of ammonium nitrate in a concentration comprised between 1 and 2 g/l, and optionally a concentration of baryum carbonate comprised between 5 and 8 g/l and a concentration of fluoride ions comprised between 5 and 20 mg/l.

Description

ELEKTROLYTBAD ZUR ERSTELLUNG VON GLÄNZENDEM SCHWARZEN CHROMÜBERZUGELECTROLYTE BATH FOR CREATING SHINY BLACK CHROME COATING
Die Erfindung ist ein Elektrolytbad zu Erstellung von glänzendem schwarzen Chromüberzug auf einem Substrat von Eisen, Stahl, Buntmetall sowie deren Legierungen.The invention is an electrolytic bath for creating a shiny black chrome coating on a substrate of iron, steel, non-ferrous metal and their alloys.
Schwarzer Chromüberzug wird in der Industrie für die verschiedensten Zwecke hergestellt. Die damit überzogenen Gegenstände haben ein elegantes, ansprechendes Aussere. In der letzten Zeit sind mit schwarzem Chrom überzogene Brillenrahmen besonders modern.Black chrome plating is manufactured in industry for a variety of purposes. The objects covered with it have an elegant, appealing exterior. Glasses covered with black chrome have been particularly modern lately.
Die allgemein gebräuchlichen galvanischen schwarzen Chromüberzüge wurden in solchem Elektrolytbad hergestellt, welches 15-27 g/l Ammonium-vanadat, ca. 3 g/l Ammonium-nitrat, 300-440 g/l .Chromsäure-anhydrid, 5-8 g/l Barium-karbonat, weiterhin Fluoridionen in einer Konzentration von 90 mg/l enthält. Solche Bäder können bei Zimmertemperatur mit einer Spannung von 5-10 V und Stromdichte von 10-20 A/dm2 unter Verwendung einer zinn- und bleihaltigen Elektrode angewandt werden, und die mit der Elektrolyse erreichbare Ablagerungsgeschwindigkeit beträgt 1,5 μ/30 Minuten. Der Überzug kann erst nach vorherigem Überziehen der Oberfläche mit Nickel hergestellt werden.The common galvanic black chrome coatings were produced in such an electrolytic bath, which contains 15-27 g / l ammonium vanadate, approx. 3 g / l ammonium nitrate, 300-440 g / l. Chromic acid anhydride, 5-8 g / l Barium carbonate, continues to contain fluoride ions in a concentration of 90 mg / l. Such baths can be used at room temperature with a voltage of 5-10 V and a current density of 10-20 A / dm 2 using a tin and lead-containing electrode, and the deposition rate achievable with electrolysis is 1.5 μ / 30 Minutes. The coating can only be produced after the surface has been coated with nickel.
Im Bad war Ammoniumvanadat zur Sicherung der erforderliehen NH4 +-Ionenkonzentration notwendig. Es ist eine praktische Erfahrung, dass das Bad keine Sulfationen enthalten darf und die Verwendung von Barium-karbonat zur sofortigen Bindung der eventuell entstehenden Sulfationen notwendig war. Die Zuführung von Fluoridionen wurde durch Zugabe von Ammonium-fluoridkristall oder Natrium-siliko-fluorid gelöst. Der in einem Elektrolytbad solcher Zusammensetzung vorgenommene elektrolytische Überzug ging mit zahlreichen nachteiligen Eigenschaften einher. Ausser der geringen Absetzgeschwindigkeit war auch die Streufähigkeit des Bades schlecht. Unter Streufähigkeit versteht man die Eigenschaft des elektrolytischen Überzuges, in welchem Masse das Absetzen in Senken, an abgedeckten Partien, die sich an gegeliederten Oberflächen des Gegenstandes sowie weit entfernt von der Elektrode befinden, erfolgt, bzw. inwieweit eine gleichmässige Überzugsstärke erreicht werden kann. Wegen der unvorteilhaften Streufähigkeit war oft die Benutzung einer Hilfselektrode notwendig, wenn Gegenstände von gegliederter Oberfläche überzogen werden sollten.In the bath, ammonium vanadate was necessary to ensure the required NH 4 + ion concentration. It is a practical experience that the bath must not contain any sulfate ions and the use of barium carbonate was necessary to immediately bind any sulfate ions that might arise. The supply of fluoride ions was solved by adding ammonium fluoride crystal or sodium silicon fluoride. The electrolytic coating carried out in an electrolytic bath of such a composition was accompanied by numerous disadvantageous properties. In addition to the slow settling speed, the spreadability of the bath was also poor. Scatterability is understood to mean the property of the electrolytic coating, the extent to which it settles in depressions, on covered areas located on articulated surfaces of the object and far away from the electrode, or to what extent a uniform coating thickness can be achieved. Due to the unfavorable spreading ability, the use of an auxiliary electrode was often necessary when objects were to be coated from an articulated surface.
Eine weitere Eigenschaft der bekannten schwarzen Chromüberzüge war der leicht matte, schleierhafte Glanz. Mit Hilfe des bekannten Bades konnte selbst durch das vorherige Polieren des Grundmetalles keine strahlende glänzende Oberfläche erreicht werden.Another characteristic of the well-known black chrome coatings was the slightly matt, foggy sheen. With the help of the well-known bath, no shiny, shiny surface could be achieved even by polishing the base metal beforehand.
Aufgabe der Erfindung ist. die Erstellung eines solchen Bades, das die Verringerung der hier aufgeführten Mängel ermöglicht, d.h. höhere Überzugsgeschwindigkeit, vorteilhaftere Streufähigkeit, Erreichung eines einwandfreien Glanzes, bei dem auf der Oberfläche des Metallgegenstandes kein vorheriger Nickelüberzug notwendig ist.The object of the invention is. the creation of such a bath, which enables the reduction of the deficiencies listed here, i.e. higher coating speed, more advantageous spreadability, achieving a perfect gloss, in which no previous nickel coating is necessary on the surface of the metal object.
Die Lösung der gestellten Aufgabe wurde durch die Erkenntnis geleitet, dass im Bad das Vorhandensein von Phosphationen not-wendig ist, deren Eingabe mit der Zugabe von Ammonium-phosphat oder Trinatrium-phosphat erfolgen kann, ersteres in 15-20 g/l und zweites in 10-30 g/l Konzentration. Das Vorhandensein der Phosphationen ermöglicht die Verminderung der im Bad befindlichen Konzentration von Nitrationen, die gewöhnliche Konzentration des Nitrates von 3 g/l kann auf 1-2 g/l vermindert werden. Das Bad enthält. übrigens eine Konzentration von 300-440 g/l Chromsäure-anhydrid und 5-8 g/l Barium-karbonat. Bei den Phosphat- und Ammoniumionen ist die Einhaltung des stöchiometrischen Gleichgewichtes nicht notwendig, jedoch ist die Absicherung eines Überschusses von Ammoniumionen zweckmässig, durch dessen Wert wird die Überzugsgeschwindigkeit nicht verbessert, sein Fehlen verschlechtert jedoch die Streufähigkeit, der Überzug kann grau werden. Der Ammoniumionen-Überfluss kann auch so abgesichert werden, dass dem Bad zeitweise Ammonium-hydroxid zugegeben wird.The solution to the problem was guided by the knowledge that the presence of phosphate ions is necessary in the bath, which can be entered with the addition of ammonium phosphate or trisodium phosphate, the first in 15-20 g / l and the second in 10-30 g / l concentration. The presence of the phosphate ions makes it possible to reduce those in the bath Concentration of nitrate ions, the usual concentration of the nitrate of 3 g / l can be reduced to 1-2 g / l. The bath contains. Incidentally, a concentration of 300-440 g / l chromic acid anhydride and 5-8 g / l barium carbonate. With the phosphate and ammonium ions, it is not necessary to maintain the stoichiometric equilibrium, but it is advisable to safeguard an excess of ammonium ions, the value of which does not improve the coating speed, but the absence thereof worsens the scatterability, and the coating can turn gray. The excess of ammonium ions can also be secured by adding ammonium hydroxide to the bath from time to time.
Die Anwendung des auf diese Weise veränderten Bades sichert bei einer Spannung von 5-10 V und Stromdichte von 10-20 A/dm2 dei Erreichung einer wesentlich grösseren Überzugsgeschwindigkeit ab, dessen Wert von 7 μ /15 Minuten charakteristisch ist, d.h. ungefähr das Zehnfache des gewöhnlichen Wertes bei bekannten Bädern beträgt. Bei Zimmertemperatur ist die Galvanisierung höchstens bis zu einer Temperatur von 26ºC durchführbar. Ausser einer wesentlichen Erhöhung der Ablagerungsgeschwindigkeit verbessert sich ebenfalls bedeutend die Streufähigkeit, das Überziehen von sehr gliedrigen Gegenständen ist auch ohne Verwendung der Hilfselektrode lösbar, die Stärke des Überzuges selbst auch an den verdeckten Stellen ist kaum merkbar geringer.The use of the bath modified in this way ensures that a much higher coating speed is achieved at a voltage of 5-10 V and a current density of 10-20 A / dm 2 , the value of which is characteristic of 7 μ / 15 minutes, ie approximately ten times of the usual value in known baths. At room temperature the electroplating can be carried out up to a temperature of 26ºC. In addition to a significant increase in the rate of deposition, the spreadability also improves significantly, the coating of very limp objects can be solved even without using the auxiliary electrode, the thickness of the coating even at the concealed areas is hardly noticeably less.
In dem vorgeschlagenen neuen Bad ist ausser der Verminderung der Ammonium-nitratkonzentration auch die Fluoridkonzentration verminderbar. Es ist ausreichend, wenn die Konzentration anstelle des gewohnten Wertes von 90 mg/l auf 5-20 mg/l sinkt. Diese Verminderung verbessert die Zähigkeit und Haftfähigkeit des Überzuges.In addition to reducing the ammonium nitrate concentration, the fluoride concentration can also be reduced in the proposed new bath. It is sufficient if the concentration drops from 90 mg / l to 5-20 mg / l instead of the usual value. This reduction improves the toughness and adhesiveness of the coating.
Die im erfindungsgemässen Bad hergestellten schwarzen Chromüberzüge sind strahlend glänzend, ergeben eine homogene Oberfläche, diesen Glanz konnte vorher kein einziges bekanntes Bad absichern. Bei Anwendung des erfindungsgemässen Bades ist die Erstellung einer Zwischenschicht aus Nickel nicht erforderlich, der schwarze glänzende Chrombezug kann auf die Oberfläche von Gegenständen aus Eisen, Stahl, Buntmetallen und deren Legierungen unmittelbar aufgetragen werden.The black chrome coatings produced in the bath according to the invention are brilliantly shiny and result in a homogeneous surface, a shine which was previously impossible for any known bath to secure. When using the bath according to the invention, the creation of an intermediate layer made of nickel is not necessary; the black, shiny chrome cover can be applied to the surface of objects made of iron, steel, non-ferrous metals and their Alloys can be applied immediately.
Die erfindungsgemässe Lösung wird im weiteren anhand von Beispielen erläutert:The solution according to the invention is explained below using examples:
1. Beispiel:1st example:
Zur Erstellung des schwarzen Chromüberzuges wurde ein Bad folgender Zusammensetzung angewandt:A bath of the following composition was used to create the black chrome coating:
Chromsäure-anhydrid 330 g/l Ammonium-phosphat 15 g/lChromic acid anhydride 330 g / l ammonium phosphate 15 g / l
Ammonium-nitrat 1,5 g/l Barium-karbonat 6 g/lAmmonium nitrate 1.5 g / l barium carbonate 6 g / l
Ammonium-fluorid 0,02 g/l x Ammonium fluoride 0.02 g / l x
x deren Konzentration von Fluoridionen entspricht 10 mg/lx whose concentration of fluoride ions corresponds to 10 mg / l
In dem derartig zusammengestellten Bad wurde der Überzug mit Hilfe einer 10 % zinnhaltigen Bleielektrode bei einer Temperatur von 20º C mit einer Spännung von 8 V und Stromdichte von 15 A/dm2 zuerst an Gegenständen aus Eisen, später Kupfer und dann aus Messing und Neusilber erstellt. Die Oberfläche der Gegenstände wurde vorher poliert. Es entstand ein gleichmassig strahlender glänzender schwarzer Chromüberzug, dessenIn the bath assembled in this way, the coating was created using a 10% tin-containing lead electrode at a temperature of 20 ° C. with a voltage of 8 V and a current density of 15 A / dm 2, first on objects made of iron, later copper and then of brass and nickel silver . The surface of the objects was previously polished. The result was an evenly shining, shiny black chrome coating, the
Zähigkeit und Haftfähigkeit bedeutend besser waren als die der bekannten Chromüberzüge.Toughness and adhesion were significantly better than those of the known chrome coatings.
Die Korrosionsbeständigkeit wurde dadurch erhöht, dass im Material der Schicht das Verhältnis des Chrom-trioxydes gegenüber dem Chrom erhöht wurde.The corrosion resistance was increased by increasing the ratio of chromium trioxide to chromium in the material of the layer.
2. Beispiel:2nd example:
Zusammensetzung des anderen Bades zur Erstellung des schwarzen Chromüberzuges:Composition of the other bath to create the black chrome coating:
Chromsäure-anhydrid 330 g/l Barium-karbonat 8 g/lChromic acid anhydride 330 g / l barium carbonate 8 g / l
85 %-ige Phosphorsäure 17 ml/l85% phosphoric acid 17 ml / l
Ammonium-hydroxyd (33 %-ig) 60 ml/l konzentrierte Salpetersäure 1,8 ml/lAmmonium hydroxide (33%) 60 ml / l concentrated nitric acid 1.8 ml / l
Fluoridion 10 mg/lFluoride ion 10 mg / l
In dem derartig zusammengestellten Bad sorgt die zwischen der Salpetersäure und dem Ammonium-hydroxyd sowie der Phosphorsäure verlaufenden Reaktion für die notwendige Nitrat- und Phosphationenkonzentration. In Anbetracht seiner Wirkung ist dieses Bad im wesentlichen äquivalent mit dem im 1. Beispiel aufgeführten.In the bath assembled in this way, the reaction between the nitric acid and the ammonium hydroxide and the phosphoric acid provides the necessary nitrate and phosphate ion concentration. Given its effect, this bath is essentially equivalent to that listed in the first example.
3. Beispiel3rd example
Die Zusammensetzung für ein weiteres verwendetes Bad zur Erstellung von schwarzen Chromüberzug ist folgende:The composition for another bathroom used to create black chrome plating is as follows:
Chromsäure-anhydrid 400 g/lChromic acid anhydride 400 g / l
Barium-karbonat 7 g/l Trinatrium-phosphat 15 g/lBarium carbonate 7 g / l trisodium phosphate 15 g / l
Ammonium-nitrat 2 g/lAmmonium nitrate 2 g / l
Fluoridion 10 mg/lFluoride ion 10 mg / l
Bei diesem Bad hat anstelle des Ammonium-phosphates das Trinatrium-phosphat die Phosphatkonzentration abgesichert. Die Charakteristik und Überzugbildungsgeschwindigkeit des Chromüberzuges sowie die Streufähigkeit ist gleichwertig mit denen in den Beispielen 1 und 2 verwendeten Bädern ähnlicher Charakteristik. In this bath, instead of the ammonium phosphate, the trisodium phosphate secured the phosphate concentration. The characteristic and coating formation rate of the chrome coating as well as the scatterability is equivalent to that of baths of similar characteristics used in Examples 1 and 2.

Claims

Patentansprüche Claims
1. Elektrolytbad zur Erstellung von glänzendem schwarzen Chromüberzug auf einem Substrat von Eisen, Stahl, Bun metall sowie deren Legierungen, das in einer Konzentration von 300-440 g/l Chromsäure-anhydrid, Nitrationen, welche vorteilhaft durch Dissoziation von Ammonium-nitrat anwesend sind, Sulfationen bindendes Mittel, zweckmässigerweise Barium-karboriat in einer Konzentration von 5-8 g/l und gegebenenfalls Fluoridionen, weiterhin Ammonium-hydroxyd enthält, dadurch g e k e n n z e i c h n e t , dass Phosphationen enthalten sind, welche zweckmässigerweise aus einer Konzentration von 15-20 g/l Ammoniumphosphat oder 10-30 g/l Trinatrium-phosphat stammen, weiterhin die Kozentration der Nitrat-ionen dem Vorhandensein von 1-2 g/l Ammonium-nitrat entspricht.1. Electrolytic bath to create a shiny black chrome coating on a substrate of iron, steel, Bun metal and their alloys, which in a concentration of 300-440 g / l chromic acid anhydride, nitrate ions, which are advantageously present by dissociation of ammonium nitrate Sulfate ion-binding agent, advantageously barium carboriate in a concentration of 5-8 g / l and optionally fluoride ions, furthermore contains ammonium hydroxide, characterized in that it contains phosphate ions, which expediently from a concentration of 15-20 g / l ammonium phosphate or 10-30 g / l trisodium phosphate, the concentration of the nitrate ions corresponds to the presence of 1-2 g / l ammonium nitrate.
2. Bad nach Anspruch 1, dadurck gekennzeichnet, dass Fluoridionen in einer Konzentration von 5-20 mg/l enthalten sind.2. Bath according to claim 1, characterized in that fluoride ions are contained in a concentration of 5-20 mg / l.
3. Bad nach Ansprüche 1 oder 2, dadurch g e k e n n zeichnet , dass die Phosphationen durch das Vorhandensein von 15-20 g/l Ammonium-phosphat abgesichert werden.3. Bath according to claims 1 or 2, characterized in that the phosphate ions are secured by the presence of 15-20 g / l ammonium phosphate.
4. Bad nach Ansprüche 1 oder 2, dadurch g e k e n n zeichnet , dass die Phosphationen durch 10-30 g/l Trinatrium-phosphat abgesichert werden.4. Bath according to claims 1 or 2, characterized in that the phosphate ions are secured by 10-30 g / l trisodium phosphate.
5. Bad nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet , dass das Vorhandensein von Phosphorsäure, Ammonium-hydroxyd und Salpetersäure die erforderliche Konzentration der Phosphat- und Nitrationen absichert.5. Bath according to one of claims 1 to 4, characterized in that the presence of phosphoric acid, ammonium hydroxide and nitric acid ensures the required concentration of the phosphate and nitrate ions.
6. Bad nach einem der Ansprüche 1 bis 5, dadureh gekennzeichnet, dass mehr Ammoniumionen enthalten sind, als zum stöchiometrischen Gleichgewicht notwendig ist. 6. Bath according to one of claims 1 to 5, characterized in that more ammonium ions are contained than is necessary for the stoichiometric equilibrium.
PCT/HU1987/000006 1986-02-19 1987-02-19 Electrolytic bath for forming a glossy black chromium coating layer WO1987005056A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
HU702/86 1986-02-19
HU70286A HU198970B (en) 1986-02-19 1986-02-19 Electrolysis bath for making bright, black chromium plating

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WO1987005056A1 true WO1987005056A1 (en) 1987-08-27

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GB (1) GB2196988B (en)
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Publication number Priority date Publication date Assignee Title
AU611957B2 (en) * 1988-10-13 1991-06-27 Council Of Scientific And Industrial Research Improved black chromium plating bath useful for solar selective coatings
NL9000310A (en) * 1989-02-27 1990-09-17 Omi Int Corp MIXTURE AND METHOD FOR CONVERSION.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1449446A (en) * 1974-04-05 1976-09-15 Kampschulte & Cie Dr W Electrolysis baths
DE1621060C3 (en) * 1966-04-08 1978-01-19 Du Pont AQUATIC BATH FOR GALVANIC DEPOSITION OF BLACK CHROME COATINGS
GB2024863A (en) * 1978-06-02 1980-01-16 Bnf Metals Tech Centre Black chromium deposits
SU827606A1 (en) * 1978-06-19 1981-05-07 Предприятие П/Я Р-6762 Electrolyte for precipitating black chrome coatings

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1621060C3 (en) * 1966-04-08 1978-01-19 Du Pont AQUATIC BATH FOR GALVANIC DEPOSITION OF BLACK CHROME COATINGS
GB1449446A (en) * 1974-04-05 1976-09-15 Kampschulte & Cie Dr W Electrolysis baths
GB2024863A (en) * 1978-06-02 1980-01-16 Bnf Metals Tech Centre Black chromium deposits
SU827606A1 (en) * 1978-06-19 1981-05-07 Предприятие П/Я Р-6762 Electrolyte for precipitating black chrome coatings

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DE3790088D2 (en) 1988-08-25
AU7036087A (en) 1987-09-09
GB2196988B (en) 1990-05-02
GB8724086D0 (en) 1987-11-18
GB2196988A (en) 1988-05-11
HU198970B (en) 1989-12-28
HUT43121A (en) 1987-09-28

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