EP0088192B1 - Überwachung von Anodengasentwicklung in einem dreiwertigen Chromplattierungsbad - Google Patents

Überwachung von Anodengasentwicklung in einem dreiwertigen Chromplattierungsbad Download PDF

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Publication number
EP0088192B1
EP0088192B1 EP82306911A EP82306911A EP0088192B1 EP 0088192 B1 EP0088192 B1 EP 0088192B1 EP 82306911 A EP82306911 A EP 82306911A EP 82306911 A EP82306911 A EP 82306911A EP 0088192 B1 EP0088192 B1 EP 0088192B1
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EP
European Patent Office
Prior art keywords
bath
ion
accordance
chromium
anode
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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.)
Expired
Application number
EP82306911A
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English (en)
French (fr)
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EP0088192A1 (de
Inventor
Edgar John Seyb, Jr.
Laurence Arthur Brown
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M&T Chemicals Inc
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M&T Chemicals Inc
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Priority to AT82306911T priority Critical patent/ATE23370T1/de
Publication of EP0088192A1 publication Critical patent/EP0088192A1/de
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Publication of EP0088192B1 publication Critical patent/EP0088192B1/de
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Classifications

    • 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
    • C25D3/06—Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium

Definitions

  • This invention relates to a process for the electroplating of chromium from aqueous plating baths and more in particular it relates to the production of chromium electrodeposits from a trivalent chromium plating bath. It also relates to a novel trivalent chromium plating bath.
  • Chromium has been electrodeposited from trivalent plating baths primarily for decorative purposes. Generally it has not been utilized for functional chromium plating since the adhesion to the substrate has been poorer than the adhesion of chromium elecroplates produced from hexavalent chromium plating baths.
  • the adhesion produced in trivalent chromium plating operations had been sufficient for decorative purposes and provides several advantages as compared to plating from hexavalent chromium plating baths. These include:
  • conventional trivgient chromium.plating bath compositions usually include sulfate ions as conductivity anions.
  • sulfate ions as conductivity anions.
  • oxygen is released during plating operations and can attack the anode causing erosion and the release of carbon particles into the bath.
  • the resultant carbon particles tend to become included in the chromium electrodeposit thereby producing defects in the plate.
  • chloride ion has been the halogen ion of choice.
  • noxious chlorine gas is given off at the anode.
  • chromium is electroplated from a trivalent chromium plating bath which include a combination of a substantial amount of chloride ion, a nitrogen containing cation and from 0.004 mole per liter to 0.008 mole per liter of bromide ion, thereby suppressing the formation of chlorine gas and hexavalent chromium at the anode during the electroplating process.
  • a trivalent chromium plating bath which include a combination of a substantial amount of chloride ion, a nitrogen containing cation and from 0.004 mole per liter to 0.008 mole per liter of bromide ion, thereby suppressing the formation of chlorine gas and hexavalent chromium at the anode during the electroplating process.
  • the optimum balance between cost and effectiveness is achieved in the above range of bromide ion.
  • the plating behavior of the bath has been found to be independent of the bromide concentration, and this formation represents an appreciable cost saving
  • the trivalent chromium electroplating bath and process of this invention are useful to provide decorative bright chromium electrodeposits. These electrodeposits may be produced on any type of metallic substrate material, but commercially, ferrous metal substrates are generally utilized. While not essential, it is standard commercial practice to first form an electroplate of bright nickel on the substrate material. Alternatively, bright electrodeposits of cobalt, nickel-iron alloy, cobalt-iron alloy, nickel-cobalt-iron alloy or copper could be utilized as the initial coating material for the substrate.
  • the nickel electrodeposit serves to provide a smooth surface onto which the chromium will be deposited. If this surface is not provided, it is believed to be unlikely that the thin chromium deposit would be sufficiently bright for consumer acceptance.
  • the nickel electrodeposit also serves to provide corrosion resistance to the substrate material which is particularly valuable for outdoor usage of the manufactured item.
  • the nickel electrodeposit is not to be confused with a nickel "strike” but is actually a substantial deposit of material. It is general commercial practice to provide a nickel deposit of about 0.1 mil (2.5 pm) to about 0.5 mil (13 pm) for indoor utilization and from about 1.0 mil (25 pm) to about 1.5 mils (38 um) for outdoor utilization.
  • the trivalent chromium plating bath of this invention is conventional with the exception of the nitrogen-containing cation or substance yielding the nitrogen-containing cation in conjunction with a bromide ion content of 0.004 to 0.008 mole per liter.
  • the process details follow normal commercial practice. Details of each may be found in the aforementioned U.S. Patent No. 3,833,485, the relevant portions of which are incorporated herein by reference. The bath and process parameters are discussed hereinafter.
  • U.S. Patent No. 3,833,485 discloses the use of a halogen, either chlorine or bromine to preclude oxygen liberation at the anode.
  • chlorine and bromine are not optional alternatives, but rather are both essential additives.
  • the chlorine is an essential conductivity anion and prevents hexavalent chromium formation at the anode.
  • the presence of hexavalent chromium in concentrations as low as several parts per million can poison the bath.
  • the bromine is critical in order to preclude chlorine generation at the carbon anode.
  • US-A-4093521 describes a trivalent chromium electroplating bath which consists essentially of an acidic aqueous solution of trivalent chromium, a carboxylate selected from formate, acetate and mixtures thereof, a bromide and ammonium, wherein certain Fe and/or Ni amounts are maintained.
  • concentration of bromide is preferably above 0.01 molar, particularly from 0.05 to 0.3 molar, best results being said to be obtained when the concentration of bromide is greater than 0.1 molar.
  • chloride is an optional and preferable addition.
  • US ⁇ A ⁇ 4167460 describes an aqueous acidic trivalent chromium electroplating solution containing a complexing agent, such as ammonium formate or ammonium acetate, a reducing agent, e.g. bromide in concentrations of from about 0.01 up to a.bout 4 molar, and a controlled amount of organic mono- di- ortri- ester phosphates. Chlorides may be present in the bath.
  • a complexing agent such as ammonium formate or ammonium acetate
  • a reducing agent e.g. bromide in concentrations of from about 0.01 up to a.bout 4 molar
  • Chlorides may be present in the bath.
  • any water soluble salt wherein chromium is present in the trivalent state may be utilized in the plating bath.
  • chromic chloride, chromic sulfate or a mixture thereof is utilized due to their low cost and ready availability.
  • chromium tanning salt This is a commonly available form of chromic sulfate, the formula of which is often written Cr(OH)S0 4 .xH 2 0. However, it is believed to be actually a mixture of hydrated basic chromic sulfates, the exact composition of which will be dependent on the pH of the solution from which it was crystallized.
  • the chromium salt may be present over a relatively wide range of concentrations.
  • the chromium ion may be present in the range of from about 0.001 mole per liter to the limit of solubility of the chromium salt.
  • the preferred range is from about 0.01 mole per liter to about 1.0 moles per liter. It is general commercial practice to utilize an initial chromium ion concentration at about the middle of the preferred range. This will ensure that the concentration does not drop during the plating process to a level so low that there may be some burn to the plated item. Further, it is commercially undesirable to have too high a chromium ion concentration as one can encounter waste disposal problems.
  • the bath will, of course, include substantial amounts of various salts to greatly increase the electrical conductivity of the bath.
  • These salts and their constituent ions are generally considered to be salts other than the chromium salt. It is general practice to utilize from about 2 moles per liter to about 6 moles per liter of total conductivity salt. A commercially preferred range is from about 3.5M to about 5.5M.
  • the terms conductivity cation and conductivity anion refer to the cations and anions respectively constituting the conductivity salt.
  • the conductivity anion includes the anionic species which is introduced with the chromium cation.
  • an important conductivity anion is sulfate ion.
  • Sulfate ion is, of course, present whenever chromic sulfate is utilized as a source of chromium ions.
  • additional sulfate ion may be introduced in any water soluble form. It may be most convenient to introduce it in the form of sulfuric acid, which may aid in pH adjustment, or as ammonium sulfate for reasons discussed below.
  • the use of sulfate ion in the plating bath is not essential, but is particularly convenient. In its broadest range, the sulfate ion may comprise any amount up to about 90% (all percentages herein on a mole basis) of the total conductivity anion in the bath.
  • chloride ion is essential for satisfactory chromium plating from the instant trivalent chromium plating bath.
  • it should be present in an amount of at least 5% of the total conductivity anion present in the plating bath.
  • chloride ion is present in an amount which constitutes from about 10% to about 90% of the total conductivity anion present in the plating bath.
  • it is generally utilized at a concentration of 50% or higher.
  • the chloride ion may be introduced in any convenient water soluble form. It is conveniently introduced as hydrochloric acid, ammonium chloride, an alkali metal chloride or mixtures thereof. Of course, it may be also added as chromic chloride.
  • the nitrogen containing cation be present in an amount equal to at least 5% of the total conductivity cation present in the bath. Preferably such cation is present in an amount equal to about 20% to about 90% of the total conductivity cation. It is most convenient to add the nitrogen containing cation to the bath in the form of an ammonium salt, such as the sulfate or chloride as described above. However, it may also be introduced in other forms, such as urea, hydrazine, hydroxylamine, or a variety of other amine materials which are generally added in the form of the sulfate or hydrochloride.
  • the nitrogen containing cation itself may be oxidized at the anode, this process is not sufficient to prevent the production of chlorine gas at the anode. However, it is believed that the nitrogen containing cation is able to reduce the bromine produced at the anode to regenerate bromide ion. Thus, while the nitrogen containing cation is consumed during the plating operations, the bromide ion will not be consumed, it is critical that the nitrogen containing cation be present if the bromide is to function at the very low levels utilized in this invention.
  • the bromide ion of this invention is present in an amount ranging from 0.004 mole per liter to 0.008 mole per liter. Commercially it will be generally utilized in amounts of about 0.0075 mole per liter to ensure that there is at least the optimum concentration present throughout the bath. If there is insufficient bromide ion present, one does not obtain a sufficiently high level of anode gas suppression to have any commercial viability. The utilization of too high a level of bromide ion provides no greater effect and is not economically viable from a commercial standpoint as bromide salts are generally quite expensive.
  • the bromide ion may be added conveniently in any manner similar to the addition of the chloride ion.
  • boric acid or a borate salt or both will also be included in the plating baths of this invention.
  • the presence of the boric acid and/or borate serves to assist in pH control of the system.
  • These materials are generally utilized in a total amount of about 0.1 to about 1 mole per liter, measured as boron.
  • Formate salt in the bath to improve the appearance of the plated product arid provide greater covering power for the bath.
  • Formate ions are generally utilized in the range of about 0.1 mole per liter to about 1.5 moles per liter. The formate may need to be replenished from time to time as it tends to be oxidized at the anode.
  • Acetate ions may also optionally be incorporated into the bath to assist in preventing the formation of hexavalent chromium.
  • the pH of the bath of this invention may be in the range of about 1 to 6 and preferably 2 to 5. Generally a commercial bath will be operated at a pH of about 2.5 to about 4.5.
  • the temperature at which the plating process of this invention is carried out is not critical. Generally it is convenient to maintain temperatures in the range of from about 15°C to about 50°C and preferably from about 15°C to about 30°C.
  • anodes utilized with trivalent plating processes are carbon or graphite or other anode materials having a low overvoltage. These are referred to as inert anodes.
  • Anode materials having a high overvoltage generally insoluble metallic anodes such as lead, tend to assist oxidation of trivalent chromium ions to the undesirable hexavalent state and are generally not used.
  • soluble chromium anodes are generally not utilized.
  • a plating bath was prepared by dissolving the following materials in water and diluting to one liter:
  • the "chromium tanning salt” is chromic sulfate used in the tanning of leather, which is made by the reduction of sodium dichromate with sulfur dioxide.
  • the material used has a "basicity" of 33%, basicity being a measure of the degree of replacement of sulfate ions by hydroxyl ions in the reduction product.
  • the equilibrium pH of the bath after standing overnight was 3.4.
  • the bath prepared above was divided into two equal portions, Part A and Part B.
  • Part A was added 6 ml/I of a solution containing 100 g/I of potassium bromide, yielding a bromide concentration of 0.005 moles per liter in the bath.
  • No bromide was added to Part B.
  • the two solutions were placed in beakers equipped for magnetic stirring and circulatory cooling. Into each was inserted a carbon anode and a steel cathode, the anode to cathode area ration being 2:1. All electrodes were totally submerged in the baths.
  • the two cells were connected in series with a source of direct current, and a current of 1.2 amps (2.4 amps/liter in each bath) was passed for one hour.
  • the current densities were about 50 amps/ft 2 (ASF) (540 amps/m 2 ) on the anodes and about 100 ASF (1100 amps/m 2 ) on the cathodes.
  • ASF amps/ft 2
  • Part A gave off a very mild odor, while the odor from Part B was strong. After 5 minutes the odor from Part B somewhat moderated, but the odor from Part A remaind much milder. For the remainder of the test period the intensity of odor from the two solutions varied, but that from Part A was always substantially lower than that from Part B.
  • a plating bath was formulated as follows:
  • the hydrochloric acid used was standard concentrated laboratory acid.
  • the pH of the bath after equilibrating overnight was 3.4.
  • a sample of this bath was electrolyzed for 5 hours at 0.63 amp/liter, using a totally-submerged carbon anode at 50 ASF (540 amps/m 2 ) and a totally-submerged steel cathode at 100 ASF (1100 amps/m 2 ),
  • the bath temperature was maintained between 17° and 22°C by the use of circulatory cooling during this operation.
  • a highly objectionable odor was produced during this operation.
  • a highly objectionable odor was produced continuously by the bath during plating.

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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)

Claims (12)

1. Ein dreiwertiges Chromplattierungsbad enthaltend eine wässerige Lösung eines dreiwertigen Chromsalzes, wenigstens eines Chloridionen abgebenden Salzes, wenigstens eines Salzes, das ein stickstoffhältiges Kation oder eine Substanz aufweist, die ein stickstoffhältiges Kation abgibt und wenigstens eines Salzes, das Bromidion abgibt, dadurch gekennzeichnet, daß der Gehalt an Bromidion zwischen 0,004 und 0,008 Mol/1 beträgt.
2. Ein Plattierungsbad nach Anspruch 1, weiters enthaltend wenigstens ein Salz, das Sulfation im genannten Bad abgibt.
3. Ein Plattierungsbad nach Anspruch 1 oder 2, weiters enthaltend wenigstens einen Bestandteil der Borsäure und Boration enthaltenden Gruppe.
4. Ein Plattierungsbad nach einem der vorhergehenden Ansprüche, weiters enthaltend Formiation.
5. Ein Verfahren zur Herstellung einer Chrom enthaltenden galvanischen Abscheidung umfassend das Durchleiten eines Stromes von einer Anode zu einer Kathode durch eine wässerige Lösung, die dreiwertige Chromionen, Chloridionen, ein stickstoffhältiges Kation und Bromidionen enthält, während eines Zeitraums, der ausreicht, um die genannte galvanische Abscheidung zu bilden, dadurch gekennzeichnet, daß der Bromidionengehalt zwischen 0,004 und 0,008 Mol/1 der Lösung beträgt.
6. Ein Verfahren nach Anspruch 5, worin die genannte Anode inert ist.
7. Ein Verfahren nach Anspruch 6, worin die genannte Anode ein Kohlenstoffanode ist.
8. Ein Verfahren nach einem der Ansprüche 5 bis 7, worin das Plattierungsbad weiters Sulfation enthält.
9. Ein Verfahren nach einem der Ansprüche 5 bis 8, worin das genannte Bad weiters wenigstens einen bestandteil der Borsäure und Boration enthaltenden Gruppe enthält.
10. Ein Verfahren nach einem der Ansprüche 5 bis 9, worin das genannte Bad weiters Formiation enthält.
11. Ein Verfahren nach einem der Ansprüche 5 bis 10, worin die Temperatur innerhalb eines bereiches von etwa 15°C bis etwa 50°C gehalten wird.
12. Ein Verfahren nach einem der Ansprüche 5 bis 11, worin der pH-Wert innerhalb eines Bereiches von etwa 1 bis etwa 6 gehalten wird.
EP82306911A 1982-03-05 1982-12-23 Überwachung von Anodengasentwicklung in einem dreiwertigen Chromplattierungsbad Expired EP0088192B1 (de)

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Application Number Priority Date Filing Date Title
AT82306911T ATE23370T1 (de) 1982-03-05 1982-12-23 Ueberwachung von anodengasentwicklung in einem dreiwertigen chromplattierungsbad.

Applications Claiming Priority (2)

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US35499982A 1982-03-05 1982-03-05
US354999 1982-03-05

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EP0088192A1 EP0088192A1 (de) 1983-09-14
EP0088192B1 true EP0088192B1 (de) 1986-11-05

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JP (1) JPS58153795A (de)
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DE (1) DE3274123D1 (de)

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Publication number Priority date Publication date Assignee Title
DE3837290A1 (de) * 1988-11-03 1990-07-05 Heraeus Elektroden Pruefung von elektroden mit aktivierungsschichten
EP1845176A4 (de) * 2004-10-18 2011-06-29 Yamaha Motor Co Ltd Motorteil
DE102006035871B3 (de) * 2006-08-01 2008-03-27 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren zur Abscheidung von Chromschichten als Hartverchromung, Galvanisierungsbad sowie hartverchromte Oberflächen und deren Verwendung
JP2009074168A (ja) * 2007-08-30 2009-04-09 Nissan Motor Co Ltd クロムめっき部品およびその製造方法
JP5379426B2 (ja) * 2007-08-30 2013-12-25 日産自動車株式会社 クロムめっき部品およびその製造方法
AT510422B1 (de) * 2010-11-04 2012-04-15 Univ Wien Tech Verfahren zur abscheidung von hartchrom aus cr(vi)- freien elektrolyten
TWI612184B (zh) * 2016-10-18 2018-01-21 德創奈米科技股份有限公司 披覆複合金屬碳化物陶瓷電鍍層之織紗導向元件及其製作方法

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BE822893A (fr) * 1973-12-13 1975-04-01 Perfectionnements relatifs au depot electroytique
US4093521A (en) * 1975-12-18 1978-06-06 Stanley Renton Chromium electroplating
US4167460A (en) * 1978-04-03 1979-09-11 Oxy Metal Industries Corporation Trivalent chromium plating bath composition and process

Also Published As

Publication number Publication date
DE3274123D1 (en) 1986-12-11
JPH0445598B2 (de) 1992-07-27
ATE23370T1 (de) 1986-11-15
JPS58153795A (ja) 1983-09-12
EP0088192A1 (de) 1983-09-14

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