• 专利附录
  • 专利说明
  • 权利要求
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  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method of electrodepositing hard chromium on a substrate from an electrolyte solution containing Cr (II), Cr (III) or mixtures thereof and halides, wherein the formation of elemental halogen is prevented by using a solution anode or complexing the elemental halogen formed during the deposition ,
    公开号:AT510422A4
    申请号:T18172010
    申请日:2010-11-04
    公开日:2012-04-15
    发明作者:Hermann Dr Kronberger；Guenter Dipl Ing Wolf
    申请人:Univ Wien Tech；Cest Gmbh Kompetenzzentrum Fuer Elektrochemische Oberflaechentechnologie；
    IPC主号:
    专利说明:

    - 1 - "Process for the separation of hard chromium from Cr (Vi) - free electrolytes"
    The invention relates to a process for the electrodeposition of chromium, preferably hard chromium, on a substrate made of an electrolyte solution containing Cr (II), Cr (III) or mixtures thereof and halides.
    Hard chrome is produced as a wear and corrosion protection according to the current state of the art in high layer thicknesses almost exclusively of chromic acid electrolyte. Depending on the deposition conditions, hardnesses of between 800 and 1150 HVo.i are achieved. A further increase in hardness can be achieved with conventional hard chrome only by post-treatment. Because of the carcinogenic potential of Cr (VI) compounds and consequent limitations, e.g. According to Regulation (EC) No. 1907/2006 (REACH Regulation), increased efforts are underway to design not only products but also manufacturing processes Cr (VI) -free. Particularly affected are the aerospace and automotive industries and their suppliers.
    Despite considerable research efforts, the deposition of hard chromium from Cr (III) electrolytes in layer thicknesses> 50 μm has not yet been satisfactorily solved. Among others, because of the desirability of avoiding undesirable anode reactions for the use of dimensionally stable (gas-evolving) electrodes, depositions have been proposed in the literature predominantly of sulfate-gel polytrins, often with the use of additives.
    GB 1 488 381 and GB 1 144 913 envisage the use of dimethylformamide (DMF), US 4,107,004 the use of hypophosphite. The deposition of thin Cr layers for decorative purposes is often made of formate oxalate or maleate-based Cr (ril) electrolytes with glycine as an additive.
    US Pat. No. 4,804,446 discloses an electrolyte based on CrCh with additions of boric acid (as buffer), KBr (as conducting salt) and various organic acids (formic acid, glycolic acid and citric acid) or their Na or K salts.
    WO 2007/115030 A1 describes the chromium deposition from trivalent chromium sulfate / chloride electrolytes. The published US patent application. 2008/0169199 A1 describes the use of a trivalent chromium electrolyte based on sulfate and / or chloride with various bromides as additives. T14340 -2 -
    The main disadvantages of the methods described so far in comparison to the deposition of hard chromium from conventional hexavalent electrolytes are usually due to a low maximum layer thickness d (usually d <15 pm) as well as inadequate layer quality or adhesion, etc. Sulfate-based electrolytes often have the disadvantage of formation of Cr (VI) as side reaction at the anode, which is undesirable for Cr (III) electrolytes. The disadvantage of halide-based electrolytes is the anodic reaction of the electrolyte under halogen evolution when using dimensionally stable electrodes.
    The object of the present invention is therefore to provide a method of the type mentioned in which these disadvantages are avoided, in particular, a method is to be provided, in which a chromium layer is deposited on a substrate, which has a good adhesion and very high Hardness and no upper limit for the achievable layer thicknesses. At the same time the chrome layer should have high gloss. Most importantly, the disadvantages of the prior art regarding the toxicity and carcinogenicity of Cr (VI) compounds should be avoided.
    This object is achieved by a process for the electrodeposition of chromium, preferably hard chromium, on a substrate of an electrolyte solution containing Cr (II), Cr (Ili) or mixtures thereof and halides, by preventing the formation of elemental halogen by using a solution anode or by complexing the elemental halogen formed during the deposition.
    The preferred halides are iodides and bromides, although preference is given to the bromides or mixed solutions of iodide / bromide.
    In an embodiment variant, it can be provided that the preparation of the electrolyte solutions takes place by dissolution of Cr metal in acid halide solutions.
    Alternatively, it can be provided that the production of the electrolyte solutions by mixing a solution of Cr (III) halide and a Cr (II) -containing solution. In this embodiment, on the one hand, it may be provided that the preparation of the Cr (II) -containing solution is carried out discontinuously by dissolving Cr metal and admixing it with the Elcktrolvtlösung. On the other hand, however, it can also be provided that the preparation of the Cr (II) -containing solution by dissolving Cr metal and the admixing with the electrolyte solution is carried out continuously by means of a bypass. -3 -
    In one embodiment, it may be provided that the preparation of the electrolyte solutions by dissolution of Cr (III) halides and the in situ - reduction of Cr (III) to Cr (II) takes place directly on the substrate or by means of at least one auxiliary electrode.
    Alternatively, however, it may also be provided that the preparation of the electrolyte solutions by dissolution of Cr (III) halides and the ex situ - reduction of Cr (III) to Cr (II) by means of at least one auxiliary electrode.
    The deposition of metallic chromium apparently proceeds via Cr (II) ions as an intermediate. When using conventional Cr (VI) or commercial Cr (III) electrolytes, these are formed "in situ", ie in the reaction vessel and, moreover, directly on the cathode surface, ie on the workpiece as an intermediate.
    Experience has shown that although a certain minimum concentration of these (very volatile) ions is indispensable for the deposition, in this situation it causes an increasing disturbance of the deposition (due to so-called oleation of the Cr (III) hydrates) which is the probable cause of the limited layer thickness of commercial Represent Cr (III) processes. This oleate ion, which prevents further chromium deposition, is favored by the simultaneous concurrence of (1.) high Cr (II) concentrations and (2.) high pH values, a consequence of the likewise immanent evolution of hydrogen.
    In the inventive method, a high Cr (II) content is generated at the same time low pH, which apparently prevents this Oleation. This is ensured either by: 1. direct dissolution of chromium metal to Cr (II), which partly further reacted directly by the acid or oxygen to Cr (III). The result is a sufficiently acidic Cr (II) / Cr (III) solution (in terms of oleate ion) with a high Cr (II) content. 2. the electrochemical generation of Cr (II) at auxiliary electrodes within (in situ) or outside (ex situ) of the reaction vessel at relatively positive potentials (-450 mV). The (local) alkalization is lower at such auxiliary electrodes than at the workpiece in the Cr metal deposition (at about -1100 mV) and, moreover, not relevant, since it is compensated for further away from the auxiliary electrode by the action of the excess acid. 3. In conventional Cr (VI) F-electrolytes too high a local concentration of Cr (II) ions at the cathode is largely prevented by the high Oxidalionskraft of the high excess Cr (VI) - ions. -4-
    If an auxiliary electrode is used, it preferably has a (negative) hydrogen overvoltage in the range of technical current densities of at least 450 mV. For this purpose, a sufficiently high hydrogen overvoltage may be provided when using an auxiliary electrode that the auxiliary electrode has a surface of Pb, Hg, amalgam, or preferably of conductive (e.g., boron doped) diamond.
    In particular, in the embodiment variants in which no solution anodes are provided, it is preferably provided that the electrolyte solutions have complexing agents for elemental halogen in order to prevent the release of toxic halogens.
    Although in principle different complexing agents are suitable, the skilled person being able to select from a series of complexing agents which are suitable for halogens, it is provided in a preferred embodiment that the complexing agent is a quaternary ammonium compound or a mixture of such compounds. Examples of suitable ammonium compounds are N-methyl-ethyl-pyrolidinium bromide and N-methyl-ethyl-morpholinium-bromide.
    Furthermore, it is preferably provided that the complex which is formed from a reaction of the complexing agent with halogen, preferably bromine or iodine during metal deposition, by reduction reaction to the complexing agent and halide, preferably bromide or iodide, regenerated and can be recycled in this way , This regeneration can be done for example by recombination with kalhodisch formed hydrogen or by dissolution of chromium metal. The aforementioned examples are suitable complexing agents.
    In variants with solution anode, it is preferably provided that the solution anode consists of chromium metal or comprises chromium alloys.
    As the embodiments will also show in detail, cs has surprisingly been found to be favorable when the galvansiche deposition takes place at temperatures below 40 ° C, preferably between 20 ° C and 37 ° C. With these process conditions, it was possible to achieve qualitatively very high-quality layers.
    As individual exemplary embodiments also show, hardnesses of up to 1650 HV are achieved by this process, in particular when using complexing agents, which thus significantly exceed the hardness range of chromium from conventional Cr (VI) baths (up to about 1150 .mu.V). -5 -
    Likewise, in contrast to commercial Cr (III) -based processes in which a maximum layer thickness of only 15 μm is often achieved, the process according to the invention has the advantage of virtually unlimited layer thicknesses, similar to the C'r (VI) -based processes.
    Consequently, it can be provided according to the invention that the hardness of the deposited chromium is above 1150 HV and / or that the layer thickness of the deposited chromium is more than 15 μm.
    Further details and advantages of the invention will be explained below with reference to examples of execution and more detailed descriptions.
    Comparative Example:
    A piece of copper sheet with 1 cm free surface was ground (grade 600), degreased and dissolved as substrate in a simple 2 liter reaction vessel with a Pt-coated titanium expanded metal anode in 1 liter of a freshly prepared solution of 52 g (1 mole) of chromium powder in 2.6 mol HBr, at 47 ° C for 40 min. coated at a constant current density of 110 [A.dm'2]. A glossy, glossy layer with a thickness of 8 pm was obtained, the hardness was 950 HV (Vickers hardness).
    A lowering of the bath temperature to 37 ° C under otherwise identical conditions (110 [A.dm'2], same solution and sample preparation, 40 min deposition time) resulted in a layer thickness of 25 μm and a hardness of 1200 HV
    Example 1:
    Steel sheet with 1 cm 2 free surface was after mechanical and chemical pretreatment in an arrangement analogous to Example 1 under inert gas with an earlier (2 weeks before) prepared solution of 52g (1 mol) chromium powder, dissolved in 2.6 mol HBr and an addition of each 0.2 mol of N-methyl-ethyl-pyrolidinium bromide and N-methyl-ethyl-morpholinium bromide at 57 [A.dm'2] constant current density for 120 minutes at 35 ° C coated. Instead of the development of Br2, the formation of a heavy, semi-liquid organic complex phase was observed at the anode, which was precipitated as a soil body. The bromine odor of the purge gas removed was perceptible, but very significantly reduced compared to the experiment without complexing agent.
    The chromium layer obtained had a thickness of 60 .mu.m with very good layer quality and a temerature of 1400 HV. - 6-
    Example 2:
    A solution of 1 mol freshly precipitated chromium (IIt) hydroxide dissolved in 2.6 mol HBr with an addition of 0.2 mol N-methyl-ethyl-pyrolidiniumbromid and N-methyl-ethyl-morpholinium bromide was to adjust of sufficient Cr (II) content is pre-electrolyzed using a 10 cm.sup.11 lead auxillary lead for 1 h at a current density of 1 [A.dm.sup.2]. Λ
    Subsequently, a piece of copper sheet with 1 cm free surface after mechanical and chemical pretreatment in an arrangement analogous to Example 2 under protective gas in this solution at 19 ° C and 30 [A.dnf2] constant current density for 120 minutes as substrate galvanically coated. The evolution of free bromine was prevented as in Example 2 by the formation of an oil complex during both pre-electrolysis and deposition. A matte layer with a layer thickness of 9 μm and a hardness of 1630 HV was obtained
    In the inventive method, the formation of free halogen is avoided either by complex formation with elimination of organic, non-water-soluble halogen complexes of higher density, or by the -in halide solutions possible use of Lösungsungsanoden.
    The invention thus relates to a process for the galvanic production of chromium layers from Cr (VI) -free electrolytes based on acid halide solutions, in particular iodide and bromide.
    In addition to the use of halogens, preferably bromides or iodides, for the preparation of a trivalent chromium electrolyte, the following aspects are additional features of the invention: 1
    The preparation of an electrolyte solution (chromium solution) comprising a mixture of 2- and 3-valent chromium ions with a high content of Cr (II) is carried out by: a. Mixing 2- and 3-valent chromium solutions or salts, b. direct dissolution of chromium metal c. a combination of resolution of trivalent chromium salts and dissolution of chromium metal or d. Electrochemical reduction of Cr (III) solutions in situ or by means of auxiliary electrodes. 2
    Avoidance of undesired formation of Cr (VI) is achieved by: -7- a. Anodic oxidation of bromide or iodide or b. Use of dissolution anodes (metal oxidation). 3. The avoidance of free bromine or iodine takes place by complex formation by means of additives, for example quaternary ammonium compounds. Solution anodes are - in contrast to the inventive method - can not be used in conventional acidic sulfonated electrolytes because of the passivation of metallic chromium.
    The deposition of chromium from Cr (III) iodide solutions was described in two patents from the 1930s (DE 575450. 1933, DE 579065, 1933) and could be reproduced in own experiments. Films with good appearance but moderate hardness were obtained on Cu substrates. A particular disadvantage of this method is the formation of free halogen at the anode.
    The present invention is based, for example, on attempts to deposit Cr from CrBr3 electrolytes, as well as from electrolytes based on Cr (II) / Cr (IV) mixtures. These gave on Cu and steel substrates very good results in terms of layer quality and high layer thicknesses &gt; 150pm.
    Even in comparison to conventional hard chrome, excellent hardness (up to approx. 1600 HV) is achieved (without heat treatment). Moreover, the halide-based Cr (III) eclipses used have remarkable strength as compared to known electrolytes, which facilitates deposition of even layers on unfavorable geometry components.
    The solutions used preferably consist predominantly of halides, preferably bromides or iodides.
    The complexing agents, for example, quaternary ammonium compounds, can effect the attachment of free halide to form separable organic bromine complexes.
    权利要求:
    Claims (16)
    [1]
    1. A method for the electrodeposition of chromium on a substrate from an electrolyte solution containing Cr (II), Cr (IIJ) or mixtures thereof and halides, characterized in that the formation of elemental halogen is prevented by using a Lösungsanode or that elemental halogen formed during the deposition is complexed.
    [2]
    2. The method according to claim 1, characterized in that the halides are iodides, preferably bromides.
    [3]
    3. The method according to claim 1 or claim 2, characterized in that the preparation of the electrolyte solutions takes place by dissolution of Cr metal in acid halide solutions.
    [4]
    4. The method according to claim 1 or claim 2, characterized in that the preparation of the electrolyte solutions by mixing a solution of Cr (IlI) halide and a Cr (II) -containing solution.
    [5]
    5. The method according to claim 4, characterized in that the preparation of the Cr (II) - containing solution by dissolving Cr metal takes place and the admixture to the electrolyte solution is discontinuous
    [6]
    6. The method according to claim 4, characterized in that the preparation of the Cr (II) - containing solution by dissolution of Cr metal takes place and the admixture to the electrolyte solution takes place continuously by means of bypass.
    [7]
    7. The method according to claim 1 or claim 2, characterized in that the preparation of the electrolyte solutions by dissolution of Cr (lII) halides and the in situ - reduction of Cr (III) to Cr (II) directly on the substrate or by means of at least one auxiliary electrode he follows
    [8]
    8. The method according to claim 1 or claim 2, characterized in that the preparation of the electrolyte solutions by dissolution of Cr (IlI) halides and the ex situ - reduction of Cr (III) to Cr (II) by means of at least one auxiliary electrode.

    • ·· A4 * · ·· I t * · «i« 4 4 4 * »«, «t« · • * m · * -9-
    [9]
    9. The method according to claim 7 or claim 8, characterized in that the auxiliary electrode at technical current densities in their magnitude after a hydrogen overvoltage of &gt; 450mV.
    [10]
    10. The method according to any one of claims 7 to 9, characterized in that the auxiliary electrode has a surface of Pb, Hg, amalgam or preferably of conductive diamond.
    [11]
    11. The method according to any one of claims 1 to 10, characterized in that the electrolyte solutions contain complexing agent for elemental halogen.
    [12]
    12. The method according to claim 11, characterized in that the complexing agent is a quaternary ammonium compound.
    [13]
    13. The method according to claim 11 or claim 12, characterized in that the complexing agent from the halogen complex formed, preferably complexed bromine, is regenerable by reduction reaction.
    [14]
    14. The method according to claim 13, characterized in that the regeneration is carried out by recombination with cathodically formed hydrogen or by dissolution of chromium metal.
    [15]
    15. The method according to any one of claims l to 14, characterized in that the solution anode consists of chromium metal or chromium alloys.
    [16]
    16. The method according to any one of claims 1 to 15, characterized in that the electrodeposition takes place at temperatures below 40 ° C, preferably between 20 ° C and 37 ° C.
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    同族专利:
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    WO2012059473A1|2012-05-10|
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    DE330317C|1920-12-11|Ludwig Schmidt|Device for switching on the fire protection equipment on cinematographs|
    DE575450C|1930-12-14|1933-04-28|Productores De Yoto De Chile A|Process for the electrodeposition of chromium|
    DE579065C|1932-07-01|1933-06-21|Productores De Yodo De Chile A|Process for the electrodeposition of chromium|
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    US4107004A|1975-03-26|1978-08-15|International Lead Zinc Research Organization, Inc.|Trivalent chromium electroplating baths and method|
    GB1488381A|1975-09-01|1977-10-12|Bnf Metals Tech Centre|Trivalent chromium plating bath|
    CA1244376A|1983-05-12|1988-11-08|Thaddeus W. Tomaszewski|Trivalent chromium electrolyte and process|
    DE3274123D1|1982-03-05|1986-12-11|M & T Chemicals Inc|Control of anode gas evolution in trivalent chromium plating bath|
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    DE4011201C1|1990-04-06|1991-08-22|Lpw-Chemie Gmbh, 4040 Neuss, De|Coating workpiece with chromium for improved corrosion resistance - comprises using aq. electrolyte soln. contg. chromic acid sulphate ions, and fluoro:complexes to increase deposition|
    KR101367924B1|2006-03-31|2014-03-17|아토테크 도이칠란드 게엠베하|Crystalline chromium deposit|
    US20080169199A1|2007-01-17|2008-07-17|Chang Gung University|Trivalent chromium electroplating solution and an electroplating process with the solution|
    WO2010069458A1|2008-12-17|2010-06-24|Merck Patent Gmbh|Hexahalochromate complexes|DE102015202910A1|2015-02-18|2016-08-18|Dr.-Ing. Max Schlötter GmbH & Co KG|Tin-nickel layer with high hardness|
    CN109056005A|2018-09-11|2018-12-21|沈阳飞机工业（集团）有限公司|A method of chromium-boron alloy is prepared using electro-deposition techniques|
    法律状态:
    2020-08-15| MM01| Lapse because of not paying annual fees|Effective date: 20191104 |
    优先权:
    申请号 | 申请日 | 专利标题
    AT18172010A|AT510422B1|2010-11-04|2010-11-04|METHOD FOR THE DEPOSITION OF HARTCHROM FROM CR- FREE ELECTROLYTES|AT18172010A| AT510422B1|2010-11-04|2010-11-04|METHOD FOR THE DEPOSITION OF HARTCHROM FROM CR- FREE ELECTROLYTES|
    ES11779627T| ES2531319T3|2010-11-04|2011-10-31|Procedure for segregation of hard chromium from electrolytes free of Cr |
    PCT/EP2011/069144| WO2012059473A1|2010-11-04|2011-10-31|Method for depositing hard chromium from cr-free electrolytes|
    EP11779627.6A| EP2635724B1|2010-11-04|2011-10-31|Process for electroplating hard chromium from a cr free electrolyte|
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