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
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
  • C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
  • C23C28/3225—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only with at least one zinc-based layer
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
  • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/06—Metallic material
  • C23C4/08—Metallic material containing only metal elements
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
  • C23C4/11—Oxides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/18—After-treatment
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/10—Electrodes, e.g. composition, counter electrode
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D21/00—Processes for servicing or operating cells for electrolytic coating
  • C25D21/12—Process control or regulation
  • C25D21/14—Controlled addition of electrolyte components
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D21/00—Processes for servicing or operating cells for electrolytic coating
  • C25D21/16—Regeneration of process solutions
  • C25D21/18—Regeneration of process solutions of electrolytes
• • 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
  • C25D3/22—Electroplating: Baths therefor from solutions of zinc
• • 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
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc

Definitions

• the present invention relates to a process for the electrodeposition of zinc and zinc alloy coatings from an alkaline coating bath with zinc and zinc alloying electrolytes and organic bath additives, e.g. Complexing agents, brighteners and wetting agents.
• the invention further relates to the use of materials as an anode for the electrodeposition of a zinc and zinc alloy coating from an alkaline coating bath with zinc and zinc alloying electrolytes and organic bath additives, and to a corresponding galvanic apparatus for the deposition of zinc and zinc alloy coatings.
• Alkaline zinc and zinc alloy baths are typically not operated with soluble zinc anodes.
• soluble zinc anodes the zinc is electrochemically oxidized to Zn (II) during anodic operation.
• the Zn (II) ions formed enter into the soluble zincate complex, the Zn [(OH) 4 ] 2- , with the surrounding hydroxide ions.
• Zinc in addition to electrochemical dissolution, is oxidized by the alkaline environment to Zn (II) to form hydrogen. This means that the zinc anode additionally dissolves chemically by the abovementioned redox reaction, which leads to an uncontrolled increase in the Zn (II) concentration in the zinc alloy electrolyte.
• alkaline zinc and zinc alloy baths are usually operated with insoluble anodes, and zinc is often dissolved in a separate zinc dissolving tank to form Zn (II) and added to the bath.
• anode material therefore come materials that are electrically conductive and chemically inert to at least bases, are used. These include metals such as nickel, iron, stainless steel, cobalt or alloys of the metals mentioned.
• metals such as nickel, iron, stainless steel, cobalt or alloys of the metals mentioned.
• organic bath additives such as complexing agents, brighteners and wetting agents are usually used in addition to the zinc or zinc alloy electrolyte.
• the anodic oxidation of the organic bath additives also undesirable by-products, such as oxalates, carbonates, etc., can be formed, which can interfere with the galvanic coating process.
• Amine-containing complexing agents are used, for example, in coating baths for the electrodeposition of a zinc nickel alloy coating.
• the nickel is used in the form of Ni (II), which forms a sparingly soluble nickel hydroxide complex in an alkaline medium with the surrounding hydroxide ions.
• Alkaline zinc nickel electrolytes must therefore contain special complexing agents with which Ni (II) is more preferably complexed than with the hydroxide ions in order to bring the nickel into solution in the form of Ni (II).
• a commonly required limit for cyanide contamination in wastewater is 1 mg / l. Due to national or regional legislation, the permitted limits for cyanide contamination in wastewater may still be below this level.
• the cyanides formed must therefore be detoxified consuming. This is done in practice by oxidation, e.g. with sodium hypochlorite, hydrogen peroxide, sodium peroxodisulfate, potassium peroxomonosulfate or similar compounds.
• the removed electrolyte contains other oxidizable substances in addition to the cyanide, so much more oxidizing agent is consumed for complete oxidation than theoretically could be determined from the cyanide content.
• increased cyanide formation further causes the problem that unwanted complexes with the bath additives can be formed.
• the cyanide content is very disadvantageous when using a zinc nickel electrolyte, since nickel with the cyanide ions formed forms the stable tetracyanonickelate complex, Ni [(CN) 4] 2- , as a result of which the nickel bound in this complex is no longer available for deposition Available. Since it is not possible to differentiate between the complexed by cyanide and the complexed by the amines nickel in the current electrolyte analysis, the increase of the cyanide content in the electrolyte means a reduction in process safety.
• the nickel concentration In order to meet the required alloy composition of 10-16 wt.% Nickel over the entire current density range, the nickel concentration must be adjusted in the course of operation according to the cyanide concentration in the electrolyte, since the complexed by cyanide nickel content is not available for deposition stands. With the increase in the cyanide content in the electrolyte, the nickel content must therefore be adjusted accordingly in order to keep the nickel content in the layer constant. In order to maintain the required alloy composition, unscheduled additions of nickel salts to the electrolyte must be made. Suitable supplemental solutions are nickel salts which have a high water solubility. Nickel sulfate solutions in combination with various amine compounds are preferably used for this purpose.
• cyanide in a zinc nickel alloy electrolyte can also adversely affect the optical appearance of the deposit. It can come in the high current density range to a milky veiled deposition. This can be partially corrected by higher dosage of brighteners again. However, this measure is associated with an increased consumption of brighteners and thereby additional costs in the deposition.
• Both processes reduce the formation of cyanides.
• a disadvantage of both methods is that very high investment costs arise from the incorporation of the ion exchange membranes.
• a device for separate circulation of the anolyte must be installed.
• the incorporation of ion exchange membranes is also not generally feasible in zinc nickel deposition processes.
• auxiliary anodes are often used to seal the frames when the hangers are tightly sealed To optimize layer thickness distribution. For technical reasons, it is not possible here to separate these auxiliary anodes by ion exchange membranes. Therefore, cyanide formation can not be completely avoided in this application.
• EP 1 702 090 B1 claims a method which provides for the separation of the cathode and anode compartments through an open cell material.
• the separator is made of polytetrafluoroethylene or polyolefin, such as polypropylene or polyethylene.
• the pore diameters have a dimension between 10 nm and 50 ⁇ m.
• ion exchange membranes where the charge transport through the membrane is carried out by the exchange of cations or anions, it can be carried out with the use of open-cell separators only by the electrolyte transport through the separator. Complete separation of the catholyte from the anolyte is not possible. It can therefore not be completely prevented that amines reach the anode and are oxidized there. Cyanide formation is therefore not completely ruled out in this process.
• a disadvantage of this method also that when using separators with a very small pore diameter (eg 10 nm) of the electrolyte exchange and thus the current transport is very much hindered, which leads to an overvoltage.
• the overvoltage is claimed to be less than 5 volts, a bath voltage of at most 5 volts overvoltage would still be nearly doubled compared to a process which operates without separation of the cathode and anode compartments. This results in a much higher energy consumption during the deposition of the zinc nickel layers.
• the up to 5 volts higher bath voltage also causes a strong heating of the electrolyte.
• the separator may also have a pore diameter of 50 microns, which may prevent the formation of overvoltage, but the relatively large pore diameter again allows a virtually unhindered exchange of electrolyte between the cathode and anode space and thus can not prevent the formation of cyanides.
• the anode and cathode space is separated there by a filtration membrane.
• the size of the pores of the filtration membrane is in the range of 0.1 to 300 nm.
• a certain transfer of electrolyte from the cathode to the anode space is deliberately accepted.
• DE 103 45 594 A1 describes a cell for the anodic oxidation of cyanides in aqueous solutions, comprising a fixed bed anode and a cathode, which is characterized in that the particle bed of the anode consists of particles of manganese or the oxides of titanium or mixtures of these particles.
• the published patent application describes that this process is suitable for reducing cyanometallate complexes in wastewaters. Accordingly, it is in the treatment of in DE 103 45 594 A1 described cyanide-containing aqueous solutions aim to remove existing cyanides and cyanometalate complexes from the wastewater. This is in contrast to the object of the present invention, in which only the formation of cyanides is to be prevented.
• the object of the present invention is to provide a process for the electrodeposition of zinc and zinc alloy coatings from an alkaline coating bath with zinc and zinc alloying electrolytes and organic bath additives, which has a reduced anodic oxidation and a concomitant reduced degradation of the organic bath additives, such as complexing agents, brighteners, wetting agents, etc., as well as a reduced formation of undesirable degradation products, such as cyanides causes.
• the method according to the invention should make it possible to be integrated into existing alkaline zinc and zinc alloy baths without additional effort, and to allow a significantly more economical operation of the method.
• electrodes made of metallic manganese or a manganese-containing alloy and suitable for use as an insoluble anode in an alkaline zinc and zinc alloy bath are suitable.
• the manganese-containing alloy is preferably selected from a manganese-containing steel alloy or a manganese-containing nickel alloy. In the process according to the invention, the use of a manganese-containing steel alloy is particularly preferred.
• the alloy content of the manganese-containing alloy has a manganese content of at least 5% by weight of manganese, preferably 10 to 90% by weight of manganese, particularly preferably 50 to 90% by weight of manganese.
• Commercially available steel electrodes have, for example, a manganese content of 12% by weight of manganese (X120Mn12 with the material number: 1.3401) or 50% by weight of manganese (mirror iron).
• the above-mentioned solid electrodes made of metallic manganese or a manganese-containing alloy there are also electrodes made of an electrically conductive substrate suitable for use as an insoluble anode in an alkaline zinc and zinc alloy bath with metallic manganese deposited thereon and / or manganese oxide-containing coating in question.
• the support material is preferably selected from steel, titanium, nickel or graphite. In the process according to the invention, the use of steel as carrier material is particularly preferred.
• the metallic manganese and / or manganese oxide-containing coating has a manganese content of at least 5% by weight of manganese, preferably 10-100% by weight of manganese, particularly preferably 50-100% by weight of manganese, and particularly preferably 80-100% by weight. Manganese, based on the total amount of manganese, which results from metallic manganese and manganese oxide, on.
• the metallic manganese and / or manganese oxide-containing coating can be applied to the support, therefore, by several methods, including by thermal spraying, cladding, or chemical vapor deposition such as physical vapor deposition (PVD of Engl. Physical vapor deposition).
• the layer thickness of the metallic manganese and / or manganese oxide-containing coating is not decisive, and depending on the method can be a few nanometers (eg by PVD method) up to several millimeters (eg by thermal spraying method).
• the coating containing metallic manganese and / or manganese oxide can be applied to the carrier by thermal spraying.
• the manganese-containing coating material used for thermal spraying can consist of both metallic manganese and of a mixture which contains iron and / or nickel in addition to metallic manganese.
• the manganese-containing coating material used for thermal spraying preferably has a manganese content of 80% by weight manganese or more, preferably 90% by weight manganese or more, particularly preferably 100% by weight manganese.
• the manganese-containing coating material is preferably used in a form suitable for thermal spraying, for example as powder or wire.
• atomizing gas e.g., compressed air or inert gas such as nitrogen and argon
• spun onto the surface of the carrier to be coated e.g., a good connection to the carrier surface and a firm metallic manganese and / or manganese oxide layer is formed, mainly by mechanical clamping.
• the carrier to be coated can be roughened by corundum blasting prior to the thermal spraying process (blasting material in this case is zirconium corundum).
• blasting material in this case is zirconium corundum.
• Another possibility is to place an additional primer between the support and the metallic manganese and / or manganese oxide-containing coating.
• the primer may for example consist of nickel.
• the primer may be produced by the same thermal spraying method as the metallic manganese and / or manganese oxide-containing coating, for example flame spraying or arc spraying.
• the primer is usually produced with a layer thickness of 50-100 ⁇ m.
• the manganese-containing coating material is usually thermally sprayed directly onto the primer.
• the manganese-containing coating material is usually thermally sprayed directly onto the substrate to be coated.
• the manganese-containing coating material can be thermally sprayed onto the carrier by means of conventional spraying methods. These include: Arc Wire Spraying, Thermo Spray Powder Spraying, Flame Spraying, High Speed Flame Spraying, Plasma Spraying, Autogenous Bar Spraying, Autogenous Wire Spraying, Laser Spraying, Cold Gas Spraying, Detonation Spraying, and Plasma Transferred Wire Arc (PTWA) Spraying. These methods are known per se to the person skilled in the art.
• the manganese-containing coating material can be applied to the carrier, in particular by means of flame spraying or electric arc spraying. For the use of a powdered manganese-containing coating material is particularly suitable flame spraying.
• the self-fluxing powders usually additionally require a thermal aftertreatment, whereby the adhesion of the sprayed layer on the carrier is considerably increased.
• the thermal aftertreatment is usually carried out with acetylene-oxygen burners.
• the sprayed layer becomes both gas-tight and liquid-tight, for which reason the manganese-containing coating material is preferably applied to the carrier by means of powder flame spraying.
• layer thicknesses of 50 ⁇ m up to several millimeters can be applied to the carrier by means of the abovementioned method.
• the thermal spraying can be carried out both under an air atmosphere and under an inert gas atmosphere.
• This can usually be regulated by the type of nebulizer gas.
• an inert gas such as nitrogen or argon
• oxidation of the manganese-containing coating material is largely prevented.
• a manganese layer of metallic manganese or a manganese alloy can be applied to the carrier.
• manganese oxides would then form in the course of the electrodeposition process on the carrier anode with the metallic manganese or manganese alloy layer applied thereon, which constitute the active surface.
• these can also be applied in advance on the carrier.
• a positive effect ie suppression of the anodic oxidation of the organic bath additives.
• the manganese-containing coating material sprayed under air atmosphere then contains, in addition to metallic, a layer applied to the carrier Manganese and optionally iron and / or nickel and manganese oxides, and optionally iron oxides and / or nickel oxides or combinations thereof.
• the coating containing metallic manganese and / or manganese oxide can also be applied by build-up welding, also known as weld-cladding.
• the manganese-containing coating material used for build-up welding can consist of both metallic manganese and a mixture which contains iron and / or nickel in addition to metallic manganese.
• the manganese-containing coating material preferably has a manganese content of 80% by weight manganese or more, preferably 90% by weight manganese or more, particularly preferably 100% by weight manganese.
• the manganese-containing coating material is preferably used in a form suitable for build-up welding, for example as a powder, wire, rod, tape, paste or flux-cored wire.
• both the coating material and a thin surface layer of the carrier to be coated are melted by suitable energy sources and metallurgically bonded together.
• an adherent and non-porous layer is produced.
• Overlay welding differs essentially from thermal spraying in that the surface of the carrier is melted during build-up welding.
• the manganese-containing coating material can be applied to the support by means of conventional build-up welding methods be applied.
• Suitable sources of energy include: arc, flame, Joule heat, plasma jet, laser beam and electron beam. These energy sources are known per se to the person skilled in the art.
• relatively high layer thicknesses of 1 mm or more can be applied to the carrier by means of the abovementioned methods.
• the energy source is guided in pendulum movements over the carrier, whereby the manganese-containing coating material is then applied in individual layers.
• the build-up welding can also be carried out both under an air atmosphere and under an inert gas atmosphere, such as nitrogen or argon.
• an inert gas atmosphere for example, a manganese layer of metallic manganese or a manganese alloy can be applied to the carrier.
• oxidation products are formed by the high temperatures from the manganese-containing coating material used.
• the layer formed under air atmosphere then contains, in addition to metallic manganese and optionally iron and / or nickel, manganese oxides, and optionally iron oxides and / or nickel oxides or combinations thereof.
• the metallic manganese and / or manganese oxide-containing coating can also be applied to the support by vapor deposition, such as physical vapor deposition (PVD).
• PVD physical vapor deposition
• the manganese-containing coating material used for the physical vapor deposition is usually metallic manganese, but others for this Process suitable manganese-containing solids, such as manganese oxide, are used.
• the manganese-containing coating material may be applied to the support by conventional vapor deposition techniques.
• the processes of physical vapor deposition include the processes: evaporation, such as thermal evaporation, electron beam evaporation, laser beam evaporation and arc evaporation, sputtering, and ion plating, as well as reactive variants of these methods.
• the manganese-containing coating material is atomized by bombardment with laser beams, magnetically deflected ions, electrons or by arc discharge (eg during sputtering) or brought into the gas phase (eg during evaporation) and subsequently as a manganese-containing solid to deposit on the surface of the carrier to be coated.
• the process In order for the gaseous manganese-containing coating material to reach the support to be coated, the process must be carried out under reduced pressure of about 10 -4 - 10 Pa.
• layer thicknesses of 100 nm-2 mm can be applied to the substrate by means of PVD methods.
• electrodes consisting of a composite material comprising metallic manganese and / or manganese oxide and a conductive material are also suitable.
• a conductive Material can be used for example carbon, preferably graphite.
• the metallic manganese and / or manganese oxide-containing composite material has a manganese content of at least 5 wt.% Manganese, preferably at least 10 wt.% Manganese, more preferably at least 50 wt.% Manganese, based on the total amount of manganese, which consists of metallic Manganese and manganese oxide yields.
• the manner of preparation of such a manganese-containing composite electrode is not particularly limited. Therefore, common methods such as sintering or pressing with binder are suitable. Furthermore, the manganese-containing composite electrode can also be produced by incorporating metallic manganese or manganese oxide in foam metal. These methods are known per se to the person skilled in the art.
• the zinc and zinc alloy baths are not particularly limited as long as they are alkaline and contain organic bath additives such as complexing agents, brighteners, wetting agents, etc.
• a typical zinc and zinc alloy bath for the process according to the invention is, for example, an alkaline zinc nickel alloy bath.
• a zinc nickel alloying bath is used for depositing a zinc nickel alloy plating from an alkaline zinc nickel electrolyte on a cathode connected substrate.
• This contains in the new batch typically a zinc ion concentration in the range of 5 to 15 g / l, preferably 6 to 10 g / l calculated as zinc, and a nickel ion concentration in the range of 0.5 to 3 g / l, preferably 0.6 to 1, 5 g / l, calculated as Nickel.
• the zinc and nickel compounds used for the production of the zinc nickel electrolyte are not particularly limited. Usable are, for example, nickel sulfate, nickel chloride, nickel sulfamate or nickel methanesulfonate. Particularly preferred is the use of nickel sulfate.
• alkaline zinc and zinc alloy baths contain organic bath additives such as complexing agents, brighteners, wetting agents, etc.
• Alkaline zinc nickel electrolytes therefore contain special complexing agents for nickel.
• the complexing agents are not particularly limited, and any known complexing agents can be used. Preferred are amine compounds such as triethanolamine, ethylenediamine, tetrahydroxopropylethylenediamine (Lutron Q 75), diethylenetetramine, or homologous compounds of ethylenediamine, e.g. Diethylenetriamine, tetraethylenepentamine, etc., used.
• the complexing agent and / or mixtures of these complexing agents is / are usually used in a concentration in the range of 5 to 100 g / l, preferably 10 to 70 g / l, more preferably 15 to 60 g / l.
• brighteners are commonly used in zinc and zinc alloy baths. These are not particularly limited, and any known brighteners may be used.
• Aromatic or heteroaromatic compounds such as benzylpyridiniumcarboxylate or pyridinium-N-propane-3-sulphonic acid (PPS), are preferably used as brighteners.
• the electrolyte used in the process according to the invention is basic.
• sodium hydroxide and / or potassium hydroxide can be used.
• Particularly preferred is sodium hydroxide.
• the pH of the aqueous alkaline solution is usually 10 or more, preferably 12 or more, more preferably 13 or more.
• a zinc nickel bath usually contains 80-160 g / l of sodium hydroxide. This corresponds to an approximately 2-4 molar solution.
• the substrate connected as a cathode is not particularly limited, and any known materials suitable for use as a cathode in a galvanic coating process for depositing a zinc or zinc alloy coating from an alkaline electrolyte may be used. In the method according to the invention, therefore, substrates of steel, hardened steel, forged or die-cast zinc can therefore be used as the cathode.
• a galvanic device for depositing zinc and zinc alloy coatings from an alkaline coating bath with zinc and zinc alloying electrolytes and organic bath additives is provided which contains as the anode an insoluble, metallic manganese and / or manganese oxide-containing electrode as described above.
• the device according to the invention does not require that the anode and cathode compartments are separated from one another by membranes and / or separators.
• the base bath batch (2 liters of SLOTOLOY ZN 80) had the following composition: Zn: 7.5 g / l as ZnO Ni: 0.6 g / l as NiSO 4 x 6 H 2 O.
• NaOH 120 g / l
• SLOTOLOY ZN 81 40 ml / l (complexing agent mixture)
• SLOTOLOY ZN 82 75 ml / l (complexing agent mixture)
• SLOTOLOY ZN 87 2.5 ml / l (base gloss additive)
• SLOTOLOY ZN 86 1.0 ml / l (top gloss)
• the above base bath mixture contains: 10.0 g / l DETA (diethylenetriamine), 9.4 g / l TEA (85% by weight triethanolamine), 40.0 g / l Lutron Q 75 (BASF; 75% by weight tetrahydroxopropylethylenediamine) and 370 mg / l PPS (1- (3-sulfopropyl) pyridinium betaine).
• the bath temperature was adjusted to 35 ° C.
• the agitation during the power pulp coating was 250 to 300 rpm.
• the stirring movement during the load plate coating was 0 rpm.
• the current densities at the anode and at the cathode were kept constant.
• Anode 1 steel (material number 1.0330) with a manganese oxide layer applied thereto by thermal spraying (hereinafter defined as "Mn oxide anode”); Production: A 2 mm thick steel sheet (material number 1.0330) was degreased, roughened with corundum (blasting material is zirconium corundum) and then freed of adhering residues with compressed air. The steel sheet was then sprayed with nickel to improve the primer by arc spraying first with nickel. A nickel wire in the arc (temperature at the burner head 3000 to 4000 ° C) was melted and sprayed with compressed air (6 bar) as atomizing gas at a distance of 15 to 18 cm on the steel sheet.
• Mn oxide anode thermal spraying
• the manganese oxide layer was thermally sprayed by means of powder flame spraying.
• metallic manganese powder (-325 mesh, ⁇ 99% from Sigma Aldrich) in an acetylene-oxygen flame (temperature of the burner flame was 3160 ° C) melted and with compressed air (maximum 3 bar) as atomizing gas at a distance of 15 to 20 cm sprayed onto the steel sheet.
• compressed air maximum 3 bar
• the deposited zinc nickel alloy amount present on the deposition plate was weighed by weight determined.
• the total amount of metal missing from deposition in the zinc nickel electrolyte was converted to 85% by weight of zinc and 15% by weight of nickel (for example, 850 mg of zinc and 150 mg of nickel were metered in for a total deposited metal amount of 1.0 g of zinc nickel alloy layer).
• SLOTOLOY ZN 85 contains nickel sulphate and the amines triethanolamine, diethylenetriamine and Lutron Q 75 (1 ml SLOTOLOY ZN 85 contains 63 mg nickel).
• the NaOH content was determined after each 10 Ah / l by acid-base titration and in each case adjusted to 120 g / l.
• the determination of the cyanide was carried out with the cuvette test LCK 319 for easily releasable cyanides from Dr. Ing. Long (today company Hach). Easily releasable cyanides are converted by a reaction into gaseous HCN and transferred through a membrane into an indicator cuvette. The color change of the indicator is then evaluated photometrically.
• Test Example 1.2 was carried out under the same conditions as described in Test Example 1.1.
• Table 7 shows that with an approximately equal nickel alloy content, depending on the applied cathodic current density, a 3 to 8% higher current efficiency could be achieved by using the Mn oxide anode according to the invention after 100 Ah / l load compared to the comparative anode commonly used as a standard anode 2 (bright nickel-plated steel, see Table 5).
• the predefined layer thickness on components can thus be achieved in practice in a shorter time. This leads to a significant reduction in process costs.
• Test Example 1.3 was carried out under the same conditions as described in Test Example 1.1.
• Scheme 1 shows the result of the test panels coated in a bath operated with Comparative Anodes 1 to 3.
• Scheme 2 shows the result of the test panel which was coated in a bath operated with the Mn oxido anode of the present invention.
• the Hull cell plate which was operated with the Mn Oxidanode invention (see Scheme 2), shows after 100 Ah / l over the entire current density range uniform semi-glossy to shiny appearance, which is a measure of the remaining and undamaged bath additives.
• the Hullzellenbleche from the zinc nickel electrolyte of the comparative anodes 1 to 3 show only in the range ⁇ 2 A / dm 2 (corresponding to a distance of 4 cm from the right sheet metal edge to the right sheet metal edge) a semi-glossy to shiny appearance.
• the remaining sheet metal area is semi-glossy to matt.
• the alkaline zinc nickel electrolyte SLOTOLOY ZN 210 (Schlötter) was subjected to load tests using different anode materials. Here, the deposition behavior was analyzed over a longer period of time with a constant cathodic and anodic current density. Depending on the amount of current applied, the zinc-nickel electrolyte has been treated with respect to the degradation products forming at the anode, e.g. Cyanide, studied. In addition, an analysis of the organic complexing agents and brighteners was carried out.
• the base bath batch (2 liters of SLOTOLOY ZN 210) had the following composition: Zn: 7.5 g / l as ZnO Ni: 1.0 g / l as NiSO 4 x 6 H 2 O.
• NaOH 120 g / l
• SLOTOLOY ZN 211 100 ml / l (complexing agent mixture)
• SLOTOLOY ZN 212 30 ml / l (complexing agent mixture)
• SLOTOLOY ZN 215 14 ml / l (nickel solution)
• SLOTOLOY ZN 213 5 ml / l (basic gloss additive)
• SLOTOLOY ZN 216 0.2 ml / l (top gloss)
• the above base bath mixture contains: 22.4 g / l TEPA (tetraethylene pentamine), 10.2 g / l TEA (85 wt%) and 5.4 g / l Lutron Q 75 (BASF; 75 wt% tetrahydroxopropylethylenediamine) and 75 mg / l PPS (1- (3-sulfopropyl) pyridinium betaine).
• the bath temperature was adjusted to 28 ° C.
• the stirring during the load plate coating was 0 rpm.
• the current densities at the anode, as well as at the cathode were kept constant.
• the deposited zinc nickel alloy amount present on the deposition plate was weighed by weight determined.
• the total amount of metal missing from deposition in the zinc nickel electrolyte was converted to 85% by weight of zinc and 15% by weight of nickel (for example, 850 mg of zinc and 150 mg of nickel were metered in for a total deposited metal amount of 1.0 g of zinc nickel alloy layer).
• the nickel consumed in the electrolyte was supplemented by the nickel-containing liquid concentrate SLOTOLOY ZN 215.
• the SLOTOLOY ZN 215 contains nickel sulphate and the amines triethanolamine, tetraethylenepentamine and Lutron Q 75 (1 ml SLOTOLOY ZN 215 contains 70 mg nickel).
• the NaOH content was determined after each 10 Ah / l by acid-base titration and in each case adjusted to 120 g / l.
• zinc pellets were introduced into the electrolyte in a manner corresponding to zero current. This leads to zinc dissolution due to the alkalinity of the electrolyte.
• the zinc content was also analyzed analytically by means of titration in the laboratory.
• the determination of the cyanide was carried out with the cuvette test LCK 319 for easily releasable cyanides from Dr. Ing. Lange (today Hach company). Easily releasable cyanides are converted by a reaction into gaseous HCN and transferred through a membrane into an indicator cuvette. The color change of the indicator is then evaluated photometrically.
• the manganese alloy anode according to the invention was also compared with the comparison anode 2 made of high-gloss nickel-plated steel in the pilot plant.
• a newly prepared SLOTOLOY ZN 80 (Schlötter) electrolyte was initially operated for about 6 months with four standard anodes of high-gloss nickel-plated steel (comparative anode 2), thereby achieving a cyanide content of 372 mg / l in the zinc nickel electrolyte.
• the standard anodes of high gloss nickel-plated steel were replaced by manganese alloy anodes according to the invention.
• the zinc nickel electrolyte was then subjected to another 4 months under the same conditions.
• the base bath batch (200 liters of SLOTOLOY ZN 80) had the following composition: Zn: 7.5 g / l as ZnO Ni: 0.6 g / l as NiSO 4 x 6 H 2 O.
• NaOH 110 g / l
• SLOTOLOY ZN 81 40 ml / l (complexing agent mixture)
• SLOTOLOY ZN 82 75 ml / l (complexing agent mixture)
• SLOTOLOY ZN 87 2.5 ml / l (base gloss additive)
• SLOTOLOY ZN 83 2.5 ml / l (base gloss additive)
• SLOTOLOY ZN 86 1.0 ml / l (top gloss)
• the above base bath mixture contains: 10.0 g / l DETA (diethylenetriamine), 9.4 g / l TEA (85% by weight triethanolamine), 40.0 g / l Lutron Q 75 (BASF; 75% by weight tetrahydroxopropylethylenediamine) and 370 mg / l PPS (1- (3-sulfopropyl) pyridinium betaine).
• the bath volume was 200 liters.
• the bath temperature was set at 33 ° C.
• the current densities at the anode and at the cathode were kept constant.
• the monthly bath load was 25000 Ah.
• the stress in the pilot plant was carried out under practical conditions, i. that the bath additives, metals and the sodium hydroxide solution were continuously added.
• the metered amount of additive SLOTOLOY ZN 86 was deliberately reduced here, since the additional degradation of the manganese alloy anodes according to the invention is lower.
• the nickel consumed in the electrolyte was supplemented by the nickel-containing liquid concentrate SLOTOLOY ZN 85.
• the SLOTOLOY ZN 85 are nickel sulphate and the amines are triethanolamine, diethylenetriamine and Lutron Q 75 (1 ml of SLOTOLOY ZN 85 contains 63 mg of nickel).
• the necessary amount of nickel was determined by means of suitable analytical methods (eg ICP, AAS).
• zinc pellets were introduced into the electrolyte in a manner corresponding to zero current. This leads to zinc dissolution due to the alkalinity of the electrolyte.
• the zinc content was also analyzed analytically by means of titration in the laboratory.
• the content of sodium hydroxide in the electrolyte was analytically analyzed by titration in the laboratory (after every 5 Ah / l load) and supplemented accordingly.
• the newly prepared SLOTOLOY ZN 80 electrolyte which was operated with four standard anodes made of high-gloss nickel-plated steel (comparative anode 2), had a cyanide content of 372 mg / l after about 6 months.
• the standard anodes of high gloss nickel-plated steel were replaced by manganese alloy anodes according to the invention (in Table 10 defined as "Start").
• the zinc nickel electrolyte was then subjected to another 4 months under the same conditions. At a distance of one month each, the influence of the manganese alloy anodes according to the invention on the cyanide content and the organic bath additives was investigated.
• the determination of the cyanide was carried out with the cuvette test LCK 319 for easily releasable cyanides from Dr. Ing. Lange (today Hach company). Easily releasable cyanides are converted by a reaction into gaseous HCN and transferred through a membrane into an indicator cuvette. The color change of the indicator is then evaluated photometrically.
• the degree of gloss of the deposited layer increased as the cyanide content decreased.
• the additive SLOTOLOY ZN 86 containing PPS could be reduced from an addition amount of 100 ml during operation with Comparative Anodes 2 to 60 ml by using the manganese alloy anodes of the present invention.
• the base bath batch (2 liters of SLOTOLOY ZN 80) had the following composition: Zn: 7.5 g / l as ZnO Ni: 0.6 g / l as NiSO 4 x 6 H 2 O.
• NaOH 120 g / l
• SLOTOLOY ZN 81 40 ml / l (complexing agent mixture)
• SLOTOLOY ZN 82 75 ml / l (complexing agent mixture)
• SLOTOLOY ZN 87 2.5 ml / l (base gloss additive)
• SLOTOLOY ZN 86 1.0 ml / l (top gloss)
• the above base bath mixture contains: 10.0 g / l DETA (diethylenetriamine), 9.4 g / l TEA (85% by weight triethanolamine), 40.0 g / l Lutron Q 75 (BASF; 75% by weight tetrahydroxopropylethylenediamine) and 370 mg / l PPS (1- (3-sulfopropyl) pyridinium betaine).
• the bath temperature was adjusted to 35 ° C.
• the agitation during the power pulp coating was 250 to 300 rpm.
• the stirring movement during the load plate coating was 0 rpm.
• the current densities at the anode and at the cathode were kept constant.
• Comparative Anode 2 Bright nickel-plated steel; Steel (material number 1.0330) with a coating layer of 30 ⁇ m bright nickel (coated with SLOTONIK 20 electrolyte from Schlötter); Production: See JN balance, Tables Galvanotechnik, 7th edition, EUGEN G. LEUZE Verlag, Bad Saulgau, p.515)
• Anode 3 steel (material number 1.0330) with a manganese iron oxide layer applied thereto by thermal spraying (hereinafter defined as "Mn-Fe oxide anode”); Production: A 2 mm thick steel sheet (material number 1.0330) was degreased, roughened with corundum (blasting material is zirconium corundum) and then freed of adhering residues with compressed air. The steel sheet was then sprayed with nickel to improve the primer by arc spraying first with nickel. A nickel wire in the arc (temperature at the burner head 3000 to 4000 ° C) was melted and sprayed with compressed air (6 bar) as atomizing gas at a distance of 15 to 18 cm on the steel sheet.
• Mn-Fe oxide anode thermal spraying
• the manganese-iron-oxide layer was thermally sprayed by means of powder flame spraying.
• the coating material used was a mixture of 90% by weight metallic manganese powder (-325 mesh, ⁇ 99% from Sigma Aldrich) and 10% by weight metallic iron powder (-325 mesh, 97% from Sigma Aldrich). Care was taken to mix the two powders homogeneously before the thermal spraying process.
• the metallic manganese-iron mixture in an acetylene-oxygen flame temperature of the burner flame was 3160 ° C
• compressed air maximum 3 bar
• Anode 4 steel (material number 1.0330) with a manganese-nickel-oxide layer (hereinafter defined as "Mn-Ni-oxidanode") applied thereto by thermal spraying;
• Production A 2 mm thick steel sheet (material number 1.0330) was degreased, roughened with corundum (blasting material is zirconium corundum) and then freed of adhering residues with compressed air.
• the steel sheet was then sprayed with nickel to improve the primer by arc spraying first with nickel.
• a nickel wire in the arc temperature at the burner head 3000 to 4000 ° C
• the manganese-nickel oxide layer was thermally sprayed by means of powder flame spraying.
• a mixture of 80 wt% metallic manganese powder (-325 mesh, ⁇ 99% from Sigma Aldrich) and 20 wt% metallic nickel powder (-325 mesh, ⁇ 99% from Alfa Aesar) was used. Care was taken to mix the two powders homogeneously before the thermal spraying process.
• the metallic manganese-nickel mixture in an acetylene-oxygen flame temperature of the burner flame was 3160 ° C
• the metallic manganese-nickel mixture in an acetylene-oxygen flame melted and sprayed with compressed air (maximum 3 bar) as atomizing gas at a distance of 15 to 20 cm on the steel sheet.
• compressed air maximum 3 bar
• SLOTOLOY ZN 85 contains nickel sulphate and the amines triethanolamine, diethylenetriamine and Lutron Q 75 (1 ml SLOTOLOY ZN 85 contains 63 mg nickel).
• the NaOH content was determined after each 10 Ah / l by acid-base titration and in each case adjusted to 120 g / l.
• the determination of the cyanide was carried out with the cuvette test LCK 319 for easily releasable cyanides from Dr. Ing. Lange (today Hach company). Easily releasable cyanides are converted by a reaction into gaseous HCN and transferred through a membrane into an indicator cuvette. The color change of the indicator is then evaluated photometrically.

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