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
  • C25D3/08—Deposition of black chromium, e.g. hexavalent chromium, CrVI
• • 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
  • C25D3/04—Electroplating: Baths therefor from solutions of chromium
  • C25D3/06—Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium
• • 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
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/1601—Process or apparatus
  • C23C18/1633—Process of electroless plating
  • C23C18/1646—Characteristics of the product obtained
  • C23C18/165—Multilayered product
  • C23C18/1653—Two or more layers with at least one layer obtained by electroless plating and one layer obtained by electroplating
• • 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
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/2006—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30
  • C23C18/2046—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30 by chemical pretreatment
  • C23C18/2073—Multistep pretreatment
  • C23C18/208—Multistep pretreatment with use of metal first
• • 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
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/2006—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30
  • C23C18/2046—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30 by chemical pretreatment
  • C23C18/2073—Multistep pretreatment
  • C23C18/2086—Multistep pretreatment with use of organic or inorganic compounds other than metals, first
• • 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
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/28—Sensitising or activating
  • C23C18/30—Activating or accelerating or sensitising with palladium or other noble metal
• • 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
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
• • 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
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
• • 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
  • C25D3/38—Electroplating: Baths therefor from solutions of copper
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
  • C25D5/14—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium two or more layers being of nickel or chromium, e.g. duplex or triplex layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
  • C25D5/38—Pretreatment of metallic surfaces to be electroplated of refractory metals or nickel
  • C25D5/40—Nickel; Chromium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
  • C25D5/611—Smooth layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance

Definitions

• the present invention relates to a method for black chrome plating of surfaces.
• Black chrome plating is a process known per se, black chrome baths are commercially available.
• a key component is chromic acid, which is added in a fresh mixture in water and dissolved with stirring. This can be about 1 kg of chromic acid, or a little less, come to 1 liter of water.
• further additives are usually added, such as, for example, potassium hexafluorosilicate and barium carbonate.
• the additives fulfill different functions, they can serve, for example, an increase in the current efficiency or elimination of sulfate impurities of chromic acid (by precipitation with barium ions).
• the present invention is based on the technical problem of specifying a particularly advantageous method for black chrome plating of surfaces.
• a hydrofluoric acid salt is used to prepare a first aqueous solution which is then metered into the bath containing the chromic acid. So it is z. B. the salt is not added directly into the bath, but first dissolved outside the bath in water. The bath, the aqueous solution, which is kept in a first reservoir, metered, ie over a longer period in multiple doses, either at intervals or continuously (see below in detail). This "longer period" is in the hour or day area, so it may, for example, extend over at least 3 h, 6 h, 12 h or 24 h.
• the fluoride content is not only of central importance in the fresh approach of the bath, but also already only slightly decreasing Fluoride content may be critical. This particularly concerns the coating of surfaces with more complex shape, such as undercuts and the like.
• Hull cell calibrated angle cell
• the proposed method is also advantageous insofar as the aqueous solution can be supplied with a metering pump in very small doses, so in other words a relatively exact dosage is possible.
• a relatively exact dosage is possible.
• the salt is added directly to the bath, at least the expense of precise metering would be higher (every single dose would have to be weighed).
• the addition of a solid in a galvanic bath usually requires a process interruption, which also has a negative effect on the throughput.
• the working temperature of the black chromium bath is typically not more than 24 ° C, preferably not more than 22 ° C, 20 ° C or 18 ° C (in the order of naming increasingly preferred, with a possible lower limit at 14 ° C). Particularly preferred may be around 16 ° C.
• the black chrome bath is cooled accordingly.
• these comparatively low working temperatures mean that hardly or only to a very limited extent water evaporates from the bath, and it is advantageous to bear that a very finely divided metered addition is possible with the method according to the invention.
• the first aqueous solution is prepared by dissolving the salt of hydrofluoric acid to saturation.
• the solution then added to the bath is thus highly concentrated, the ratio of fluoride ions to water is thus significantly higher than in the bath itself.
• the salt of hydrofluoric acid is potassium fluoride.
• sodium fluoride is generally also conceivable in the alternative, the potassium fluoride may be preferred in the present case because of better conductivity.
• a preferred embodiment relates to the metered amount. Since this depends not only on the bath volume, but also on the size of the coated surfaces and the resulting layer thicknesses, the amount is based on the energy consumption of the electrochemical deposition of the black chrome, specifically on the resulting in the electroplating by the introduction of electrical power consumption (a possible energy consumption for cooling and stirring, etc. is therefore out of the question). Based on an energy consumption of 1000 kWh, at least 1 ml of the first aqueous solution is preferably metered in, with at least 1.5 ml, 2 ml or 2.5 ml being increasingly preferred in the order in which they are mentioned.
• Advantageous upper limits may be 10 ml, 8 ml, 6 ml, 5 ml and 4 ml, respectively, also in the order of naming increasingly preferred.
• An upper limit may generally also be preferred independently of a lower limit (and vice versa), the values should also be disclosed independently of one another.
• the daily energy consumption of a black chromium bath is around 20,000 kWh, about 50 to 100 ml of the first aqueous solution are replenished per day, for example.
• a second aqueous solution other than the first is further prepared and then metered into the bath (the second aqueous solution is maintained in a second reservoir, which is preferably different from the first reservoir).
• a reducing agent available as a solid, preferably sugar (sucrose) is brought into aqueous solution.
• the reducing agent brought into aqueous solution can also be supplied to the black chromium bath with a metering pump in small or relatively precisely metered doses. In general, can be reduced with the reducing agent chromium VI to chromium III, so can increase the proportion of chromium-III ions.
• a suitably adjusted chromium III content for example between 12 g / l and 20 g / l, helps to prevent brownish-black black chrome layers.
• the inventor has found that even with an initially matching chromium III content, the dispersion can become worse after a comparatively short time, which is particularly evident on components with a complex surface and can be measured via the Hull cell (see above). This is prevented by the subsequent dosing.
• the reducing agent or the sugar is dissolved to saturation. Accordingly, relatively little water must be supplied to the bath, which is advantageous in view of the low discharge discussed above. Pure sugar is preferably used in this case, ie in particular no mixture with non-soluble additives, such as barium carbonate.
• At least 1 ml, 1.5 ml, 2 ml or 2.5 ml of the second aqueous solution, based on an energy consumption of 1000 kWh, are increasingly replenished in the order in which they are mentioned.
• Advantageous upper limits which in general may also be of interest independently of this (and vice versa), are increasingly preferred in the order in which they are mentioned at most 10 ml, 8 ml, 6 ml, 6.5 ml and 4 ml, respectively a coincidence that for the first and the second solution, the same quantities have been found to be advantageous.
• the first and the second aqueous solution are each supplied with their own metering pump, thus discharging, for example, for each solution a separate hose in the bath. Also, regardless of the feeding of the solution (s) by means of metering pump with respect to z. B. a manual dripping preferred, it may, for example. Effort and error-prone to be reduced.
• the inlet side, the pump is connected to a reservoir with the respective solution, the outlet side, it flows into the Schwarzchrombad, preferably via an outlet in the bath, z. B. a submerged hose. This can help prevent unwanted crystallization.
• a third aqueous solution is prepared with potassium nitrate and metered into the bath. This is preferably done with its own metering pump, so there is a first metering pump for the first bath, a second for the second bath and a third for the bath with the potassium nitrate solution.
• the potassium nitrate may be advantageous in terms of the appearance of the resulting black chrome layers.
• the potassium nitrate has a worse solubility product than, for.
• potassium fluoride or sugar which is why it is present in the third solution with a lower concentration compared. Based on an energy consumption of 1000 kWh, for example, about 5 ml of the third solution can be post-dosed.
• a fourth aqueous solution is prepared with chromic acid (the chromic acid is dissolved outside the bath with the chromic acid, in a fourth reservoir, which is preferably different from the other reservoir (s); the fourth aqueous solution is metered into the bath with a fourth metering pump.
• the chromic acid in the fourth reservoir is dissolved to saturation.
• the chromic acid can generally be replenished as a solid, because the intervals are usually significantly larger ( ⁇ 1 x per week).
• a first batch with first components is introduced into the bath and black-chromed and then, after a discharge of the first batch, a second batch is introduced and black-chromed. These are followed by more batches.
• a "batch" so far form a plurality of components, which are black chromed in the bathroom at the same time.
• the components are preferably per batch identical to each other; they have the same shape and were pretreated in the same way.
• the first and / or the second and / or the third and / or the fourth aqueous solution is metered in between the black chromium plating of two batches, for example during which one batch is discharged and / or while the other batch is introduced.
• the information on when to re-dosing is not to be read in such a way that it is compulsory only to be dosed exclusively during the specified periods of time, it should in any case be replenished in a correspondingly specified period. Conversely, it is not necessary to replenish it over the entire period, but it can only be replenished temporarily during the period.
• a charge is replenished during black chromium plating, that is, during the galvanic deposition, at least temporarily.
• Black chromium layers can then be deposited under very constant conditions, which may be advantageous in view of the above-discussed sensitivity of the individual parameters.
• the additional metering during the deposition can be carried out alternatively or also in connection with a replenishment between the batches.
• the bath may preferably have a fluoride content between 0.03 g / l and 0.2 g / l.
• Further advantageous lower limits are in the order of naming increasingly increasingly at least 0.035 g / l, 0.04 g / l, 0.045 g / l, 0.05 g / l, 0.055 g / l and 0.06 g / l; further advantageous and independent upper limits are in the order of naming increasingly preferred at most 0.18 g / l, 0.16 g / l, 0.14 g / l, 0.12 g / l, 0.1 g / l, 0.095 g / l, 0.09 g / l, 0.085 g / l and 0.08 g / l, respectively.
• a chromium III content between 6 g / l and 50 g / l is preferred, with further preferred lower limits at 8 g / l, 10 g / l, 11 g / l and 12 g / l and (independently of each other) Upper limits at 45 g / l, 40 g / l, 35 g / l, 30 g / l, 25 g / l and 20 g / l, respectively.
• This cleaning step after black chromium plating is preferably carried out in an alkaline solution in a pH range between 9 and 13, with pH values below 12 or below 11 being preferred, for example at pH 10.
• the solution may optionally also contain surfactants. These improve the cleaning properties, but do not make the ultrasonic treatment unnecessary.
• the ultrasonic treatment is carried out in a temperature range between 50 and 60 ° C.
• the ultrasound treatment itself preferably lasts at least 30 s.
• the ultrasound power can range between 0.5 and 2 W / l.
• the black chrome plating requires a metallic surface, which in individual cases, for example, in metallic copper workpieces or stainless steel workpieces, even in an uncoated workpiece surface itself can exist.
• an additional metallization preferably a galvanic metallization, is preferred.
• nickel metallizations into consideration.
• a cathodic activation of the metallized surface is preferably additionally provided before the black chrome plating.
• a cathodic activation significantly improves the quality of the black chrome plating, above all, it leads to a lower crack formation and thus supports the cleaning options by the ultrasonic cleaning step according to the invention.
• the cathodic activation of the metallized surface before the black chromium plating also ensures a particularly efficient cleaning of the surface, also with regard to organic impurities remaining from previous metallization steps.
• the cathodic activation provides a particularly fine-grained germination in the course of the following black chrome plating. This may be related to the reduction of particles on the surface by the cathodic circuit.
• the layers according to the invention show a good and even improved abrasion resistance on the substrate compared to conventional layers and at the same time a significantly reduced cracking of the black chromium plating layer.
• the initial metallization prior to cathodic activation is preferably a galvanic metallization, even in the case of materials other than nickel, such as in the case of copper.
• a galvanic high-gloss nickel layer that is to say a nickel layer deposited from a galvanic bath with brightener additives.
• metal is preferably first germinated, preferably with palladium. Germination may be preceded by a chemical pretreatment step, such as sulfonation or pickling in chromic acid solution.
• the germination is followed by a chemical nickel coating, ie a nickel layer deposited without external current.
• This nickel layer can then be galvanically reinforced, in particular with nickel or copper. Preference is given to pure galvanic nickel layers, ie without brightener additives in the galvanic bath, or copper layers of acidic electroplating solution, ie to sulfuric acid-based and not to cyanide-based.
• the procedure according to the invention is also suitable for metal surfaces.
• Particularly suitable metals are: non-ferrous metals, zinc die casting, light metals and light metal alloys, iron and steel materials.
• An initially conventional layer structure is predefined on metal surfaces, for example with a galvanic metallization, in particular copper, and then a subsequent galvanic high-gloss metallization, in particular copper coating of acidic solution or nickel coating.
• the high-gloss layers have the function of leveling the surface. The following procedure then continues as already explained in connection with the plastic surfaces; so it follows the cathodic activation.
• Another aspect of the invention relates to possibilities of adjusting the gloss or mattness of the black-chromed surface.
• Here are to be created by fotomatten to high-gloss layers of play.
• To set certain degrees of matting here is provided to produce the initial metallization of the surface by applying a matte nickel layer on a smooth surface of the workpiece by electrodeposition without organic matting additives and further applying a Sulfamatnickel Anlagen.
• the basic idea of this aspect of the invention is to apply a matt nickel layer on a smooth workpiece surface and adjust the mattness over the thickness of the nickel layers. This is aimed at galvanic nickel layers, where no organic matting additives are used. Rather, in a preferred embodiment, it may be a known Wattsche nickel layer, which is technically simple and easy to control.
• the smooth surface on the workpiece under the matt nickel layer may, for example, be a polished workpiece surface itself or else an applied metal layer. If a preferred bright nickel coating is used here, this has the particular advantage of very well leveling any surface defects and defects. Thus, it can improve the quality of the final gloss content of the finished metal surface according to the invention. Galvanic processes for bright nickel coatings are well known and need not be detailed here.
• the matte galvanic nickel layer is preferably applied as a known and technically well-controlled Wattsche nickel layer, ie as a galvanic nickel layer without organic matting additives. This results in a microscopically bulbous layered structure in which the tuber sizes and nodule distances are adjusted via the current intensity and / or coating time let that ultimately determine the dullness. A maximum dullness arises when the tubers are practically close to each other.
• the electrodeposition of a sulfamate nickel layer is also conventional and known.
• the corresponding solutions contain nickel sulfamate, that is, the salt of amidosulfuric acid.
• the sulfamate nickel coating rounds and reinforces the aforementioned nodular or otherwise matt nickel layer, but does not really level it.
• the sulfamate nickel layer also enhances the grain size without changing fundamentals at the granularity referred to above as "nodular". It thus receives the matte character, possibly only slightly increases the gloss, but above all provides increased material strength for reasons of stability and resilience and for better wiping sensitivity or better dirt-repellent properties.
• the roughness reduced by the rounding provides less grip to soiling.
• a particular advantage of this embodiment is that the degree of gloss or degree of matting can be adjusted by galvanic parameters in a very simple manner and also has the desired effect after black chromium plating.
• Different optical properties can be generated with one and the same basic process, that is, the same solution compositions, identical baths, etc. In particular, can be adjusted from batch to batch simply on the current, or even cheaper over the treatment time, the dullness. The thicker the matt nickel layer is, the higher the degree of matting results. This also applies after the application of the following black chrome layer.
• the invention also relates to a method for producing a black-chrome-plated component, wherein this component is black-chrome-plated in a method disclosed here.
• the components to be coated may, for example, be interior trim parts for a motor vehicle, for example fan blades, switches, diaphragms or the like. It may in particular be injection-molded parts, for example of acrylonitrile-butadiene-styrene (ABS) or another plastic act.
• ABS acrylonitrile-butadiene-styrene
• the components are then pretreated, for example, by pickling in chromic acid, and after a Palladiumbekeimung chemically nickel-plated (with a layer thickness typically less than 1 micron). This is followed by a reinforcement with a matt nickel plating of thickness 3 - 15 ⁇ m, followed by a galvanic high-gloss nickel layer for leveling the thickness 15 - 25 ⁇ m.
• plastic components are not mandatory, the method of the invention can of course also be applied to metal parts.
• An example from the automotive sector are head restraint struts, but also grids (grille) can be coated, which can also be used outside the automotive sector.
• Examples are covers for electronic devices called, for example. Grille for jukeboxes, black chrome screened for microwave ovens are possible.
• the nickel-plated plastic component and the metal parts do not differ.
• the embodiment with "component” refers to both variants.
• the components are cathodically activated before black chromium plating (in aqueous solution of 60 g / l sodium hydrogen sulfate at pH ⁇ 1.8 and 3 A / dm 2 for 30 s).
• the solution may contain surfactants and fluorides.
• chromic acid is added to water ( ⁇ 450 g / l chromic acid), and further, for example, potassium hexafluorosilicate and barium carbonate are added.
• a chromium III content of about 16 g / l is advantageous, which can be achieved by appropriate addition of sugar.
• the initial proportion of fluoride is increased, for example. To about 0.06 g / l fluoride.
• the current density during the deposition may, for example, be at least 5 A / dm 2 , preferably at least 15 A / dm 2 , with upper limits at, for example, at most 40 A / dm 2 or 25 A / dm 2 .
• a first aqueous solution is prepared in a first reservoir by dissolving potassium fluoride in water until saturated.
• sugar is dissolved to saturation (second aqueous solution).
• second aqueous solution sugar is dissolved to saturation (second aqueous solution).
• second aqueous solution sugar is dissolved to saturation.
• second aqueous solution sugar is dissolved to saturation.
• second nitrate is dissolved to saturation.
• Each reservoir is connected via a respective metering pump to the bath, so that the respective solution can be added to the bath metered in small quantities.
• the present subject matter relates to mass production in which a large number of components are black-chromed in succession in a plurality of batches.
• the inventor has found that even a comparatively small drop in the fluoride or chromium III content can be disadvantageous, cf. the description introduction in detail. Therefore, the individual solutions are fed via the metering pumps continuously, so in particular continuously dissolved potassium fluoride and dissolved sugar is replenished.

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• 2018
  • 2018-01-25 EP EP18153360.5A patent/EP3517655A1/fr not_active Withdrawn

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