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
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/38—Chromatising
• • 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
  • 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
• • 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
  • C25D5/54—Electroplating of non-metallic surfaces
  • C25D5/56—Electroplating of non-metallic surfaces of plastics
• • 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
• • 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
  • C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel
• • 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
  • C25D5/42—Pretreatment of metallic surfaces to be electroplated of light metals

Definitions

• the present invention relates to a process for producing grayish chrome surfaces.
• the invention is therefore based on the problem to provide an advantageous method for producing gray-chromium surfaces, the sufficient layer qualities, also in terms of resilience produced.
• the basic idea of the invention consists in the combination of a chrome layer, in particular a bright chrome layer, with a subsequent black chrome layer.
• the black chrome layer should be adjusted in thickness so that the desired gray cast is achieved. It has been found that with this combination of two layers known per se on the one hand a very good corrosion and abrasion resistance can be achieved and on the other hand an aesthetically pleasing and demanded "titanium look" can be achieved.
• the chrome plating can be carried out by a process known per se and in particular by depositing a so-called bright chrome layer.
• This is a galvanic process with which, in particular, layer thicknesses of 1 to 3 ⁇ m, which are favorable for this invention, can be easily produced.
• Advantageous current densities can be in the range of 0.5-3 A / dm 2 .
• Typical treatment times (current times) are between 5 and 25 min. With such processes, it is possible to deposit high-quality bright galvanic chromium layers in an already controlled and controlled manner.
• the chromium plating is merely rinsed, for example in deionized water, and then begun without further intermediate steps, ie directly (but not necessarily immediately in time) with the black chromium plating.
• the black chrome is also known and mastered. Layer thicknesses between 0.1 and 1 ⁇ m, depending on the desired optical effect, current densities between 0.5 and 10 A / dm 2 and galvanic treatment times of 1 min-5 min are considered as preferred framework data.
• Black chrome In black chrome, more or less polychromates are deposited in addition to metallic chrome, depending on the morphology. Black chromed surfaces moreover, they usually contain hexavalent chromium ions. The presence of hexavalent chromium is fundamentally disadvantageous because of the health hazard it poses and the environmental imperatives prevailing, especially in the automotive industry (eg RoHS compliance).
• the invention proposes an ultrasonic cleaning step after the black chrome plating in an alkaline solution, i. H. from pH 8, before.
• the purification step 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 cleaning step of the invention following the black chromium plating becomes efficient only through the combination of ultrasonication with the alkaline pH. It has surprisingly been found that both chemical cleaning and heat, such as cook-out, could not effectively reduce the Cr-VI loading of the black plating layer alone, but the use of ultrasound in alkaline setting provides quite significant advances. In this case, with the ultrasonic cleaning step, the Cr-VI load can be reduced to practically insignificant values, as can be verified in subsequent standard tests, such as by boiling with Diphenylcarbazidtest.
• a cathodic activation of the metallized surface is preferably additionally provided prior to the chromium plating.
• a cathodic activation significantly improves the quality of the chrome plating and the black plating, above all it leads to a lower crack formation and thus supports the cleaning possibilities by the ultrasonic cleaning step according to the invention.
• the cathodic activation of the metallized surface before chrome plating also ensures a particularly efficient cleaning of the surface, also in terms of out possibly previous metallization steps still existing organic impurities.
• the cathodic activation provides a particularly fine-grained germination in the course of the subsequent chrome plating. This may be related to the reduction of particles on the surface by the cathodic circuit.
• the layers according to the invention in particular with this step, show a good 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 metallic surface before 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.
• the procedure according to the invention is also suitable in particular for plastic surfaces.
• 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 electroplating bath, or copper layers of acidic electroplating solution, d, h. based on sulfuric acid and not on cyanide.
• 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 predetermined, for example with a galvanic metallization, in particular copper, and then a subsequent galvanic high-gloss metallization, in particular copper coating from 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.
• the cathodic activation both on top as plastic coated original plastic surfaces so also metal surfaces, preferably takes place from an acidic solution, preferably at a pH between 1 and 2.
• an acidic solution preferably at a pH between 1 and 2.
• Preferred are aqueous solutions based on sodium sulfate and sulfuric acid or on the Base of sodium hydrogen sulfate.
• the solution may optionally also contain surfactants and / or fluorides.
• a correspondingly converted amount of sodium sulfate can be dissolved and adjusted with sulfuric acid, the pH.
• Preferred electrical parameters are 1 - 5 A / dm 2 at treatment times in the order of 10 - 300 s. The voltage is adjusted to give the desired current density.
• the purification step 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.
• Another aspect of the invention relates to possibilities of adjusting the gloss or degree of mattness of the finished 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 even an applied metal layer. If a preferred bright nickel layer 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 layers are well known and need not be explained in detail here. Commercial solutions are available, which may include, for example, nickel sulfate, organic brighteners, and so-called levelers. Suitable current densities in this range are 1 to 3 A / dm 2 . It may also be advantageous to provide a bright metal layer, such as a copper layer, below the bright nickel layer.
• 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.
• Current strengths in the range of 0.1 to 2 A / dm 2 , better 0.1 to 1 A / dm 2 are preferred here.
• the layer thickness of the matt layer should be comparatively low and may be between 0.05 and 5 .mu.m, with upper limits of 4 .mu.m, 3 .mu.m, 2 .mu.m and more preferably 1 .mu.m and lower limits of 0.075 .mu.m and more preferably 0.1 .mu.m even cheaper.
• the layer thickness is ultimately determined by optical / aesthetic considerations.
• 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". So it gets the matte character, possibly only slightly increases the gloss, but above all provides for reasons of stability and resilience increased material thickness and for better Wischpfndige or better soil repellency.
• the roughness reduced by the rounding provides less grip to soiling.
• a favorable thickness for the sulfamate nickel layer is in the range of 5 and 20 microns, with a lower limit of 10 and an upper limit of 15 microns are more preferred.
• 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.
• a Kunststoffeinnenhand or shift knob for automobiles of glass fiber or mineral fiber reinforced polyamides, ABS or ABS-PC according to the invention are coated by initially in the case of ABS and ABS PC a pickling with chromic acid or sulfonation in the case of polyamides.
• the bright Ni layer 2 becomes in a standard electroplating process at 2 A / dm 2 deposited from an aqueous solution containing about 180 g / l nickel sulfate, about 150 g / l nickel chloride and about 50 g / l boric acid as a pH buffer as well as glossy Ni baths commercially available organic brighteners.
• the bath Slotonik-50 of the company Schlötter comes into consideration.
• the purpose of the glossy Ni layer 2 is to provide a flawless glossy base as possible, and is distinguished by its good ability to level initially imperfections present.
• Their thickness is not really essential to the subsequent process and depends, on the one hand, on the overall material thickness targeted, especially with regard to durability, and on the surface defects to be leveled. Typical orders of magnitude are in the range of 10 to 30 ⁇ m.
• a metal part namely an automotive headrest support strut or a shift knob made of an aluminum alloy, first copper plating electrolytically with a thickness of 3-10 microns. This is followed by an acidic high-gloss copper layer of thickness 20-25 ⁇ m and optionally another high-gloss nickel layer.
• Both examples are then cathodically activated in an aqueous solution of 60 g / l sodium hydrogen sulfate at a pH of about 1.8, namely at 3 A / dm 2 for a time of 30 s.
• the solution contains relatively small amounts of surfactants and fluorides to support the cleaning and activation function.
• the high-gloss chromium layer according to the invention can be deposited, for example, from a bath with an aqueous solution of hexavalent chromium, trivalent chromium and sulfate ions.
• hexavalent chromium, trivalent chromium and sulfate ions are 150 - 350 g / l Cr-VI, preferably 200 - 300 g / l Cr-Cl, useful. In this example 250 g / l were used.
• Useful concentrations for the trivalent chromium ions are 1 to 20 g / l, preferably 2 to 10 g / l and in this example 5 g / l.
• sulfate ions may be present, preferably between 1 and 2.5 g / l, in this example 1.5 g / l.
• the approach can be easily prepared by the addition of hexavalent chromium oxide (CrO 3 ), so that chromic acid is formed (H 2 CrO 4 ).
• CrO 3 hexavalent chromium oxide
• the desired proportion of it can be converted to trivalent by a reducing agent, such as sugar or oxalic acid Chrome can be reduced.
• the sulfation concentration is generated by adding sulfuric acid (H 2 SO 4 ).
• a layer thickness of about 2 ⁇ m can be achieved with a treatment time of the order of 10 min.
• the black plating layer is electrolytically deposited from a bath of about 300-800 g / l, preferably 400-500 g / l, here 450 g / l chromic acid, about 5-10 g / l, preferably 7-8 g / l, here 7.5 g / l chromium-III-sulfate, of the order of 2-8 g / l sodium or potassium carbonate or nitrate and about 1 g / l hexafluorosilicate at about 4 A / dm 2 for about 2 - 3 min.
• This black plating layer has a thickness of about 0.3-0.6 ⁇ m.
• Chromium VI oxides and polychromates are initially present on this layer. These impurities can be removed very successfully by a first simple water bath and then an ultrasound assisted cleaning in an alkaline solution at pH 10 and about 50-60 ° C for preferably at least 1-2 minutes. According to experience, treatments beyond 5 minutes do not bring any significant improvements. After the ultrasonic treatment in the alkaline solution again a water bath is run through.
• the success of the cleaning can be checked by a standard test by boiling with water and a Diphenylcarbazidtest the cooking water. It can be z.
• the method validated by Gottvalmaschinentechnik ZVO ZVO-0101-UV-05
• a test part is boiled under specified conditions and the Cr-VI content in the extraction solution according to DIN 38405 part 24 determined.
• Cr-VI oxidizes 1,5-diphenylcarbazide to 1,5-diphenylcarbazone, which forms a violet-colored complex with the resulting Cr-III.
• the absorbance of the dye at 540 nm is linearly related to the Cr-VI concentration, which can be evaluated by the calibration function or a comparative solution. With a standard test plate of 5 cm by 5 cm, it is possible to boil for 10 minutes in 130 ml of water under the standard conditions. According to the invention, values below 300 ⁇ g / l Cr-VI can be achieved here.
• an adjustable dullness in the manner already explained, follows the already mentioned galvanic high-gloss nickel layer of 15 to 25 microns, a matte Wattsche nickel layer. This is carried out at a current density of about 0.5 A / dm 2 from an aqueous solution containing 210 g / l nickel sulfate, 35 g / l nickel chloride and 40 g / l boric acid without further additives.
• the preferred layer thickness range is between about 0.1 and 2 .mu.m, the mattness of the layer ultimately resulting being adjusted via the layer thickness. In this embodiment, 0.2 microns are deposited.
• This layer thickness is meaningful only in terms of averaging. In fact, the growth is very grainy or "bulbous", with the individual grains becoming larger with increasing average layer thickness and decreasing mean distances. At significantly greater layer thicknesses, the grains are ultimately close to each other, resulting in a matte layer that does not let the gloss of the underlying Glanznickei Anlagen more.
• a sulfamate nickel layer is deposited on the wadding nickel layer.
• the grains are thereby reinforced, rounded the corners a bit and in particular the niches and angles lying on the edge of the grains filled.
• a 12 ⁇ m thick layer is deposited at a galvanic current density of 1 A / dm 2 .
• the aqueous solution contains 36% by volume of 60% by weight nickel sulphamate solution.
• the galvanic solution contains 5 g / l nickel chloride and 35 g / l boric acid. Considered, for example, the bathroom Schlötter MS.
• the overall layer is well protected against environmental influences and resistant to oxidation. It ultimately shows a gray metallic Cr gloss, which is desirable here. Due to the somewhat rounding properties of the sulfamate-Ni layer (as far as desired dullness), the dirt resistance and roughness are significantly improved and well suited for applications in the interior of motor vehicles.

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• 2006
  • 2006-10-24 EP EP08014210A patent/EP1995355A1/fr not_active Withdrawn
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