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
• • 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
  • C25D3/10—Electroplating: Baths therefor from solutions of chromium characterised by the organic bath constituents used
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N7/00—Shells for rollers of printing machines
  • B41N7/04—Shells for rollers of printing machines for damping rollers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N2207/00—Location or type of the layers in shells for rollers of printing machines
  • B41N2207/02—Top layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N2207/00—Location or type of the layers in shells for rollers of printing machines
  • B41N2207/10—Location or type of the layers in shells for rollers of printing machines characterised by inorganic compounds, e.g. pigments

Definitions

• the present invention relates to a galvanic bath and a method for producing structured hard chrome layers and its use for producing structured hard chrome layers on components. It has long been common state of the art to provide objects of technology or general use with surface coatings by means of galvanic processes. This is necessary in order to give the objects special functional and / or decorative surface properties, such as hardness, corrosion resistance, metallic appearance, gloss, etc.
• a bath that contains at least the metal to be deposited as a salt is converted into metal deposited by means of direct current on the object connected as cathode.
• the object to be coated usually consists of a metallic material. If the base material is not electrically conductive per se instead, the surface can be made conductive by a thin metallization.
• Galvanic baths containing nickel or chrome are mostly used in technical applications to produce particularly hard, mechanically resistant layers.
• an electroplated hard chrome layer has a rough surface structure.
• decorative tops for example, a matt appearance or a pleasant, not smooth "handle" should be created.
• rough hard chrome layers or structured chrome layers fulfill certain functional properties.
• printing drums, ink rollers and, in particular, dampening cylinders with a special, rough surface are required for printing machines. Chromium-plated tools can be used in forming technology to give the workpiece to be machined a structured surface.
• objects with a hard chrome coating and a rough surface structure are obtained by mechanical processing, such as grinding, sandblasting, spark erosion, etc., or by chemical etching processes before, between or after the chrome plating.
• mechanical processing such as grinding, sandblasting, spark erosion, etc.
• chemical etching processes before, between or after the chrome plating.
• DE 42 11 881 discloses a galvanic method for applying surface coatings to machine components, in which, for example, chromium is deposited in a structured form.
• at least one initial pulse and at least one subsequent pulse of voltage or current and certain guidance of the voltage or current function initially cause nucleation on the surface of the machine component and subsequent growth of the germs of the separating material.
• the chromium is deposited in the form of statistically evenly distributed, dendritic or approximately hemispherical (dome-shaped) elevations.
• EP 0 722 515 contains a further development of the method according to DE 42 11 881, the increase in electrical voltage or current density taking place in stages.
• DE 34 02 554 C2 describes a saturated aliphatic sulfonic acid with a maximum of two carbon atoms and a maximum of six sulfonic acid groups or salts or halogen acid derivatives thereof for increasing the current efficiency in the electrodeposition of hard chromium on a workpiece made of steel or aluminum alloy from an aqueous, chromic acid and Use non-caustic electrolytes containing sulfuric acid.
• US-A-5 176 813 discloses a process for the electrodeposition of chromium from a galvanic bath with a lead-containing anode in the absence of monosulfonic acid, the galvanic bath containing chromic acid, Contains sulfate ions and at least one optionally halogenated alkylpolysulfonic acid or its salt with 1 to 3 carbon atoms.
• the object of the present invention is therefore to simplify the production of structured hard chrome layers considerably and, in particular, to enable structure layers with a more uniform surface topography and significantly higher roughness values.
• the galvanic bath according to the invention preferably contains chromium (VI) ions in an amount which corresponds to 200 to 250 g / l chromic acid anhydride.
• the chromium (VI) ion-providing compound is preferably selected from chromic anhydride (CrO 3 ) and / or alkali dichromates such as Na 2 Cr 2 O 7 and K 2 Cr 2 O 7 . Of the alkali dichromates, K 2 Cr 2 O 7 is preferred.
• the chromium (VI) ion-providing compound is chromic anhydride.
• part of the chromium (VI) ion-providing compound is one or more alkali dichromate (s), preferably potassium dichromate.
• alkali dichromate preferably potassium dichromate.
• preferably less than 30% and particularly preferably less than 15% of the chromium (VI) ions are supplied by alkali dichromate.
• the molar concentration ratio of chromium (VI) ions to sulfate ions in the electroplating bath is preferably 100: 1 to 105: 1.
• the soluble salts of sulfuric acid which can be used are preferably selected from sodium sulfate, potassium sulfate, lithium sulfate, ammonium sulfate, magnesium sulfate, strontium sulfate, aluminum sulfate and potassium aluminum sulfate. Strontium sulfate is particularly preferred
• the bath comprises 2-hydroxyethanesulfonate ions in an amount corresponding to 0.07 to 1.5 / l of the sodium salt.
• the 2-hydroxyethanesulfonate ions contained in the galvanic bath according to the invention can be provided by the 2-hydroxyethanesulfonic acid itself or a salt thereof, preferably the sodium salt.
• the electroplating chrome bath according to the invention can be used in the electroplating systems usually used in this technology and with the usual working methods as well as for the usual coating purposes on the normally provided basic materials.
• Such base materials can be, for example, objects made of conductive materials such as metal, in particular steel, and metallized, non-conductive objects.
• the galvanic bath according to the invention is expediently used at temperatures between 30 and 70 ° C.
• chrome layers with a largely uniform dome-shaped microstructure and roughness values Rz of up to approximately 40 ⁇ m can be produced.
• Such a deposition is preferably carried out in the temperature range 40 and 50 ° C., preferably between 42 and 48 ° C. and particularly preferably between 44 and 46 ° C.
• Such a deposition is preferably carried out in the temperature range between 51 and 61 ° C., preferably between 53 and 59 ° C. and particularly preferably between 55 and 57 ° C.
• chrome bath according to the invention can be used to deposit directly onto the base material, for example steel. Galvanic precoatings, especially with nickel, are not necessary.
• the latter In order to deposit a structured hard chrome layer on an object, the latter, when connected as a cathode, is introduced into the galvanic bath according to the invention. It is sufficient if the object is ground to size. Further surface processing and in particular electroplating are not necessary. For a particularly uniform coating, it is advantageous to continuously circulate the bath and / or to keep the object to be coated rotating in the bath.
• the current density can be up to 50 A / dm 2 .
• a deposition time TP 10 to 15 minutes
• a base layer thickness of 6-9 ⁇ m can be achieved.
• a waiting time TW is expediently inserted before the start of the deposition while the object takes on the temperature of the bath. This time can be 1 to 10 minutes depending on the size of the object and the temperature difference.
• the current density can be up to 30 A / dm 2 . 1 to 2 minutes is sufficient as the duration TP.
• the base layer obtained generally has a microhardness of 800 to 950 HV 0.1.
• the actual deposition of the structured chrome layer takes place from the same bath.
• the bath temperature is to be set to 30 to 50 ° C., preferably to 40 to 50 ° C., particularly preferably to 42 to 48 ° C. and most preferably to 44 to 46 ° C.
• a waiting time TW and an activation step with the parameters already mentioned before the start of the deposition.
• the deposition is expediently carried out at a current density of 75 to 90 A / dm 2 . With a deposition time TP of 10 to 30 minutes, a thickness of the structural layer of 14 to 40 ⁇ m can be achieved.
• the structure layer obtained normally has a microhardness of 850 to 900 HV 0.1.
• the structure layer has a roughness Rz of up to about 40 ⁇ m.
• the structural chrome layer is coated with a thin, smooth hard chrome layer, the functional layer, again from the same bath.
• the bath is brought to a temperature in the range from 50 to 70 ° C., preferably from 51 to 61 ° C., particularly preferably from 53 to 59 ° C. and most preferably from 55 to 57 ° C. and then at a current density up to 50 A / dm 2 deposited.
• a deposition time TP of 5 to 15 minutes, a layer thickness of the functional layer of 3 to 9 ⁇ m can be achieved.
• the functional layer normally has a microhardness of 1,000 to 1050 HV 0.1.
• the final thin hard chrome layer practically does not change the roughness of the structural layer.
• the ramp time TR can be 1 to 5 minutes each.
• the method is distinguished by a particularly simple current density control.
• it is simply sufficient to linearly increase the current density to the respective setpoint or the respective descent in the respective steps.
• otherwise required, technically complex and thus expensive current and voltage regulating units and their complex programming are not required.
• it can also be favorable and advantageous in individual cases to regulate the current density in steps to the maximum value or down again.
• a structured hard chrome layer is obtained on the surface of the object, which is characterized by a particularly dense and uniform distribution of very well-formed dome-shaped elevations.
• a layer with a peak number of 75 to 100 / cm can be obtained.
• roughness values Rz up to 40 ⁇ m can be achieved.
• the method according to the invention can be used to generate a chrome layer on components, in particular machine components.
• the method is used to produce a structured hard chrome layer on machine components in sliding contact with one another, in particular pistons, cylinders, bushings and axle bearings, on rollers, drums or cylinders in the graphics industry, in particular ink rollers and dampening cylinders, and on tools ,
• 100 l of bath contain 20.450 kg of chromic anhydride, 2.500 kg of potassium dichromate, 0.550 kg Strontium sulfate and 3.5 g of 2-hydroxyethanesulfonic acid sodium salt. This results in the concentration values in the bath of 222 g / l chromic anhydride, 2.2 g / l free sultate and 0.035 g / l 2-hydroxyethanesulfonic acid sodium salt.
• the structure chrome layer obtained has a roughness Rz of 35 to 40 ⁇ m and a peak number of 75-100 / cm with an extremely uniform distribution of very well-formed dome-shaped elevations.
• FIG. 1 shows the SEM image of the surface of the roll cylinder, which is chromium-plated by way of example with the chrome bath according to the invention and according to the method according to the invention, at a magnification of 30: 1.
• the dense and even distribution of dome-shaped elevations can be clearly seen.
• 3 shows the SEM image of a cross section through the layer at an enlargement of 400: 1.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Electroplating Methods And Accessories (AREA)
• Cosmetics (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1998
  • 1998-06-26 DE DE19828545A patent/DE19828545C1/de not_active Revoked
• 1999
  • 1999-06-21 US US09/701,530 patent/US6447666B1/en not_active Expired - Fee Related
  • 1999-06-24 CA CA002334708A patent/CA2334708A1/en not_active Abandoned
  • 1999-06-24 AT AT99931178T patent/ATE231933T1/de not_active IP Right Cessation
  • 1999-06-24 RU RU2001102496/02A patent/RU2202005C2/ru not_active IP Right Cessation
  • 1999-06-24 JP JP2000557019A patent/JP2002519514A/ja active Pending
  • 1999-06-24 KR KR1020007014501A patent/KR100573531B1/ko not_active Expired - Fee Related
  • 1999-06-24 DE DE59904174T patent/DE59904174D1/de not_active Expired - Lifetime
  • 1999-06-24 WO PCT/EP1999/004412 patent/WO2000000672A2/de not_active Ceased
  • 1999-06-24 CN CNB998079324A patent/CN1191392C/zh not_active Expired - Fee Related
  • 1999-06-24 CZ CZ20004789A patent/CZ299000B6/cs not_active IP Right Cessation
  • 1999-06-24 EP EP99931178A patent/EP1097261B1/de not_active Expired - Lifetime
  • 1999-06-24 BR BR9912214-6A patent/BR9912214A/pt not_active IP Right Cessation

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