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
  • C25D3/46—Electroplating: Baths therefor from solutions of silver
• • 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
• • 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
  • C25D3/48—Electroplating: Baths therefor from solutions of gold
• • 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
  • C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
  • C25D3/52—Electroplating: Baths therefor from solutions of platinum group metals characterised by the organic bath constituents used

Definitions

• the invention relates to a gel-shaped Precious metal electrolyte for the galvanic deposition of Precious metal layers on metallic workpieces.
• One of the most common methods for producing flat Precious metal coatings on metallic workpieces is the galvanic deposition.
• one Electrolytic bath which is essentially an aqueous solution represents a precious metal salt, with the help of DC the precious metal on the workpiece surface deposited.
• Special forms of galvanic Precious metal deposition is pad plating and that Pen electroplating. With these procedures you can Surface elements of the workpiece are selectively galvanized locally will. This becomes one with the cathode Workpiece connected to a DC voltage source handle-shaped anode, the tip of which one has an absorbent tampon or pen head with Electrolyte is soaked, processed manually, the processed surface is galvanized.
• the present invention was therefore based on the object the well-known precious metal electrolyte baths in With regard to their processability with the tampon or To improve pen electroplating or electrolytes develop the prescribed disadvantages no longer exhibit.
• a gel-like gold electrolyte is known in specialist circles become, which basically also for the application in the Tampon or pen plating is suitable. With this is the gel-like consistency, the advantages in the Dosing or placement on the workpiece with it brings, by a content of fumed silica generated.
• the disadvantage of this product is that it is gold contains in the form of potassium gold cyanide, so not cyanide free is. It has been shown that a replacement of cyanide with non-cyanide gold salts in this system immediately Decomposition leads to the elimination of elemental gold.
• Another disadvantage is the particulate nature of the as Fumed silica added to thickener. As a result, the meterability of the gel, for example by a thin cannula, limited. With the striking or wiping processing can the "smear effect" of Silica particles to damage the electroplated Lead gold layer. Furthermore, the long-term stability this precious metal gel is not sufficient because it the particles settle and secondly by decomposition Gold plating occurs.
• the invention thus relates to a gel-shaped Precious metal electrolyte for the galvanic deposition of Precious metal layers on metallic workpieces, containing a salt of a noble metal in aqueous solution and a gelling agent which is characterized in that this is a cyanide-free precious metal salt and as a gel former a hydrophilic organic polymer from the classes of Polysaccharides, the polyacrylic acid derivatives or the Contains polyethylene glycols.
• the invention further relates to a method for Production of a gel-shaped noble metal electrolyte in the to a cyanide-free solution of a precious metal salt as a gelling agent a hydrophilic organic polymer from the Classes of polysaccharides, polyacrylic acid derivatives or of polyethylene glycols.
• the invention also relates to the use such gel-like noble metal electrolytes for local limited galvanic deposition of precious metal layers on metallic workpieces, especially with the tampon or Pin plating.
• the invention finally relates to a method for Generation of flat precious metal coatings metallic workpieces through locally limited galvanic Deposition, in which one has a gel-shaped Precious metal electrolytes selectively on the surface of a connected to the cathode of a DC voltage source Applying the workpiece and bringing it into contact with a Anode locally galvanized.
• the gel-like noble metal electrolytes according to the invention contain a non-cyanide in aqueous solution Precious metal salt and no other cyanide additives. For this reason, they are just manual Processing as it is for the tampon and Pen plating is typical to handle safely.
• the precious metals are the elements gold and Understand silver and the platinum group metals. From essential for the galvanic generation of Precious metal layers, especially for decorative purposes, are gold, silver, platinum, palladium and rhodium. From the wide range of non-cyanide precious metal salts are the The following are examples:
• Precious metal electrolytes have a precious metal content of 10 to 200 g / l and in particular 20 to 100 g / l.
• the gel-like noble metal electrolytes according to the invention contain a hydrophilic organic as a gelling agent Polymer from the classes of polysaccharides, the Polyacrylic acid derivatives or the polyethylene glycols. Polymer products from these classes of substances prove themselves characterized in that they are mixed with water or with aqueous media form homogeneous stable colloidal solutions or hydrogels, with practically that with a small quantity entire viscosity spectrum can be covered.
• Polysaccharide gum such as in particular xanthan gum, Cellulose derivatives such as, in particular, ethoxymethyl cellulose and hydroxyethyl cellulose, as well as modified starch proven.
• polyacrylic acid derivatives preferably crosslinked polyacrylic acid as a gel former and polyacrylamide.
• polyethylene glycols according to the invention preferably those with molecular weights between 1000 and 10,000 used.
• the gel-like noble metal electrolytes according to the invention these gelling agents can be used in a proportion of 1 to 100 g / l, preferably 10 to 50 g / l.
• that precious metal gel according to the invention has a viscosity of 1500 to 4000 mPa ⁇ s, preferably 2000 to 3000 mPa ⁇ s.
• the gel works well at such viscosity values dose, for example drop by drop from a syringe or through a cannula and it remains without getting lost and drain at the location of the workpiece surface where it is has been placed.
• the gel-like noble metal electrolytes according to the invention can be easily made by the way a cyanide-free solution of a precious metal salt, for example, a corresponding commercially available Precious metal bath, one of the aforementioned gelling agents and until a viscous, gel-like consistency is reached homogenized.
• a precious metal salt for example, a corresponding commercially available Precious metal bath
• the noble metal gels according to the invention additionally a biocidal preservative to admit. This prevents, in particular prolonged storage or if the opening is not used decomposition of the organic gelling agent biological germs such as bacteria or fungi occur.
• the wide range available to the expert Biocides are primarily those of the PHB ester class proven. P-Hydroxy-benzoic acid n-propyl ester is preferred for use.
• the durability of the precious metal gel can be increased to at least 3 years.
• the gel-like noble metal electrolytes according to the invention can be particularly advantageous with the locally limited galvanic deposition of precious metal layers use metallic workpieces.
• the use is made preferably in the case of tampon or pen plating, such as especially in the case of decorative gilding, Silvering, platinum plating or rhodium plating in use is.
• the process for producing flat precious metal coatings on metallic workpieces through locally limited galvanic deposition, especially after the tampon or Pen procedure is done in such a way that the gel-like noble metal electrolytes according to the invention selectively on the surface of one with the cathode one DC voltage source connected workpiece and locally galvanized by contacting an anode.
• Galvanizing devices suitable for this are known and customary. In principle, these consist of one adjustable rectifier, which has a DC voltage of about Can deliver 4 to 25 volts.
• the object to be galvanized with the cathode for example via a clamp (Minus pole) of the rectifier connected.
• the layer hardness is comparable to that of conventional ones Precious metal electrolytes can be obtained.
• a corresponding one Galvanizing device has in addition to the Rectifier supplying another DC voltage Pulse generator on, the DC voltage pulse adjustable Output frequency on the electrodes.
• a commercially available neutral, cyanide-free gold bath Basis of ammonium gold sulfite (AURUNA® 591, Degussa AG) adjusted to a gold content of 20 g / l.
• this Solution become 25 g powder in 30 minutes Carboxymethyl cellulose sodium salt and 5 g p-hydroxybenzoic acid n-propyl ester (Preservative) stirred in portions.
• the solution is given a gel Consistency with a viscosity of 2500-3000 mPa ⁇ s.
• the Gel is filled into 10 ml dosing cartridges and is unchanged, even after opening, for at least 2 years durable.
• a coin blank prepared by thorough degreasing, activation of the surface in 5% H 2 SO 4 solution and rinsing in deionized water is connected to the cathode of a commercially available tampon electroplating device (e.g. Degussa rectifier TG 511) via a clamp.
• a drop of the gold gel is dosed onto the coin blank and applied to an area of 1 cm 2 with the tampon stick connected to the anode.
• the electroplating is carried out at a deposition rate of 2 ⁇ m / min at a direct voltage of 4.3 V, which is pulsed at a frequency of 150 Hz.
• the gold layer obtained has a hardness of 180 HV.
• Rhodium 270 Rhodium 270, Degussa AG
• Rhodium 270 Rhodium 270, Degussa AG
• Rhodim content 20 g / l becomes 25 g within 30 min powdered xanthan gum and 5 g of n-propyl p-hydroxybenzoate stirred in portions.
• Get the solution a gel-like consistency with a viscosity of 2500-3000 mPas.
• the gel comes in 10 ml dosing cartridges Contents filled and is, even after opening, at least 2 Years unchanged.
• Preparation and electroplating A coin blank is made analogously to example 1.
• the Separation speed is 2 ⁇ m / min with a a frequency of 150 Hz pulsed DC voltage of 9-10 V.
• the rhodium layer obtained has a hardness of 900 HV.

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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)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

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Family Applications (1)

Country Status (2)

Cited By (4)

Citations (6)

• 1997
  • 1997-03-27 EP EP97105203A patent/EP0867528A1/fr not_active Withdrawn
• 1998
  • 1998-03-13 DE DE1998111006 patent/DE19811006A1/de not_active Ceased

Patent Citations (6)

Non-Patent Citations (2)

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