Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
• • 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
  • C25D11/02—Anodisation
  • C25D11/34—Anodisation of metals or alloys not provided for in groups C25D11/04 - C25D11/32
• • 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
  • C25D11/36—Phosphatising
• • 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

Definitions

• This invention relates to a new method of treating surfaces of zinc and zinc alloys.
• the aim of the treatment is a cleansing and certain Preservation of the cleaned surface.
• the zinc alloys to which this Invention contain a substantial proportion Zn, in particular at least 90% by weight Zn.
• This invention is based on the overall technical problem, both in terms its cleaning properties as well as its insensitivity efficient against the alloy composition as well as economically Process for cleaning and passivating zinc and zinc alloy surfaces specify.
• the invention is directed to a method in which the surface is passivated, characterized by a treatment step in a solution, the phosphoric acid and an alcohol in which the surface is anodically connected.
• the anodic cleaning step in the solution with phosphoric acid and The alcohol has both a degreasing and etching of the surface a good efficiency and is also able to handle even problematic residues such as to remove polysilane release agents.
• the cleaning method of the invention especially with a low water content of the solution (electrolyte) a certain inhibiting Inherent effect, so that excessive material removal is prevented.
• the water content is preferably at most 5% by volume.
• the cleaning and passivation process according to the invention can advantageously with a neutral rinse step, such as in water, with a pH of about 7 completed.
• a neutral rinse step such as in water
• a pH of about 7 completed.
• other steps are conceivable in which a zinc phosphate passivation layer is formed, in particular aqueous rinsing and Treatment steps at different pH values, as long as these with the zinc phosphate layer are compatible.
• the cleaning effect and in particular the etching can be through set the selection of the electrical parameters of the anodic cleaning operation and thus optimize it depending on the alloy of interest. For example, you can work with a certain anodic current density become. This gives you an optimization parameter in your hand that determines the solution composition not changed. It can be synonymous with one and the same Solution to work optimally with different alloys. Of course, lets Also optimize the solution composition alloy-dependent, although the inventors could not find any critical dependencies here.
• alcohol the usual alcohols such as methanol, ethanol, propanol, butanol and higher alcohols and their derivatives such as isopropanol into consideration. But also also diols, polyethers and other alcohols. A cheap choice are Butanol and isopropanol. Of course, two or more alcohols may be mixed occur.
• the anodic current density on the anodically poled surface can advantageously be between 10, 30 or 50 A / m 2 as the lower limit and 500 A / m 2 as the upper limit and, as previously stated, as the optimization parameter depending on the alloy composition, the acceptable material removal and the required cleaning effect used.
• the total treatment time of the anodic cleaning steps can for example be between 10 seconds and 5 minutes and depends strongly on the set current density, the reasonable material removal and the degree of pollution.
• the proportion of phosphoric acid in the solutions for the anodic purification steps is 30-90% by volume, the phosphoric acid being within this volume fraction 50-95 weight percent can be.
• the solutions are advantageously except the said volume fraction of phosphoric acid of 30-90 vol.% In the rest substantially from the alcohol (mixture).
• the cleaning effect of the method according to the invention is so thorough and broad scattered that chemical pretreatment steps before incorporation into the phosphoric acid and the alcohol-containing solution can be omitted and for reasons of economy should also advantageously be eliminated.
• the surfaces to be treated can therefore be introduced directly and dry.
• a particular advantage of the invention is also that also regenerated Alloys can achieve good results, especially no sludge arises.
• the metallic contaminants of regenerated material have in conventional Procedures led to significant problems in cleaning and frequent a cleaning and subsequent good coating completely prevented.
• a preferred application of the invention is in the preparation of zinc alloy surfaces for a subsequent coating of any kind.
• the coating depends on the cleanliness of the surface, and although both in terms of optical properties as well as on the load capacity the coating.
• the invention relates to a subsequent Metallization, which can be done galvanically or without external power. in this respect The invention is also directed to the overall method of the described Cleaning and passivation and the subsequent coating, in particular Metallization.
• a part of a standard zinc die-casting alloy in question, for example, the alloys Z400 to Z430
• the current density is, for example, 20 A / m 2 at a temperature of 25 ° C and a treatment time, which may be about 30 s.
• the parts are rinsed in neutral water (pH about 7).
• neutral water pH about 7
• the surface is now passivated and can be metallized in a conventional manner.
• This is an electrolytic coating with Ni or Cu or an alloy selected from it.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Electroplating Methods And Accessories (AREA)
• ing And Chemical Polishing (AREA)

Priority Applications (5)

Applications Claiming Priority (1)

Publications (2)

Family

ID=29225588

Family Applications (1)

Country Status (5)

Citations (4)

• 2002
  • 2002-04-12 EP EP02008422A patent/EP1361297B1/fr not_active Expired - Lifetime
  • 2002-04-12 DE DE50200704T patent/DE50200704D1/de not_active Expired - Fee Related
  • 2002-04-12 AT AT02008422T patent/ATE272133T1/de not_active IP Right Cessation
  • 2002-09-11 WO PCT/EP2002/010195 patent/WO2003087438A1/fr not_active Application Discontinuation
  • 2002-09-11 AU AU2002329277A patent/AU2002329277A1/en not_active Abandoned

Patent Citations (4)

Non-Patent Citations (1)

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