Classifications

• • 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
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/02—Coating starting from inorganic powder by application of pressure only
  • C23C24/04—Impact or kinetic deposition of particles
  • C23C24/045—Impact or kinetic deposition of particles by trembling using impacting inert media

Definitions

• the invention relates to a method for applying metallic coatings to metallic workpieces by mechanical-chemical treatment of the workpieces in a bath containing an inner impact body from an aqueous acidic solution, the workpieces being immersed in the bath and producing a relative movement between workpieces and impact bodies or bath and an activator and a little later the powdered coating metal and a reaction mixture are added to the bath.
• Such a method has the advantage over galvanically operating methods that the risk of hydrogen embrittlement of the treated workpieces is largely eliminated.
• the process is carried out in such a way that the degreased workpieces are introduced into a drum together with the impact bodies, which generally consist of a glass ball mixture.
• the impact bodies which generally consist of a glass ball mixture.
• the workpieces are freed of rust and scale and the surface is prepared for receiving an intermediate layer of a non-ferrous metal, in particular copper, which is then to be applied.
• the intermediate layer is deposited from a copper solution, which is filled into the drum.
• a so-called promoter chemical is entered, which ensures that what is also added powdered coating metal cleaned and a uniform surface distribution is achieved.
• the glass balls act as carriers for the metal powder particles and bring them to the workpiece surface to which they adhere due to cold welding.
• the mechanical pressure generated during the relative movement ensures that the structure is strengthened accordingly.
• the size of the glass spheres is chosen so that the powdered coating metal also gets into recesses, for example to the bottom due to thread grooves, and thus an optimal coating is achieved.
• a disadvantage of the known method is the relatively large outlay for the application of the intermediate layer and for the production of the so-called promoters, which act as catalysts in the production of the intermediate layer.
• the intermediate layer is applied in a separate chemical bath in one or more other treatment containers before the workpieces are treated to apply the actual metallic coating. But even if the application of the intermediate layer does not take place in a separate treatment container, it takes a relatively large amount of time and the above-mentioned expenditure on promoters and the like. the like
• the object of the invention is to provide a method of the type described in the introduction in which the formation of an intermediate layer is no longer necessary and with which metallic coatings can be applied more quickly to metallic workpieces.
• This object is achieved in that the pH of the bath is adjusted between 1 and 2, in that an oxyethylated nonylphenol polyglycol ether is used as activator and in that metal ions are added to the reaction mixture to form local elements.
• reaction mixture can contain hydrazine dichloride and / or hydrazine sulfate and / or iron (II) sulfate as well as tin (II) and / or antimony (II) compounds to form a spongy tin or antimony layer adhering to the metal powder particles.
• the method according to the invention is particularly suitable for the use of zinc, tin, cadmium, silver, gold or their alloys as coating material.
• the metal powder should have a grain size of ⁇ 10 ⁇ m.
• metallic coatings can be applied to metallic workpieces without an intermediate layer having been applied beforehand.
• the use of oxyethylated nonylphenol polyglycol ether achieves solidification and leveling of the coating to be applied.
• local elements arise during the development of hydrogen when metal and acid meet.
• a coherent hydrogen often forms skin that prevents further reactions. This is especially true when pure zinc meets acid.
• impurities in the form of copper or tin ions are added to the zinc, a local element forms because Zn 2 + dissolves in the zinc, the electrons migrate to the copper and discharge the hydrogen ion there, thus avoiding the formation of the hydrogen skin.
• tin II is converted into metallic tin or antimony II into metallic antimony, which deposits spongily, enveloping one or more zinc particles.
• ethylated nonylphenol polyglycol ether prevents the individual particles from redissolving, oxidizing or agglomerating until they reach the surface of the material and are firmly connected to the workpiece surface by mechanical action (impact of the glass balls) and the resulting short-term temperature increase.
• the workpieces treated with them have a corresponding corrosion resistance.
• coating metals e.g. Tin, zinc, cadmium, lead, but also silver or gold
• the workpieces treated with them have a corresponding corrosion resistance.
• coating metals that have only a low corrosion resistance e.g. Zinc
• a further reaction mixture with a metal salt of a metal other than the coating metal or with a plastic can be added to the bath.
• the additional reaction mixture can contain in particular 50% metal salt or plastic, 30% potassium chloride, 15% sodium acetate and 5% silica.
• tin-II sulfate or antimony-II sulfate or lead chloride are particularly recommended as metal salts.
• plastic it should be in granulate form with a grain size of less than 8 ⁇ m.
• Granules made of PVC or melamine resin are particularly suitable as plastics.
• the procedure for carrying out the method is such that the metallic workpieces are placed in an acid-proof drum which rotates about its own axis or are hung on a rotating frame which rotates in a bath.
• Impact bodies which have been washed out with water, e.g. Glass balls, introduced.
• the diameter of the impact body is kept so that it also fits in depressions, e.g. Thread grooves of screws can get.
• the pH of the bath is adjusted to a value of approx. 1 to 2 with mineral acids.
• a quantity of metal powder particles for example zinc particles, the diameter of which is 10 micrometers, which is determined with regard to surface and desired layer thickness, is used and dispersed in the bath by a few revolutions.
• This consists of a metal salt or plastic granulate as well as potassium chloride, sodium acetate and silica.
• a metal salt or plastic granulate as well as potassium chloride, sodium acetate and silica.
• potassium chloride sodium acetate
• silica silica
• the zinc powder was activated immediately, deposited on the base metal and formed a uniform, matt glossy coating of 8 my.
• the running time was 10-15 minutes, after which the pH rose to pH 5-6.
• the screws were separated from the glass balls by unloading them onto a sieve plate.
• the frame was continuously passed through 50 1 glass balls (composition as in test 1), which 1 1 of an activator consisting of: 1 were added to adjust the pH. Then immediately 1000 g of zinc powder and 100 g of a reaction mixture consisting of:

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Citations (3)

• 1979
  • 1979-12-08 EP EP79105012A patent/EP0012399B2/fr not_active Expired
  • 1979-12-08 DE DE7979105012T patent/DE2964070D1/de not_active Expired

Patent Citations (3)

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