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
  • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
  • C23D5/00—Coating with enamels or vitreous layers
  • C23D5/04—Coating with enamels or vitreous layers by dry methods

Definitions

• the invention relates to a method for applying electrostatically sprayable enamel powder to workpieces with the addition of protective gas.
• enamel powder i.e. powdered, hydrophobized enamel frits u. Suspend the like in air, in this form to a sprayer and spray there under the influence of an electric field, the electric field being generated by a high voltage.
• DE-OS 27 15 128 describes a method for applying a glazed enamel to metallic workpieces by generating a strong, directed electrostatic field which directs the charged powder onto the workpiece.
• the particles of enamel powder cannot initially be sprayed electrostatically without additional technological means, such as coating with silicone compounds, since they have an organic composition and the required high electrical surface resistances are not present.
• enamel powder air mixtures are not explosive.
• the enamel powders produced with the known preparation processes are subject to a high degree of negative influence by air humidity and temperature during the application process.
• DE-AS 24 51 672 describes a process for the electrostatic spraying of powdery substances onto preheated metal pipes, in which, in addition to other technological features, the powdery substances are sprayed with intergas.
• intergas is necessary for the purpose of preventing the oxidation of the workpiece and to reduce the risk of explosion of the plastic powder-air mixture.
• the use of this solution for coating with enamel powder is not possible due to the structural design of the device used and the technological process sequence, since electrostatically sprayable enamel powders do not adhere to heated materials in accordance with quality.
• the invention seeks to remedy this.
• the invention as characterized in the claims, solves the problem of creating a method for applying electrostatically sprayable enamel powder to workpieces with the addition of gas, by means of which the layer thickness differences are reduced to a minimum by means of increased spraying and deposition rates and the dependency on temperature and humidity fluctuations is reduced.
• electrostatic powder application is understood to mean the process of charging the enamel particles, their migration to the workpiece and the subsequent deposition of the particles on the workpiece.
• the advantages achieved by the invention are essentially to be seen in the fact that the charging behavior of the enamel powder is improved by the addition of CO2, at the same time preventing the possibility of discharge, so that the spray yield is increased and the powder adhesion on the workpiece is increased. Furthermore, the dependency of the coating process on the temperature and humidity of the surrounding working atmosphere is reduced, the effectiveness of the electrostatic enamel powder coating significantly improved, while at the same time the investment costs by reducing the necessary facilities, such as air conditioning for the spray room, the number of sprayers required, and reducing the differences in layer thickness by generating a uniform layer thickness to a minimum.
• a baking room of an electric oven with electrostatic enamel powder is using known devices, such as application booth with multiple spray guns, to which the processed enamel powder is fed, high voltage generator, conveyor chain for workpiece conveying and. Like., The powder application carried out.
• the uncharged enamel powder intended for spraying is conveyed from the powder storage container by means of CO2-containing gas and fed to the spray guns, the electrostatic charging of the enamel powder taking place directly in the spray guns via electrodes.
• the application booth can advantageously also be supplied through existing openings to improve the powder adhesion on the workpiece CO2.
• the powder particles are applied to the workpiece being passed.
• no air conditioning measures are generally carried out when individual coatings are necessary.
• the layer thicknesses which occur during the application of enamel powder fluctuate very strongly as a function of room temperature and room air humidity.
• the spraying and separation rate is increased by approx. 20%.
• the amount of powder adhering to the workpiece increases by approx. 10%.
• the coating result is constant under various external climatic conditions, which is not possible under the naturally changing conditions (temperature, air humidity) when using known methods.
• a CO2-air mixture (1: 3) is used in a system in which the outer parts of the hearth are coated on a running conveyor chain by means of powder enamelling.
• the spray yield increases by approx. 15%.
• the spray booth is supplied with ambient air and CO2-containing, dewatered exhaust gas from an enamelling furnace.
• the powder adhesion improves by approx. 15%.
• the number of spray guns required can be reduced from 12 to 10 previously.
• the more uniform layer thickness distribution achieved results in a 20% lower enamel powder consumption.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Electrostatic Spraying Apparatus (AREA)
• Prostheses (AREA)
• Materials For Medical Uses (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Paints Or Removers (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=5583947

Family Applications (1)

Country Status (6)

Cited By (2)

Families Citing this family (1)

Family Cites Families (2)

• 1986
  • 1986-11-18 DD DD29636886A patent/DD253647B1/de not_active IP Right Cessation
• 1987
  • 1987-10-27 SU SU877774620A patent/SU1581777A1/ru active
  • 1987-11-02 CS CS877854A patent/CS785487A1/cs unknown
  • 1987-11-12 EP EP19870116719 patent/EP0268211B1/fr not_active Expired - Lifetime
  • 1987-11-12 ES ES87116719T patent/ES2031109T3/es not_active Expired - Lifetime
  • 1987-11-12 DE DE8787116719T patent/DE3779054D1/de not_active Expired - Lifetime

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