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
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/30—Fluxes or coverings on molten baths

Definitions

• My invention relates to a new method of applying metallic coatings to ironor metal-articles and is particularly applicable in coating iron articles with zinc.
• the coating-metal itself especially the zinc contains oxides and is likely to oxidise while in -a molten state. These oxides too hinder a perfect coating.
• My invention does away with these difliculties. To this end I use with great suc cess fluorine-compounds as a means for dissolving the oxides and promoting the coating process. The use of the fluorine-compounds may take place in different stages of the process in a different way.
• their surfaces may be powdered or coated with a protective layer of salts of fluorine or of a mixture of these salts with zinc-chloride, ammonium-chlo- 50 ride or the like ,as well as with resins, fats or The adherent the like.
• the articles are then being metal-coated.
• This bath consists according to my invention of fluorine-compounds or of mixtures of fluorine-compounds with salts of Zinc-chloride or the like andin some instances also with resins, fats or the like.
• the saltbath cleans intensively andperfectly the surfaces of'the articles treated from the oxides and the protective layer formed on these surfaces prevents in a high degree a new oxida tion. -At the same time the articles dipped into the hot bath are dried and can be brought directly into the metal-bath without anyintermediate treatment.
• the metalbath is covered with a layer of the said salts or of a mixture of the salts.
• a constant protective layer is used to be em ployed which consists of molten salts of zincchlorides, and through which the articlcs to 35 be treated are passed into the zinc-bathl
• This protective layer is produced during the application of the zinc-coatings by the decom position of ammonium-chloride upon the surface of the molten metal at a temperature of about 450 C.
• the salts of zinc-chlorides thus formed melt at thetemperature of the zinc-bath to a liquid salt-mass floating on the surface of the equation may serve for
• the surface of the. bath is 80 v in a wet state from the treatment with acid are completely dried and preheated on being passed through the molten, fusible mass of zinc-chlorides.
• the articles to be coated can be dipped into the molten metal-bath without any danger.
• aluminium to the zinc-bath, as the aluminium; reduces the zinc-oxides of the bath to metallic zinc.
• the quantity of the aluminium to be added depends.
• the zinc-bath is constantly enriched on its surfaces by oxides which can be removed only by a constant addition of aluminium.
• An alloy of such a proportion does not sensibly change the amount of metallic aluminium contained in zinc-bath which is preferably O.30.5%.
• the solid block of this alloy dissolves relatively quick, and has the remarkable advantage of being specifically heavier than the molten zinc bath, so that it drops on the bottom of the bath and its solution takes place underneath the articles dipped into the bath.
• the zinc-bath remains constantly clean, fusible and by the reduction of the zinc-oxides only very small quantities of aluminium-oxides are formed.
• the aluminium used for zinc-coating in the from of zinc-aluminium alloys cleans the zincbath by its deoxidizing effect.
• the zinc-bath becomes more fusible and gives remarkably adherent metal coatings which may be bent and folded.
• the use of aluminium in applying zinc-coatings much zinc is saved.
• a protective layer which consists of a mixture of salts of zinc-chlorides and of fluorine-compounds.
• a salt-mixture of ammonium-zinc-chlorides and fluorine-compounds melts upon the surface of the bath of zinc having a large percentage of aluminium to a readily fusible mass of salt, which generates no vapors, which does not decompose, which exerts an oxide cleanin efiect, and brings about the application 0 zinc-coatings in an excellent and easy manner.
• the previous drying of the articles to be treated is quite superfluous with the process I of the invention.
• the new protective layer absorbs all moisture from the goods to be treated so that the said goods enter the molten zinc-bath containing aluminium in a -perfectly dry state, preheated and metallically pure.
• the proportion of the several ingredients of the protective layer containing fluorine depends on the amount of aluminium con-- tained in the zinc-bath. An average proportion of O.56% of fluorideof potassium, 10- 20% of ammonium-chloride and 74.-89.5% of zinc-chloride will do.
• the protective layer consisting of fluorinezinc-salts may also be used in applying coatings with crude zinc without any addition of aluminium. It has as against the protective layer of ammoniuni-chloride the great advantage'that it withdraws less zinc from the metal-bath. As a consequence its use is connectedwith smaller losses of zinc as the use of the known protective layers.
• the use of the fluoric protective layer has further proved practicable and better in aplying zinc-coatings according to the leadoath process than the protective layer of ammonium chloride and zinc-chloride.
• the lead-bath process only at the emerging point of the articles treated a floating film of zinc is present.
• the fluoric layer forms considerably less chloride of plumbum, than the layer of ammonium chloride and zinc-chloride.
• the articles coated according to the lead-bath process witha protectivefluoric layer show a-smooth, well-adhering, homogeneous coating of zinc. On Sherardizing a considerable improvement of the process is attained, in that in lieu of pure dust of zinc a mixture of dust of zinc and fluorine compounds, as for instance fluorid of calcium, .is used.
• This mixture may consist of 90 percent of fluoride of calcium and 10 percent of zincpowder. It will yield a more homogeneous, denser, lighter and more adhering coating of .zinc free from pores than the pure zinc- ;powder without this admixture of fiuorlnecompounds.
• fluoride of calcium or any other fluorine compounds keeps the'zinc-powder in a loose condition, prevents spontaneous combustion of the zine-powder in the air, and allows also to keep during the process a proper temperature, which lies 150 degrees to 200 degrees Centigrade below the fusing point of the zinc.
• the mixture of fluorine and zinc-powder renders the Sherardizing operation cheap since with the proportion of mixture mentioned the loss in material and zinc is very small.
• he machines for carrying out the process of metal-coating are provided with rotating rollers which on one side introduce the iron sheets or the other articles into the bath and remove them on the other side after the coating has taken place.
• in the metal bath and partly in order to be cleaned from oxides in a bath of salts, fats or resins. It is very important to keep the rollers thoroughly clean as otherwise the sheetstreatcd become stained while leaving the metal-hath.
• compounds of fluorine are added to the said cleaning salts which now become more eifective and which in some instances become effective in which they have hitherto not been effective altogether.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Coating With Molten Metal (AREA)

Applications Claiming Priority (4)

Publications (1)

Family

ID=61021891

Family Applications (1)

Country Status (4)

Cited By (8)

Families Citing this family (5)

• 0
  • BE BE335274D patent/BE335274A/fr unknown
• 1926
  • 1926-07-27 US US125321A patent/US1914269A/en not_active Expired - Lifetime
  • 1926-08-13 FR FR620770D patent/FR620770A/fr not_active Expired
  • 1926-08-17 GB GB20250/26A patent/GB257262A/en not_active Expired
• 1928
  • 1928-12-17 FR FR36224D patent/FR36224E/fr not_active Expired

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