US2100179A - Method of coating metal articles with zinc - Google Patents

Method of coating metal articles with zinc Download PDF

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Publication number
US2100179A
US2100179A US131183A US13118337A US2100179A US 2100179 A US2100179 A US 2100179A US 131183 A US131183 A US 131183A US 13118337 A US13118337 A US 13118337A US 2100179 A US2100179 A US 2100179A
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Prior art keywords
zinc
bath
article
coating
metal
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US131183A
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Williams Allan Heathcote
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    • 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
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon

Definitions

  • This invention relates to an improved method of and means forcoating metal articles with zinc, and has for its chief Object to provide an improved process by means of which metal win- 5 dow frames may be very effectively and efliciently galvanized although, as will be appreciated from the following description, the present invention is by no means limited to a process for galvanizing metal window frames but is also applicabl to the galvanizing of other metal articles.
  • the process of galvanizing a metal article according to the present invention is characterized in that the article to be galvanized is first given a coating of zinc by immersion in a bath of molten zinc, which coating is then heated out of ,contact with oxygen, or other gas or substance likely to have an injurious effect on the coating,
  • the apparatus for carrying out the present invention conveniently consists of a bath, the major portion of which is filled with molten lead or some other suitable substance of higher specific gravity than spelter, a comparatively thin layer 30 of molten spelter floating on top of the lead or the like.
  • the articles to be coated are passed through the spelter into the molten lead where they are allowed to remain until they acquire the requisite temperature to enable the zinc to form an alloy with the surface of the metal.
  • the articles are then withdrawn through the layen oi. spelter where they receive a further coating of zinc.
  • the bath is preferably narrower at the bottom than at the top and has the heat applied to the sides of the same so that the heat lost on immersion of an article may be quickly 7 made up.
  • the spelter When molten spelter is heated to a sufliciently high temperature to enable it to forman alloy with the article to be coated, it tends to attack the iron walls of the spelter bath and so rapidly increases the formation of dross and consequent wastage of spelter. To a very large extent this disadvantage is overcome in the apparatus according to the present invention due to the relatively thin layer of zinc employed but, if desired, the spelter may be contained in a relatively shallow retaining frame having its walls partly imsame temperature or approximately the same (Cl. ill-20.2)
  • the bath is about seven feet deep and tapers downwardly so that 0 it is only about one foot wide at the bottom.
  • the bath is filled to the extent of about ninetenths of its depth, viz., about six feet four inches, with molten lead or other suitable metal and on top of this molten lead or the like floats a layer of about eight or ten inches of molten zinc.
  • the window frame, or other article to be galvanized is, after being suitably pickled in the usual way, passed quickly through the thin upper layer of molten zinc into the molten lead beneath the same.
  • Thearticle is then allowed to remain in the molten lead until it acquires the temperature as the molten lead which is conveniently heated to about 550 5'70 C.
  • the pores of the metal article seem to open and the preliminary coating of zinc which the article has received due to its initial passage through the molten zinc appears to form an alloy with the iron of the article to be galvanized.
  • the invention is capable of general application for zinc coating articles, but is particularly intended for forming a zinc coating on metal window frames which are very liable to rust.

Description

Patented Nov. 23, 1937 METHOD or coarnvc METAL narrows WITH ZINC
Allan Heathcote Williams, Chester, England No Drawing. Application March 16, 1937, Se-
rial No. 131,183. In Great Britain August 9, 1935 1 Claim.
This invention relates to an improved method of and means forcoating metal articles with zinc, and has for its chief Object to provide an improved process by means of which metal win- 5 dow frames may be very effectively and efliciently galvanized although, as will be appreciated from the following description, the present invention is by no means limited to a process for galvanizing metal window frames but is also applicabl to the galvanizing of other metal articles. The process of galvanizing a metal article according to the present invention is characterized in that the article to be galvanized is first given a coating of zinc by immersion in a bath of molten zinc, which coating is then heated out of ,contact with oxygen, or other gas or substance likely to have an injurious effect on the coating,
for such a time and to such a temperature that the coating forms an alloy with the metal to .be coated and is finallywhilst still hot immersed inmolten zinc, without contact with oxygen or other injurious gas or substance, whereby a coating of zinc firmly adhering to the previously produced alloy is obtained.-
The apparatus for carrying out the present invention conveniently consists of a bath, the major portion of which is filled with molten lead or some other suitable substance of higher specific gravity than spelter, a comparatively thin layer 30 of molten spelter floating on top of the lead or the like. The articles to be coated are passed through the spelter into the molten lead where they are allowed to remain until they acquire the requisite temperature to enable the zinc to form an alloy with the surface of the metal. The articles are then withdrawn through the layen oi. spelter where they receive a further coating of zinc.
The bath is preferably narrower at the bottom than at the top and has the heat applied to the sides of the same so that the heat lost on immersion of an article may be quickly 7 made up.
- When molten spelter is heated to a sufliciently high temperature to enable it to forman alloy with the article to be coated, it tends to attack the iron walls of the spelter bath and so rapidly increases the formation of dross and consequent wastage of spelter. To a very large extent this disadvantage is overcome in the apparatus according to the present invention due to the relatively thin layer of zinc employed but, if desired, the spelter may be contained in a relatively shallow retaining frame having its walls partly imsame temperature or approximately the same (Cl. ill-20.2)
mersed in the lead and having a clearance from the sides of the tank. a.
, at the top at its widest part. The bath is about seven feet deep and tapers downwardly so that 0 it is only about one foot wide at the bottom. By this means the heat ofthe furnace which is arranged on the sides of the bath is distributed over a wide area of the bath (which is conveniently made of iron) and so the heat lost on the immersion of the article to be galvanized'into the bath can be quickly made up.
The bath is filled to the extent of about ninetenths of its depth, viz., about six feet four inches, with molten lead or other suitable metal and on top of this molten lead or the like floats a layer of about eight or ten inches of molten zinc.
In use the window frame, or other article to be galvanized is, after being suitably pickled in the usual way, passed quickly through the thin upper layer of molten zinc into the molten lead beneath the same. Thearticle is then allowed to remain in the molten lead until it acquires the temperature as the molten lead which is conveniently heated to about 550 5'70 C. During this time and when the article attains a temperature of about 490? C. the pores of the metal article seem to open and the preliminary coating of zinc which the article has received due to its initial passage through the molten zinc appears to form an alloy with the iron of the article to be galvanized. V
Whenthe article has attained the desired'temperature it is withdrawn from the bath, passing again through the thin layer of zinc at the top of the bath. A skin-bond is formed through the zinc entering into the pores of the iron of the article to be galvanized and the coating ismuch more firmly attached than with the ordinary process of hot zinc galvanizing as carried out at the present time. For example, with the ordiwhich will prevent it coming into contact with the sides of the bath.. I r ,4
The invention is capable of general application for zinc coating articles, but is particularly intended for forming a zinc coating on metal window frames which are very liable to rust.
I claim:--- 7 A method of coating metal articles and more particularly window frames with zinc carried out 10 in a bath comprising athin layer of molten zinc l 1 I I
US131183A 1935-08-09 1937-03-16 Method of coating metal articles with zinc Expired - Lifetime US2100179A (en)

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GB2100179X 1935-08-09

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