US2101553A - Coating iron or steel with aluminum or an alloy thereof - Google Patents

Coating iron or steel with aluminum or an alloy thereof Download PDF

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US2101553A
US2101553A US8722A US872235A US2101553A US 2101553 A US2101553 A US 2101553A US 8722 A US8722 A US 8722A US 872235 A US872235 A US 872235A US 2101553 A US2101553 A US 2101553A
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bath
aluminum
molten
flux
article
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US8722A
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Mattsson Ernst Johan Mauritz
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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
    • C23C2/30—Fluxes or coverings on molten baths

Definitions

  • the invention relates to a method of coating or alloying with aluminium or an aluminium alloy thesurfaceof an artlcleof iron orsteel by-immersionfof the article in a bath of molten aluminium or aluminiumalloy.
  • the article to be treated is cleaned by mechanical means and/or corroded in a dilute acid and/or subjected to a treatment-by which volatile products are formed which when heated volatilize, thereby removing the impurities.
  • the article is thereupon immersed in a molten flux consisting of CaClz, fi'aCl, KCI; Na3AlFs and ZnClz.
  • the article heated in this flux is then removed to the molten aluminium bath.
  • the article to be treated in order to obtain a good coating is first immersed in a flux bath containing a molten mixture, of alkali or other fluorides or fluorine compounds.
  • alkali or other fluorides or fluorine compounds such as NaaAlFs, and alkali salts such as alkali chlorides, and optionally other salts, preferably chlorides such as ZnClz, but not containing any compound of calcium; the article is kept in this bath until oxides and'the like have been removed and the article has been properly heated, after which the article is removed and immersed in the bath of molten aluminium .or aluminium containing up to 5 per cent of other metal ingredients.
  • the flux bath should contain no calcium compound, since calcium is apt to form insoluble compounds such as calcium carbide which prevent the proper adhesion of the aluminium to the metal. It'is recommended that a substantial amount of fluoride (more than 5 per cent. of NaaAlFt) should be present in the bath. If this be the case and no calcium compound is present the fiux will quickly remove rust and other oxides from the surface of the article to be treated. A pre-treatment for the removal of rust or the like as prescribed in the earlier art is thus made superfluous.
  • the articles to be treated are coated by a thick layer of oxides as a result of prolonged heating during the manufacture (as by casting) it may be serviceable first to remove this layer in any known manner in order to shortenthe treatment in the flux bath, but once this is done the articles may be allowed to corrode and become rusty without this being any serious obstacle to obtaining a faultless coating of aluminium or aluminium alloy.
  • the proportion of potassium chloride should not be too great.
  • the proportion of the salts to each other should be according to their equivalent weights viz. about 40 parts by weight potassium chloride to 30 parts of sodium chloride.
  • the temperature of the flux bath depends upon that of the metal bath which again may vary according to the kind of article to be treated and the kind of result to be attained, as known to those skilled in the art.
  • the temperature of the flux bath should not be much lower and preferably a little higher than that of the metal bath.
  • composition of the flux bath will vary according to circumstances.
  • a flux which has been found useful for several purposes is given below:
  • a method of aluminizing surfaces of ferrous metal bodies which comprises cleaning and heating the body by immersing the body in a molten flux bath of the salt type containing about 10 per cent by weight of sodium alumirium fluoride,
  • a method of aluminizing the surface of a ferrous metal body which comprises cleaning and heating the body by immersing the same in a molten flux bath of the salt type the active ingredients of which consists oi alkali metal fluoride and chloride selected from the chlorides of one or more of the metals oi the group consisting of the alkali metals and zinc but free from any salt of calcium, removing the body from said bath and immersing the body in a molten bath containing aluminum.
  • a method'oi aluminizing the surface of a ferrous metal body which comprises cleaning and heating the body by immersing the same in a molten flux bath of the salt type the active ingredients of which consist of alkali metal fluoride and chloride selected from the chlorides of one or more 0! the metals of the group consisting of the alkali metals and zinc but free from any salt of calcium, removing the body from said bath and immersing the body in a molten bath containing aluminum, the amount of alkali metal fluoride being more than live per cent.
  • a method of aluminizing the surface oi. a ferrous metal body which comprises cleaning and heating the body by immersing the same in a molten flux bath of the salt type the active ingredients of which consist of alkali metal fluoride and chloride selected from the chlorides of one or more of the metals of the group consisting of the alkali metals and zinc but free from any salt oi calcium, removing the body from said bath and immersing the body in a molten aluminum bath containing up to live per cent of metal ingredients.
  • a method of aluminizing surfaces of ferrous metal bodies which comprises cleaning and heating the body by immersing the remain a molten flux bath of the salt type consisting of sodium aluminum fluoride, sodium chloride, potassium chloride and zinc chloride but free from any salt oi calcium and in which bath the sodium aluminum fluoride is more than i'ive per cent and the proportions of the sodium chloride and the potassium chloride are substantially in accordance with their equivalent weights, removing the heated body from said bath and immersing the same while in a heated state in a molten bath containing aluminum.
  • the salt type consisting of sodium aluminum fluoride, sodium chloride, potassium chloride and zinc chloride but free from any salt oi calcium and in which bath the sodium aluminum fluoride is more than i'ive per cent and the proportions of the sodium chloride and the potassium chloride are substantially in accordance with their equivalent weights

Description

Patented Dec. 7, 1937 r V FF or COATKNG IRQN R STEEL WITH ALUMINUM OR AN ALLOY THEREOF Ernst Johan Mauritz Mattsson, Stockholm. Sweden, assignor to Frans Nilsson, Stockholm,
Sweden No Drawing. Application February 28, 1935. Se-
rial No. 1934 8,722. In Great Britain March 5,
s v e I i Claims. (Cl. 91-102) The invention relates to a method of coating or alloying with aluminium or an aluminium alloy thesurfaceof an artlcleof iron orsteel by-immersionfof the article in a bath of molten aluminium or aluminiumalloy.
It isknown that the surface of articles to be treated in this manner-must be clean and free from impurities during the treatment.
In order to ensure this cleanliness the following procedure has been proposed: The article to be treated is cleaned by mechanical means and/or corroded in a dilute acid and/or subjected to a treatment-by which volatile products are formed which when heated volatilize, thereby removing the impurities. The article is thereupon immersed in a molten flux consisting of CaClz, fi'aCl, KCI; Na3AlFs and ZnClz. The article heated in this flux is then removed to the molten aluminium bath. a r
In this procedure dlfliculties have arisen. First, it has been found necessary to immerse the article in the flux bath immediately after the mechanical cleaning or corroding operation, because the least quantity of oxide prevents the 'adhesion of the coating to the oxidized surface. Secondly, even if the utmost attention has been given to the thorough removal of oil, oxides or the like before immersion in the flux bath, the procedure has often failed to procure the necessary adhesion of the coating.
According to the present invention, in order to obtain a good coating the article to be treated is first immersed in a flux bath containing a molten mixture, of alkali or other fluorides or fluorine compounds.such as NaaAlFs, and alkali salts such as alkali chlorides, and optionally other salts, preferably chlorides such as ZnClz, but not containing any compound of calcium; the article is kept in this bath until oxides and'the like have been removed and the article has been properly heated, after which the article is removed and immersed in the bath of molten aluminium .or aluminium containing up to 5 per cent of other metal ingredients.
It is essential that the flux bath should contain no calcium compound, since calcium is apt to form insoluble compounds such as calcium carbide which prevent the proper adhesion of the aluminium to the metal. It'is recommended that a substantial amount of fluoride (more than 5 per cent. of NaaAlFt) should be present in the bath. If this be the case and no calcium compound is present the fiux will quickly remove rust and other oxides from the surface of the article to be treated. A pre-treatment for the removal of rust or the like as prescribed in the earlier art is thus made superfluous. Of course, if the articles to be treated are coated by a thick layer of oxides as a result of prolonged heating during the manufacture (as by casting) it may be serviceable first to remove this layer in any known manner in order to shortenthe treatment in the flux bath, but once this is done the articles may be allowed to corrode and become rusty without this being any serious obstacle to obtaining a faultless coating of aluminium or aluminium alloy.
It has further been found that if potassium chloride is used along with sodium chloride the proportion of potassium chloride should not be too great. Preferably the proportion of the salts to each other should be according to their equivalent weights viz. about 40 parts by weight potassium chloride to 30 parts of sodium chloride. Other proportions, however, maybe used, but when too great a quantity of potassium chloride is present the flux is apt to adhere to the article treated when the latter is transferred to the metal bath, instead of rising properly to the surface of the bath and leaving the article well cleaned and suitable iorbecoming coated with aluminium or its alloy.
Otherwise the proportions andnumber of ingredients of the flux bath may vary within wide limits; The temperature of the flux bath depends upon that of the metal bath which again may vary according to the kind of article to be treated and the kind of result to be attained, as known to those skilled in the art. The temperature of the flux bath should not be much lower and preferably a little higher than that of the metal bath.
The composition of the flux bath, therefore, will vary according to circumstances. As an example of a flux which has been found useful for several purposes is given below:
Per cent by weight NaaAiFe 2.11012 (dehydrated) 2o NaCl 3o KCl 40 It is to be understood that this composition of the flux bath is given as an example only.
What I claim is:--'
l. A method of aluminizing surfaces of ferrous metal bodies, which comprises cleaning and heating the body by immersing the body in a molten flux bath of the salt type containing about 10 per cent by weight of sodium alumirium fluoride,
about per cent by weight of sodium chloride, about per cent by weight oi potassium chlo ride and about 20 per cent by weight of zinc chloride but free from any salt of calcium, removing the heated body from said bath and immers; ing same while in heated state in a molten bath containing aluminium.
2. A method of aluminizing the surface of a ferrous metal body which comprises cleaning and heating the body by immersing the same in a molten flux bath of the salt type the active ingredients of which consists oi alkali metal fluoride and chloride selected from the chlorides of one or more of the metals oi the group consisting of the alkali metals and zinc but free from any salt of calcium, removing the body from said bath and immersing the body in a molten bath containing aluminum.
3. A method'oi aluminizing the surface of a ferrous metal body which comprises cleaning and heating the body by immersing the same in a molten flux bath of the salt type the active ingredients of which consist of alkali metal fluoride and chloride selected from the chlorides of one or more 0! the metals of the group consisting of the alkali metals and zinc but free from any salt of calcium, removing the body from said bath and immersing the body in a molten bath containing aluminum, the amount of alkali metal fluoride being more than live per cent.
4. A method of aluminizing the surface oi. a ferrous metal body which comprises cleaning and heating the body by immersing the same in a molten flux bath of the salt type the active ingredients of which consist of alkali metal fluoride and chloride selected from the chlorides of one or more of the metals of the group consisting of the alkali metals and zinc but free from any salt oi calcium, removing the body from said bath and immersing the body in a molten aluminum bath containing up to live per cent of metal ingredients. I
5. A method of aluminizing surfaces of ferrous metal bodies which comprises cleaning and heating the body by immersing the remain a molten flux bath of the salt type consisting of sodium aluminum fluoride, sodium chloride, potassium chloride and zinc chloride but free from any salt oi calcium and in which bath the sodium aluminum fluoride is more than i'ive per cent and the proportions of the sodium chloride and the potassium chloride are substantially in accordance with their equivalent weights, removing the heated body from said bath and immersing the same while in a heated state in a molten bath containing aluminum.
' ERNST JOHAQI MAURITZ MATTSSQN.
US8722A 1934-03-05 1935-02-28 Coating iron or steel with aluminum or an alloy thereof Expired - Lifetime US2101553A (en)

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2515488A (en) * 1946-03-12 1950-07-18 Du Pont Process of cleaning and coating ferrous metal
US2544670A (en) * 1947-08-12 1951-03-13 Gen Motors Corp Method of forming composite aluminum-steel parts by casting aluminum onto steel andbonding thereto
US2544671A (en) * 1948-02-12 1951-03-13 Gen Motors Corp Method of forming composite products consisting of ferrous metal and aluminum or aluminum-base alloy
US2569097A (en) * 1951-02-20 1951-09-25 Gen Motors Corp Method of coating ferrous metal with aluminum or an aluminum alloy
US2671737A (en) * 1950-10-10 1954-03-09 Chrysler Corp Aluminum coating process and flux
US2723449A (en) * 1954-04-23 1955-11-15 Aluminum Co Of America Method of dip brazing aluminous metal members
US2755542A (en) * 1949-05-14 1956-07-24 Gen Motors Corp Method of providing brazed ferrous metal parts with aluminum coating
US2809423A (en) * 1953-03-30 1957-10-15 Gen Motors Corp Salt flux and method for brazing aluminum parts therewith
US2881491A (en) * 1953-03-23 1959-04-14 Chrysler Corp Method of casting aluminum on ferrous base to form duplex structure
US2963384A (en) * 1959-02-24 1960-12-06 Hubbard & Co Method of aluminizing ferrous materials
US3468770A (en) * 1965-12-22 1969-09-23 Tarun Kumar Ghose Coating of aluminium and/or aluminium alloys on steel surfaces
US4451287A (en) * 1981-12-08 1984-05-29 American Can Company Flux in recovery of aluminum in reverberatory furnace
US4501614A (en) * 1981-12-08 1985-02-26 American Can Company Flux in recovery of aluminum in reverberatory furnace and method of making

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2515488A (en) * 1946-03-12 1950-07-18 Du Pont Process of cleaning and coating ferrous metal
US2544670A (en) * 1947-08-12 1951-03-13 Gen Motors Corp Method of forming composite aluminum-steel parts by casting aluminum onto steel andbonding thereto
US2544671A (en) * 1948-02-12 1951-03-13 Gen Motors Corp Method of forming composite products consisting of ferrous metal and aluminum or aluminum-base alloy
US2755542A (en) * 1949-05-14 1956-07-24 Gen Motors Corp Method of providing brazed ferrous metal parts with aluminum coating
US2671737A (en) * 1950-10-10 1954-03-09 Chrysler Corp Aluminum coating process and flux
US2569097A (en) * 1951-02-20 1951-09-25 Gen Motors Corp Method of coating ferrous metal with aluminum or an aluminum alloy
US2881491A (en) * 1953-03-23 1959-04-14 Chrysler Corp Method of casting aluminum on ferrous base to form duplex structure
US2809423A (en) * 1953-03-30 1957-10-15 Gen Motors Corp Salt flux and method for brazing aluminum parts therewith
US2723449A (en) * 1954-04-23 1955-11-15 Aluminum Co Of America Method of dip brazing aluminous metal members
US2963384A (en) * 1959-02-24 1960-12-06 Hubbard & Co Method of aluminizing ferrous materials
US3468770A (en) * 1965-12-22 1969-09-23 Tarun Kumar Ghose Coating of aluminium and/or aluminium alloys on steel surfaces
US4451287A (en) * 1981-12-08 1984-05-29 American Can Company Flux in recovery of aluminum in reverberatory furnace
US4501614A (en) * 1981-12-08 1985-02-26 American Can Company Flux in recovery of aluminum in reverberatory furnace and method of making

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