EP0080903A1 - Durch Heisstauchen hergestellte Aluminium-Zink-Überzüge - Google Patents

Durch Heisstauchen hergestellte Aluminium-Zink-Überzüge Download PDF

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Publication number
EP0080903A1
EP0080903A1 EP19820306407 EP82306407A EP0080903A1 EP 0080903 A1 EP0080903 A1 EP 0080903A1 EP 19820306407 EP19820306407 EP 19820306407 EP 82306407 A EP82306407 A EP 82306407A EP 0080903 A1 EP0080903 A1 EP 0080903A1
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EP
European Patent Office
Prior art keywords
zinc
silicon
bath
aluminum
coatings
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19820306407
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English (en)
French (fr)
Inventor
Ralph William Leonard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
USS Engineers and Consultants Inc
Original Assignee
USS Engineers and Consultants Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by USS Engineers and Consultants Inc filed Critical USS Engineers and Consultants Inc
Publication of EP0080903A1 publication Critical patent/EP0080903A1/de
Withdrawn legal-status Critical Current

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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
    • C23C2/12—Aluminium or alloys based thereon

Definitions

  • a widely employed practice for coating ferrous metal surfaces is the hot-dip method in which the surface to be coated is immersed in a molten bath of the coating metal.
  • baths containing aluminum or baths containing zinc are most generally employed.
  • zinc is anodic to steel and therefore offers sacrificial, galvanic protection to the steel; even if the zinc barrier itself should be damaged or cut, exposing the underlying steel surface.
  • Aluminum is cathodic to steel in many corrosive environments.
  • United States Patent Specification No. 3,343,930 describes a hot-dip coated article containing a combination of zinc and aluminum which, as a result of its zinc content, overcomes the problem of premature discoloration caused by rust-stain bleeding and, as a result of its aluminum content, exhibits an overall "general" corrosion rate significantly less than that of zinc coatings. While this patent discloses a coating bath containing from 28 to 75% zinc, balance aluminum and silicon, further studies have shown that optimum results are achieved with a bath containing about 43% zinc, 55% aluminum and 2% silicon. This optimum product is sold commercially under the trade name Galvalume. Due to such optimization, however, in most environments the overall or "general" corrosion rate of Galvalume is far greater than that of-commerical aluminum-coated products.
  • hot-dip coated products can be produced which exhibit resistance to rust staining about equal to that of Galvalume, while concomitantly providing a "general" corrosion resistance car superior to that of Galvalume--aproaching that of aluminum-coated steels.
  • Such an improved combination of corrosion resistance is achieved by utilizing a hot-dip bath consisting essentially of 12 to 24% zinc, less than 4% silicon, 0.3 to 3.5% iron (which is an incidental impurity normally encountered in commercial hot-dip plating baths) and balance aluminum.
  • the coatings of this invention are more ductile in that they exhibit lower tendencies towards crazing during forming operations.
  • a method of producing corrosion-resistant coatings metallurgically bonded to ferrous-base articles comprising dipping a clean surface of said article into a molten bath containing aluminum and zinc for a period at least sufficient to form an aluminum-zinc coating thereon with an interfacial alloy layer, resulting from reaction of the ferrous surface with the bath, at least 0.01 mils (0.25 micron) thick, removing the coated surface from said bath and cooling the molten layer adhering thereto, wherein the bath consists essentially, by weight, of 12 to 24% zinc, 0 to 4% silicon, 0.3 to 3.5% iron and the balance aluminum.
  • Hot-dip coating was accomplished by a procedure analogous to that shown in U. S. Patent 3,393,089.
  • the steel sheet was cleaned in an aqueous silicate solution, annealed in-line under reducing conditions and cooled to a temperature slightly above bath temperature prior to entry into the bath.
  • Coating baths were maintained at a temperature of 75 to 100OF (40 to 55°C) above the liquidus temperature for each bath concentration. No changes in bath temperature were made to account for the relatively small effect of the silicon additions on the liquidus temperature.
  • the annealing temperatures employed were higher than those disclosed in the above-noted U. S. Patent, that is, the annealing cycle included heating to a temperature of 1450°F (790°C).
  • the reducing furnace atmosphere was maintained by introducing a hydrogen-nitrogen mixture into a snout just above the bath surface.
  • a baffle was located inside the snout to prevent incoming cold gases from impinging directly onto the strip.
  • Air-knives were used to control the thickness of the coating on the strip. No special measures were employed to provide enhanced cooling rates to cool the strip after it exited from the coating bath. However, because of the low line speeds of the coating line employed in this investigation, the air knives themselves caused a considerable degree of cooling. The cooling rate caused by the air knives averaged about 30°F (17°C) per second within the first 8 inches (20cm) after the strip emerged from the bath.
  • cooling resulting from normal, ambient air cooling provided a cooling rate within the range of 8 to 10°F (4 to 5°C) per second, while the strip was at a temperature greater than 700°F (370°C). All the baths exhibited good fluidity characteristics, in that smooth, uniformly thick coatings of about 1 mil thick (25 microns) were readily attained.
  • Forming-test results - Coating adherence was evaluated in bead-forming tests, 100-inch-pound impact tests and ASTM-A525 coating bend tests. No flaking was observed in the latter two tests, but a considerable amount was observed on some samples in the bead-forming tests. It is generally accepted that for a given hot-dip coated product, coating adherence is primarily a function of the alloy-layer thickness--the thicker the alloy layer, the poorer the adherence. However, this expected behavior was not encountered with respect to the inventive coatings--coatings from baths with lower zinc contents generally exhibited better adherence, even when the alloy-layer was significantly thicker.
  • the ductility of the outer coating metal layer has an influence on the overall tendency to exhibit flaking.
  • overall flaking tendency appears to be a complex function both of the alloy-layer thickness and the outer coating metal ductility.
  • FIG. 1 shows the rust staining encountered after about fifteen months exposure at a test siteinMonroeville, Pennsylvania, comparing two coatings produced in accord with the invention: (a) 18% zince and (b) 24% zinc, with that of (c) the Galvalume-type coating and (d) the commercial aluminum coating containing 7% silicon.
  • the rust staining in the area adjacent to the grooves for the aluminum coating (d) was significantly greater than that of the Galvalume sample (c). It may be seen, however, that the discoloration exhibited by the inventive samples is essentially the same as that of the Galvalume sample.
  • the seven samples depicted are: (a) aluminum - 7% silicon, (b) 12.4% zinc - no silicon, (c) 15% zinc - 8% silicon, (d) 17.8% zinc - no silicon, (e) 43% zinc - 2% silicon (Galvalume-Type), (f) 2% zinc - 6% silicon and (g) 33% zinc - 2% silicon (another Galvalume-type).
  • Patent 3,393,089) had been employed, such bath reactivity as measured by the parabolic rate constant "a" for the silicon-free baths, varied from about 0.05 to 0.07 mil per second (32 to 45 micron per second), depending on the amount of zinc employed, and none of the silicon-free baths exhibited a reactivity greater than that of a pure-aluminum coating bath.
  • the general corrosion resistance provided by coatings of the invention was evaluated by the Kesternich method-DIN 50018. This test is a well accepted, rapid corrosion test for comparison of the resistance of similar-type protective coatings to industrial atmospheres, particularly those rich in sulphur dioxide.
  • the weight loss of four different zinc concentrations within the scope of this invention was compared with that of three different Galvalume-type zinc concentrations, after 20 cycles of exposure. The results thereof are shown in the Table below. It is seen that the Galvalume-type samples exhibit general corrosion rates about 2 to 3 times greater than those of the invention.
  • interfacial alloy layers of the order of 0.25 to 1 mils (6 to 25 microns), or even greater, may result.
  • the thickness of the interfacial layer will generally be significantly thinner than, preferably.less than 10% of, the overall coating thickness.

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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)
EP19820306407 1981-12-02 1982-12-02 Durch Heisstauchen hergestellte Aluminium-Zink-Überzüge Withdrawn EP0080903A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US32673281A 1981-12-02 1981-12-02
US326732 1981-12-02

Publications (1)

Publication Number Publication Date
EP0080903A1 true EP0080903A1 (de) 1983-06-08

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19820306407 Withdrawn EP0080903A1 (de) 1981-12-02 1982-12-02 Durch Heisstauchen hergestellte Aluminium-Zink-Überzüge

Country Status (4)

Country Link
EP (1) EP0080903A1 (de)
JP (1) JPS58144462A (de)
AU (1) AU9104782A (de)
BR (1) BR8206921A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3845682A4 (de) * 2018-08-30 2021-07-14 Posco Mit einer aluminium-zink-legierung plattiertes stahlblech mit ausgezeichneter warmverarbeitbarkeit und korrosionsbeständigkeit und verfahren zur herstellung davon

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2777571B2 (ja) * 1991-11-29 1998-07-16 大同鋼板株式会社 アルミニウム−亜鉛−シリコン合金めっき被覆物及びその製造方法
KR102153164B1 (ko) * 2017-12-26 2020-09-07 주식회사 포스코 열간 프레스 성형용 도금강판 및 이를 이용한 성형부재

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0028822A1 (de) * 1979-11-08 1981-05-20 Bethlehem Steel Corporation Verfahren zur Herstellung eines mit einer Aluminium-Zink-Legierung beschichteten Eisengegenstandes zur Verbesserung der Korrosionsbeständigkeit
EP0028821A1 (de) * 1979-11-08 1981-05-20 Bethlehem Steel Corporation Verfahren zur Verbesserung der Dehnbarkeit der Beschichtung aus einer Aluminium-Zink-Legierung eines Gegenstandes aus Eisen

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0028822A1 (de) * 1979-11-08 1981-05-20 Bethlehem Steel Corporation Verfahren zur Herstellung eines mit einer Aluminium-Zink-Legierung beschichteten Eisengegenstandes zur Verbesserung der Korrosionsbeständigkeit
EP0028821A1 (de) * 1979-11-08 1981-05-20 Bethlehem Steel Corporation Verfahren zur Verbesserung der Dehnbarkeit der Beschichtung aus einer Aluminium-Zink-Legierung eines Gegenstandes aus Eisen

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3845682A4 (de) * 2018-08-30 2021-07-14 Posco Mit einer aluminium-zink-legierung plattiertes stahlblech mit ausgezeichneter warmverarbeitbarkeit und korrosionsbeständigkeit und verfahren zur herstellung davon

Also Published As

Publication number Publication date
BR8206921A (pt) 1983-10-04
JPS58144462A (ja) 1983-08-27
AU9104782A (en) 1983-06-09

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Inventor name: LEONARD, RALPH WILLIAM