EP0080903A1 - Révêtements en aluminium-zinc obtenus par procédé de plonge à chaud - Google Patents
Révêtements en aluminium-zinc obtenus par procédé de plonge à chaud Download PDFInfo
- 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
- Authority
- 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- Withdrawn
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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
- C23C2/04—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.
Landscapes
- 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 (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 (fr) | 1983-06-08 |
Family
ID=23273451
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19820306407 Withdrawn EP0080903A1 (fr) | 1981-12-02 | 1982-12-02 | Révêtements en aluminium-zinc obtenus par procédé de plonge à chaud |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0080903A1 (fr) |
| JP (1) | JPS58144462A (fr) |
| AU (1) | AU9104782A (fr) |
| BR (1) | BR8206921A (fr) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3845682A4 (fr) * | 2018-08-30 | 2021-07-14 | Posco | Tôle d'acier plaquée d'alliage d'aluminium et de zinc présentant une excellente aptitude au façonnage à chaud et une excellente résistance à la corrosion, et son procédé de fabrication |
Families Citing this family (2)
| 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)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0028822A1 (fr) * | 1979-11-08 | 1981-05-20 | Bethlehem Steel Corporation | Procédé pour la production d'un objet en métal ferreux recouvert d'une couche mince d'alliage d'aluminium-zinc en vue d'améliorer la résistance à la corrosion |
| EP0028821A1 (fr) * | 1979-11-08 | 1981-05-20 | Bethlehem Steel Corporation | Procédé pour l'amélioration de la ductilité du revêtement d'un objet en métal ferreux recouvert d'un alliage d'aluminium-zinc |
-
1982
- 1982-11-30 BR BR8206921A patent/BR8206921A/pt unknown
- 1982-12-01 AU AU91047/82A patent/AU9104782A/en not_active Abandoned
- 1982-12-02 JP JP21068482A patent/JPS58144462A/ja active Pending
- 1982-12-02 EP EP19820306407 patent/EP0080903A1/fr not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0028822A1 (fr) * | 1979-11-08 | 1981-05-20 | Bethlehem Steel Corporation | Procédé pour la production d'un objet en métal ferreux recouvert d'une couche mince d'alliage d'aluminium-zinc en vue d'améliorer la résistance à la corrosion |
| EP0028821A1 (fr) * | 1979-11-08 | 1981-05-20 | Bethlehem Steel Corporation | Procédé pour l'amélioration de la ductilité du revêtement d'un objet en métal ferreux recouvert d'un alliage d'aluminium-zinc |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3845682A4 (fr) * | 2018-08-30 | 2021-07-14 | Posco | Tôle d'acier plaquée d'alliage d'aluminium et de zinc présentant une excellente aptitude au façonnage à chaud et une excellente résistance à la corrosion, et son procédé de fabrication |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58144462A (ja) | 1983-08-27 |
| BR8206921A (pt) | 1983-10-04 |
| AU9104782A (en) | 1983-06-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
| AK | Designated contracting states |
Designated state(s): AT BE CH DE FR GB IT LI LU NL SE |
|
| 17P | Request for examination filed |
Effective date: 19831118 |
|
| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN |
|
| 18W | Application withdrawn |
Withdrawal date: 19840824 |
|
| RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: LEONARD, RALPH WILLIAM |