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
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
  • C23C14/14—Metallic material, boron or silicon
  • C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C18/00—Alloys based on zinc
  • C22C18/04—Alloys based on zinc with aluminium as the next major constituent
• • 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
• • 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
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12785—Group IIB metal-base component
  • Y10T428/12792—Zn-base component
  • Y10T428/12799—Next to Fe-base component [e.g., galvanized]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12951—Fe-base component
  • Y10T428/12972—Containing 0.01-1.7% carbon [i.e., steel]

Definitions

• the present invention relates generally to an improved zinc metal alloy protective coating, and more particularly to a method of providing an improved magnesiumaluminum-Zinc alloy protective coating and to a ferrous metal article having a novel magnesium-aluminum-zinc base alloy protective coating.
• the zinc hot dip coatings which have heretofore been used to protect ferrous metal surfaces against attack by corrosion, have contained various alloying metals for the purpose of improving the properties of the metal coating or for improving the hot dip coating process.
• various alloying metals for the purpose of improving the properties of the metal coating or for improving the hot dip coating process.
• the metals which have been added to a molten zinc coating bath are lead, tin, silicon, aluminum, cadmium, antimony and magnesium.
• Ternary magnesium-aluminum-zinc base alloy compositions containing from 2 to 5% magnesium and 2% aluminum have heretofore been prepared and tested as cast block for corrosion resistance. While these alloy compositions were found to exhibit good corrosion resistance under the test conditions, the alloy compositions were incapable of being applied as a hot dip protective coating on a ferrous metal or like surface (see Corrosion, volume 6, pages 195-2'00, June 1950).
• An improved zinc-magnesium alloy coating composition which has been found suitable for hot dip applications on a ferrous metal surface has more recently been discovered and contains between about 1.5% and 4% by weight magnesium and preferably a fraction of 1% by weight aluminum (i.e. up to 0.2% by weight aluminum) in order to reduce top skimming losses and to prevent formation of objectionable intermetallic compounds.
• magnesium and aluminum are used at the foregoing concentrations in the magnesium-zinc coating bath, however, a small but definite intermetallic layer is formed and irregularities are present in the surface of the coating which detracted from the appearance of the coating. Thus, a definite need still remains for a protective metal alloy coating bath and coating composition having improved properties.
• a protective metal alloy coating having markedly improved properties can be provided on a metal article, such as a ferrous metal strip, by applying thereto a zinc base alloy coating comprising about 1% to about 5% by weight magnesium and from about 3% to about 17% by weight aluminum with the balance being formed essentially of Zinc which can contain the usual minor amount of impurities in a zinc spelter.
• the improved alloy coatings of the present invention when applied to a ferrous metal base exhibit extremely good corrosion resistance.
• Table I illustrates the significant improvement in corrosion resistance of a relatively thin hot dip alloy coating containing magnesium, aluminum and zinc within the range of concentrations specified by the present invention compared with a 3% magnesium-zinc hot dip alloy coating containing 0.2% by weight aluminum and a conventional zinc hot dip coating of substantially the same thickness made with standard zinc spelter on a conventional continuous hot dip galvanizing line:
• the coating compositions of the present invention which contain a major proportion of the eutectic mixture composition comprising 2.49% by weight magnesium, 4.39% by weight aluminum and the balance zinc and having a melting point of about 640 F. can be applied as a hot dip coating at a temperature below the normal operating temperature of the conventional continuous zinc galvanizing bath or at a bath temperature below about 850 F. Only when the aluminum content of the ternary alloy bath reaches a level of about 8% by weight and above is it necessary to operate the bath at a temperature above 850 F.
• the protective alloy coating formed has improved physical properties, including improved drawability and formability, because of the substantial absence of a layer of brittle intermetallic compound.
• EXAMPLE 1 A series of 4" x 8" steel test panels were obtained from 2-0-gauge full hard steel sheets which had a thickness of .034 and chemical compositions of about 04% car- 'bon, .29% to .35% manganese, 01% to 011% phosphorus, .019% to 020% sulfur and .04% copper, with the balance essentially iron. All panels were precleaned by oxidizing in a furnace at 1650 F. for 30 seconds, and the oxidized panels were then transferred into the dry box which contained the laboratory galvanizing equipment. The atmosphere inside the dry box contained 10% hydrogen with the balance nitrogen. The dew point inside the dry box was always kept below F. during the dipping operation. The cleaned panel was preheated at 1800 F. for 3 minutes in the reducing atmosphere of the dry box to effect removal of all surface oxides and then cooled to the bath temperature for dipping while maintained within the reducing atmosphere of the dry box.
• EXAMPLE 2 A series of panels were prepared and coated as in Example 1 by immersing the panels in a hot dip coating bath containing 2% magnesium, 4% aluminum and 94% zinc spelter to to provide an average coating weight of .33 oz./ft. per side. These test panels in a 5% salt spray test were resistant to corrosion failure (red rust) for about 2000 hours, as compared with hours for panels having the same weight of a conventional hot dip zinc coating.
• EXAMPLE 3 A series of panels were prepared and coated as in Example 1 by immersing in a hot dip coating bath containing 2.4% magnesium, 3.8% aluminum and 93.8% zinc spelter to provide an average coating weight of .41 oz./ft. per side.
• the test panels in 5% salt spray test were resistant to corrosion failure (red rust) for 2100 hours, as compared with 228 hours for panels having the same weight of a conventional hot dip coating.
• EXAMPLE 4 A series of panels were prepared and coated as in Example 1 by immersing in a hot dip coating bath containing 2.4% magnesium, 3.2% aluminum and 94.4% zinc spelter to provide an average coating weight of .39 oz./ft. per side.
• the test panels in 5% salt spray test were resistant to corrosion failure (red rust) for about 1600 hours, as compared with 200 hours for panels having the same coating weight of a conventional hot dip zinc coating.
• EXAMPLE 5 A series of panels were prepared and coated as in Example 1 immersing in a hot dip coating bath containing 2.5% magnesium, 43% a uminum and about 93% zinc face oxidation until substantially solidified, the hot dip alloy coatings formed on a ferrous metal surface has optimum Salt Fog corrosion resistance and alsoexhibits a brighter, more lustrous appearance than the ternary hot dip alloy coatings containing a smaller percentage of aluminum.
• the following table summarizes the Salt Fog test data:
• the hot dip alloy coatings of the present invention containing between 8 and 17 by weight aluminum also have good adherence properties and have an unobjectionable amount of intermetallic compound formed. When the aluminum content of the alloy is greater than 17%, however, there appears to be an abrupt change in the hot dip coating characteristic, and an aluminum-iron alloy layer of considerably increased thickness is formed.
• the change in the coating characteristic may be due to the change from a coating containing the ternary eutectic mixture composition to a coating comprised of the tat-aluminumzinc solid solution which occurs at about 17.2% by weight aluminum in the aluminum-zinc phase diagram.
• Ternary zinc-aluminum-magnesium alloy coating compositions of the present invention containing at least 8% by weight aluminum also exhibit unexpectedly good corrosion resistence in a high humidity atmosphere, as shown by the Humidity Cabinet Test Data in the following Table VI:
• novel alloy coatings of the present invention can be applied to a ferrous metal surface or other corrodible metal surface by means other than by the hot dip coating method specifically used herein to illustrate the present invention, particularly where it is desired to apply very thin alloy coatings of the order spelter to provide an average coating weight of .43 oz./ft. per side.
• the test panels in 5% salt spray test were resistant to corrosion failure (red rust) for 2800 hours, as compared with 228 hours for panels having the same weight of a conventional hot dip zinc coating.
• EXAMPLE 6 A series of panels were prepared and coated as in EX- ample 1 immersing in a hot dip coating bath containing 1.5% magnesium, 4.4% aluminum and about 94% zinc spelter to provide an average coating weight of .41 oz./ft. per side.
• the test panels in 5% salt spray test are resistant to corrosion failure (red rust).
• EXAMPLE 7 A series of panels were prepared and coated as in Example 1 immersing in a hot dip coating bath containing 3% magnesium, 6% aluminum and 91% zinc spelter to provide an average coating weight of .41 oz./ft. per side.
• the test panels in 5% salt spray test were resistant to corrosion failure (red rust) for over 1000 hours without failure, as compared with 300 hours to failure of panels of a conventional hot dip zinc coating having the same coating weight.
• EXAMPLE 8 A series of panels were prepared and coated as in Example l immersing in a hot dip coating bath containing 5% magnesium, 4% aluminum and 91% zinc spe ter to provide an average coating weight of .43 oz./ft. per side.
• the test panels in 5% salt spray test are highly resistant to corrosion failure (red rust).
• EXAMPLE 9 A series of panels were prepared and coated as in Example 1 immersing in a hot dip coating bath containing 3% magnesium, 8% a uminum and 89% zinc spelter to provide an average coating weight of .41 oz./ft. per side.
• the test panels in 5% salt spray test were resistant to corrosion failure (red rust) for over 1000 hours without failure, as compared with 300 hours to failure of panels of a conventional hot dip zinc coating having the same coating weight.
• EXAMPLE 10 A series of panels were prepared and coated as in Example l immersing in a hot dip coating bath containing 3% magnesium, 10% aluminum and 87% zinc spelter to provide an average coating weight of .41 oz./ft. per side.
• the test panels in 5% salt spray test were resistant to corrosion failure (red rust) for over 1000 hours without failure, as compared with 300 hours to failure of panels of a conventional hot dip zinc coating having the same coating weight.
• EXAMPLE 1 l A series of panels were prepared and coated as in Example 1 immersing in a hot dip coating bath containing 5% magnesium 8% aluminum and 87% zinc spelter to provide an average coating weight of .43 oz./ft. per side.
• the test panels in 5% salt spray test are highly resistant to corrosion failure (red rust).
• EXAMPLE 12 A standard steel hot mill band having a thickness of about 0.080 inch is cold reduced on a five-stand tandem mill to form a steel strip having a thickness of about 0.0153 inch thick (Le. 28 U.S.S.G.).
• the full hard 0.0153 inch strip thus formed having a Rockwell hardness (30 T-scale) of about 80 is cleaned by passing through a continuous cleaning line, followed by conventional box annealing heat treatment to restore the ductility lost when the strip was cold reduced.
• the annealed strip is then temper rolled to provide a suitable surface for continuous hot dip coating.
• the annealed endless steel strip after cleaning as in Example 1 or by other suitable means was passed into a zone having a dry reducing atmosphere of the type used in Example 1 to remove all surface oxidation and whi e in the protective reducing atmosphere is immersed in a molten aluminum-magnesium-zinc alloy bath having the following compositions:
• the alloy bath was maintained at a temperature of 900 F. and the steel strip conveyed through the bath at a uniform line speed maintained at about 30 to 40 feet per minute.
• the strip while enclosed in the protective reducing atmosphere was fed into the alloy bath at an angle of about 70 to the horizontal.
• the strip was allowed to remain in the alloy bath about 5 seconds (and not more than 10 seconds), and was continuously Withdrawn from the bath at an angle of about to the horizontal.
• the molten alloy coating was rapidly cooled and the coating weight controlled by blowing thereover nitrogen gas having a temperature below F. and preferably at about 50 F.
• the nitrogen also serves to protect the coating against oxidation until the coating solidifies to form a uniformly smooth surface.
• An alloy coating was obtained having a substantially uniform thickness on each side of the strip maintained between about 0.2 mil and 0.6 mil, depending on the line speed and the nitrogen blowing conditions maintained. The latter alloy coating exhibited the improved properties of the coating of Example 1.
• EXAMPLE 13 A 28 gauge steel strip was prepared and coated as in Example 12, but wherein the ternary alloy hot dip coating bath had a temperature of about 910 F. and contained on a weight basis 12% aluminum, 3% magnesium and the balance zinc. The resultant coating had an average coating weight per side of 0.2 mil and exhibited good corrosion resistance and a smooth surface appearance.
• EXAMPLE 14 A 28 gauge steel strip was prepared and coated as in Example 12, but wherein the ternary alloy hot dip coating bath had a temperature of about 940 F. and contained on a weight basis 16% aluminum, 3% magnesium and the balance zinc. The resultant coating had an average coating wcight per side of 0 .2 mil and exhibited good corrosion resistance and a smooth surface appearance.
• EXAMPLE 15 A 28 gauge steel strip was prepared and coated as in Example 12, but wherein the ternary alloy hot dip coating bath had a temperature of about 920 F. and contained on a weight basis 13% aluminum, 5% magnesium and the balance zinc. The resultant coating had an average coating weight per side of 0.2 mil and exhibited good corrosion resistance and a smooth surface appearance.
• EXAMPLE 16 A 28 gauge steel strip was prepared and coated as in Example 12, but wherein the ternary alloy hot dip coating bath had a temperature of about 950 F. and contained on a weight basis 17% aluminum, 5% magnesium and the balance zinc. The resultant coating had an average coating weight per side of 0.2 mil and exhibited good corrosion resistance and a smooth surface appearance.
• ternary magnesium-aluminum-zinc base alloy compositions of the present invention containing about 3 to 4% by weight aluminum and about 3% by weight magnesium which corresponds to about the ternary alloy euthetic point are applied to a ferrous metal surface free of oxides and preferably where the alloy coating is also protected against surof about 0.1 oz./ft.
• a thin alloy coating can be applied by the vapor deposition technique, wherein a strip of steel is continuously passed through a chamber substantially free of oxygen having the interior at a pressure of about 10" mm. Hg and providing therein adjacent the surface of the moving strip a source of the coating alloy in gaseous form which condenses on the surface of the moving strip.
• Very thin alloy coatings of the present invention can also be formed by using special wiping techniques on the strip emerging from a hot dip coating bath.
• the alloy coating of the present invention can also be applied by powdered metallurgy techniques, wherein a powdered alloy having the herein specified proportion of magnesium, aluminum and zinc is formed into a suitable paste and a thin layer is applied which is then cold reduced, sintered, rolled, and heat treated in accordance with conventional practice.
• a ferrous metal sheet having on at least one surface thereof an adherent smooth zinc base alloy coating comprised essentially on a weight basis of between about 1% and 5% magnesium and between about 3% and 17% aluminum with the balance being essentially zinc.

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

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Citations (4)

• 1969
  • 1969-01-08 US US789943A patent/US3505043A/en not_active Expired - Lifetime
  • 1969-05-01 CA CA050314A patent/CA924195A/en not_active Expired
  • 1969-05-21 FR FR6916497A patent/FR2027888A1/fr not_active Withdrawn
  • 1969-05-22 BE BE733433D patent/BE733433A/xx unknown
  • 1969-05-30 NL NL6908299A patent/NL6908299A/xx unknown
  • 1969-05-30 DE DE19691927774 patent/DE1927774A1/de active Pending

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