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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/10—Oxidising
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B37/00—Cases
  • G04B37/22—Materials or processes of manufacturing pocket watch or wrist watch cases

Definitions

• the present invention relates to an aluminum alloy, and more particularly to an aluminum alloy preferably used in goods or articles which often directly contacts with the human skin, such as necklace, bracelet, and band of wristwatch.
• watch external parts are conventionally formed by using stainless steel, brass, zinc, titanium or its alloy, aluminum or its alloy, and other metals.
• a plating film containing nickel is formed, and the nickel causes metal allergy.
• anodic oxide film To resist corrosion, in both, the surface is treated by anodic oxidation to form an anodic oxide film.
• nickel acetate is used as sealing promoter, nickel is contained in the anodic oxide film, which causes metal allergy.
• aluminum alloy since impurities such as iron and copper are contained, the gloss of the anodic oxide film is poor, which is a restriction in design. If, as countermeasure, an aluminum alloy of high purity is used, the strength is lowered, and the strength required for watch case or watch band cannot be maintained.
• the present invention is intended to solve the above problems of metal materials.
• the invention provides an aluminum alloy consisting essentially of 2.3 to 5.0 wt.% of magnesium, 0.03 to 0.15 wt.% of iron, 0.05 to 0.15 wt.% of copper, and the balance of aluminum.
• the aluminum or the balance contains a trace amount of inevitable or unavoidable impurities such as manganese and zinc.
• the alloy of the present invention contains magnesium in an amount of 2.3 to 5.0% wt.%, and magnesium in this range offers sufficient strength required for watch external parts.
• the aluminum alloy of the invention having the composition defined above does not contain any nickel, and thus metal allergy due to nickel is not induced.
• the surface of the aluminum alloy of the invention can be covered with an anodic oxide film sealed by pressurized steam method.
• the anodic oxide film can be formed by electrolysis, using the aluminum alloy as the anode, and is formed on the surface of the anode.
• the anodic oxide film can preferably be formed by electrolysis in sulfuric acid at a temperature of about 15 to 25°C and a voltage of about 10 to 20 volts for about 35 to 55 minutes.
• This anodic oxide film is a dense film and protects the underlying aluminum alloy.
• an anodic oxide film free from cloud spots can be formed due to the characteristic of this composition. As a result, watch external parts having a sufficient surface gloss can be obtained.
• the thickness of the anodic oxide film is preferably 5 to 25 ⁇ m.
• the anodic oxide film having this range of thickness has a sufficient durability to maintain a favorable film thickness for a long period, in addition to the advantages noted above.
• This anodic oxide film is sealed, and the invention is characterized by effecting the sealing by the pressurized steam method.
• the pressurized steam does not require nickel, and hence the anodic oxide film does not contain nickel. Therefore, the anodic oxide film does not cause metal allergy due to nickel.
• the sealing treatment may preferably be effected by placing the alloy covered with the anodic oxide film in a steam at about 3 to 7 atmospheric pressures for about 5 to 15 minutes.
• the wristwatch cases of the compositions 2 to 5 and 7 to 10 exhibited a tensile strength of 195 N/m 2 or more, which is higher by more than two times that of the comparative example. This strength was sufficient for wristwatch case.
• the tensile strength of wristwatch case of the compositions 1 and 6 was 80 N/m 2 or less, and the mechanical strength was insufficient. It is considered because the content of magnesium is smaller.
• manganese, silicon and zinc were inevitable impurities in aluminum alloys, and were not added intentionally, but were found to be present by analysis of the prepared aluminum alloys.
• the watch cases made from aluminum alloys of the compositions 1 to 10 were worn by ten subjects for three days. Then patch test was conducted, and metal allergy was not found in the skin of any subject.
• an anodic oxide film was formed on the surface in a thickness of 15 ⁇ m by electrolysis in sulfuric acid at 20°C and 14 volts for 44 minutes. Then, the anodic oxide film was sealed by pressurized steam method by placing the wristwatch cases in steam at 5 atmospheric pressures for 10 minutes. The metallic gloss of the anodic oxide films was observed visually, and the wristwatch cases of the compositions 2 to 4 had a sufficient gloss. By contrast, the compositions 1 and 5 were slightly inferior in gloss. It was considered because the magnesium content was too small and too much, respectively.
• the wristwatch cases covered with such anodic oxide films were similarly worn by ten subjects for three days. Then, patch test was conducted, and metal allergy was found in none of the subjects. The tensile strength of these wristwatch cases was measured, and the results were same as the values before coating with the anodic oxide film.
• the invention has been described particularly on the wristwatch cases, but the invention may be similarly applied in other watch external parts such as back lid, hands, bezel, winding crown, push-button, watch band, and assembling screws, and also other merchandise than watch external parts such as necklace and bracelet.
• the aluminum alloys of the invention have a sufficient strength and do not contain nickel, and hence will not induce metal allergy if worn directly on the skin.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Adornments (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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