Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Patent
1995-11-28
1997-12-23
Silverberg, Sam
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
148275, C23C 2244
Patent
active
057003343
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a treatment process for imparting a blue color to the surface of zinc aluminum alloys, particularly the hot-dip Zn/Al alloy-plated steel sheet that is widely used as a construction material and for household electrical appliances, without at the same time impairing the bright surface appearance (metallic luster or gloss) that is possessed by such plated steel sheet. (The invention will often be described below with respect to plated steel sheet, but it should be understood that most of this discussion applies equally well to any other surface with the same chemical nature.) More specifically, the present invention relates to a novel composition and process for imparting a bright or brilliant blue color to hot-dip Zn/Al alloy-plated steel sheet, wherein the treatment bath in said process is very stable and the process can be run in simple equipment using lower temperatures and shorter times than in prior methods.
BACKGROUND ART
Metal coloring methods generally consist of inorganic chemical methods, organic chemical methods, electrolytic methods, and painting. Among these, the inorganic chemical coloring methods are the most advantageous in terms of equipment, cost, and workability. However, while various inorganic chemical coloring methods have been devised for application to aluminum sheet, aluminum alloy sheet, and zinc-plated steel sheet, an inorganic chemical coloring process has yet to be established for application to hot-dip zinc/aluminum alloy-plated steel sheet.
In specific terms, the following methods are known for the inorganic chemical coloring of aluminum and aluminum alloy: 10 minutes with an aqueous solution of 10 to 20 g/L of ammonium molybdate and 5 to 15 g/L of ammonium chloride; 50.degree. C. to 70.degree. C. with an aqueous solution of 8 g/L of zinc sulfate, 3.3 g/L of sodium molybdate, and 2 g/L of sodium fluoride; and material using a composition that contains hexavalent chromium, fluoride ion, and a compound selected from molybdic acid and its sodium, potassium, and ammonium salts (Japanese Patent Publication Number Sho 45-32922 Shinbun-sha, 1969).
Various coloring methods for zinc-plated steel sheet have also been examined, and, as for aluminum and aluminum alloy, the inorganic chemical coloring methods offer advantages in terms of equipment, cost, and workability and are therefore in wide use. With regard to the inorganic chemical coloring of zinc-plated steel sheet, for example, Japanese Patent discloses solution that contains copper ion and nickel ion.
In addition, the prior art for the coloration of zinciferous-plated steel sheet primarily yields blacks and browns, and a blue color and particularly a bright blue with a metallic gloss have heretofore been unavailable.
The application of prior-art methods (1) to (4) as described above to hot-dip zinc/aluminum alloy-plated steel sheet will now be considered. In the case of treatment methods (1) and (2), their application to hot-dip zinc/aluminum alloy-plated steel sheet does not produce the colors obtained by their application to aluminum or aluminum alloy, and in fact almost no change in color is obtained in either case. Moreover, since these treatments are intended principally for application to moldings, they require lengthy treatment times of at least 5 minutes. Because the treatment bath used in treatment method (3) is essentially a chromate treatment bath, the precipitated coating consists of a chromate film whose principal component is chromium oxide and which is therefore yellowish. Moreover, when the pH is increased to 3.5 to 6 in this method, the reactivity is diminished, the chromate coating weight therefore declines, and coloration does not occur. While treatment method (4) does rapidly produce a matte black appearance, this black coating is weakly adhesive, and the execution of some type of post-treatment is required as a result in order to improve its adherence.
In short, it has been determined that the rapid generation of a bright blue appearance cannot be obtained
REFERENCES:
patent: 3703418 (1972-11-01), Iijima
Ishii Hitoshi
Ogino Takao
Henkel Corporation
Jaeschke Wayne C.
Silverberg Sam
Szoke Ernest G.
Wisdom, Jr. Norvell E.
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