| 摘要 |
PROBLEM TO BE SOLVED: To obtain an Al alloy material for building material, capable of controlling a color tone of metallic luster and excellent in aesthetic characteristic, at a low cost by forming a film of specific thickness, consisting of smut of Zn, Zn oxide, and Al alloy, on the surface of a main body of Al alloy containing specific amounts of Zn. SOLUTION: A main body of Al alloy, which has a composition consisting of, by weight, 5-20% Zn and the balance Al with inevitable impurities and further containing, if necessary, either or both of 0.1-2.0% Cu and 0.1-2.0% Mn, is prepared. This main body of Al alloy is immersed in an alkaline solution of about 1-20% NaOH at about 30-70 deg.C for about 3-180sec. By this method, a film consisting of smut of Zn, Zn oxide, and Al alloy is formed on the surface of the main body of Al alloy to >=0.02μm thickness with superior adhesion. This film has a black color tone and can control metallic luster of surface and improve aesthetic characteristic.
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