| 摘要 |
1,239,788. Aluminium alloy; anodizing. KAISER ALUMINUM & CHEMICAL CORP. Oct. 23, 1968 [Nov. 1967], No.50423/68. Headings C7A and C7B. An aluminium base alloy comprises:- Cr 0À25-0À8% Mg 0À25-0À6% and Si 3À2-3À8% the balance, apart from normal amounts of impurities and incidental elements, being Al. The other elements present may include 0À01-0À05% Ti or B as well as a residual amount of Na from the "modification" of the alloys. The alloy is suitable for casting and for colour anodizing in the as cast condition as follows: - (a) The cast alloy is etched in an oxidizing acid (e.g. HNO 3 + HF) to avoid the production of a grey cast on anodizing, and (b) The etched body is anodized in an electrolyte which may contain H 2 SO 4 , or a source of sulphate ions plus sulphosalicylic acid, sulphophthalic acid or sulphoresorcinal, or oxalic acid. If a grey or black coating is required the body must be heat-treated above 300‹ F, for at least 2 hours and then cooled prior to anodizing (preferably before the etching step). The heating may be a solution treatment above 700‹ F. which may be followed by quenching and ageing. Machined surfaces do not require to be etched to produce a haze free anodic coating. |
