| 摘要 |
1,139,390. Cleaning aluminium alloys. AMCHEM PRODUCTS Inc. Oct.31, 1967 [Oct.31, 1966], No.49325/67. Heading C7E. Copper containing aluminium alloys are deoxidized in an aqueous acid solution containing ferricyanide ions or ferro-cyanide which forms ferricyanide ions in situ and/or nitro-ferricyanide ions which act as copper sequestering agents and minimise the formation of copper smut. The ferricyanide may be added as the ammonium or alkali metal salts and the nitro-ferricyanide as the ammonium, alkali metal, alkaline earth metal, Ce, Mn, Zn, Co or Pb salts. The preferred concentration is at least 0À34 gms ferricyanide per 0À1 gm. Cu present in solution. The preferred solutions contain hexavalent Cr, fluoride and nitric acid e.g. chromic acid, a bifluoride and nitric acid. Make up solutions in dry or liquid form may contain chromic acid or chromates, hydrofluoric acid or its salts and the salts of ferricyanide or nitro-ferricyanide. The deoxidized surface may be chromate coated. |
