| 摘要 |
The surface of aluminium or an aluminium alloy is treated with a solution of hexavalent chromium and a fluorine compound in proportions sufficient to produce a coating on such surface, the solution also containing a soluble complex cyanide. The latter may be a ferrocyanide, ferricyanide, cobalticyanide, manganicyanide, chromic cyanide or cobaltocyanide, e.g. sodium, ammonium or potassium ferricyamide. Fluorine compounds referred to include sodium and ammonium fluosilicates, ammonium fluoride and bifluoride, hydrofluoric aid, hydrofluosilicic acid, sodium borofluoride and fluoboric acid; chromium compounds include chromic anhydride, potassium and sodium bichromates; and additional ingredients include boric acid, sodium aluminate and, to adjust pH, sulphuric acid and sodium bisulphate. U.S.A. Specifications 2,276,353 and 2,507,956 are referred to. |
