| 摘要 |
PCT No. PCT/NO80/00036 Sec. 371 Date Jun. 29, 1981 Sec. 102(e) Date Jun. 29, 1981 PCT Filed Nov. 7, 1980 PCT Pub. No. WO81/01424 PCT Pub. Date May 28, 1981.A dark-colored, wave-length selective oxide film on aluminum is prepared thereby that the metal subsequent to a cleaning treatment is submerged into a bath consisting of an aqueous solution having pH 8.9-10.9 and at a temperature of from 20 DEG to 100 DEG C. under conditions which result in an electrode potential of between -1.1 and -0.6 volt relative to a saturated calomel electrode. The said potential can advantageously be maintained by either addition of H2O2 to the bath or by electric polarization. In a more specific embodiment of the process there is used an aqueous solution of 1-100 g NH4Cl or (NH4)2SO4 per liter solution with or without addition of aluminate ions AlO2- or Ca++, the pH of the solution, if necessary, being adjusted to pH 9 by addition of NH3, NaOH, KOH, Ca(OH)2 and that the content of silicon, chromium and phosphorus each is maintained under 10 ppm. |
