| 摘要 |
<p>Process comprises (a) polishing in a bath comprising conc. H3PO4, HNO3, H2SO4 and an acid which will not complex with H3PO4, (b) anodising in a bath containing 150-200 g/l H2SO4, temp. 20-30 degrees C, current density 1A/dm2 for 5-10 mins. (c) Chromic anodising in 15-19 wt% chromic acid at 30 degrees C and at 25 pref. 21-23 volts, the anodic surface in dm2 being 1.7B- 2.3B, "B" being volume of bath in litres. The cathodic surface in dm2 being 0.06B pref. 0.03B-0.05B. Electrolysis is carried out without agitation. The relationship between atoms dissolved chrome in the hexavalent state and atoms disolved chrome in the trivalent state remains constant at a value always >70 and opt. >120. All operations are pref. separated by rinsing and followed by settling in deionised boiling water.</p> |
