DIRECT COLOURING ANODIC OXIDATION PROCESS FOR USE ON ALUMINIUM OR ITS ALLOYS FOR PRODUCING A BLUE OR GREYISH-BLUE OXIDATION COVER ON THE METALLIC SURFACES

摘要

The electrolyte comprises (g/l): 20-250 sulphuric acid, 1-20 alkaline hexacyano-ferrate (II), 1-50 ascorbic acid as reductant, 10-80 sulphonic acid and 5-50 additives. Voltage is 10-50 V, and current density 0.1-10 A/dm2 single current. The obtd. oxide layer powder is treated in the usual way.