| 摘要 |
371,213. Electrolytic treatment of aluminium and its alloys. SIEMENSELEKTRO-OSMOSE GES., Rohrdamm, Siemensstadt, Berlin. June 24, 1931, No. 18313. Convention date, June 1, 1930. [Class 41.] In a process for forming corrosion-resisting protective coatings on articles of aluminium and its alloys by alternating current treatment in an acid bath, uniformly coloured coatings are produced by the use of a counter-electrode consisting of a similar metal which has already been exposed to a similar treatment. The counter-electrode preferably has a coating of light colour produced by alternating current treatment in a dilute chromic acid solution, e.g. of 0À05 per cent strength. The electrolyte employed in coating the articles themselves may be chromic acid of strength from 1 to 50 per cent; the voltage may be gradually raised to 40-50 and maintained at this value for up to an hour. Detailed examples for the production of pearl grey, brownish yellow and deep black coatings are given. An aluminium alloy containing 3-4 per cent copper, 0À5-1 per cent manganese and 0À5 per cent magnesium and an alloy containing 4 per cent copper, 2 per cent silicon and 0À3 per cent iron may be treated. |
